Biology - ORGANISATION (B2)

Principles of Organisation -

What is the hierarchical organisation of living organisms?

Cells → Tissues → Organs → Organ systems → Organism

Principles of Organisation -

Define a tissue + give an example.

A group of similar cells working together to perform a specific function, e.g. muscular tissue contracts to bring movement.

Principles of Organisation -

What is an organ system?

A group of organs working together to carry out a particular function, e.g. the digestive system.

The Human Digestive System -

What is the function of the digestive system?

To break down large, insoluble molecules into smaller, soluble molecules for absorption into the blood.

The Human Digestive System -

Name the main organs of the digestive system in order.

Mouth → Oesophagus → Stomach → Small intestine → Large intestine → Rectum → Anus (Liver + pancreas - accessory organs)

The Human Digestive System -

What is the role of the mouth in digestion?

Mechanical breakdown by teeth + chemical digestion by amylase (saliva).

The Human Digestive System -

What happens in the stomach during digestion?

Proteins begin digestion by pepsin (a protease); hydrochloric acid kills bacteria + provides the optimum pH (around 2).

The Human Digestive System -

What does the pancreas do?

Produces digestive enzymes (amylase, protease, lipase) released into the small intestine.

The Human Digestive System -

What is bile, + what are its functions?

Bile’s made by the liver, stored in the gall bladder. It emulsifies fats + neutralise stomach acid to provide alkaline conditions for enzymes in the small intestine.

Enzymes -

What are enzymes?

Biological catalysts that speed up reactions without being used up.

Enzymes -

What is the “lock and key” model?

The enzyme has a specific active site that only fit a complementary substrate - like a lock fits a key.

Enzymes -

What affects enzyme activity?

Temperature + pH.

Enzymes -

What happens to enzymes at high temperatures / extreme pH?

The enzyme becomes denatured - the active site changes shaoe + no longer binds the substrate.

Enzymes -

Which enzymes break down carbohydrates, proteins, + lipids?

Carbohydrase (amylase) - Breaks starch → glucose.

Protease - Breaks proteins → amino acids.

Lipase - Breaks lipids → fatty acids + glycerol.

The Circulatory System (heart & blood) -

What type of circulatory system do humans have?

Double circulatory system - one loop to the lungs, one to the body.

The Circulatory System (heart & blood) -

Describe the structure + function of the heart.

Four chambers: right atrium → right ventricle → lungs (via pulmonary artery); then left atrium → left ventricle → body (via aorta). The valves prevent backflow.

The Circulatory System (heart & blood) -

What is the role of the coronary arteries?

Supply oxygenateed blood to the heart muscle.

The Circulatory System (heart & blood) -

What is the pacemaker of the heart + where is it located?

A group of cells in the right atrium that control heart rate via electrical impulses.

The Circulatory System (heart & blood) -

Name the three types of blood vessels + their characteristics.

Arteries - Thick, muscular walls; carry blood away from heart under high pressure.

Veins - Thinner walls, valves; carry blood back to heart.

Capillaries - Very thin walls for efficient diffusion.

The Circulatory System (heart & blood) -

Name the four components of blood + their functions.

Red blood cells - Carry oxygen (contains haemoglobin).

White blood cells - Defend against infection.

Platelets - Help blood clot.

Plasma - Transports substances like glucose, CO2, hormones, etc.

Cardiovascular disease -

What causes coronary heart disease?

Build-up of fatty material in coronary arteries, reducing blood flow to the heart muscle.

Cardiovascular disease -

Name two treatments for coronary heart disease.

Stents - Keep arteries open.

Statins - Lower cholesterol levels in the blood.

Cardiovascular disease -

What are the risks of faulty heart valves + how are they treated?

Can leak / not open properly; treated w/ mechanical / biology replacement valves.

Cardiovascular disease -

What is an artificial pacemaker?

A device implaneted under the skin to regulate the heart rate using electrical impulses.

Cardiovascular disease -

What is artificial blood used for?

To replace lost fluid volume temporarily when someone loses a lot of blood, giving time for transfusion.

Health & Disease -

What is a communicable disease?

A disease that can be spread between individuals, caused by pathogens.

Health & Disease -

Give examples of non-communicable diseases.

Coronary heart disease, cancer, diabetes.

Health & Disease -

How can different diseases interact in the body?

One disease can make you more susceptible to others, e.g. HIV weakens immune system → more infections.

Health & Disease -

What factors can affect your health?

Diet, stress, lifestyle, access to healthcare, genetic disorders.

Cancer -

What is cancer?

Uncontrolled cell division forming a tumour.

Cancer -

What is the difference between benign + malignant tumours?

Benign - Doesn’t spread; usually harmless.

Malignant - Invades other tissues + spreads (metastasis); cancerous

Cancer -

Name some risk factors for cancer.

Smoking (lung cancer), UV exposure (skin cancer), viruses (e.g. HPV → cervical cancer), genetics.

Plant tissues, organs & transport -

Name the main tissues in a leaf + their functions.

Epidermis (upper/lower): Transparent, protective.

Palisade mesophyll: Packed w/ chloroplasts for photosynthesis.

Spongy mesophyll: Air spaces for gas exchange.

Xylem: Transports water + minerals.

Phloem: Transports sugars (translocation).

Stomata & guard cells: Control gas exchange + water loss.

Plant tissues, organs & transport -

What is the function of xylem vessels?

Transport water + minerals from roots to leaves (via transpiration stream).

Plant tissues, organs & transport -

What is the function of phloem vessels?

Transport dissolved sugars from leaves to the rest of the plant - both directions (translocation).

Plant tissues, organs & transport -

What is transpiration?

Loss of water vapour from the leaves through the stomata, driving the uptake of water via xylem.

Plant tissues, organs & transport -

What factors affect the rate of transpiration?

Temperature, humidity, air flow, light intensity.