1. Cell Biology

What are the main features of all eukaryotic cells?

Cell membrane, cytoplasm, nucleus

What extra organelles do animal cells have?

Mitochondria, ribosomes

What extra organelles do plant cells have?

Chloroplasts, cell wall (cellulose), permanent vacuole

How are prokaryotic cells different from eukaryotic cells?

Smaller, no nucleus, DNA is a loop in the cytoplasm

What is a plasmid?

A small ring of DNA found in some bacterial cells

What is the difference between light and electron microscopes?

Light microscopes have lower resolution/magnification; electron microscopes have higher resolution/magnification

What does Required Practical 1 involve?

Observe, draw and label plant/animal cells using a microscope and include a magnification scale

What is the formula for magnification?

Magnification = Image size ÷ Real size

What units should magnification answers be given in?

Standard form

What is cell specialisation?

When a cell gains structures to perform a specific function

Give three examples of specialised animal cells.

Sperm, nerve, muscle cells

Give two examples of specialised plant cells.

Root hair cells, xylem and phloem cells

When do animal cells differentiate?

Mainly early in life

When can plant cells differentiate?

Throughout their life

What is the purpose of the cell cycle?

Growth, development and repair

What happens in the first stage of the cell cycle?

Cell grows and organelles double

What happens to the DNA before mitosis?

It is replicated

What happens during mitosis?

Chromosomes are pulled apart and the nucleus divides

What happens after mitosis?

Cytoplasm and cell membrane divide to form two identical cells

What are embryonic stem cells?

Cells that can become most types of human cells

What are adult stem cells and where are they found?

Cells that can become some types of cells, found in places like bone marrow

Where are plant stem cells found?

In meristems

Give two uses of stem cells.

Treating diabetes and paralysis, cloning plants

Give two risks or issues with stem cell use.

Viral infection, ethical/religious concerns

What is therapeutic cloning?

Creating an embryo with the patient’s DNA so it isn’t rejected

What is diffusion?

Movement of particles from a high to low concentration

Give three examples of substances that move by diffusion.

Oxygen, carbon dioxide, urea

What factors affect the rate of diffusion?

Concentration gradient, temperature, surface area

What is osmosis?

Movement of water from a dilute to a concentrated solution through a partially permeable membrane

What does Required Practical 2 investigate?

Effect of sugar/salt solution on the mass of plant tissue

How do you calculate percentage change in mass?

% change = (change ÷ original) × 100

What is active transport?

Movement of substances against a concentration gradient using energy

Give two examples of active transport.

Mineral ions into plant roots, sugar from the gut into the blood

Why do small organisms rely on diffusion?

They have a large surface area to volume ratio

Why do larger organisms need exchange surfaces?

Because their surface area to volume ratio is too small for diffusion alone

What makes a good exchange surface?

Large surface area, thin membrane, good blood supply, and (for gases) ventilation

Give examples of specialised exchange surfaces.

Lungs, small intestine, fish gills, plant roots, plant leaves