international turkish hope school 2014 – 2015 …

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INTERNATIONAL TURKISH HOPE SCHOOL2014 – 2015 ACADEMIC YEAR

CHITTAGONG SENIOR SECTIONBIOLOGY HANDOUT – CELLS

CLASS 9Name : ………………….... Date:........................

A cell is the basic structural and functional unit of Life. Usually all cells consist of a membrane,cytoplasm and a nucleus.

1. Cell membraneStructure:

· Also called plasma membrane.· A thin, delicate layer made of layers of proteins and fats.· Completely surrounds and holds in the constituents of the cell.

Function:· High surface area of the cell provides for absorption of nutrients and the disposal of wastes.· Differentially permeable, controlling the transport of materials in and out of the cell.· Allows certain small substances like glucose, water and oxygen to enter the cell.· Prevents larger molecules like protein and starch from leaving the cell.

2. NucleusStructure:

· Most prominent structure of the cell· Usually spherical in shape.· Found near the center of the animal cell.· Bound by two membranes forming the nuclear membrane.· Isolates the genetic material from the rest of the cell.· Nuclear pores are scattered over the surface of this envelope.· Found within the nucleus is one or more small, spherical structures called nucleolus which is not

bound by a membrane.· Nucleoplasm is the cytoplasm-like material that fills up the nucleus. It contains chromatin, which

is made up of DNA.Function:

· Involved in cell division.· Controls all cellular activity.· Carries the instruction for protein synthesis.· Houses the organism’s genetic material (chromosomes).· Nuclear pores act as channels, permitting certain molecules to enter or leave the nucleus.

3. CytoplasmStructure:

· Jelly-like substance.· Fills up the cell.· Suspension of various organelles.

Functions:· It is here that metabolism takes place.


4. Organelles: All the tiny structures present within the cytoplasm.a) MitochondriaStructure:

· Rod-shaped organelles.· Structures with inner folded membranes.· Permanent structure in the cell.

Function:· “Power houses” of the cell.· Site for aerobic respiration which generates energy for all the cellular activities.· Inner folds carry respiratory enzymes which help to control respiration and the release of energy

from glucose molecules in the cell.· Involved in chemical energy conversion during metabolic activities of the cell.

b) Protoplasm (Cell Membrane + Nucleus + Cytoplasm)Structure:

· Combination of the living parts of the cell.Functions:

· Cells with protoplasm are regarded as living.

c) Vacuoles· Sacs filled with cell sap, a watery solution of sugars, salts and pigments.

d) Endoplasmic ReticulumStructure:

· Endoplasmic reticulum is a maze of membranes which runs although the cytoplasm.· It is found in all cells.· It is described as rough when it has ribosomes attached to it and smooth when ribosomes are

absent.Function:

· They are assembly-lines for making fats and proteins out of smaller molecules in the cell.· It provides shelter to the ribosomes.· Protein synthesis occurs on the ribosomes in the endoplasmic reticulum.

e) RibosomesStructure:

· Tiny round objects.· Often attached to the endoplasmic reticulum.


Parts of a plant cell:1. Starch grainsStructure:

· Insoluble carbohydrates.· Occurs as very small grains.

Function:· Food source plants.

2. Cell wallStructure:

· Rigid wall made up of a layer of cellulose.Function:

· Provides support and shape to the individual plant cell.

3. VacuoleStructure:

· Large components.· Known as the sap vacuole.· Filled with a fluid called cell sap.· Membrane that surrounds a vacuole is called a tonoplast.

Function:· Plays a role in osmoregulation.· Maintaining the shape of the cell.

4. ChloroplastsStructure:

· Collection of organelles known as plastids.· Plastids that store chlorophyll are known as chloroplasts.


SIMILARITIES AND DIFFERENCES BETWEEN PLANT AND ANIMAL CELL

Similarities:1. Cell membrane2. Cytoplasm3. Nucleus

Differences:

Structures Plants Animals

Cell wall Rigid cell wall made of cellulose. Itdetermines the size and shape of the cell.It also helps to support and strengthen theplant.

Not present.

Chloroplasts Stores food as starch. Can be found inplastids. It contains chlorophyll to traplight energy for photosynthesis.

Not present.

Excess carbohydrate is stored asglycogen granules.

Sap vacuole Large and centrally located. It is usuallyfilled with cell sap.

Small in size. There may be some foodvacuole or contractile vacuoles present.

Tonoplast This is the membrane that surrounds thesap vacuole, formed by a layer ofcytoplasm.

Not present.

Starch grain Found in green leaves. Actually it givesthe leaves the characteristic green colour.

Not present.

TISSUES IN PLANTSa) Epidermal tissueStructure:

1.One layer of cells.2.Maybe covered with a waxy cuticle.3.The tissue is very thin.

Function:1.Covers surface of plant.2.Protects from physical damage and infection.3.Reduces water loss by transpiration.

b) Meristamatic tissue:Structure:

1.Is made up of undifferentiated cells.Function:

1.Undergoes cell division to produce new cells.


c) Vascular tissueStructure:

1.Made of vascular bundle of xylem, phloem and cambium.Function:

1.Transports water and mineral salts in plants.2.Transports food.3.Provides support.4.New tissue growth in the cambium.

d) Photosynthetic tissueStructure:

1.Contains cells with chloroplasts.Functions:

1.Cells with chlorophyll.2.Absorption of sunlight.3.Carrying out photosynthesis.

TISSUES IN ANIMALS (More important for Human Biology)

a) Bone (connective tissue)

Structure:Bone is alive. It consists of living cells which are supplied with food and oxygen by blood vessels.The cells are arranged in rings around the blood vessels. Bone is mostly made of mineral substances(such as calcium, phosphate with small amounts of magnesium salts) which make it very hard. Bonealso contains collagen which gives it elasticity. Collagen is a type of protein.The hardest bone is called compact bone is on the outside. Underneath this is a layer of spongybone which has spaces in it and stops the bone from becoming too heavy. In the center is the bonemarrow which is very soft and has a good supply of blood. Red blood cells, white blood cells andplatelets are made here.

Function:1. Provides protection and support.2. Allows movement to occur.3. Joins body structure together.

b) Muscle tissuei) Voluntary (striated muscle) e.g. all muscles attached to bones are striated.Structure:

1. Striated muscles are striped.2. Striated muscle contains striated cytoplasm which is not divided into cells.3. They are isolated from each other.

Function:1. The striated muscles are under conscious control.2. They help to carry out locomotion.


ii) Involuntary (smooth muscles) e.g. the walls of the alimentary canal and bladder.Structure:

1. Smooth muscles are isolated from each other.2. Smooth muscles are elongated.3. They contain non-striated cytoplasm.

Functions:1. Smooth muscles are involuntary muscles and carry out involuntary actions i.e. actions which

are not controlled by the will.2. The elongated cell can shorten its length and so contribute to muscle contraction.3. Help in breathing and peristalsis.

iii) Cardiac muscle (found only in the heart).Structure:

1. Adjacent cells in cardiac muscle are linked by bridges between cells.2. They contain striated cytoplasm.

Function:1. Cardiac muscle makes up the walls of the atria and ventricles.2. It controls the movement of the heart.

c) Blood (connective tissue)Structure:

1.The liquid part of blood is called plasma.2.Floating in the plasma are mostly red blood cells and a much smaller number of white blood

cells.3.There are also small fragments formed from special cells in the bone marrow, called platelets.

Function:1.Red blood cells carry oxygen.2.Glucose, amino acids, salts, hormones, blood proteins and antibodies are substances which are

essential for the body and are found in plasma.3.White blood cells fight infection.4.Platelets help blood to clot.5.Blood acts as a transport.6.Blood helps in regulation of body temperature.

d) Nervous tissueStructure:

1. Is made up of nerve cells and neurons

Function:1. Conducts nerve impulses throughout the body.

e) Epithelial tissuei) Squamous surface for e.g. the cells lining the cheek are squamous.Structure:

1.It is made up of sheets of cells.


2.It is smooth and does not contain any hair.Function:

1.Covers internal and external surfaces of the body.2.Serves as a protective lining.

ii) Ciliated muscleStructure:

1.Contains tiny hair-like projections called cilia.

Functions:1. The cilia helps to sweep dust particles up the bronchi and trachea into the pharynx.2. The cilia are always moving and bacteria or dust particles get trapped in them in the mucus.3. Cilia in the nose also waft the mucus into the oesophagus where it is swallowed.4. Some epithelial cells are specialized to secrete substances e.g. mucus in the lining of the nose.

These are gland cells. Gland cells may clump together in large groups forming the glands ofthe body.

Specialization of cells: The changing of the shape and size (adaptation) of a cell forperforming a particular function is known as Specialisation or Differentiation of cells.[After MITOSIS, one of the cells retains the ability to divide further and the other celladapts for a particular task.]

In Plants1. Root hair cell: It has long hairs to increase surface area of the cell. It has a large number ofmitochondria to provide energy for active up take.2. Xylem vessels: It transports water and minerals to the plant. The xylem cells are dead and aremade of long hollow tubes running throughout the root, stem, and leaves. It has thick cell walls.3. Phloem cells: They transport sugar and amino acids to the body from the place they were made(the leaf). The phloem cells are long cells joined together. The cell wall where 2 phloem cells jointogether has holes which allows the cytoplasm of both cells to communicate passing down thedissolved food.4. Guard cell (stomata): Allows O2 and CO2 to pass in and out the leaf. They can change theirshape thus can open and close their holes.

In Animals5. Red blood cells: It transports oxygen from the lungs to tissues. It has no nucleus, t hashemoglobin which absorbs oxygen, its shape gives it a high surface area and it is small to fit incapillaries.6. Nerve cells: they conduct electrical impulses which travel to & from the brain. They are very longand their chemical reactions cause impulses to travel through their fibers. They also have a layer offat for insulation.7. White blood cells: These occur in large amounts in the blood stream. They get rid of bacteria andviruses. They are able to change shape and can penetrate the blood vassals to enter tissues. They alsocontain enzymes that kill microorganisms in their cytoplasm.8. Ciliated cell: These have cilia (hairs) which can move mucus away from the lungs by a wavymotion.


9. Muscle cells: These cam contract to move the body (they don’t relax but they return to theiroriginal shape by the influence of other cells) they contain a lot of mitochondria to provide theenergy needed.


ORGANS

Types of organs Function

Animals · Alimentary canal · To digest food.· Nose, trachea, lungs · Gaseous exchange.· Heart, blood vessels. · Transport oxygen and dissolved substances.

Plants · Leaf · Photosynthesis· Transpiration

· Flower · Reproduction.

ORGAN SYSTEMS

Organ system Function

Integumentarysystem(skin)

· Waterproof barrier.· Regulate temperature.

Respiratory system · Takes in oxygen· Releases carbon dioxide.

Circulatory system · Regulates body temperature.· Transports food, wastes, and gases to and from cells.

Muscular system · Movements of parts of the body.· Muscles found in internal organs serve to move substances in the organs.

Skeletal system · Supports body.· Protects internal organs.

Lymphatic system · Filters bacteria.

Digestive system · Takes in and breaks down food.· Absorbs nutrients.· Undigested food is eliminated.

Excretory system · Removes wastes from the body (includes lung and skin).

Nervous system · Controls and co-ordinates body movement.· Transmits information from the brain.

Immune system · Defends against infection.

Endocrine system · Secretes hormones.· Produces response in the body.

Reproductive system · Produce sex cells.· Protects and nourishes young during development.


PLANT CELL

ANIMAL CELL


Preparing a slide/ Mounting of a cell:1. Plant Cell:

i. Take an onion.ii. Peel the inner membrane from the flesh of an onion cell.

iii. Place the membrane on a glass slide.iv. Drop few drops of iodine solution.v. Carefully place a cover slip.

vi. Transfer the slide to a microscope and observe.

*The cover slip prevents the lens from coming in contact with the specimen. It also prevents theentry of dust, the cover slip should be lowered carefully, so that no air bubbles are trapped, using asharp needle.

*Chloroplast are absent in an onion cell as they do not photosynthesize.

STAINS: They allow the organelles to be vivid while observing under a microscope. The organelles likenucleus, chloroplast, and cell membrane become clear as they absorb the stain.

*Iodine is one of the more commonly available stains and is used to identify starch in a variety ofsamples. It will stain carbohydrates in plants and animal specimens brown or blue-black. Glycogenwill show as red.*Methylene Blue is an alkaline stain useful in identifying acidic cell nuclei and DNA in animal,bacteria or blood samples. It’s also useful in aquariums to prevent the spread of fungal infections infish.*Eosin Y is an acidic stain which stains pink for alkaline cells (cytoplasm, for example). It colorsred for blood cells, cytoplasm and cell membranes. Eosin's most important medical uses are in bloodand bone-marrow testing.*Gram's Stain is one of the most frequently used processes in identifying bacteria – used daily inhospitals. It is a primary test that quickly and cost effectively divides bacteria into one of two types:Gram positive or Gram negative.

2. Animal Cell:i. Take some liver cells or using a cotton bud gently scrape the inner surface of your cheeks.

ii. Rub the glass slide using the cotton bud.iii. Drop some methylene blue on the glass slideiv. Gently lower a cover slip.v. Transfer the slide to a microscope and observe.

· Organizations of cells:Cells Tissues Organs System Organisms.Cells-It is a structural and functional unit of life.Tissues-They are a group of similar cells with a particular function.Organs-Organs are a group of tissues with a particular function.System-A group of organs with a particular function. E.g. digestive system.Organism-Many organ systems make up an organism.

http://www.microscope.com/education-center/how-to-guides/basic-stains/

http://www.microscope.com/education-center/how-to-guides/basic-stains/

http://www.microscope.com/education-center/how-to-guides/grams-stain/

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