Biology IGCSE Guide

1. Draw a typical animal and plant cell and label different parts2. Transport/Diffusion. Explain main features.3. Define aerobic respiration: Final products. Name,etc. 4. Bread is made mainly of starch, protein, lipid, and fibre. Imagine a piece of bread about to

start its journey along the alimentary canal. State in each organ: Enzymes, fluids etc. Explain digestive process. Table-Thinking Map, etc.

5. Circulatory System: A – Make a simple diagram of a human heart, label different chambers, arteries, veins, valves. Show blood flow.

6. How can coronary blockage be produced? Why are coronary arteries so important? 7. Breathing: A- Where does gaseous exchange take place? Structures: Characteristics that

enable exchange.

B- What are the effects of cigarette smoke in lungs, and bronchi

8. Draw a simple diagram of excretory System. A. Label parts, B Define ultrafiltration and selective reabsorption

9. What is ADH: Importance. Function. 10. Homeostasis: Mention different homeostatic mechanisms, develop one of them.

1-

2-

Sometimes substances are required to be moved against the Concentration Gradient, or faster than they would by Passive Transport. In these cases, Active Processes are used, which require energy.

Diffusion is the net movement of molecules from a region of its higher concentration to a region of its lower concentration. Molecules move down a concentration gradient, as a result of their random movement.

Factors favoring diffusion- Distance (the shorter the better), e.g. thin walls of alveoli and capillaries.- Concentration gradient (the bigger the better). This can be maintained by

removing the substance as it passes across the diffusion surface. (Think about oxygenated blood being carried away from the surface of alveoli).

- Size of the molecules (the smaller the better).- Surface area for diffusion (the larger the better).- Temperature (molecules have more kinetic energy at higher temperature).

Two big differences between diffusion and active transport:- Direction of movement (down or up a gradient)- Use of energy for movement

The active transport is carried out by ‘carrier proteins’ in the membrane, which bind to the solute molecule, change shape and carry the molecule across the membrane.

3-A. Aerobic respirationThe release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of O2.(Oxidation)

Glucose + Oxygen Enzymes Carbon Dioxide + Water + Energy

B. Anaerobic respirationAnaerobic respiration: the release of a relatively small amount of energy by the breakdown of food substances in the absence of O2.(Fermentation)

Glucose Enzymes Alcohol + CO2 + Energy

4-

Region of alimentary

canalDigestive

gland

Digestive juice

produced

Enzymes in the juice

Class of food acted upon

Substances produced

MOUTH SALIVARY GLANDS

SALIVA SALIVARY AMYLASE

STARCH MALTOSE

STOMACH GLANDS IN STOMACH LINING

GASTRIC JUICE

PEPSIN PROTEINS PEPTIDES

DUODENUM PANCREAS PANCREATIC JUICE

PROTEASES

AMYLASELIPASE

PROTEINS ANDPEPTIDES

STARCHFATS

PEPTIDES AND AMINOACIDS

MALTOSEFATTY ACIDS AND GLYCEROL

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6-Deposits of fatty substance, called atheroma are laid down in patches. The patches may join up a continuous layer which reduces the internal diameter of the vessel. The surface of a patch of atheroma sometimes becomes rough and causes fibrinogen in the plasma to deposit fibrin on it

From lungs

To heart and bodyTo lungsPulmonary artery Aorta Pulmonary vein

Vena Cava

From head and body

Oxygenated

Deoxygenated

VentricleVentricle

BicuspidTricuspid

AtriumAtriumSemilunar valve

Right Left

causing a blood clot (thrombus). If the blood clot blocks the coronary artery the blood cannot pass through, so the muscles of the ventricle won’t be supplied with oxygenated blood, and the heart may stop beating.

7- A-Gas exchange usually involves 2 or more gases transferred in opposite directions across

a respiratory surface. Gaseous exchange relies on diffusion. To be efficient, the gaseous exchange surface must:

1. Thin – shorter distance to diffuse2. Moist – allow gases to dissolve3. Large surface area4. Have a concentration gradient across surface – maintained by movement of air and

transport/ use of gas.

These features are present in alveoli.

B-The smoke stops the cilia in the air passages from beating and so the irritant substances in the smoke and the excess mucus collect in the bronchi. This leads to the inflammation known as bronchitis. Emphysema is a breakdown in the alveoli. The action of one or more of the substances in tobacco smoke weakens the walls of the alveoli. The irritant substances in the smoke cause a ‘smokers cough’ and the coughing bursts some of the weakened alveoli. The absorbing surface of the lungs it’s greatly reduced. The smoker cannot oxygenate his blood properly and the least exertion makes the person breathless and exhausted.

8-

Urine is made by filtration and selective reabsorption

As blood passes through the kidneys, it is filtered. This removes most of the urea from it, and also excess H2O and salts.

As this liquid moves through the kidneys, any glucose in it is reabsorbed back into the blood. Most of the H2O is also reabsorbed along with some of the salts.

The final liquid produced by the kidneys is a solution of urea and salts in water.

It is called urine, and it flows out of the kidneys, along the ureters and into the bladder. It is stored in the bladder for a while, before being released from the body through the urethra.

9-The relative amount of water reabsorbed depends on the state of hydration of the body (how much water is in the blood), and is controlled by secretion of the hormone ADH. Changes in the concentration of the blood are detected by an area in the brain called the hypothalamus. If the blood passing through the brain is too concentrated, the

hypothalamus stimulates the pituitary gland beneath it to secrete into the blood a hormone called the ADH. When this hormone reaches the kidneys it causes the kidney tubules to absorb more water from the glomerular filtrate back into the blood. 10-Homeostasis is the maintenance of a constant internal environment. It is achieved using negative feedback.

The control of body temperature in humans involves the hypothalamus, the skin and muscles. When the body becomes too hot, sweating and vasodilatation increase the rate of heat loss from the skin. When the body becomes too cold, shivering increases heat production, and vasoconstriction reduces the rate of heat loss from the skin.

The pancreas, working in conjunction with the liver, controls blood glucose concentration. When this rises too high, the pancreas secretes insulin which causes the liver to remove glucose from the blood and convert it to glycogen. When blood glucose concentration falls to low, the pancreas secretes glucagon which causes the liver to convert glycogen to glucose.