Topic 1 - Cell Biology

Question 1

Compare eukaryotic and prokaryotic cells.

Answer 1

• Eukaryotic cells have a nucleus, prokaryotic cells don’t have a nucleus.
• Prokaryotic cells are smaller than eukaryotic cells.
• Eukaryotic cells are complex, prokaryotic cells are simpler.

Question 2

What are the structures found in an animal cell and what are their functions?

Answer 2

• Nucleus: contains genetic information that control the activities in the cell
• Cytoplasm: where reactions take place
• Mitochondria: where respiration takes place
• Cell membrane: controls what leaves and enters the cell
• Ribosomes: make proteins for the cell

Question 3

What are the structures found in a plant cell and what are their functions?

Answer 3

• Nucleus: contains genetic information which controls the activity of the cell
• Cell membrane: controls what leaves and enters the cell
• Cell wall: gives the cell support to make it rigid and is made out of cellulose
• Cytoplasm: where chemical reactions take place in the cell
• Vacuole: contains cell sap
• Mitochondria: where respiration takes place
• Ribosomes: where proteins are made
• Chloroplasts: contains chlorophyll where photosynthesis takes place

Question 4

Describe the features of a bacterial cell.

Answer 4

• A single circular strand of DNA
• Rings of DNA called plasmids
• Small in size compared to animal and plant cells
• Flagelllum to help bacteria move
• Cytoplasm
• Cell membrane
• Cell wall
• No mitochondria or ribosomes

Question 5

What is the difference between a light and electron microscope?

Answer 5

Electron microscope has a higher resolution and higher magnification

Question 6

What is the equation for magnification?

Answer 6

Magnification = Image size / Actual size

Question 7

What is cell differentiation?

Answer 7

Cell differentiation:

— When an unspecialised cell becomes specialised to perform a specific function.

Question 8

Give examples of specialised cells and their functions.

Answer 8

Nerve cells: rapid signalling and carry electrical impulses
Sperm cells: reproduction
Muscle cells: contraction
Root hair cells: absorbing water and minerals
Xylem/Phloem cells: transporting food and water around a plant

Question 9

What are chromosomes and how many chromosomes in a body cell?

Answer 9

Chromosomes are coiled up dna that contain gentic information. There are 23 pairs of chromsomes in a body cell (diploid number)

Question 10

What is mitosis?

Answer 10

Mitosis is cell division used for growth and repair in the body.

Question 11

Describe the process of the cell cycle.

Answer 11

Growth and replication:

• – Cell growth
• – DNA replicates

Mitosis:

• – Chromosomes line up in the centre of the nucleus
• – Chromosomes are pulled apart by cell fibres to opposite ends of the cell
• – Two new membranes form around each set of chromosomes
• – Cytoplasm and cell membrane divides
• – Two identical daughter cells are produced

Question 12

How does bacteria divide and explain the process.

Answer 12

Bacteria divides using binary fisssion.

• – Plasmid and circular DNA replicates
• – Cell growth
• – Cytoplasm divides and cell mebrane begins to form
• – Two daughter cells produced.

Question 13

Why do embryonic stem cells tend to be used more than adult stem cells?

Answer 13

Embryonic stem cells can differentiate into any type of cell in the body whereas adult stem cells cannot. Also adult stem cells can only be found in certain places such as the bone marrow

Question 14

What are some reasons that people are against embyonic stem cell research?

Answer 14

• – Using embryonic stem cells is a potential human life

- – As not all stem cells are used, they are just destroyed and wasted

Question 15

Where are stem cells found in plants?

Answer 15

Meristems

Question 16

Define diffusion

Answer 16

Diffusion:

— The movement of particles from an area of higher concentration to lower concentration

Question 17

What things affect the rate of diffusion?

Answer 17

• – Concentration gradient (higher concentration = faster rate of diffusion)
• – Temperature (higher temperature = faster rate of diffusion)
• – Surface area (larger surface area = faster rate of diffusion)

Question 18

Define osmosis

Answer 18

The movement of water molecules from an area of higher water concentration to lower water concentration across a partially permeable membrane.

Question 19

Define active transport

Answer 19

The movement of particles from an area of lower concentration to higher concentration against a concentration gradient.

Question 20

Why are root hair cells covered in lots of microscopic hairs?

Answer 20

So that the root hair cells have a larger surface area which increases substance absorption

Question 21

What are the main adaptations to maximise effectiveness of exchanging substances?

Answer 21

• – Thin membrane which provides a shorter distance for substances to diffuse across
• – Larger surface area so more exchanging substances

Question 22

How are alveoli adapted for gas exchange?

Answer 22

• – Covered in network of blood capillaries
• – Moist lining
• – Thin walls
• – Large surface area

Question 23

How does gas exchange happen in leaves?

Answer 23

The underneath of leaves are covered in stomata which allows gases to diffuse in and out of the cells. It allows carbon dioxide to enter while oxygen and water vapour leave. The guard cells control the opening and closing of stomata.