Biology B3

Osmosis and Diffusion involve movement of substances from a high to low concentration.

Active Transport is the movement of a substance from a low concentration to a high concentration. This is against the concentration gradient.

Key Points -

• Substances move in and out of cells through Diffusion, Osmosis and Active Transport.

Oxygen is exchanged in the lungs for Carbon Dioxide, by the alveoli that give the lungs it's huge surface area.

Oxygen is needed for anaerobic respiration, where carbon dioxide is the waste product which needs to be removed.

KEY POINTS -

- The lungs and the thorax are protected by the ribcage.
- The lungs exchange carbon dioxide and oxygen with the atmosphere.
- They have a large surface area, moist and have a rich blood supply which makes them well adapted for the exchange.

- Digested food is made to small, soluble molecules. They are absorbed by the villiin the small intestine.

- Food is absorbed by diffusion and active transport.

KEY POINTS -

- Digested food is absorbed by the capillaries alongside the small intestine.
- The small intestine has a rich blood supply.
- The surface area of the intestine is increased by the villi.
- Absorption by the blood is by diffusion and active transport.

- All organisms need to exchange gases, oxygen for respiration and all need to remove carbon dioxide.

- All other living organisms have many features in common;
*They have a large surface area.
*They are moist.
*The gases are transported quickly to maintain the high concentration gradient.
*The membranes for diffusion are thin.

KEY POINTS -
-Fish exchange oxygen through their gills.
-Frogs exchange oxygen through their skin.
-Insects exchange oxygen through holes in their sides leading to a series of tubes.

-Gases diffuse in and out of leaves through holes called stomata.
-Oxygen is needed for respiration and is a waste product of photosynthesis.
-Carbon dioxide is needed for photosynthesis and is a waste product of respiration. The movement of these gases depends on which process is taking place most quickly.
-Leaves are flat and thin so gases need not diffuse far. There are also internal air spaces. Water and minerals are taken up by the roots. Roots have thousands of tiny projections called Root Hairs. The only problem is that water can evaporate from the leaves.

KEY POINTS
- Plants exchange gases through their leaves.
- Plants take up water and minerals through their roots.
- Leaves and roots have adaptations for efficient exchange of materials.

-Plants take up water through the roots. It evaporates from the leaves in a process called transpiration.
-Tiny holes called stomata, usually on the underside of the leaf allow gases to be exchanged but also water to be lost :(
-If too much water is lost the plant will wilt. Guard cells control the size of the stomata. They stomata can close to prevent water loss. More water is lost on hot, windy and dry days.

GET IT RIGHT!!
-On hot days there is more energy for water to evaporate.
-On dry days the air can hold more water.
-On windy days any build up of water vapour around the plant is blown away.

KEY POINTS
- Plants take up gases through the stomata.
- They take up water and lose water through the stomata.
- If plants lose too much water they will wilt.

-The heart is an organ that pumps blood around the body. It pumps to the lungs where it picks up oxygen and loses carbon dioxide. After returning to the heart it is then pumped to the rest of the body. This is called double circulation.
-Arteries take blood away from the heart. (The pulmonary artery takes blood to the lungs, and the aorta takes the blood to the body.) Arteries stretch as blood flows through, this is felt as your pulse. They also have thick walls because of high pressure and a small lumen.
-Veins carry blood to the heart. (The vena cava carries blood from the body to the heart and the pulmonary vein carried blood from the lungs to the heart.) It is under low pressure so they have thinner walls and a large lumen. They have valves to prevent a backflow of blood, and because the blood is deoxygenated the blood is a deep purple colour.
-Capillaries are very narrow with very thin walls. They make it easier for oxygen and glucose to enter blood and remove carbon dioxide from cells.
KEY POINTS
-The heart pumps blood around the body with double circulation.
- Arteries, veins and capillaries are the vessels for blood transport.

-Blood is 55% liquid plasma.
-Blood is 45% cells (red blood cells, white blood cells, platelets)
-Within the plasma, there are antibodies (for fighting infection), nutrients, water, carbon dioxide, glucose and urea.
-A red blood cell is bi-concave, has a large surface area, contains haemoglobin (or carboxyhaemoglobin if a person has inhaled carbon monoxide) and carries the oxygen.
-The haemoglobin is a red pigment that carries the oxygen around the body. It is made with iron so a lack of haemoglobin results in the condition anaemia.
-Anaemia means the red blood cells cannot carry enough energy around the body. The symptoms of anaemia are tiredness, lack of energy and thirst.
-Urea is a waste product formed in the kidneys. In the kidney the urea is removed from the blood to make urine.
GET IT RIGHT!!!
-Red blood cells only carry oxygen!!! The rest of the substances are transported in the plasma.
KEY POINTS
-Red blood cells transport oxygen.
-Blood plasma transport carbon dioxide, urea and the products of digestion.

ENERGY IS NEVER MADE OR DESTROYED
- When you exercise the muscles in your body need more energy so that they can contract and move. You need to increase the rate at which oxygen and glucose reach the muscles, this also means carbon dioxide needs to be removed more quickly.
-Blood vessels supplying the blood dilate so more oxygen and glucose can reach the muscles.
-Breathing and depth of breath is also increased during exercise, this allows a better intake of oxygen and a better release of carbon dioxide.
-Exercise may also mean you use up glycogen which is stored in the muscles.
Dont forget to write about the oxygen and glucose needed and carbon dioxide to be excreted.
KEY POINTS
-During exercise muscles need more energy.
-More glucose and oxygen are needed in the muscles.
-To do this there are changes in the heart rate, breathing and in blood supply to give to actively respiring muscles.

-If you use muscles over a long period of time they will become tired. When your muscles have insufficient oxygen they start to respire anaerobically.
-Respiring anaerobically is inefficient and means that lactic acid is produced as a waste product.
-The lactic acid causes fatigue and once you have finished exercising the lactic acid must be completely broken down and destroyed. You need to take in a lot of oxygen to do this, this is known as oxygen debt. The oxygen oxidises the lactic acid into carbon dioxide and water.
KEY POINTS
-Muscles can become fatigued after a long period of activity. They may be respiring anaerobically as they cannot get enough oxygen.
-Lactic acid is produced in anaerobic respiration. When activity has stopped the lactic acid must be broken down. This is the cause of oxygen debt.

-The body has two kidneys, they filter the blood to keep substances the body needs and excrete substances you do not want.
-After filtration, all of the sugar and many dissolved ions and water needed by the body are reabsorbed. All the urea and some ions dissolve into the remaining water and are excreted into the urine.
-Sugar and dissolved ions may be reabsorbed against the concentration gradient. If they are, this is active transport and requires energy.
GET IT RIGHT!!!
-Urea is made by the liver from excess amino acids. Urine is the liquid excreted by the kidneys which has urea dissolved in it. It is also important to know the difference between filtration and reabsorption.
KEY POINTS
-Chemical reactions in the body produce toxic substances (urea).
-The kidneys excrete substances that are unwanted by the body.
-The kidneys first filter substances out from the blood. They then reabsorb the substances the body needs.

Dialysis is an artificial kidney.
-A dialysis machine carries out the same job as the kidneys, within the machine there are partially permeable membranes.
-The dialysis fluid contains the same concentration of useful substances as the patients blood, which means that they are not filtered out of the blood.
-Urea is filtered out of the blood.
GET IT RIGHT!!!
-In dialysis the useful subtances are not filtered out so there is no need for a system to reabsorb them. The membranes do the same job in the machine as the cells do in a real kidney.
KEY POINTS
-If your kidneys fail you would die if no action were taken.
-A dialysis machine does the work of a kidney and keeps the patient alive.
-If a successful transplant were to be carried out, then a dialysis machine would be no longer necessary.

-For most patients a kidney transplant is a better option than dialysis.
-A donor kidney must be found, often from a recently dead person. The new kidney must be a very good tissue match.
-The immune system is likely to reject a new kidney so the patient must take immunosuppresant drugs to suppress the immune system. This means that the patient must be kept in very sterile conditions to avoid them catching any infection.
AQA Examiner says - "It is very important that when answering questions about kidney transplants you include information about suppressing the immune system to prevent a new kidney being rejected."

KEY POINTS
-A diseased kidney can be replaced by a healthy kidney.
-The healthy kidney must be a very good tissue match.
-The immune system has to be supressed otherwise it is likely to reject the new kidney.

-Microorganisms are grown on agar in petri dishes.
-Agar contains carbohydrate as an energy source, but may also contain some minerals, proteins and vitamins as a supplementary nutrient.
-To prepare an uncontaminated culture;
*Petri dishes and the agar must be sterilised.
*Inoculating loops, used for transferring must be sterilised by passing through a bunsen burner.
*The lid of the petri dish must be sealed to prevent organisms entering or escaping.
-In schools and colleges cultures should be incubated at 25 degrees celcius. If grown at higher temperatures, especially body temperature, harmful pathogens are likely to grow.
KEY POINTS
-On a small scale, microbes are grown on agar in petri dishes.
-Carbohydrate is the energy source for the microbes.
-Special precautions are taken to grow microorganisms safely.
-In schools and colleges they must be incubated at 25 degrees celcius.

-Yeast cells have a nucleus, cytoplasm and a cell membrane surrounded by a cell wall. When oxygen is present they respire aerobically and reproduce quickly.
-If there is no oxygen, they respire anaerobically and produce ethanol. This is called fermentation.
- When beer is brewed, the malted barley is used as the energy source. Hops are added to give beer flavour and enzymes break down the starch.
-The grapes used for making wine use natural sugars as the energy source for the yeast.
KEY POINTS
-Yeast is a single celled organism.
-Yeast is used in making bread and alcoholic drinks.
-Yeast respires aerobically and anaerobically.
-Anearobic respiration of yeast produces ethanol and carbon dioxide.
-Bacteria are used to help produce cheese and yoghurtb.
-In yoghurt production, bacteria convert lactose sugar into lactic acid.

-Industrial fermenters are large vessels for growing microorganisms. The conditions are always carefully monitored;
*There is an air supply providing oxygen for respiration.
*There is a stirrer used to keep the microorganisms spread out and make sure the temperature is the same in all parts of the vessel.
*There is a water cooled jacket used to regulate the temperature which is increasing from the respiration.
-Fusarium is a fungus used to produce mycoprotein used as a subsitute for meat for vegetarians.

KEY POINTS
-Microorganisms can be grown on a large scale by fermenters.
-The conditions must be constantly carefully controlled.
-Mycoprotein for vegetarians is made with the use of fusarium.
-Antibiotics are produced in fermenters.
-The mould penicillium produces the antibiotic.

-Plants and waste material can be broken down by microorganisms anaerobically to produce methane (biogas).
-This can be done on a large scale with waste from sugar or sewage works.
-On a small scale it can be used from home or on a farm.
-Sugar juices can be fermented to produce ethanol, microorganisms repire anaerobically in this process.
-Distilled ethanol can be used as a fuel for motor vehicles.
KEY POINTS
-Biogas is mainly methane.
-It is made by anaerobic fermentation of a wide range of waste substances and plant material.
-Biogas can be made on large or small scales.
-Many different microorganisms are involved in biogas production.
-Ethanol-based fuels can be used to power cars but must be distilled first.
-Microorganisms respire anaerobically to produce ethanol using sugars as an energy source.