2.2 cell organisation (biology)

Cell organisation

TISSUETissue can be classified into four types:- epithelial tissue- Muscle tissue- Connective tissue- Nerve tissue

1. Epithelial tissueConsists of one or more layers of cellsAre tightly interconnected and form a continuous layer

over body surfaces(skin&mouth area) and inner lining of cavities(digestive tract&lungs)

Some epithelial tissue undergo changes to form glands(exocrine&endocrine glands)

On skinforms a protective barrier against infection,mechanical injuries & dehydration

Lining of the human intestine form mucus-secreting goblet cells which secrete mucus into the digestive tract

Lining of the tracheaconsists of elongated cells called cilia

2. Muscle tissueComposed of cells called muscle fibresHave 3 types – smooth muscle, cardiac muscle,

skeletal muscle(a)Smooth muscle(can be found in intestine,blood

vessels, urinary and reproductive tract)- contraction&relaxationresponsible for involuntary

body activities(ex:perilstaltic movement)- Contract more slowly than skeletal muscle but remain

contracted for a longer period of time(b)Skeletal muscle- Voluntary movementscontract & relax to move the

bones(c) Cardiac muscle- Contract to pump blood (involuntary)

3. Nerve tissueComposed of neuronesSpecialised to detect stimuli and transmit

electrical signals called nerve impulses to muscles or glands

Control and coordinate activities of the body

4. Connective tissueConsists of various types of cell and fibres separated

by an extracellular matrixi. Loose connective tissuebinds epithelia to

underlying tissues and hold organs in placeii. Dense fibrous connective tissuefound in

tendons & ligamentsiii. Cartilage strong&flexible;provides support to the

nose,ears and covers the ends of bones at jointsiv. Bone protection to organs and support the bodyv. Blood cells regulate,transport& protectvi. Adipose tissue acts as an energy

reserve,insulation&protection

Red blood cells

Bone

cartilage

OrgansIs formed by two or more types of tissue

working together to perform a particular function

Examples: heart,skin,lungs,kidneys,eyes and ears

SystemsConsists of several organs that work

together to perform a common functionThere are 11 major systems which carry

out major body functions in human

Cell organisation in plantTwo main types:(i)The meristematic tissues- small cells which have thin walls, large

nuclei,dense cytoplasm & no vacuole- Are young,actively dividing cell which have

not undergone differentiation and are located at the tips of roots and the buds of the shoots

(ii) The permanent tissues- Tissue that have undergone differentiation or

are still undergoing differentiation- Have three types:(a) Epidermal tissue(b) Ground tissue(c) Vascular tissue

1. Epidermal tissueOutermost layer that covers the

stem,leaves and roots of young plantsAre flat and have large vacuolesCuticle minimizes water loss & prevent

invasion of diseasesRoot hairsincrease surface area for water

absorptionSpecialised epidermal tissue,ex: guard

cells control the opening & closing of stomata

Guard cell

2. Ground tissueConsists of parenchyma tissue,

collenchyma tissue and sclerenchyma tissue

Parenchymathin walls& large vacuole;store sugar and starch

Collenchyma supports herbaceous(non-woody) plants

Sclerenchyma have cell wall thickened by lignin;give support & mechanical strength to mature regions of a plant

Collenchyma cells

3. Vascular tissueConsists of xylem & phloemXylem transport water and mineral salts

to all part of the plantPhloem transport food(organic)

substances to all parts of the plant

Organs and systems in plant

Organs root,stem, leaf and flowerFlowering plants have 2 systems:(a) Root system consists of all root of the

plant(b) Shoot system consists of stem, leaves,

buds, flowers and fruits

Regulating the internal environment

What is internal environment?- Refers to the environment inside an

organism, which is the fluid(blood plasma and interstitial fluid) surrounding the cells

The necessity for maintaining an optimal internal environment

The physical factors and chemical factors of the internal environment must be maintained for the cells to function optimally

Physical factor includes: temperature, blood pressure & osmotic pressure

Chemical factors: salt&sugar content, PH value

Homeostasis

Is the maintenance of a relatively constant internal environment for the cells to function optimally

Any increase in the value of a physical or chemical factor will trigger the homeostatic mechanism to bring it back to normal

Any decrease will trigger the homeostatic mechanism to raise it back to normal

The mechanism that governs homeostasis is called the negative feedback mechanism

The involvement of various systems in maintaining an optimal internal environment

Systems in the body function interact with one another to maintain a stable internal environment

For example: body temperature, concentration of oxygen & carbon dioxide, the blood glucose level, blood osmotic pressure, chemicals contents and PH level

Body temperatureIs regulated by the integumentary system(skin and sweat

glands), nervous system, circulatory system, muscular system and endocrine system

Body temperature RISES

The receptors in the skin detect the changes

Information is transmitted to the hypothalamus(temperature regulatory centre in the brain)

activates

activatesBlood

vessels

Sweat gland

Dilate and allow more blood to flow near the surface of the body

Increase heat loss to the external environment

Produces more sweat that will lower the body temperature

Increase heat loss through evaporation

Body temperatur

e is restored to

normal

2.3 Appreciating the uniqueness of the cell

The state of certain cells without a particular cellular components

Organelle missing

Predicted state of the cell

Nucleus • All cell activities stop• Cell does not live for long• The cell dies

Mitochondrion • No energy for cell activities• The cell dies

Ribosome • Cell is unable to synthesis enzymes (proteins)• Cell growth stops• Cell is unable to repair itself• Finally, the cell dies

Endoplasmic reticulum

• Less enzymes produced• Synthesis and transport of proteins and glycerol stop

Golgi Body • Proteins produced become defective• Cell is unable to produce certain types of protein

Most of cells are specialised for the function that they perform

1. Muscle cells - Cell is able to contract

Specialised function produces movement

2. Neurone- Shaped into a long thin fibre

Specialised function conducts nerve impulses

3. White blood cell- Changes its shape

Specialised function Engulf and destroys microorganisms by phagocytosis

4. Red blood cell- Disc shape, biconcave and without nucleus

Specialised function Transports oxygen (its nucleus is absent so that there is more room to transport oxygen)

Exercises1. How does an amoeba feed, move, reproduce, respond

to stimulus, grow, excrete waste, and rid its body of excess water?

2. What are the problems of a multicellular organisms?3. What advantages does a cockroach have over an

amoeba?4. What is internal environment?5. What are the four factors controlling the internal

environment?6. What human body systems regulate:(a) Body temperature(b) Osmotic pressure(c) Blood glucose level(d) pH of the plasma