Y9 Biology

What is the purpose of the microscopy practical?

To use a light microscope to observe cells and record key structures using labeled drawings.

Name four parts of a light microscope and their functions.

Eyepiece: view the image; Objective lens: magnifies; Stage: holds slide; Focusing wheels: adjust clarity.

What is the independent variable in the potato osmosis practical?

The concentration of the sugar solution.

What are some control variables in the osmosis experiment?

Temperature, time, surface area, and volume of solution.

What is the expected outcome if the potato is placed in a high concentration sugar solution?

It will lose mass as water moves out of the cells.

What is the expected outcome if the potato is placed in pure water?

It will gain mass as water moves into the cells.

How do you convert millimetres to micrometres?

Multiply by 1,000.

What is 5.0 × 10⁻³ in standard form as a decimal?

0.005

What is the magnification equation?

Magnification = Image size / Actual size

What is a prokaryotic cell?

A cell without a true nucleus, like bacteria. DNA floats freely in the cytoplasm.

Name three structures present in both prokaryotic and eukaryotic cells.

Cytoplasm, cell membrane, and ribosomes.

What is a eukaryotic cell?

A cell with a nucleus and membrane-bound organelles, like plant and animal cells.

What structures are found in a bacterial cell?

Cytoplasm, cell membrane, cell wall, plasmid, flagella, free-floating DNA (no nucleus).

How is a muscle cell specialised?

Contains many mitochondria for energy; contracts to cause movement.

What is the function of a root hair cell?

Absorbs water and minerals from the soil; has large surface area.

What is the function of a phloem cell?

Transports sugars around the plant.

What is the function of a xylem cell?

Transports water and minerals from roots to leaves.

What is the function of a nerve cell?

Carries electrical impulses throughout the body.

What is the function of a sperm cell?

Fertilises an egg; has a tail and many mitochondria.

Which organelles are found in plant cells but not animal cells?

Cell wall, chloroplasts, permanent vacuole.

Which structures are present in all three cell types (animal, plant, bacterial)?

Cytoplasm, cell membrane, ribosomes.

What is diffusion?

The movement of particles from an area of high concentration to an area of low concentration, down a concentration gradient.

Is diffusion passive or active?

Passive – it does not require energy.

Give an example of diffusion in the body.

Oxygen diffuses from the alveoli into the blood in the lungs.

What is active transport?

The movement of substances against the concentration gradient using energy from respiration.

Give an example of active transport in plants.

Minerals are absorbed by root hair cells from the soil, even when in lower concentration in the soil.

Give an example of active transport in animals.

Sugar is absorbed in the small intestine even when the concentration in the gut is lower than in the blood.

Why is surface area to volume ratio important?

Affects how efficiently substances diffuse in and out of cells; smaller organisms have a larger SA:V ratio and can exchange materials more efficiently.

Why do multicellular organisms need exchange surfaces?

Because they have a small surface area to volume ratio, they need specialised structures to increase efficiency of exchange.

Name the main organs in the human digestive system.

Mouth, oesophagus, stomach, liver, gallbladder, pancreas, small intestine, large intestine, rectum, anus.

What is the function of the stomach?

Produces hydrochloric acid to kill bacteria and pepsin to begin protein digestion.

What is the function of the small intestine?

Absorbs nutrients from digested food into the blood.

What solution is used to test for starch?

Iodine – turns blue-black if positive.

What solution is used to test for sugars?

Benedict's solution – turns from blue to brick red when heated if positive.

What solution is used to test for protein?

Biuret solution – turns purple if positive.

What solution is used to test for lipids?

Ethanol – gives a cloudy white emulsion if positive.

What are enzymes?

Biological catalysts that speed up chemical reactions without being used up.

What is the effect of temperature on enzyme activity?

Enzyme activity increases with temperature up to the optimum; beyond that, enzymes denature.

What is the effect of pH on enzymes?

Each enzyme has an optimum pH; too high or too low can denature the enzyme.

What is the enzyme required practical?

Investigating how temperature affects the rate of amylase activity by measuring starch breakdown.

What are the four chambers of the heart?

Right atrium, right ventricle, left atrium, left ventricle.

What is the function of valves in the heart?

Prevent the backflow of blood.

What is the function of the coronary arteries?

Supply oxygenated blood to the heart muscle.

Name the blood vessels connected to the heart.

Vena cava, pulmonary artery, pulmonary vein, aorta.

What is osmosis?

The movement of water molecules across a semi-permeable membrane from an area of high concentration to an area of low concentration.