Biology Topic 2 - Organisation

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What's the difference between cells, tissues and organs?
Cells are the basic building blocks that make up all living organisms. A group of similar cells makes a tissue, a group of different tissues makes an organ and a group organs makes an organ system.
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What are enzymes?
Enzymes are biological catalysts- they reduce the need for the high temperatures and speed up the useful chemical reactions. Enzymes are large proteins, which are made up of chains of amino acids.
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How many reactions is an enzyme able to catalyse and why?
Usually only one specific reaction, because they have an active site with a unique shape that fits with the substrate.
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How does temperature affect enzyme activity?
A higher temperature increases the rate at first, but if it gets too hot some of the bonds holding the enzyme together will break. This changes the shape of the enzyme's active site so the substrate won't fit anymore and is known as denaturing.
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What else affects enzyme activity?
All enzymes have an optimum pH that they work best at, and if the pH is too high or low this will cause the enzyme to denature.
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What are the two formulas for calculating rate of reaction?
Rate= 1000/time OR Rate= amount of product formed/time
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Why do digestive enzymes break down big molecules (e.g. starch, proteins and fats) into smaller molecules (e.g. glucose and maltose)?
This is because big molecules don't fit through the walls of the digestive system- they need to be broken dow so they can be absorbed into the bloodstream
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What does amylase do, where is it found and what is its optimum pH?
Amylase breaks down starch into glucose, it is found in the salivary glands and the small intestine and it works best at pH7.
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What does protease do, where is it found and what is its optimum pH?
Protease breaks down proteins into amino acids, it is found in the stomach and the small intestine and it works best at pH1.6
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What does lipase do, where is it found and what is its optimum pH?
Lipase breaks down lipids into fatty acids and glycerol, it is found in the small intestine and it works best at pH8.
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Where is bile produced and stored?
Bile is produced in the liver. It's stored in the gall bladder before it's released into the small intestine.
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What does bile do?
Bile is alkaline, so it neutralises the hydrochloric acid in the stomach for enzymes to work. It also emulsifies fats, breaking them into tiny droplets to give them a much bigger surface area for lipase to work on and making the digestion faster.
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Mouth
Salivary grands produce amylase in the saliva. The teeth chop food into smaller pieces and the tongue pushes food down.
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Oesophagus
Circular and longitudinal muscles work together to produce wave like contractions, which have a squeezing action to push food through the gut. This is known as peristalsis.
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Liver and gall bladder
The liver produces bile and the gall bladder stores bile before it's released into the small intestine.
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Stomach
Muscular layer to churn the food (peristalsis), glandular layer to produce enzymes (pepsin-protease) and acid (hydrochloric to kill bacteria), epithelial layer covers the inner and outer surfaces of the stomach.
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Pancreas
Produces digestive enzymes and releases them into the small intestine.
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Small intestine
Digested food is absorbed out of the intestine into the blood.
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Large intestine
Excess water is reabsorbed into the body.
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Rectum and anus
The faces are stored in the rectum before being expelled by the anus.
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Describe the structure of the lungs.
The lungs are in the thorax, which is the top part of your body, separated from the lower part by the diaphragm. The lungs are like big pink sponges, protected by the ribcage and surrounded by the pleural membranes.
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Describe the structure of the lungs (continued)
The air you breath in goes through the trachea, which splits into two tubes called bronchi, one going to each lung. The bronchi split into smaller tubes called bronchioles, which end at alveoli.
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How is blood oxygenated by the lungs?
Blood passing the alveoli contains lots of carbon dioxide and very little oxygen, so oxygen diffuses out of the alveolus into the blood and carbon dioxide diffuses out of the blood into the alveolus.
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What happens when the blood reaches body cells?
Oxygen is released from the red blood cells and diffuses into the body cells. Carbon dioxide diffuses out of the body cells into the blood and is carried back to the lungs.
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Why is the heart called a double circulatory system?
It involves two circuits joined together. The right ventricle pumps deoxygenated blood to the lungs to the in oxygen, and the blood returns to the heart. The left ventricle pumps oxygenated blood to other organs, and deoxygenated blood returns.
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Describe how the heart pumps blood around the body.
Blood flows into the two atria from the vena cava and the pulmonary vein. The atria contract, pushing blood into the ventricles. The ventricles contract, forcing blood into the pulmonary artery and the aorta, out of the heart and flows to organs.
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What do coronary arteries do?
Coronary arteries branch off the aorta and surround the heart, making sure it gets oxygenated blood.
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What do valves do?
They make sure that blood flows in the right direction and prevent it flowing backwards
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What is the pacemaker?
A group of cells in the right atrium wall act as a pacemaker and control your resting heart rate. They produce a small electric impulse which spreads to the surrounding muscle cells and causes them to contract.
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What is an artificial pacemaker and why is it used?
An artificial pacemaker can be used to control heartbeat if the natural cells don't work properly (irregular heartbeat). It is implanted under the skin and has a wire going to the heart, producing an electric current to keep the heart beating.
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Arteries
Arteries carry blood away from the heart. The artery walls are strong (thick layers of muscle) and elastic (elastic fibres), with a small lumen. They carry blood under high pressure.
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Capillaries
Arteries branch into capillaries, which are really small- they carry the blood really close to every cell in the body. They have permeable walls so substances can diffuse and have walls that are only one cell thick.
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Veins
Capillaries join up to form veins, where blood is at lower pressure. They have a bigger lumen to help the blood flow, and they also have valves.
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What are the food components of the blood?
Red blood cells, white blood cells, platelets and plasma.
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Red blood cells
Red blood cells carry oxygen from the lungs to all the cells in the body. They are shaped like a biconcave disc (for a large surface area) and they don't have a nucleus. They contain haemoglobin which binds to oxygen to become oxyhemoglobin.
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White blood cells
White blood cells defend against infection. Some can change shape to engulf pathogens (phagocytosis) and others produce antibodies (bind to antigens) as well as antitoxins (neutralise toxins). They do have a nucleus.
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Platelets
These are small fragments of cells with no nucleus. They help blood to clot at a wound, stopping blood pouring out and pathogens getting in. Lack of platelets can cause excessive bleeding and bruising.
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Plasma
This is a yellow liquid that carries: red and white blood cells, platelets, nutrients (glucose, amino acids), carbon dioxide, urea, hormones, proteins, antibodies and anti toxins.
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What is coronary heart disease?
This is when the coronary arteries that supply blood to the heart get blocked by layers of fat building up. This causes the arteries to become narrow, so blood flow is restricted causing a lack of oxygen to the heart muscle (can lead to heart attack)
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How are stents used?
Stents are tubes that are inserted inside arteries to keep them open and make sure blood can pass through.
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What are the advantages and disadvantages of stents?
Advantages- they are effective for a long time and the recovery time is fairly quick. Disadvantages- there is a risk of complications and infections, and the patient could develop a blood clot near the stent (thrombosis).
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How do statins work?
Statins are drugs that reduce the amount of LDL cholesterol present in the bloodstream. This slows down the rate of fatty deposits forming.
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What are the advantages of statins?
They can reduce the risk of strokes, coronary heart disease and heart attacks. They can also increase the amount of HDL cholesterol in your blood, which removes LDL cholesterol. Some studies suggest that statins may prevent other diseases.
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What are the disadvantages of statins?
Statins are a long term drug that must be taken regularly, and they can cause side effects (e.g. headaches, kidney failure, liver damage and memory loss). The effect of statins isn't instant, it takes time for their effect to kick in.
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What is an artificial heart?
Artificial hearts are mechanical devices that pump blood for a person whose own heart has failed. They can be used as a temporary or permanent fix.
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What is the main advantage of artificial hearts?
They're less likely to be rejected by the body's immune system than a donor heart, because they are made of metal or plastics so the body doesn't recognise them as 'foreign'.
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State 3 disadvantages of an artificial heart.
Surgery to fit an artificial heart can lead to bleeding and infection, and artificial hearts don't work as well as healthy natural ones (parts of the motor could fail/the heart could wear out). Blood doesn't flow through these hearts as smoothly, whi
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How can valves in the heart be damaged or weakened?
Heart attacks, infection or old age.
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What can this damage cause?
Valve tissue to stiffen so it won't open properly or a valve may become leaky, allowing blood to flow in both directions.
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How can severe valve damage be treated?
Replacing the valve- can be taken from humans or other valves (biological) or man-made (mechanical).
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Evaluate replacing a valve.
It is a much less drastic procedure than a whole heart transplant but is still major surgery and can cause blood clots.
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What is artificial blood and how is it used?
A blood substitute (e.g. a salt solution-saline used to replace the lost volume of blood. It can give the patient enough time to produce new blood cell.
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What is a communicable disease?
Those that can spread from person to person or between animals or people (e.g. malaria or measles).
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What is a non-communicable disease?
A disease that cannot spread between people- generally last for a long time and get worse slowly (e.g. asthma and cancer)
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What are risk factors?
Things that are linked to an increase in the likelihood that a person will develop a certain disease in their lifetime.
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Name some risk factors.
Smoking, obesity, alcohol, radiation, poor diet and lack of exercise.
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How can non-communicable diseases be costly?
human cost (people dying), lower quality of life, cost for NHS to research and treat diseases, families may have to move or adapt homes, reduction in the number of people able to work.
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What is cancer?
Mutation leads to uncontrolled cell growth and division, forming a tumour.
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What is a benign tumour?
The tumour stays in one place rather than invading other tissues- it is a contained mass.
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What is a malignant tumour?
The tumour grows and spreads because cells break off and spread to other parts of the body in the bloodstream.
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Epidermal tissue
Covers the whole plant, covered with a waxy cuticle to reduce water loss
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Upper epidermis
Transparent so light can pass through for photosynthesis
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Palisade mesophyll tissue
Lots of chloroplasts, near the top of the leaf where they can get the most light for photosynthesis
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Spongy mesophyll tissue
Big air spaces to allow gases to diffuse in and out of cells.
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Meristem tissue
Found at the growing tips of shoots and roots and is able to differentiate into different types of plant cell, helping the plant to grow.
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Lower epidermis
Full of little holes called stomata which let CO2 diffuse directly into the leaf.
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Phloem
Made of elongated living cells with small pores in the end walls to allow cell sap through. Transport food substances (e.g. dissolved sugars) made in the leaves to the rest of the plant and goes in both directions. (Translocation)
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Xylem
Made of dead cells joined end to end with no end walls between them, strengthened by lignin. They carry water and mineral ions from the roots to the stem and leaves (transpiration steam).
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What causes transpiration?
The evaporation and diffusion of water from a plants surface, mostly at the leaves. This causes a slight shortage in water so more is drawn up from the rest of the plant through xylem. Then more water is drawn up from the roots- constant stream.
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How does light intensity affect transpiration?
The brighter the light, the greater the transpiration rate. Stomata close as it gets darker, and photosynthesis can't happen in the dark so they don't need to be open to let CO2 in. Very little water can escape then.
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How does temperature affect transpiration?
The warmer it is, the faster transpiration happens. Water particles have more energy to evaporate and diffuse out of the leaf.
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How does air flow affect transpiration?
The better the air flow, the greater the transpiration rate. If air flow is poor, water surrounds the leaf so diffusion doesn't happen as fast.
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How does humidity affect transpiration?
The drier the air around the leaf, the faster transpiration happens because it means there is a larger difference between water concentration in and out of the leaf.
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How can you estimate the rate of transpiration?
Measure the uptake of water by a plant (measure the starting position of the air bubble and record the distance moved the the bubble.
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How do guard cells open and close stomata?
-kidney shape -lots of water= cells go plump and turgid, open stomata so gases can be exchanged. Lack of water= cells become flaccid, stomata close to stop water vapour escaping.
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How are guard cells adapted?
-thin outer walls and thickened inner walls -sensitive to light (close at night to save water) -more stomata on underside of leaves so less water is lost through them
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Enzymes are biological catalysts- they reduce the need for the high temperatures and speed up the useful chemical reactions. Enzymes are large proteins, which are made up of chains of amino acids.

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