2. Structure and Functions in Living Organisms

Question 1

List the levels of organisation in living organisms.

Answer 1

Organelles → cells → tissues → organs → systems.

Question 2

Name the main structures found in cells.

Answer 2

Nucleus, cytoplasm, cell membrane, cell wall, mitochondria, chloroplasts, ribosomes, vacuole.

Question 3

What is the function of the nucleus?

Answer 3

Contains genetic material, controls cell activities.

Question 4

What is the function of the cytoplasm?

Answer 4

Site of chemical reactions.

Question 5

What is the function of the cell membrane?

Answer 5

Controls entry and exit of substances.

Question 6

What is the function of the cell wall (plants, fungi, some bacteria)?

Answer 6

Provides support and protection.

Question 7

Function of mitochondria?

Answer 7

Site of aerobic respiration and energy production.

Question 8

Function of chloroplasts?

Answer 8

Site of photosynthesis (contain chlorophyll).

Question 9

Function of ribosomes?

Answer 9

Site of protein synthesis.

Question 10

Function of vacuole (plants)?

Answer 10

Contains cell sap, maintains cell shape.

Question 11

Similarities and differences between plant and animal cells?

Answer 11

Both have nucleus, cytoplasm, cell membrane, mitochondria, ribosomes. Plant cells also have cell wall, chloroplasts, and vacuole; animal cells do not.

Question 12

What elements are present in carbohydrates, proteins, and lipids?

Answer 12

Carbohydrates: Carbon, hydrogen, oxygen; Proteins: Carbon, hydrogen, oxygen, nitrogen (and sometimes sulfur); Lipids: Carbon, hydrogen, oxygen.

Question 13

What are the basic units of carbohydrates, proteins, and lipids?

Answer 13

Starch/glycogen: made from simple sugars; Proteins: made from amino acids; Lipids: made from fatty acids and glycerol.

Question 14

What is the role of enzymes?

Answer 14

Biological catalysts that speed up metabolic reactions.

Question 15

How does temperature affect enzyme activity?

Answer 15

High temperatures can denature enzymes by changing the shape of the active site, reducing activity.

Question 16

How does pH affect enzyme function?

Answer 16

Extreme pH changes can alter the active site and denature the enzyme.

Question 17

Define diffusion.

Answer 17

The net movement of particles from a high to a low concentration.

Question 18

Define osmosis.

Answer 18

The diffusion of water molecules from a dilute to a concentrated solution through a partially permeable membrane.

Question 19

Define active transport.

Answer 19

The movement of substances against a concentration gradient using energy.

Question 20

What factors affect the rate of movement of substances?

Answer 20

Surface area to volume ratio, distance, temperature, concentration gradient.

Question 21

What is photosynthesis?

Answer 21

The process by which plants convert light energy to chemical energy.

Question 22

Word equation for photosynthesis?

Answer 22

Carbon dioxide + water → glucose + oxygen.

Question 23

Symbol equation for photosynthesis?

Answer 23

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

Question 24

What factors affect photosynthesis rate?

Answer 24

Carbon dioxide concentration, light intensity, temperature.

Question 25

How is a leaf adapted for photosynthesis?

Answer 25

Large surface area, thin, chloroplasts, stomata, network of veins.

Question 26

Why do plants need mineral ions?

Answer 26

Magnesium for chlorophyll, nitrate ions for amino acids.

Question 27

Components of a balanced human diet?

Answer 27

Carbohydrate, protein, lipid, vitamins, minerals, water, dietary fibre.

Question 28

Functions and sources of key nutrients?

Answer 28

Carbohydrate: energy (bread, pasta); Protein: growth/repair (meat, beans); Lipids: energy/store (butter, oils); Vitamin A: vision (carrots); Vitamin C: healthy tissues (oranges); Vitamin D: bones/teeth (sunlight, dairy); Calcium: bones/teeth (milk); Iron: haemoglobin (red meat); Fibre: digestion (vegetables); Water: all cells (drinks, food).

Question 29

What is peristalsis?

Answer 29

Wave-like muscle contractions that move food through the gut.

Question 30

What are the roles of digestive enzymes?

Answer 30

Amylase/maltase: starch → glucose; Proteases: proteins → amino acids; Lipases: lipids → fatty acids + glycerol.

Question 31

What is the role of bile?

Answer 31

Neutralises stomach acid, emulsifies fats.

Question 32

How is the small intestine adapted for absorption?

Answer 32

Villi increase surface area, thin walls, good blood supply.

Question 33

What is respiration?

Answer 33

The process of releasing energy (ATP) from food molecules.

Question 34

What is ATP?

Answer 34

A molecule that stores and provides energy for cells.

Question 35

Difference between aerobic and anaerobic respiration?

Answer 35

Aerobic uses oxygen, more energy; anaerobic does not use oxygen, less energy.

Question 36

Word equation for aerobic respiration?

Answer 36

Glucose + oxygen → carbon dioxide + water (+ energy).

Question 37

Symbol equation for aerobic respiration?

Answer 37

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ energy).

Question 38

Word equation for anaerobic respiration (animals)?

Answer 38

Glucose → lactic acid (+ energy).

Question 39

Word equation for anaerobic respiration (plants/yeast)?

Answer 39

Glucose → ethanol + carbon dioxide (+ energy).

Question 40

Key structures of the thorax?

Answer 40

Ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli, pleural membranes.

Question 41

Role of intercostal muscles and diaphragm?

Answer 41

They contract and relax to ventilate the lungs.

Question 42

How are alveoli adapted for gas exchange?

Answer 42

Large surface area, thin walls, moist, rich capillary supply.

Question 43

Consequences of smoking?

Answer 43

Lung damage, increased risk of coronary heart disease.

Question 44

Why can unicellular organisms rely on diffusion?

Answer 44

Short distances for substances to move.

Question 45

Why do multicellular organisms need transport systems?

Answer 45

Diffusion alone is too slow for large organisms.

Question 46

Role of phloem?

Answer 46

Transports sucrose and amino acids.

Question 47

Role of xylem?

Answer 47

Transports water and mineral ions.

Question 48

Composition of blood?

Answer 48

Red blood cells, white blood cells, platelets, plasma.

Question 49

Role of plasma?

Answer 49

Transports CO₂, digested food, urea, hormones, heat.

Question 50

Adaptations of red blood cells?

Answer 50

Biconcave shape, no nucleus, haemoglobin.

Question 51

How does the immune system respond to disease?

Answer 51

Phagocytes ingest pathogens; lymphocytes release antibodies.

Question 52

Heart structure and function?

Answer 52

Four chambers; pumps blood around the body.

Question 53

Effects of exercise/adrenaline on heart rate?

Answer 53

Both increase heart rate.

Question 54

Risk factors for coronary heart disease?

Answer 54

Diet, smoking, lack of exercise, genetics.

Question 55

Structure/function of arteries, veins, capillaries?

Answer 55

Arteries: thick walls, carry blood away from heart; Veins: thinner walls, valves, carry blood to heart; Capillaries: very thin walls, exchange substances.

Question 56

Structure of circulation system?

Answer 56

Heart, arteries, veins, capillaries; blood to/from lungs, liver, kidneys.

Question 57

Main excretory products in humans?

Answer 57

Lungs: carbon dioxide; Kidneys: urea; Skin: sweat (water, salts, urea).

Question 58

Origin of waste gases in plants?

Answer 58

Carbon dioxide and oxygen from metabolism, lost through stomata.

Question 59

What is homeostasis?

Answer 59

Maintenance of a constant internal environment.

Question 60

What is required for a coordinated response?

Answer 60

Stimulus, receptor, effector.

Question 61

What are phototropism and geotropism?

Answer 61

Plant growth responses to light (phototropism) and gravity (geotropism).

Question 62

Role of auxin in phototropism?

Answer 62

Promotes cell elongation on shaded side, causes stem to bend toward light.

Question 63

Difference between nervous and hormonal responses?

Answer 63

Nervous: fast, electrical, short-term. Hormonal: slower, chemical, longer-lasting.

Question 64

What is the central nervous system (CNS)?

Answer 64

Brain and spinal cord, linked to sense organs by nerves.

Question 65

How do receptors send signals?

Answer 65

Electrical impulses along nerves into and out of the CNS.

Question 66

Role of neurotransmitters?

Answer 66

Chemicals that transmit signals across synapses.

Question 67

Structure/function of a simple reflex arc?

Answer 67

Receptor → sensory neuron → relay neuron (CNS) → motor neuron → effector (e.g., muscle).

Question 68

Structure/function of the eye?

Answer 68

Detects light, focuses images, enables vision.

Question 69

How does the eye focus?

Answer 69

Lens changes shape (accommodation) for near/distant objects.

Question 70

How does skin regulate temperature?

Answer 70

Sweating, vasoconstriction, vasodilation.

Question 71

Sources/roles/effects of key hormones?

Answer 71

Adrenaline: increases heart rate (adrenal glands); Insulin: lowers blood glucose (pancreas); Testosterone: male secondary sex traits (testes); Oestrogen: female secondary sex traits/menstrual cycle (ovaries); Progesterone: maintains uterus lining (ovaries).