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Some examples from this set of practice questions
1.
Evaluate the use of an electron microscope and a light microscope, giving one example where each type of microscope might be used. (6 marks)
Answer: Electron microscopes magnify up to around ×2 000 000 have a resolving power of about 10 nm (scanning electron microscope) or 0.2 nm (transmission electron microscope) may be used to examine subcellular structures (e.g., chromosomes during cell division) light microscopes magnify up to around ×2 000 have a resolving power of about 200 nm may be used to look at cells dividing (e.g., stained onion cells)
2.
Chloroplasts are found in many plant cells but not all of them. Suggest two types of plant cells that are unlikely to have chloroplasts and in each case explain why they have none.
Answer: Any two from: • root cells – no exposure to light • cells in centre of tree trunk – no exposure to light • cells in flowers of plants – their function is not to photosynthesise
3.
Suggest why the nucleus and the mitochondria are so important in all cells.
Answer: Nucleus controls all cell activities contains instructions for making new cells or new organisms mitochondria site of aerobic respiration releasing energy for the cell
4.
Describe the similarities and differences between the features found in prokaryotic and eukaryotic plant and animal cells (6 marks)
Answer: All cells have cell membranes and cytoplasm and both prokaryotes and eukaryotes can have cell wall. Prokaryotes have no nucleus and no chloroplasts whilst eukaryotes have no plasmids.
5.
Describe the features you would look for to decide on the function of an unknown specialised animal cell. (6 marks)
Answer: Transmitter chemicals are required to pass impulse from cone cell to another nerve cell and then on to brain. The many mitochondria supply energy from cellular respiration needed to make transmitter chemicals.
6.
Cone cells are specialised nerve cells in the eye. They contain a chemical that changes in coloured light. As a result of the change, an impulse is sent along another nerve cell to the brain. Cone cells usually contain many mitochondria. Suggest why this is an important adaptation. 4 marks
Answer: Transmitter chemicals are required to pass impulse from cone cell to another nerve cell and then on to brain. The many mitochondria supply energy from cellular respiration needed to make transmitter chemicals.
7.
Describe the features you would look for to decide on the function of an unknown specialised animal cell.
Answer: Any three from: • number of mitochondria indicates how much energy cell uses • flagella or cilia – presence indicates whether cell moves around or moves substances such as mucus • nucleus – presence indicates whether cell is capable of reproduction • storage materials such as fat or starch – presence indicates whether cell stores materials it can use for respiration.
Some examples from this set of practice questions
1.
Describe how the stomach is adapted for its role in the digestion of food. 5 marks
Answer: Layer of muscular tissue contracts to churn up food, mixing it with digestive juices to help physical and chemical digestion. Glandular tissue produces enzymes to break down food. Folded lining provides increased surface area. Tough epithelial tissue covers and protects inside and outside of organ.
2.
Explain the difference between organs and organ systems, giving 2 examples. 4 marks.
Answer: An organ is a collection of several different tissues that work together to carry out a particular function (any two examples). An organ system is a number of organs working together to carry out a major function (any two examples).
3.
Using the human digestive system as an example, how the organs in an organ system rely on each other to function properly. 6 marks
Answer: Each part of digestive system relies on preceding parts. Stomach relies on mouth, teeth, and salivary glands to deliver chunks of chewed food. Small intestine depends on stomach to continue digestive process and on enzymes made by pancreas to help with the digestive process. Large intestine can only deal with remains of food already digested in the small intestine (soluble molecules absorbed into blood, leaving waste material and water), absorbing water and removing faeces from body.
4.
Describe the main similarities and differences between the 3 main groups of chemicals ( carbohydrates, proteins and lipids) in the body. 6 marks
Answer: similarities: • vital components of a balanced diet • contain carbon, hydrogen, and oxygen • large molecules made up of smaller molecules joined together differences: • carbohydrates made up of sugar units • lipids made up of fatty acids and glycerol • proteins made up of long chains of amino acids • lipids insoluble in water • proteins contain nitrogen
5.
Explain in detail how enzymes act to speed up reactions in your body. 5 marks.
Answer: Substrate of reaction to be catalysed fits into active site of enzyme like a lock and key. Once in place, enzyme and substrate bind together. Reaction takes place rapidly and products are released from active site. Enzyme then ready to catalyse another reaction.
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