Biology B3

Substance are sometimes absorbed against a concentration gradient by active transport

Active Transport uses energy from respiration

Cells can absorb ions from very dilute solutions and move molecules through cell membranes using active transport

Your breathing system takes air into and out of your body

Oxygen from the air diffuses into your bloodstream and carbon dioxide diffuses out

The alveoli of the lungs provide a very large, moist surface area with rich blood supply and thin walls to make diffusion as effective as possible

The villi in the small intestine provide a large area with an extensive network of capillaries. This makes them well adapted to absorb the product digestion by diffusion and active transport.

In material exchanges, the surface area : volume ratio is always important - big surface area is vital for successful diffusion

Whatever the organism, gas and solute exchange depends on large surface area, moist surfaces, short diffusion distances and a large concentration gradient

Plants have stomata which allow them to obtain carbon dioxide from the atmosphere

Carbon dioxide enters the leaf by diffusion. Leaves have a flat thin shape and internal air spaces to increase the surface area available for diffusion

Most of the water and mineral ions needed by a plant are absorbed by the root hair cells which increase the surface area of the roots

The loss of water vapour from the surface of plant leaves is known as transpiration

Water is lost through the stomata which are opened and close by guard cells to let in carbon dioxide for photosynthesis

water is pulled up through the xylem from the roots to replace the water lost from the leaves in the transpiration stream

The body transport system consist of blood vessels, the heart and the blood

Human have double circulation

The heart works as a pump, moving blood around the body

The 3 main types of blood vessels are the arteries, veins and capillaries

Your blood is the main transport medium of your body

Your blood plasma transports dissolved food molecules, carbon dioxide and urea

Your red blood cells are adapted to transport oxygen from your lungs to the organs of your body

Red blood cells are biconcave discs which have no nucleus and are packed with are pigment haemoglobin

Oxygen is carried by haemoglobin which becomes oxyhaemoglobin in reversible reaction

The energy that is released during respiration is used to enable muscles to contract

When you use your muscles you need glucose and oxygen to be supplied at a faster rate. The rate at which carbon dioxide is removed from the muscle tissues needs to increase too

Body responses to exercise include and increase in heart in heart rate, and increase breathing rate and depth of breathing . The arteries supplying blood to the muscles dilate and the glycogen stores in the muscles are converted to glucose to use as fuel for respiration

Regular exercise benefits the muscles, heart and lungs

If muscles work hard for a long time they become fatigued and don't contract properly. If they don't get enough oxygen they will respire anaerobically

Anaerobic respiration is respiration without oxygen. Glucose is broken down to form lactic acid, water and a small amount of energy

After exercise, oxygen is still needed to break down the lactic acid which has built up. The amount of oxygen needed is known as the oxygen debt

A healthy kidney produces urine by filtering the blood. It then reabsorbs all of the sugar, and the mineral ions and water needed by your body

Excess mineral ions and water along with urea are removed in the urine

Sugar and dissolved ions can be actively reabsorbed against a concentration gradient

People suffering from kidney failure may be treated by regular sessions on a kidney dialysis machine by having a kidney transplant

In a dialysis machine , the concentration of dissolved substance in the blood is restored to normal levels

The levels of useful substance in the blood are maintained, while urea and excess salt pass out from the blood into the dialysis fluid

In a kidney transplant diseased or damaged kidneys are replaced with a healthy kidney from a donor

The donor kidney may be rejected by the recipient's immune system. To try and prevent rejection the tissue types of the donor and recipient are matched as closely as possible and immunosuppressant drugs are used

Microorganisms can be grown in an agar culture medium with a carbohydrate energy source and various minerals, vitamins and protein

You need to take careful safety measures and use sterilised equipment to grow uncontaminated cultures of microorganisms and to avoid the growth of harmful pathogens

Yeast is a single celled organism which respire aerobically producing carbon dioxide and water. This reaction is used in bread making to make the dough rise

Yeast can also respire anaerobically producing ethanol and carbon dioxide in aprocess known as fermentation

The fermentation reaction of yeast is used to produce ethanol in the production of beer and wine

Bacteria are used in making both yogurt and cheese

In the production of yogurt a starter culture of bacteria acts on warm milk. Lactose is converted to lactic acid in a lactic fermentation reaction. This changes the texture and taste of the milk to make yogurt

In cheese-making a different starter culture is added to warm milk giving a lactic fermentation which results in solid curds and liquid whey. The curds are often mixed with other bacteria or moulds before they are left to ripen into cheese

Microorganisms can be grown on a large scale in vessels known as fermenters to make useful products such as antibiotics and mycoprotein food

Industrial fermenters usually have a range of features to make sure the fermentation takes place in the best possible conditions for a maximum yield of the product

The fungus Fusarium is grown on sugar syrup in aerobic conditions to produce mycoprotein food

The antibiotic penicillin was discovered by Alexander Fleminig. The method of mass production was the work of Howard Florey and Ernst Chain

Penicillin is made by growing the mould Pencillium in fermenter

The medium contains sugars and other nutrients and has a good supply of oxygen

The mould only starts making penicillin after most of the nutrients are used up

Biogas - mainly methane- can be produced by anaerobic fermentation of a wide range of plant products and waste materials that contain carbohydrates

Many different organisms are involved in the breakdown of material in biogas production

Ethanol based fuels can be produced by the anaerobic fermentation of sugar cane juices and from glucose derived from maize starch by the enzyme carbohydrase

Ethanol is distilled from the fermentation products and can be used as a fuel in motor vehicles on its own or mixed with petrol to produce gashol