Unit 2 - organisation

A cell is the basic building block of all multicellular living organisms. Multicellular means made of many cells.Cells are grouped into tissues…..

A tissue is a group of cells with similar structure and function. Groups of tissues make up organs.Examples of tissues found in animals include:

■ muscular tissue, which can contract to bring about movement.

■ glandular tissue, which can produce substances such as enzymes, acid and hormones.

■ epithelial tissue, which covers some parts of the body(e.g. skin)

Organs are made of groups of tissues. One organ may contain several tissues. The stomach is an organ that contains:

■ muscular tissue, to churn the contents. ■ glandular tissue, to produce digestive juices

(acid and enzymes) ■ epithelial tissue, to cover the outside and the

inside of the stomach.

Organ systems are groups of organs that perform a particular function. The digestive system is one example of a system in which humans and other mammals break down and absorb food into their bloodstream.

UNIT 2 - cell organisation - information…

Plant organs Plant organs include stems, roots and leaves.Plant TissuesExamples of plant tissues include:

1. Epidermal tissues, which cover the plant2. Mesophyll, which carries out photosynthesis3. Xylem carries water and minerals up the stem from the roots

to the leaves.4. Phloem carries sugars down from the leaves where they are

made to the rest of the plant.

A plant organ….roots

Roots absorb water and minerals into a plant.They also anchor the plant into the ground.Roots have lots of root hair cells.Root hair cells increase the surface area of the roots so there is a large surface for the roots to absorb enough water and minerals.Root hair cells also have thin walls to allow easy passage of water and minerals into the plant.

What is a cell?

Name an cell in humans.

What is a tissue?

Name an tissue in humans.

What is an organ?

Name an organ in humans.

What is an organ system?

Name an organ system in humans.

Unit 2 Organisational hierarchy – Tissues, organs and organ systems

What are the main organs of a plant?

What is an organ system?

The digestive system’s function is

Label the stomach, small intestine, large intestine,, oesophagus, and mouth.

Tissue Function Animal/ Plant

Glandular Secretes substances e.g. acid

Epithelial Covers surfaces

Epidermal Covers surfaces

Mesophyll In the leaf

Xylem Transports water and minerals

Phloem Transports sugars

cells

-----------

----------------

--------------------

Cells are the basic building _______ of all living organisms.A __________ is a group of cells with a similar structure and function._____________ are groups of tissues performing specific functions.Organs are __________ into organ systems,which work together to form organisms. Missing words: Organs, organised, tissue, blocks

Gall bladder

pancreas

Digestive system help sheet.• Some enzymes work outside the body cells. • These are called extracellular enzymes.• They catalyse the breakdown of large molecules into smaller

soluble molecules.• Digestion is the process where food is broken down into small

soluble products that the body can absorb through the small intestine wall into the bloodstream.

• The products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration.

1. Digestion in the mouthFood is chewed (physical digestion) to create a larger surface area for the action of enzymes.Saliva is released which contains amylase.Saliva has a pH of 7.Amylase digests starch into smaller sugars (glucose).Further chewing enables swallowing.The food enters the oesophagus.

2. Digestion in the stomachFood enters the stomach from the oesophagus.The walls of our stomach produce juice.This juice contains:A protease enzyme (called pepsin).This digests proteins into amino acids.Hydrochloric acid – this kills bacteria in our food. It creates pH 2-3.Mucus – this protects the wall of our stomach from acid and pepsin.The wall of our stomach is muscular, and churns our food (physical digestion).The food remains in our stomach for a few hours. The proteins are digested into amino acids.Food leaves our stomach in small squirts into the small intestine.

3. Digestion and absorption in the small intestineThe small intestine has 2 main jobs:To complete the digestion of the foodTo absorb the soluble products of digestion into the blood.Digestion in the small intestine3 juices are released:1. Bile Produced by the liver.Stored in the gall bladder.Released into the small intestine.2 main things in bile:It is Alkali to neutralise the stomach acid and create a pH of 8Bile salts emulsify fats (convert large fat droplets to small fat droplets) – for a large surface area for the enzymes to act on. Both increase the rate of fat breakdown by lipase. Emulsifying fats is a type of physical digestion.There are no enzymes in bile.2. Pancreatic juice and 3. Intestinal juiceBoth are released into the small intestine.Both contain 3 main enzymes:Amylase to complete the digestion of starch into sugars.Protease to complete the digestion of proteins into amino acids.Lipase to break down fats into fatty acids and glycerol.

Unit 2 - Human digestive system - information

Unit 2 – Human Digestive system.

Part Physical digestion

Enzymes made Food digested Products of digestion

pH, and substance that creates the pH

Mouth

Stomach

Pancreas X X

Gall bladder X X X X XSmall intestine

CLUES TO HELP Carbohydrases break down carbohydrates to simple sugars. Amylase is a carbohydrase which breaks down starch.Proteases break down proteins to amino acids.Lipases break down lipids (fats) to glycerol and fatty acids.

Digestive enzymes convert food into _________ soluble molecules that can be absorbed into the ______________. The products of digestion are used to _________ new carbohydrates, lipids and proteins. Some glucose is used in R____________.

Bile is made in the _______ and stored in the __________. It is _________ to neutralise hydrochloric acid from the stomach. It also _________ fat to form _______ droplets which ___________the surface area. The alkaline conditions and large surface area increase the rate of ______ breakdown by _________.

Salivary amylase 8, bile Chewing Carbohydrates (starch)

Protein Glucose

2-3, hydrochloric acid

7, saliva Amino acids Emulsifying fats

Churning food Protease

FatsProteins Carbohydrates

LipaseProteaseAmylase

Fatty acids and glycerolGlucoseAmino acids

Fatty acids and glycerolGlucoseAmino acids

FatsProteins Carbohydrates

LipaseProteaseAmylase

To help with the

table below

Enzymes structure and function• Enzymes are biological catalysts.• Catalysts increase the rate of chemical reactions.• Enzymes are protein molecules made up of long

chains of amino acids.• These long chains are folded to produce a special

shape which enables other molecules to fit into the enzyme.

• This shape is vital for the enzymes function.• Normally only one type of molecule (the substrate)

will fit into the enzyme.• The active site is the part of the enzyme which the

substrate fits into, because it is a certain shape enzymes only fit one substrate (they are specific).

Unit 2 – Enzymes - information

The effect of pH on enzymespH can also affect the shape of the active site.It does this by affecting the forces that hold the enzyme molecule together.A change in pH can denature the enzyme.Different enzymes work best at different pH values (they have different optimum pHs)Eg. Stomach enzymes work best in acidic conditions.Mouth enzymes work best in neutral conditions.

Effect of temperature on enzymesLike most chemical reactions, the rate of enzyme-controlled reactions increases as the temperature increases.The enzyme and substrates move around faster so they collide more often.The temperature when the enzyme is working fastest is called the optimum.This is true up to approximately 40˚C, higher than this and the structure of the enzyme changes.As a result, the active site becomes a different shape and the substrate no longer fits.It is then described as denatured.

This is how

digestive enzymes

work

This is how molecules are built up in the

body. E.g. muscle tissue

KEY WORDS:Denatured, Bile, Enzymes, Active site, Substrates , amylase

Proteins, Catalysts & Enzymes

Unit 2 – Enzymes

What are protein molecules made of?

What are enzymes made from?

Enzymes are biological ____________ that __________ up chemical reactions in living organisms

The ___________ in a reaction can be held in the active site and either be connected to another molecule or be broken down.

Factors Affecting Enzyme Action.

The warmer the temperature the faster enzymes will work until ______ oC. At temperatures higher than this the enzyme stops working, the enzyme becomes ________________. Each enzyme works best at a particular _____ value, e.g. enzymes in the mouth have an o_________ pH of ______. Enzymes in the stomach have an o_________ pH of ______.

Explain why an enzyme can’t catalyse a reaction if it is denatured?

What does optimum temperature mean?

What does optimum pH mean?

Speeding up Digestion

What type of acid is produced in the stomach?

Why is the stomach acidic?

Why wont amylase from the mouth work when it reaches the stomach?

SpecificityWhy do enzymes only catalyse a specific reaction?

Mode of action – explain using the lock and key hypothesis how enzymes work.

Write an equation to show how enzymes break molecules down.

Write an equation to show how enzymes build molecules up.

How the alveoli are adapted for gaseous exchange…they have a • large surface area. • moist surface to allow oxygen to dissolve.• thin lining to allow easy diffusion of gases.• Lots of blood capillaries surrounding them for easy gas

exchange.

This is a diagram of the lungs

Unit 2 – the lungs - information

The main wind pipe is called the trachea. It is strengthened by rings of cartilage, these rings prevent the trachea from collapsing. The trachea splits into two branches called bronchi, each one delivers air to each lung. The bronchi split into smaller tubes called bronchioles. Bronchioles end in air sacs called alveoli. Alveoli is the location of gaseous exchange. Gaseous exchange involves the diffusion of oxygen into the blood and carbon dioxide out of the blood. Thee oxygen is delivered to every cell in the body, where it is needed for respiration. The waste gas of respiration is carbon dioxide, this is transported back to the lungs. Carbon dioxide then diffuses into the alveolus and is breathed out.

Label the alveolusLabels: red blood cell, capillary wall, alveolus wall, alveolus air space, oxygen entering the blood, carbon dioxide leaving the blood, oxygenated blood, deoxygenated blood.

Deoxygenated blood

Oxygen diffusing into the blood

Alveolus wall

Alveolus wall

Alveolus air space

Red blood cell

Oxygenated blood

Capillary wall

carbon dioxide diffusing out of the blood.

Direction of blood flow

Blood becomes oxygenated in the lungs. Deoxygenated blood is blood that has no oxygen in it. Oxygenated blood is blood that has oxygen in it.Gaseous exchange is by diffusion.

Characteristic ReasonLarge surface

area: volume ratioIncreases rate of

exchangeEpithelia is 1 cell

thicShort diffusion

pathwayConstant

movement of air and blood

Maintains diffusion gradient

Moist Gases dissolve to allow diffusion

The following points ensure gaseous exchange is efficient

•Circle the correct word out of each choice. The alveoli have....•A small/large surface area. •A moist/dry surface to allow oxygen to dissolve.•A thin/thick lining to allow easy diffusion of gases.•A few/many blood capillaries surrounding them for easy gas exchange.

Label the diagram of the lungs:

Labels•Trachea•Alveoli•Bronchi•Bronchioles

Unit 2 – the lungs

alveolus

bronchi

Bronchioles

trachea

oxygen

carbon dioxide

Ribs

There are thousands of these tiny air-sacs in the lungs Bronchi divide into two smaller and smaller tubes. The main breathing tube, it is strengthened by cartilage. A gas that we need for respiration. Bones that protect the lungs Respiration produces this waste gas that moves out of the blood. The tube between the trachea and a bronchiole

Join up the left side words with their correct meaning or explanation.

Label the alveolusLabels: red blood cell, capillary wall, alveolus wall, alveolus air space, oxygen entering the blood, carbon dioxide leaving the blood, oxygenated blood, deoxygenated blood.

1

6

7

2

8

4

9

Direction of blood flow

5

3

y

UNIT 2 – THE HEART

The heart has four chambers and is divided into two separate halves. Each half has an upper chamber - the atrium, and a lower chamber - the ventricle.•The atria receive blood into the heart.•The ventricles pump blood out of the heart.Because the ventricles pump blood out of the heart, they have thicker walls than the atria. The atria only pump blood into the ventricles.The left ventricle wall is thicker than the right ventricle because the left ventricle has to pump blood further (to the body) whereas the right ventricle only has to pump blood to the lungs. Valves are present - between the atria and ventricles

- in the pulmonary artery and the aortaValves are essential to prevent the backflow of blood. If they are damaged the delivery of oxygenated blood is slowed.

The heart - function - an organ that pumps blood around the body in a double circulatory system. Double circulatory system It is a double circulatory system. It comprises two separate circuits and blood passes through the heart twice. Tthe right ventricle pumps blood to the lungs where gas exchange takes place and the left ventricle pumps blood around the rest of the body.The heart is made of cardiac muscle.The natural resting heart rate is controlled by a group of cells located in the right atrium that act as a pacemaker. Artificial pacemakers are electrical devices used to correct irregularities in the heart rate.

Deoxygenated blood is pumped to the lungs via the pulmonary artery. The blood picks up oxygen (becomes oxygenated) and is returned to the heart via the pulmonary vein. The oxygenated blood is then pumped to the body via the aorta. Once the oxygen has been delivered to the tissues the blood becomes deoxygenated again and returns to the heart via the vena cava.The right side of the heart always carries deoxygenated blood and the left side always carries oxygenated blood.

The heart muscle requires a large amount of oxygen and glucose. This is supplied by the coronary artery. If this becomes blocked a heart attack results – this could lead to a cardiac arrest.

aortaPulmonary artery

Pulmonary vein

Left atrium

Right ventricle

Left atrium

Left ventricle

valves

Vena cava

Cardiac muscle wall

The heart and cholesterol•Cholesterol is a substance found in the blood. It is made in the liver and is needed for healthy cell membranes. •There are two types of cholesterol – good and bad cholesterol

1. Low-density lipoproteins (LDLs) are bad - they carry cholesterol from your liver to your artery walls.

2. High-density lipoproteins (HDLs) are good, they reduce the cholesterol in your blood and prevent build up of fatty tissues in the artery wallls.•Saturated fats increase bad cholesterol. Mono- and polyunsaturated fats reduce bad cholesterol levels.•If someone has a high level of bad cholesterol fat builds up in the artery walls, reducing the diameter of the artery. When this happens in the coronary arteries leading to the heart muscle, the blood flow is reduced. This can cause pain and may lead to blood clots lodging in the artery. This is a heart attack.

Label the heart

Unit 2 - The HeartWhat is meant by a double circulatory system?

Why do humans need a double circulatory system but fish do not?

Why are the ventricle walls thicker than the atria walls?

Why is the left ventricle wall thicker than the right ventricle wall?

What side of the heart carries oxygenated blood?

What vessel provides the heart muscle wall with glucose and oxygen?

What causes a heart attack?

What do heart valves do?

Where are the hearts natural pacemaker found?

What does the hearts natural pacemaker do?

What do we call blood with oxygen in it?

What do we call blood with no oxygen in it?

What is cholesterol?

What does bad cholesterol do?

What does good cholesterol do?

What type of fats contains a lot of bad cholesterol?

What types of fat contain good cholesterol?

UNIT 2 – BLOOD VESSELS

The pulmonary artery carries blood to the lungs to pick up oxygen, it is the only artery that carries deoxygenated blood.The pulmonary vein carries blood away from the lungs back to the heart., it is the only vein that carries oxygenated blood.

Vein Capillary Artery ArteriesFunction – to carry blood away from the heart at a high pressure.Have thick muscular walls, that can constrict to keep the blood pressure high. Have small internal lumen. They have no need for valves.Arteries have a tough outer layer and an elastic layer inside -they can cope with the pulses of blood. The walls allow a small amount of stretch to prevent the walls tearing.CapillariesFunction – to allow exchange of gases ((oxygen and carbon dioxide), nutrients (glucose and amino acids) and waste products (urea and carbon dioxide) between the blood and the tissues. E.g. Oxygen passes through the capillary wall and into the tissues, carbon dioxide passes from the tissues into the bloodThey carry blood between the arteries and veins.They are very small – their walls are one cell thick – this allows them to be permeable. They carry blood at a low pressure.The capillaries in the lungs are where gas exchange takes place. Here oxygen passes from the air spaces in the lungs through the capillary wall into the blood. Carbon dioxide passes from the blood into the air spaces.Capillaries are adapted for exchange because they have thin wall to allow easy exchange and they are narrow so have a large surface to volume ratio. This means there is more surface for exchange.

Large lumen and thin walls

Very small – penetrate all tissues. Wall one cell thick and permeable.

Small lumen and thick walls

VeinsFunction – to carry blood to the heart at a low pressure.Carry blood to the heart Have thin walls with a larger internal lumen.Have valves to prevent blood flowing backwards

UNIT 2 – BLOOD VESSELS

Why do arteries need a thick muscle wall and narrow lumen?

Why do veins have valves?

Why do capillaries need permeable walls.

Arteries Capillaries Veins

function

Blood direction

Blood pressure

Wall thickness

Size of internal diameter (lumen)

Valves present?

Is blood usually oxygenated or deoxygenated?

Fill in the table below

Which artery carries deoxygenated blood? Explain why?

Which vein carries oxygenated blood? Explain why?

Describe the differences in the substances that are exchanged in the tissues and in the lungs.

How are capillaries adapted for exchange?

1. PlasmaThe following substances are carried in the plasma:• Dissolved carbon dioxide: This is the waste gas produced by respiration in cells.• Dissolved glucose and amino acids: Food molecules for respiration, building and

repairing cells• Dissolved Urea: Waste product produced by the liver and filtered out of the blood by

kidneys• Antibodies and antitoxins: Chemicals that protect us from disease and poisons• Hormones: Chemicals that control some of our body functions – e.g. insulin.Plasma has a yellowish appearance. It sometimes oozes out of blisters.

4. Red blood cellsThey carry oxygen for aerobic respiration.They absorb oxygen in the lungs, pass through narrow blood vessels, and release oxygen to respiring cells.Red blood cells have adaptations that make them suitable for this:• Red blood cells contain the oxygen carrying

molecule haemoglobin; this is a special pigment that gives blood its red colour. Iron is needed in the production of haemoglobin; if your diet lacks this mineral you can develop the condition anaemia.

• Red blood cells do not contain a nucleus, this is so there is more space in the cell for haemoglobin.

• They are small and flexible so that they can fit through narrow capillaries.

• They have a biconcave shape (flattened disc shape) to maximise their surface area for oxygen absorption

The biconcave shape provides a large surface area compared to the volume of the red blood cell, allowing diffusion to happen efficiently.When blood picks up oxygen we say that it has been oxygenated. This happens because haemoglobin molecules form weak bonds with oxygen to make a new complex molecule called oxyhaemoglobin.

UNIT 2 – THE BLOOD

Blood has four key components:

2. White blood cellsAn important part of the immune system. There are thousands of different types each with a specific job in defending the body against disease.Some white blood cells 'eat' invading cells. Others produce antibodies to destroy harmful microorganisms.

3. PlateletsThese are not really cells in their own right. They are fragments of cells.They protect the body by stopping bleeding and sealing wounds to prevent the entry of bacteria.Their job is to form part of a clot so that they plug a wound and stop too much blood being lost. Without that clotting mechanism you would cut your finger and bleed to death!

Red blood cells contain a substance which helps it to absorb oxygen. 

Their biconcave shape means that the cell has a large surface area  

this creates more room for haemoglobin inside the cell allowing them to carry more oxygen. 

Red blood cells do not contain a nucleus  

them to become distorted as it squeezes through narrow capillaries and then restores  to its original shape.

Red blood cells are small and flexible this allows

called haemoglobin, which combines with oxygen to form oxyhaemoglobin.  

Plasma1. Name 4 substances that are dissolved in the plasma

2. Name 3 things that are suspended in the plasma

Red blood cellsWhat is the role of the red blood cell?

List the 4 adaptations that allow red blood cells to carry out its function.

How does the biconcave disc shape help the red blood cell carry out is job?

Why don’t red blood cell live for very long?

What is formed when oxygen combines with the red pigment found in red blood cells?

UNIT 2 – THE BLOOD

What part of the blood fights pathogens that enter the body?

What is a pathogen? PlateletsWhat is the role of the platelets?

Label the components of the blood

Match the beginnings t the ends of the sentences below …..

UNIT 2 – Blood and Treatment of Heart Conditions

x

Treatments for faulty heartsStents are used to keep the coronary arteries open.

Statins are widely used to reduce blood cholesterol levels which slow down the rate of fatty material deposit.

In some people heart valves may becomefaulty, preventing the valve from opening fully,or the heart valve might develop a leak.

Faulty heart valves can be replaced using biological or mechanical valves.

Statins are a group of medicines that can help lower rates of low-density lipoprotein (LDL) cholesterol (so called ‘bad cholesterol’) in the blood. They do this by reducing the production of LDL cholesterol inside the liver. The British Heart Foundation reports than only 1 in every 10,000 people who take statins will experience a potentially dangerous side effect. Also the risks of any side effects have to be balanced against the benefits of preventing serious conditions such as heart attack and stroke.It is estimated that statins save 7,000 lives a year in the UK.

Many people who take statins experience no or very few side effects. Others do experience troublesome but usually minor side effects, such as an upset stomach, headache or problems sleeping (insomnia).

The coronary artery is labelled XIn coronary heart disease layers of fattymaterial build up inside the coronary arteries, narrowing them. This reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen for the heart muscle. If they are narrowed blood clots are more likely to lodge. If a blood clot does lodge then a heart attack will occur.

Statins

UNIT 2 – Blood and Treatment of Heart ConditionsWhat is the vessel that is labelled x?

What causes the blockage?

Describe how a stent could be used to treat this.

1)

2)

x

How could the build up of fatty tissue cause a heart attack?

What are statins?

What are the advantages of taking statins?

What are the disadvantages of taking statins?

What are the advantages of treating someone with a faulty heart with a heart transplant?

What are the disadvantages of treating someone with a faulty heart with a heart transplant?

The valves in the heart control the direction of flow of the blood . Disease can cause the valves to degenerate and stop opening and closing correctly. This makes the person very tired and listless. There are two types of replacement valves: - Mechanical valve: made from man-made material such as metal, cloth or ceramic- Biological valve: made form human or animal tissue (mostly pigs).Advantages·The success rate is high, they prolong life and can expect the new valve to last up to 20 yearsDisadvantages·May need to have blood thinners to stop clotting·There is always a risk of serious complications with surgery

Arteries can get blocked, weakened or narrowed due to coronary heart disease and can cause heart attacks. A stent can be placed in the artery to keep the artery open so blood can flow through it. Advantages·The success rate is high, they lower the risk of a heart attack and last for a long time.·No need for open heart surgery.Disadvantages·Complications like bleeding, irregular heartbeat and infection. ·Arteries sometimes reclose·Drugs needed to stop blood clotting

Artificial hearts have been used temporarily to keep people alive while they wait for a heart transplant. The artificial heart is not living so needs a power source, early power sources were so large that the patient had to stay in hospital. New advances mean that the patient can now use a portable power supply and can go home. Advantages·The artificial heart is not rejected by the body·Keeps the patient alive whilst waiting for a transplant (can be used as a short term mesure)Can be used to allow the heart to rest as an aid to recovery.Disadvantages·Surgery can lead to bleeding and infection.· Blood does not flow as easily and can led to clots so blood thinners (such as warfarin) need to be taken.·Parts of the heart can wear out or stop working. ·Need an external power supply·Often people have had to stay in hospital·Huge expense

Artificial Hearts StentsReplacement valves

List the advantages and disadvantages of artificial hearts

List the advantages and disadvantages of replacement valves

List the advantages and disadvantages of inserting stents

Mechanical valves are made of materials such as titanium and polymers. They last for a very long time. However with a mechanical valve you have to take medication to prevent clots from forming and antibiotics to prevent infections setting in. Biological valves are taken from animals such as pigs or cattle or can be donor valves from humans. When fitted with a biological valve there is not usually the requirement to take anti clotting drugs however they are not as durable as mechanical valves and will need to be replaced after about 15 years.

Compare advantages and disadvantages of artificial and biological valves.

Types of disease1. Communicable diseases These spread from one person to another or from an animal to a person via viruses, bacteria, blood or bodily fluid. The diseases tend to be infectious and contagiousExamples• cold • Chicken pox • Influenza • Mumps • Malaria • Sexually transmitted

infections 2. Non-communicable diseasesAlso known as chronic diseases and are not passed from person to person. They can last many years and progress slowly. Examples• Heart attacks• Strokes• Cancers• Respiratory diseases• Diabetes• Epilepsy

Unit 2 REVISION – Health issues Non-communicable diseases

Different types of disease may interact.

• Defects in the immune system mean that an individual is more likely to suffer from infectious diseases.

e.g. HIV is a virus that kills the white blood cells of the immune system leading to diseases such as Tuberculosis (lung disease) - this is the leading cause of death of people who develop AIDS.It develops because the immune system is weakened.

• Viruses living in cells can be the trigger for cancers.e.g. Human papilloma virus. This virus can be transmitted from an infected person through unprotected sex and will live inside her cells.Some strains of the virus living are known to INCREASE the risk of developing cervical cancer.

• Immune reactions initially caused by a pathogen can trigger allergies such as skin rashes and asthma.

• Severe physical ill health can lead to depression and other mental illness.

Non-communicable diseases are caused by the interaction of a number of factors

Risk factors increase the chance of an individual developing a diseaseThree types:-(a) Aspects of a persons lifestyle (diet, exercise)(b) Substances in the body (drugs)(c) Substances in the environment (pollution).

A CAUSAL mechanism has been proven for some risk factors but not others.e.g. Carcinogens are cancer causing agents. For example, excessive exposure of UV radiation has been proven to be the CAUSE of melanoma (a type of skin cancer) other proven risk factors• The effects of poor diet, smoking and lack of exercise on cardiovascular disease (heart disease).• Obesity as a risk factor for Type 2 diabetes.• The effect of excess alcohol on the liver and brain function.• The effect of smoking on lung disease and lung cancer.• The effects of smoking and alcohol on unborn babies (causes foetal alcohol syndrome).

Non-communicable disease is on the increase, especially in developed countries. This is putting a strain on health systems.

What causes communicable diseases ?

Give some examples of Communicable diseases .

What causes non-communicable diseases ?

Give some examples of non-communicable diseases .

Unit 2 REVISION – Health issues Non-communicable diseases

Different types of disease may interact.

What disease is HIV linked to?

How are these two diseases linked?

What disease is human papilloma virus linked to?

How are these two diseases linked?

What is a risk factor?

Which type of disease is linked with risk factors, communicable or non-communicable?

What are the three types of risk factors? Give an example of each one?

What do we call a risk factor that has been proven to cause a disease?Fill in the risk factor or the disease.

Risk Factor Non-Communicable Disease

Alcohol

Type 2 Diabetes

Heart Disease

Smoking

Foetal abnormalities

Ionising radiation

Symptoms of stress such as low energy, headaches, chest pain, fast heart beat, insomnia

Points for discussion…How is this rise in disease currently impacting on our society?What will be the cost to human life if this continues?What may be the financial implications? How far may this go?

Scientists have identified lifestyle risk factors for various types of cancer including smoking, obesity, common viruses and UV exposure. There are also genetic risk factors for some cancers.

Unit 2 – Cancer

• Cancer happens when cells begin to divide out of control

• Mitosis is no longer controlled• They form tumours that can sometimes be felt as an

unusual lump in the body.

.

Malignant tumours Tumours cells that are able to invade the surrounding tissue and spread into nearby organs where they can cause serious and, eventually, fatal damage.In many malignant tumours, the cells continue to divideThey may spread into blood vesselsGet carried around the body May get stuck in a smaller blood vessel in another part of the bodyThey may begin to divide and grow again forming a new tumourThese form secondary tumoursThe process is called METASTASIS

Benign tumoursThe cells stay in the same place and the tumour stops growing before it gets very large - often because it simply runs out space to grow. These are called benign tumours and they are not normally dangerous. We all have benign tumours, such as moles and warts.

What is the link between mitosis and cancer?

List some risk factors and the types of cancer they increase the chance of.

Draw an annotated diagram to summarise the process of metastasis and formation of a secondary tumour.

Design a table to summarise the differences between a benign and malignant tumour?

•They may spread into blood vessels and get carried around the body and they may begin to divide and grow to form a new secondary tumour•The cells stay in the same place and do not spread to other parts of the body.•The tumour stops growing before it gets very large - often because it simply runs out space to grow. •They are not normally dangerous. •Examples are moles and warts.•They spread into nearby organs where they can cause serious and, eventually, fatal damage.•Tumours cells that are able to invade the surrounding tissue.•The cells continue to divide and the tumour doesn’t stop growing.

Unit 2 – Cancer

Benign Malignant

Part DescriptionStomata Pores on the underside of the leaf that allow

gases to enter and leave the leaf.Vein Contains the xylem that transports water to

the leaf.Spongy Mesophyll Layer of cells with air-spaces between them.

The spaces allow easy movement of gases through the leaf.

Waxy Cuticle Waxy layer on the top of the leaf - this waterproofs the leaf to stop water evaporating out of the top surface.

Upper Epidermis Single layer of flat cells covering the top surface of the leaf. They are transparent to let light through.

Palisade Cells Layer of long cells just under the upper epidermis they have lots of chloroplasts to carry out photosynthesis. They are near the top so they can absorb more sunlight. They have thin walls so they can exchange gases easily.

Guard Cells Cells that control the closing and opening of the stomatal pores.

Lower Epidermis Single layer of flat cells covering the bottom surface of the leaf.

Unit 2 – PLANT TISSUES AND THE LEAF

Stomata

Stomata are pores, mainly on the underside of the leaf, they allow gases to enter and leave the plant.They are surrounded by guard cells whose function is to close the stomata (usually at night) to prevent too much water loss.Plants that live in dry environments usually have less stomata.Water loss is a problem for plants as leaves collectively have a very large surface area.Plants that live in dry areas have less stomata.

The leaf is a plant organ. The structures of tissues in the leaf are related to their functions.

Meristem tissue is found at the growing tips of shoots and roots. Meristem tissue will differentiate into different plant cells.

This was discussed in unit 1 – these cells are used to carry out tissue culture, they are essentially stem cells.

6 marks

1. What is the function of stomata?

2. What is the function of the guard cells?

3. When do the guard cells open the stomata?

4. When do the guard cells close the stomata?

5. Where are there more stomata found, the top or the bottom of the leaf?

6. What would happen if the stomata did not have guard cells?

7. Some types of plants may have less stomata, what type of habitat would they be from?

8. What can meristem tissue do? Where is it found?

Unit 2 – PLANT TISSUES AND THE LEAF

Past paper question….

Rearrange the table to match the parts with the jobs

Answer to past paper question…

• Epidermis covers the top and bottom of the leaf.• Upper epidermis has no chloroplasts so allows light to reach

the palisade cells.• Palisade cells have lots of chloroplasts to trap light to carry

out photosynthesis.• Palisade cells are situated near the top of the leaf for

receiving more light for photosynthesis.• Phloem transports sugars• Xylem transports water and minerals• The waxy cuticle reduces water loss from the surface of the

leaf.• The stomata allow CO2 in and O2 out of the leaf.• Guard cells can open and close the stomata to control water

loss. • Spongy mesophyll has lots of air spaces for rapid movement

of gases

Unit 2 – xylem, phloem and meristems

Plants have transport systems to move food, water and minerals around. These systems use continuous tubes called xylem and phloem:

Xylem

FunctionXylem tissue transports water and mineral ions in the transpiration stream from the roots to the stems and leaves.

Structure of the xylem tissueXylem vessels consist of dead cells. They have a thick, cell wall strengthened with lignin and a hollow lumen. The end walls of the cells have disappeared, so a long, open tube is formed. The walls of the xylem vessel contains holes called pits which water enters through.In woody plants (trees!) the xylem makes up the bulk of the wood and the phloem is found just beneath the bark

Phloem

Function….Phloem tissue transports dissolved sugars from the leaves to the rest of the plant for use or storage. The movement of food through phloem tissue is called translocation.

Structure…Phloem is composed of tubes of elongated cells. Cell sap can move from one phloem cell to the next through the end walls that form sieve plates. Unlike the xylem, the phloem tissue is made of columns of living cells, which contains a cytoplasm but no nucleus, and its activities are controlled by a companion cell next to it which has a nucleus.

How is Phloem adapted for its function1. Sieve tube where glucose is transported has no nucleus –

there is only strands of cytoplasm so the flow of glucose is not interrupted.

2. The end walls have perforated sieve plates along the length to allow sugars to move across them easily.

3. Each sieve tube has a companion cells next to it. The companion cell has a nucleus which allows it to control the sieve tube.

Root hair cells are adapted for the efficient uptake of water by osmosis and mineral ions by active transport.

Function:Absorbs minerals and water from soilStructure:Thin walls to allow easy entry of water and mineralsExtension of cell – collectively create a large surface area to allow enough surface area for water and minerals to enter.

Unit 2 – xylem, phloem and meristems

How is the root hair cell adapted to increase absorption?

What substances are absorbed by the roots?

Name the two transport vessels

1)-__________ 2) -___________• What does vessel 1 transport?• Where does vessel 1 transport substances?• What causes the movement of water up the plant?

• What does vessel 2 transport?• Where does vessel 2 transport substances?• What is the name for the movement of water up the vessel?

• What is the name for the movement of sugars through vessels?

How is xylem adapted to transport water and minerals up the stem?

How is phloem adapted to transport sugars from the leaves?

Remember diffusion happens faster if the difference in concentration is larger.Factors which affect the rate of transpiration are:• temperature - If it is hotter the water vapour particles have more kinetic energy and will diffuse faster.• humidity - If the air is dry the difference in concentration is bigger and diffusion is faster.• air flow - If it is windy the water vapour that evaporates out of the leaf is moved away. The difference in concentration stays large and diffusion is faster.• light intensity. - Stomata are open during the day and closed during the night. Water cannot escape when the stomata are closed.

Precautions to use when you use a potometer…• Cut stem under water• Insert stem into apparatus under water.• Make sure all joints are sealed.

A Potometer actually measures the rate of water uptake. This is quite accurate because any water that is lost through the leaves is replaced by water entering the plant. The more water lost the more water enters.

•Transpiration is the loss of water vapour through the stomata on the under surface of the leaves of a plant.•It is the evaporation of water from the cells in leaves followed by diffusion of the water vapour out of the stomata.•As water evaporates from the surface of the leaves more water is pulled up through the xylem to take its place.•This is how water gets pulled up from the roots – it is called the transpiration stream.

Unit 2 – Transpiration

List the 4 factors that affect the rate of transpiration and explain why they affect it.

What is the name for this piece of equipment:

How can it be used to measure transpiration?

What precautions should you use when setting this equipment up?

•Describe transpiration.

•What causes water to move up the xylem?

Unit 2 – Transpiration