P1 Biology p2

What is the formula for magnification?

Magnification = Image size ÷ Real size

Units for magnification

1 mm = 1000 μm

Why is mitosis important?

Growth and repair tissues, asexual reproduction

The Cell Cycle — 3 main stages:

1. Cell grows — increases in size, copies organelles

2. Mitosis — one set of chromosomes pulled to each end, nucleus divides

3. Cytoplasm divides — two identical cells formed

What happens before mitosis starts?

The cell copies its DNA — so each new cell gets a full set of instructions

What are chromosomes?

Long strands of DNA, found in the nucleus

Explain why reduced blood flow to heart muscle causes problems (4‑5 mark style) (For CHD aswell)

Cholesterol builds up in coronary arteries narrowing them (CHD only)

Less blood → less oxygen + glucose delivered to heart muscle cells

Rate of aerobic respiration falls → less energy released

Cells use anaerobic respiration instead

This makes lactic acid → muscle fatigue; heart cannot contract efficiently

May lead to heart attack / breathlessness