y10 salma

• why do simple, unicellular organisms rely on diffusion for movement of substance in and out of the cell?

  its surface area is large compared to its volume , so nutrients and other substances can pass quickly through the membrane and around its 'body'.
• what is the need for a transport system in multicellular organisms?

  multicellular organisms have a small surface area to volume ratio. they need transport systems to be able to get all of the substances that cells need to the correct place.
• describe the composition of blood:

  red blood cells, white blood cells, platelets, plasma
• what role does plasma take in the transport of substances?

  plasma transports carbon dioxide, digested food, urea, hormones and heat energy. it provides a medium for them to be suspended in.
• describe the adaptions of a red blood cell?

  biconcave: more surface area for oxygen

  haemoglobin: proteins that bind to oxygen

  no nucleus: more surface area for oxygen
• how does the immune system respond to disease?

  - lymphocytes release antibodies that stick to the antigens to the pathogen

  - once the complementary antibody has been found, the lymphocytes release them en masse

  - the antibodies stick the pathogens together

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  - phagocytes sense which microorganisms are foreign by sensing the antigens on them

  - they engulf and digest pathogens using digestive enzymes

  - they are non-specific (they will engulf and digest any foreign cells )

  - lobed nucleus to allow them to engulf easier
• what do platelets do?

  - they are small fragments of cells that have no nucleus

  - they stick together forming a clot on the wall of the bleeding blood vessel

  - this stops blood leaving and pathogens entering the blood stream and infecting the body
• what do red blood cells do?

  transport oxygen
• what do white blood cells do?

  fight infection
• how do vaccines lead to the manufacture of memory cells?

  - a dead/weakened version of the virus is injected into the bloodstream

  - the immune system reacts as if the threat is real and imminent

  - lymphocytes release complementary antibodies

  - lymphocytes remain in the body as memory cells

  - next time when the real virus enters the bloodstream, the memory cells will react so quickly that you won't even realise that you're sick
• describe the structure of the heart and how it functions

  - de-oxygenated blood enters through the vena cava

  - it flows through the right atrium and past the tricuspid valves (atrioventricular) into the right ventricle

  - the right ventricle contracts and blood flows through the pulmonary artery to the lungs (through the semi-lunar valves)

  - oxygenated blood flows through the pulmonary vein into the left atrium

  - it flows past the bicuspid valves (atrioventricular)into the left ventricle

  - the left ventricle contracts and sends the blood all around the body through the aorta (and semi-lunar valves)
• discuss the differences between the left ventricle and the right ventricle

  - left ventricle wall is more muscular because blood needs to be transported all around the body

  - right ventricle wall is less muscular because blood at high pressures can't be sent to the lungs; they won't be able to withstand such pressure because they are fragile
• how does the heart rate change during exercise and under the influence of adrenaline?

  exercise: the heart rate increases because the body cells (particularly the muscle cells) respire more to release more energy, so the blood is needed to be transported faster, as it contains oxygen and glucose which are needed for respiration, hence the increasing heart rate

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  adrenaline: the adrenal glands release adrenaline into the blood which causes the heart to beat faster to transport oxygen and glucose around the body at a faster rate, because the body cells (muscle cells mostly) need it for increased energy release (respiration)See an expert-written answer!We have an expert-written solution to this problem!
• what factors increase the risk of developing coronary heart disease?

  - smoking (nicotine quickens the heart rate)

  - diet (foods high in saturated fats means that fatty deposits (plaque) build up in the blood vessels, constricting the lumen meaning that less blood can flow to the cells)

  - high blood pressure (puts extra strain on the heart, causes damage to the blood vessels, promotes the promotion of plaque)
• describe the (function of) the arteries, veins and capillaries

  arteries: small lumen, ring of muscle, they pump blood around the body, high blood pressure, mostly oxygenated blood, no valves, carries blood away from the heart

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  veins: large lumen, less muscle, they allow blood to flow back to the heart, low blood pressure, mostly deoxygenated blood, valves

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  capillaries: small lumen, thin muscle walls, medium pressure blood, no valves, carries both oxygenated and deoxygenated blood, carries blood away from and towards the heart
• describe the journey of blood from the aorta

  aorta ➡️ hepatic artery ➡️ liver ➡️
• what should a balanced diet include?

  appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre.
• sources and functions of: carbohydrates, proteins, lipids, vitamin A C & D, calcium and iron, water and dietary fibres


  carbohydrates: bread, potatoes, cereal + respiration

  proteins: meat, chicken, nuts + maintaining muscles

  lipids: butter + insulation and protection

  vitamin a: carrots + maintaining normal vision

  vitamin c: citrus fruits + protecting cells

  vitamin d: eggs, milk, cheese + keeping bones strong

  calcium (mineral): milk and dairy products + muscle movement, nerves, teeth and bones

  iron (mineral): red meats + production of haemoglobin

  fibre: beans, lentils + keeping the digestive system healthy

  water: watermelon, cucumber, everything tbh + restoring fluids lost through metabolism, breathing, sweating, excretion
• how do energy requirements alter with activity levels, pregnancy and age

  if you're a highly active person you'll need more energy because you burn more calories in exercise. if you're pregnant, you'll need more energy because you have to provide for yourself and your baby. if you're younger, you'll typically require more energy for growth and development
• describe the structure and functions of the human alimentary canal

  mouth to oesophagus to stomach to small intestine (duodenum + ileum) to large intestine (colon and rectum)

  
  

  mouth: breaks down the food manually (emulsifies it per se)

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  oesophagus: transports the food from the mouth to the stomach

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  stomach: contains hydrochloric acid to kill pathogens and provide the optimum pH for pepsin which chemically breaks down (digests) proteins

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  duodenum: bile travels from the gallbladder to neutralise the acidic 'food' coming from the stomach and emulsify the lipids (physically break down). pancreatic enzymes digest (chemically break down) the lipids, what's left of the proteins and the carbohydrates (amylase, lipase and protease)

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  ileum: all the nutrients are absorbed

  colon: all the water is absorbed

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  rectum: faeces gathers for excretion
• how is food moved through the gut?

  peristalsis (a wave of muscle contraction)
• how do the enzymes digest proteins, carbohydrates and lipids

  amylase: starch to maltose

  maltase: maltose to glucose

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  lipase: fat to glycerol + fatty acids

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  protease: protein to fatty acids
• where are the different enzymes produced and used? (salivary amylase, pancreatic amylase, maltase, protease, pepsin, lipase, bile— not an enzyme)


  salivary amylase: salivary glands + mouth

  pancreatic amylase: pancreas + small intestine

  maltase: pancreas + small intestine

  protease: pancreas + small intestine

  pepsin: stomach + stomach

  lipase: pancreas + small intestine

  bile— not an enzyme: gallbladder + small intestine
• what is the role of bile?

  it emulsifies lipids and neutralises stomach acid
• how is the small intestine adapted for absorption?

  1. wall of the small intestine is covered in villi and each villus is covered in microvilli. These increase the surface area for absorption.

  2. the wall of the small intestine is thin which shortens the distance that the digested food products have to diffuse across

  3. each villus has a rich blood supply which maintains a steep concentration gradient for diffusion to occur rapidly
• describe the structure of a villus?

  large surface area

  capillaries (absorbs glucose and amino acids)

  lacteal (where fatty acids and glycerol go)

  epithelium (only one cell thick)
• practical: investigate the energy content in a food sample

  1. add water to the boiling tube.

  2. clamp the boiling tube to the clamp stand.

  3. measure the temperature of water with the thermometer and record it.

  4. choose a sample of food, weigh it using an electronic balance and record the mass.

  5. carefully place the food on a mounted needle.

  6. hold the food in the Bunsen burner fame until it catches alight.

  7. as soon as the food is alight, hold it directly under the boiling tube.

  8. hold the food in place until it is burnt completely.

  9. as soon as the food is burnt completely, measure and record the temperature of the water again.

  10. probably do repeats to find an average, then repeat the procedure at least twice more for other foods, replacing the water each time.

  11. calculate the rise in temperature each time.

  12. calculate the energy released from each food using the key equation

  energy (J) = temperature change (degrees C) x mass of food (g) x 4.2
• describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops


  in glasshouses and polythene tunnels conditions can be controlled. This control means that all the limiting factors (CO2, light intensity, temperature) for plant growth can be set to the optimum conditions; this will result in more growth, so higher yield
• what are the effects of increasing the temperature and CO2 conc inside of a glasshouse?

  CO2: more photosynthesis, as CO2 is needed. they can respire more efficiently due to more ATP being made. they'll grow better. too much and they won't grow as much because of the lack of O2 for respiration

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  temperature: too low and the enzymes don't have enough kinetic energy, so less collisions and less enzyme substrate complexes are made. too high and the enzymes denature.
• how does fertiliser increase crop yield?

  fertilisers provide plants with the essential mineral ions (Mg.2+, PO4.2-, NO3.2-, K+) needed for growth
• advantages and disadvantages of pesticides

  advantages:

  - kills pests therefore increases yield

  - can be produced en masse

  - no biological knowledge required to use

  - easy to apply (physically)

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  disadvantages:

  - non specific

  - can disrupt food chains

  - chemicals on the food can be harmful to humans, reduces appeal to consumes

  - can pollute water and soil

  - insects and pest can develop resistance

  - have to reapply

  - bioaccumulation!
• advantages and disadvantages of biological control

  advantages:

  - better for the environment

  - only applied once

  - specific

  
  

  disadvantages:

  - slow

  - a lot of knowledge required

  - expensive

  - can disrupt food chains
• what's the role of yeast in the production of food, including bread?

  - yeast is a type of fungus, therefore it respires both aerobically and anaerobically.

  
  

  
  

  bread:

  - enzymes in the yeast break down the carbohydrates into sugars

  - the enzymes use the oxygen to produce carbon dioxide (which makes the bread rise)

  - the carbon dioxide is trapped in the bread

  - the pockets of gas expand

  - the bread is baked in the oven, where the high temperatures kill the yeast and any alcohol produced (by anaerobic respiration)

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  alcohol:

  - the yeast (and water mix)is put in an environment with no oxygen (you could achieve this by placing a layer of oil over it), just sugar (normally in the form of fruits)

  - the yeast enzymes respire anaerobically, producing CO2 and ethanol (alcohol)
• investigate the role of anaerobic respiration by yeast in different conditions


  as the temperature increases, so should the rate of respiration, until the optimum temperature

  
  

  1. mix together sugar, yeast and water

  2. to create anaerobic conditions, place a layer of oil over the mixture

  3. attach a bung with a tube leading to a second test tube of water

  4. place the yeast mixture in a water bath at a fixed temperature

  5. count how many bubbles (CO2) are released

  6. to calculate the rate of respiration, divide the number of bubbles produced by the time taken

  7. repeat the experiment at different temperatures
• understand the role of bacteria in the production of yoghurt

  specified bacteria = lactobacillus

  
  

  - the bacteria are placed in anaerobic conditions, and respire the lactose, releasing lactic acid and CO2.

  - lactic acid causes the milk to clot and solidify into yoghurt
• how do you make yoghurt?

  pasteurise the milk (heat it to 78degrees): to kill all unwanted bacteria and to avoid contamination

  sterilisation: (use steam to sterilise the container): to kill all harmful bacteria and to avoid contamination

  add milk: milk contains lactose and cassine

  add some bacteria (lactobacillus bulgaricus): they respire lactose from the milk to release lactic acid (ANAEROBIC!!!)

  cover with an airtight lid: so no O2 gets in, no bacteria get in (contamination)

  place in a warm place: (optimum temp)

  add fruits: yoghurt is sour because it's acidic

  eat: you need energy <3
• what are industrial fermenters used for?

  - fermenters are containers used to culture (grow) microorganisms like bacteria and fungi in large amounts

  - these can then be used for brewing beer or making yoghurt (or making penicillin/insulin)

  - the advantage of using a fermenter is that conditions can be carefully controlled to produce large quantities of exactly the right type of microorganism
• why and how can you provide optimum conditions inside the fermenter?

  nutrients: eg glucose + needed to respire

  optimum temp: temperature probe, water bath, stirring + too hot and the enzymes denature, too cold and the enzymes don't have enough kinetic energy to move

  pH: pH probe + too high/low enzymes denature

  oxygen: valve + needed to respire

  aseptic conditions: vessels are sterilised by heated steam that kills unwanted microbes + stops the microorganisms competing with each other, the product doesn't get contaminated
• what methods are used to farm large numbers of fish

  selective breeding: to produce fish with the most desirable traits

  genetic modification: see above

  nets: to protect from interspecific predation

  separation by size and sex: to protect from intraspecific predation

  feeding (little and often): to make sure they don't get hungry, and to ensure that leftover food isn't allowed to rot (which encourages bacteria to grow which can harm the fish and also respire all the oxygen therefore lowering the water quality)

  removal of dead fish waste: to prevent bacteria growing (see above)

  wrasse/ other forms of biological control: to feed on sealice
• what's the difference between sexual and asexual reproduction?

  sexual: an organism combines the genetic information from each of its parents and is genetically unique

  asexual: one parent copies itself to form a genetically identical offspring