Topic 2 bio Organisation

Q: What are the three main nutrients in food?

A: Carbohydrates (e.g., starch), proteins, lipids (fats)

Q: Why must large food molecules be digested?

A: They are too large to be absorbed into the bloodstream, so enzymes break them into small molecules.

Q: What happens in the mouth during digestion?

A: Food is chewed, and enzymes in saliva start digesting starch into smaller sugars.

Q: What is the role of the liver in digestion?

A: Produces bile, which emulsifies lipids (speeds up digestion) and neutralizes stomach acid.

Q: What happens in the large intestine?

A: Water is absorbed into the bloodstream and feces are formed for excretion.

Q: What is a substrate?

A: The molecule that an enzyme acts on and breaks down.

Q: What does it mean that enzymes are specific?

A: Each enzyme only works on one substrate that fits perfectly into its active site (lock and key theory).

: Which enzyme breaks down proteins, and where is it found?

A: Proteases; found in the stomach, pancreatic fluid, and small intestine

Q: What are proteins broken down into by proteases?

A: Amino acids, which are absorbed into the bloodstream and used to make new proteins in the body.

Q: Which enzyme breaks down starch, and where is it found?

A: Amylase (a carbohydrase); found in saliva and pancreatic fluid.

Q: What is starch broken down into by amylase?

A: Simple sugars, like glucose.

Q: Which enzyme breaks down lipids, and where is it found?

A: Lipase; found in pancreatic fluid and the small intestine.

Q: What are lipids broken down into by lipase?

A: Glycerol and fatty acids.

Q: What is the role of bile in digestion?

A: Bile emulsifies large lipid droplets into smaller droplets, increasing surface area for lipase to act and speeding up lipid digestion.

Q: How does bile help lipase in terms of pH?

A: Bile is alkaline and neutralizes stomach acid, creating alkaline conditions in the small intestine that increase the rate of lipid digestion.

What are emzymes

A: Enzymes speed up chemical reactions (they are biology al catalysts).

Q: What is the active site of an enzyme?

A: A groove on the enzyme’s surface where the substrate binds.

Q: What is a substrate?

A: The molecule that an enzyme reacts with and breaks down.

Q: Why are enzymes specific?

: Because only substrates with a complementary shape fit into the active site.

Q: How does increasing temperature affect enzyme activity at first?

: Enzyme activity increases because enzymes and substrates move faster, causing more collisions.

Q: Why does enzyme activity increase with temperature?

A: Higher temperature gives particles more kinetic energy, increasing successful collisions with the active site.

Q: What is the optimum temperature of an enzyme?

A: The temperature at which the enzyme works at its fastest rate.

Q: What is the optimum temperature for most human enzymes?

A: 37°C (body temperature).

: What happens to enzyme activity above the optimum temperature?

A: Activity rapidly decreases to zero because the enzyme becomes denatured.

: What does it mean when an enzyme is denatured?

A: The active site changes shape so the substrate can no longer bind.

Q: How does pH affect enzyme activity?

A: Each enzyme has an optimum pH; activity decreases if conditions are too acidic or too alkaline.

Q: Why does extreme pH stop enzymes from working?

A: The active site denatures and the substrate no longer fits.

: Which enzymes work best at acidic pH?

A: Proteases in the stomach.

Q: What safety precaution must be used when carrying out food tests?

A: Safety goggles must be worn because the chemicals are hazardous.

Q: Why is the food sample ground with distilled water at the start?

A: To dissolve chemicals from the food into a solution that can be tested.

Q: What chemical is used to test for starch?

A: Iodine solution.

Q: What is the positive result for starch?

A: Iodine changes from orange to blue-black.

Q: What does it mean if iodine stays orange?.

A: No starch is present

Q: What chemical is used to test for reducing sugars?

A: Benedict’s solution.

Q: What must be done for the Benedict’s test to work?

A: The solution must be heated in a hot water bath.

Q: What colour change shows a large amount of sugar?

A: Blue → brick red.

Q: What type of sugars does Benedict’s test detect?

A: Reducing sugars (e.g. glucose).

Q: Give an example of a sugar Benedict’s test does NOT detect.

: Sucrose (a non-reducing sugar).

Q: What chemical is used to test for protein?

A: Biuret solution.

Q: What is the positive result for protein?

A: Blue → purple/lilac.

Q: What chemicals are used to test for lipids?

A: Ethanol and water.

Q: What is the positive result for lipids?

A: A white cloudy emulsion forms.

Q: Why is the lipid test solution NOT filtered?

A: Lipids can stick to filter paper.

Q: What safety risk is associated with ethanol?

A: It is highly flammable (no naked flames).

Q: What is the function of the small intestine?

A: To absorb the products of digestion into the bloodstream.

Q: Why is the small intestine very long?

A: It provides a large surface area for absorption.

Q: What structures line the inside of the small intestine?

A: Villi

Q: How do villi help absorption?

A: They massively increase the surface area for absorption.

: What are microvilli?

A: Tiny projections on the surface of villi.

: Why do villi have a good blood supply?

A: To rapidly remove absorbed molecules and maintain a steep concentration gradient.

Q: Why is maintaining a steep concentration gradient important?

A: It increases the rate of diffusion into the blood.

Q: Why do villi have a thin membrane?

A: To provide a short diffusion distance.

Q: How are most digested food molecules absorbed?

A: By diffusion.

Q: How are molecules absorbed if diffusion cannot occur?

A: By active transport.

Q: Give four adaptations of the small intestine for absorption.

A:

• Very long

• Villi

• Microvilli

• Good blood supply

• Thin membranes (any four)

Q: What type of tissue is the heart mainly made of?

A: Muscle tissue.

Q: What is a single circulatory system?

A: Blood passes through the heart once per complete circuit of the body.

Q: What is a double circulatory system?

A: Blood passes through the heart twice per complete circuit.

Q: What is the advantage of a double circulatory system?

A: Blood travels at higher pressure, delivering oxygen more quickly to cells.

Q: How many chambers does the heart have?

A: Four.

Q: Name the four chambers of the heart.

A:

• Left atrium

• Right atrium

• Left ventricle

• Right ventricle

Q: Where are the atria located?

A: At the top of the heart.

Q: What separates the atria from the ventricles?

A: Valves.

Q: What is the function of heart valves?

A: To prevent blood flowing backwards.

Q: Which vessel brings deoxygenated blood from the body to the heart?

A: Vena cava.

Q: Which vessel carries blood from the heart to the lungs?

A: Pulmonary artery.

Q: Which vessel carries oxygenated blood from the lungs to the heart?

A: Pulmonary vein.

Q: Which vessel carries oxygenated blood from the heart to the body?

A: Aorta.

Q: What happens when the atria contract?

A: Blood is forced into the ventricles.

Q: What happens when the ventricles contract?

A: Blood is forced out of the heart.

Q: Why is the left ventricle wall thicker than the right?

A: It pumps blood to the whole body at higher pressure.

Q: What are coronary arteries?

A: Blood vessels that supply the heart muscle with oxygenated blood.

Q: Why do heart muscle cells need oxygen?

A: For respiration to release energy for contraction.

Q: Where is the natural pacemaker found?

A: In the right atrium.

Q: What does the pacemaker do?

A: Controls the resting heart rate.

Q: What is an artificial pacemaker?

A: A small electrical device used to correct irregular heart rhythms.

Q: Explain how the heart pumps blood around the body.

A: The atria contract to push blood into the ventricles, then the ventricles contract to force blood out of the heart. Valves prevent backflow, and the left ventricle has a thicker wall to pump blood at high pressure around the body.

Q: What are the four main parts of blood?

A:

• Plasma

• Red blood cells

• White blood cells

• Platelets

Q: What is blood plasma?

A: The liquid part of blood that transports cells and dissolved substances.

Q: What does plasma transport?

A: Red blood cells, white blood cells, platelets, nutrients, hormones, antibodies, carbon dioxide, and urea.

Q: What is the function of red blood cells?

A: To transport oxygen from the lungs to body cells.

Q: What molecule in red blood cells carries oxygen?

A: Haemoglobin.

Q: What is oxyhaemoglobin?

A: Haemoglobin combined with oxygen.

Q: Why do red blood cells not have a nucleus?

A: To provide more space for haemoglobin.

Q: Describe the shape of a red blood cell.

A: A biconcave disc.

Q: Why is the biconcave shape important?

A: It increases surface area so oxygen diffuses in and out quickly.

Q: What is the function of white blood cells?

A: To defend the body against pathogens as part of the immune system.

Q: Give one function of white blood cells.

A: They produce antibodies.

Q: What key feature do white blood cells have?

A: A nucleus.

Q: What are platelets?

A: Tiny fragments of cell

Q: What is the function of platelets?

A: To help the blood clot and prevent excessive bleeding.

Q: Why might a patient be given platelets?

A: To help with blood clotting.

Q: Why must donor blood be the same blood type as the patient’s?

A: To prevent the immune system rejecting the blood.

Q: What could happen if incompatible blood is transfused?

A: The immune system attacks the blood and the patient could die.

Q: What is another risk of blood transfusions?

A: Infection from diseases carried in blood.

Q: Why is the risk of infection low in the UK?

A: Donated blood is carefully screened.

Q: What are cardiovascular diseases (CVDs)?

A: Diseases of the heart and blood vessels.

Q: Are cardiovascular diseases communicable?

A: No, they are non-communicable (not infectious).

Q: What is coronary heart disease?

A: A disease where fatty material builds up inside the coronary arteries.

Q: What is the function of the coronary arteries?

A: To supply oxygenated blood to the heart muscle.