Practise Metabolism. 11 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Name the waste product formed when excess proteins are broken down.
Urea
One lipid molecule is made from one molecule of glycerol and three molecules of fatty acids. How many fatty acid molecules are needed to make 20 lipid molecules?
60
In which organ do many important metabolic reactions, such as the breakdown of excess amino acids, take place?
Liver
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Metabolism involves many different reactions in cells.
(a) What is meant by metabolism?[1]
(b) Which two of these are part of metabolism? Tick (✓) two boxes.[2]
Breakdown of excess proteins to form urea
Diffusion of oxygen into the blood
Evaporation of sweat from the skin
Formation of lipids from glycerol and fatty acids
Osmosis into root hair cells
(c) Name the waste product formed when excess proteins are broken down.[1]
(d) Name the carbohydrate made from glucose that is stored in animal cells.[1]
Show the answer and mark scheme
(a)
the sum of all the reactions in a cell or the body
(b)Answer: Breakdown of excess proteins to form urea; Formation of lipids from glycerol and fatty acids
(c)Answer: Urea
urea
(d)Answer: Glycogen
glycogen
Question 2Medium7 marks
The energy transferred by respiration is used for the enzyme-controlled reactions of metabolism.
(a) One lipid molecule is made from one molecule of glycerol and three molecules of fatty acids. How many fatty acid molecules are needed to make 20 lipid molecules?[1]
(b) Name two carbohydrates that plant cells make from glucose.[2]
(c) Explain why these metabolic reactions need energy from respiration.[2]
(d) Plant cells make amino acids. Give the two substances plant cells use to make amino acids.[2]
Show the answer and mark scheme
(a)Answer: 60
60
(b)Answer: Starch and cellulose
starch
cellulose
(c)
they build larger molecules from smaller molecules
building larger molecules requires energy (which is transferred by respiration)
(d)Answer: Glucose and nitrate ions
glucose
nitrate ions
Question 3Hard5 marks
An advert for a weight-loss supplement claims: 'Our pill boosts your metabolism by 50%, so you burn more energy without any extra exercise!' The company's own trial gave the supplement to 30 volunteers for 4 weeks. Their mean resting metabolic rate increased from 6800 kJ per day to 7200 kJ per day. There was no control group given a placebo.
(a) Calculate the actual percentage increase in mean resting metabolic rate found in the trial.[2]
(b) Evaluate the company's claim, using the information given.[3]
Show the answer and mark scheme
(a)Answer: 5.9%
(7200 − 6800) ÷ 6800 × 100
5.9 (%)
(b)
the trial found an increase of only about 5.9%, far less than the advertised 50% increase, so the claim is not supported by the company's own data
there was no placebo or control group, so it is not clear whether the small increase was really caused by the supplement, or by another factor, e.g. a change in activity or diet during the trial, or the placebo effect
with only 30 volunteers and no independent replication, the result may not be reliable or repeatable
conclusion, e.g. the evidence given does not support the claim that the supplement boosts metabolism by 50%, and a properly controlled, larger, independently reviewed trial would be needed before the claim could be trusted