Marking Scheme Flashcards: Structures and Functions of Living Organisms

Explain why the fermenter is cleaned using steam before the fungus and nutrients are added.

To kill pathogens. To prevent contamination.

Give two ways that the student could modify this apparatus to achieve an answer nearer to the energy value given on the packaging of the bread.

Use lid. Stir contents.

Units for cardiac output.

dm3 min-1

(a) (ii) The changes that will happen in the limewater in flask A and B are...

(Limewater in) flask A stays clear. (Limewater in) flask B goes (more) cloudy.

(a) Describe the functions of the paddles in the fermenter. (b) Explain why the fermenter has a filtered air supply. (c) Explain why the temperature recorder is connected to the liquid in the fermenter and the water input of the cooling jacket.

(a) To distribute oxygen. (b) Oxygen for respiration. Filter bacteria. (c) Monitor temperature in fermenter. Prevent enzymes being denatured.

(a) (i) The flask exhaled air passes through is...

- (Flask B) as (mouthpiece is) connected to the long tube in flask B. - (In flask B the) tube (from the mouthpiece is) in limewater.

Age may affect the likelihood of dying from lung cancer because...

- As age increases the incidence of cancers also increases. - (This is because) DNA (inside cells) is more likely to mutate.

(c) (ii) Children with coeliac disease grow more slowly because... [4]

- Children with coeliac disease have shorter microvilli. - This means a reduced surface area. - Therefore, less absorption of digested food. - As a result there will be less glucose for ATP.

Suggest why using e-cigarettes may be thought to be less harmful than smoking normal cigarettes.

- Contains less tar. - Contain fewer carcinogens. - There is less risk of emphysema. - There is less Carbon Monoxide in the smoke.

Suggest why many doctors are concerned about promoting the use of e-cigarettes to young people.

- E-cigarette use may lead to smoking. - E-cigarettes are addictive, as they contain nicotine.

Suggest why the cow absorbs a lower percentage of energy from the food it eats than the fish.

- Eats more plants/eats grass. - Food difficult to digest. - Cellulose.

The concentration of lactic acid changes at running speeds greater than 18 km h-1 because.

- Lactic acid increases. - Aerobic respiration at its maximum rate. - So anaerobic respiration occurs (producing lactic acid).

(d) Explain why reducing the blood supply to the heart muscle cells can cause a heart attack.

- Less oxygen. - Less aerobic respiration. - Anaerobic respiration. - Lactic acid. - Enzymes denatured.

John suggested that a more accurate value could be obtained if a larger volume of water was used. Explain why John's suggestion might be correct.

- Lower surface area to volume ratio. - Less heat loss.

In animals, exercise cannot be sustained for long periods by anaerobic respiration. [3]

- Not enough energy is released for muscular contractions. - Lactic acid causes the pH of enzymes to decrease. - Enzymes cannot function well at low pH.

(ii) Suggest the consequences of having a diet that contains too much fat.

- Obesity. - Blockage of arteries. - High blood pressure.

Having no appendix may increase the likelihood of bacterial infections of the colon because... [2]

- Removes useful bacteria. - Reduces competition (between pathogenic and useful bacteria). - Pathogenic bacteria increase.

(d) The student could have ensured the reliability of the results by...

- Repeating the experiment (while keeping every factor within the experiment the same). - Ensuring that the results are similar/consistent.

Explain one effect, other than lung cancer, that smoking has on health.

- Smoking may cause CHD. - Due to damage to artery/blood vessel lining.

(b) (iii) A discussion on the use of the lipase inhibitor as a treatment for obesity is...

- Starting levels of blood lipid were equal (so were controlled). - Lower blood lipid/fat when taking inhibitor. - (Because) less fat is absorbed (when taking inhibitor). - Two suffered side effects when taking the drug. - Sample size is very small / not representative. - No information on age / sex / health / diabetes.

Suggest one other modification and explain how it would improve the accuracy of the result.

- Stir. - Even temperature.

(b) The person with lung disease is often breathless and unable to exercise because...

- The (maximum) lung volume of people with lung disease is lower. - People with lung disease cannot exhale as rapidly. - Less carbon dioxide removed / less oxygen taken in.

(b) (ii) Three other variables that the student needs to control are...

- The mass of the locusts. - Because more cells means more respiration. - Temperature. - Because it affects enzymes. - Concentration of KOH - Because that affects the amount of carbon dioxide absorbed.

(b) The changes in the percentage of total blood flow in these body parts is...

- There is more blood supplied to muscles. - (Blood flow) supplies oxygen. - (For aerobic) respiration. - To release energy / ATP.

Suggest why the rate of Carbon Dioxide production in part (b) decreased between 50 and 60 seconds.

- There is no more glucose. - Respiration slows down. - Ethanol has built up. - Yeast cells are killed.

Earthworms cannot survive for very long in heavily waterlogged soil. Suggest why this is the case.

- They cannot respire anaerobically for very long. - Lactic acid lowers the pH of their cells.

(e) (ii) This process differs between fit people and unfit people by...

- Unfit people take longer to recover. - (Unfit people) lactic acid levels go down slower. - Cardiac muscle is weaker in unfit people.

(b) (ii) The difference in the changes of pH of the solutions in the two test tubes during the 20-minute period were... [2]

- Without the inhibitor, there's a greater change in pH. - There is a greater pH fall, without the inhibitor, because fats are broken down into fatty acids and glycerol.

Calculate the percentage increase in the recommended daily energy requirement of person B compared to person C.

167-84/84 x 100

(a)(i) Complete the table by giving the missing information. (a)(ii) Calculate the ratio of the total surface area of the small cubes to the surface area of the large cubes.

6, 48,000 20:1

Salivary amylase works best...

Above pH 7.

Alveoli are moist...

Allows gases to dissolve in solution.

(b) Evaluate the student's model as a representation of the lungs.

Alveoli not one large cube. Not all surfaces of alveoli are exposed.

Name the bacteria added to milk to make yoghurt.

Lactobacillus

Name an enzyme used by scientists to genetically modify the yeast.

Ligase.

A student reads the following statement in a textbook; 'Respiration and metabolic reactions are intrinsically linked to temperature.' Explain why this statement is true. [4]

Metabolic reactions are the chemical reactions in a cell. [1] Respiration is an example of a metabolic reaction. [1] Respiration is controlled by enzymes OR metabolic reactions are controlled by enzymes.[1] Enzyme-controlled reactions are affected by temperature. [1]

Explain why a mouse uses more oxygen per gram than a human.

Mouse is smaller. Larger surface area to volume ratio. Maintain body temp.

The energy value given on the packaging of the bread is 10,400 J for 1g of bread. Comment on why the student's method gives a different value.

Not completely combusted. Energy not all transferred to tube. Energy lost to atmosphere. Energy lost as light. Water not evenly heated.

(ii) Suggest how to find the dry mass of yeast in each flask.

Pour contents onto filter paper. Weigh the residue.

A high fat diet increases the risk of heart disease. Give two other factors that can increase the risk of heart disease.

Smoking. Obesity.

(v) Age is not the only variable that can change vital capacity. Give two other variables that can affect a person's vital capacity.

Smoking. Sex.

(c) The rate of digestion by enzymes in the small intestine is not reduced by stomach acid because.

Stomach acid is neutralised by the (alkaline) bile. Pancreatic amylase is released into the duodenum, which has a neutral pH.

A student examines this data and concludes that smoking is the main factor that causes low birth mass. Use the data and your own biological knowledge to comment on this conclusion.

The conclusion is correct because: - Large numbers (of participants were used) in the study. The conclusion is incorrect because: - No information on the number of years mothers have smoked for. - No information on frequency of smoking or when during pregnancy. - No information on mothers' mass. - No information on mothers' health care. Use of own knowledge is: - Smoking reduces oxygen (supply to baby/foetus).

The table lists the solutions added to the oil and water mixture. Complete the table to show which diagram the mixture would look like after each solution is added. You may use each letter once, more than once or not at all. One has been done for you.

A (C) B A

Explain why increasing acidity can be used as a measure of yoghurt production.

Anaerobic respiration. By bacteria. Produces lactic acid.

Discuss whether cow's milk is a suitable alternative to breast milk for young babies. Use data from the table and your knowledge to support your answer. [6]

Arguments against cow's milk as a suitable alternative: - Cow's milk may contain antibiotics. - Cow's milk contains too many minerals. - Cow's milk contains too much protein. - Cow's milk contains too little carbohydrate. Arguments for cow's milk as a suitable alternative: - Cow's milk contains the same amount of vitamins. - Cow's milk contains the same amount of water.

Describe how you would test a sample of cow's milk and a sample of human milk to show they contain different masses of protein.

Biuret. Darkest purple contains most protein.

Describe an investigation to find out if adding vitamin D to the diet of young children will help to prevent rickets (a deformation of the legs). Your answer should include experimental details and be written in full sentences.

C - With and without Vitamin D. O - Same age/same ethnicity/same gender. R - Repeat investigation. M - Measure straightness of legs. M - Time period must be minimum one month. S - Same exposure to sunlight.

Suggest why vitamin D deficiency is more of a problem for children than for adults.

Children still growing/developing bones.

Several different enzymes are required because... [2]

Each enzyme has an active site that is complementary to one substrate. Lipases only break down lipids / amylase only breaks down starch/proteases only break down proteins;