Eduqas GCSE Biology 1 Cell Biology Exam Questions

About Eduqas GCSE Biology 1 Cell Biology

Cell biology is the first topic in the Eduqas GCSE Biology specification and is split into three parts: prokaryotic and eukaryotic cells, growth and development of cells, and cell metabolism. It covers cell structure and microscopy, mitosis, differentiation and stem cells, meiosis, enzymes, respiration and the digestion of large food molecules. The ideas here run through the whole course, from osmosis in transport systems to DNA in inheritance. Examiners like asking you to compare plant, animal and bacterial cells, explain enzyme graphs using the active site and denaturation, and compare aerobic with anaerobic respiration. Three specified practicals sit in this topic: cell drawings, enzyme action and food tests.

What you need to know

• 1.1 Cell structure Animal and plant cells have a nucleus, cytoplasm, cell membrane and mitochondria; plant cells also have a cellulose cell wall, chloroplasts and a permanent vacuole. Prokaryotic cells such as bacteria have no nucleus: their DNA is a single loop in the cytoplasm and they may contain plasmids.
• 1.1 Microscopy Light microscopes show cells and large organelles; electron microscopes have much higher resolution and magnification, revealing structures such as mitochondria in detail. SP1.1: examine plant and animal cells with a light microscope and produce labelled scientific drawings.
• 1.2 Mitosis and differentiation Mitosis produces two genetically identical cells for growth, replacing worn-out cells and repairing tissue. Cells then differentiate into specialised cells. Cancer results from uncontrolled cell growth and division.
• 1.2 Stem cells and meiosis Stem cells are found in embryos, some adult tissues and plant meristems, and can differentiate into other cell types; their use raises benefits, risks and ethical issues. Meiosis halves the chromosome number and produces genetically different gametes.
• 1.3 Enzymes Enzymes are protein catalysts made of folded chains of amino acids. The substrate fits the active site (lock and key model) to form an enzyme-substrate complex. High temperatures and extreme pH change the shape of the active site and denature the enzyme. SP1.3A: factors affecting enzyme action.
• 1.3 Respiration Aerobic respiration: glucose + oxygen → carbon dioxide + water, releasing energy as ATP. Anaerobic respiration in muscles: glucose → lactic acid, causing an oxygen debt; in yeast: glucose → ethanol + carbon dioxide. Anaerobic respiration releases much less ATP per glucose.
• 1.3 Digestion and food tests Enzymes break starch into glucose, proteins into amino acids and fats into fatty acids and glycerol so they are small and soluble enough to absorb. SP1.3B: iodine turns blue-black with starch, Benedict's gives an orange-red colour with glucose when heated, and biuret turns purple with protein.

Common mistakes in 1 Cell Biology

• Saying enzymes are killed at high temperature. Enzymes are not alive; they are denatured because the active site changes shape so the substrate no longer fits.
• Writing that respiration produces energy. Energy cannot be made: respiration releases energy from glucose, transferred to ATP.
• Saying bacteria have no DNA because they have no nucleus. Prokaryotes have a loop of DNA free in the cytoplasm, plus plasmids.
• Mixing up mitosis and meiosis. Mitosis gives two identical cells for growth and repair; meiosis gives four genetically different gametes with half the chromosome number.
• Forgetting to heat Benedict's reagent. The test for glucose only works in a hot water bath.

Try three 1 Cell Biology exam-style questions