Biology - CELL BIOLOGY (B1)

Cell types & structures -

What is the main structural difference between prokaryotic + eukaryotic cells?

Eukaryotic cells have a true nucleus enclosed by a membrane and ogranelles such as mitochondria and chloroplasts. Prokaryotic cells have no nucleus - their DNA is free in the cytoplasm - and they lack membrane bound organelles.

Cell types & structures -

Name five organelles found in both plant and animal cells + describe their functions.

Nucleus - contains DNA; controls cell activity

Cytoplasm - site of most chemical reactions

Cell membrane - controls entry + exit of substances

Mitochondria - site of aerobic respiration

Ribosomes - site of protein synthesis

Cell types & structures -

What additional structures are found in plant cells but not animal cells, + what are their roles?

Cell wall (cellulose) - provides support + structure

Chloroplasts - contains chlorophyll for photosyntheiss

Permanent vacuole - filled w/ cell sap; maintains turgor pressure

Cell types & structures -

What are plasmids, + where are they found?

Plasmids - small circular loops of DNA found in prokaryotic cells such as bacteria. They carry additional genes, e.g. for antibiotic resistance.

Microscopy -

Compare light + electron microscopes in terms of magnification + resolution.

Light microscope - Max 2000x magnification; lower resolution (200 nanometers).

Electron microscope - Over 1 000 000x magnification; higher resolution (0.2 nanometers); can view ultrastructure like ribosomes + internal membranes.

Microscopy -

What is the equation for calculating magnification?

Magnification = image size/ actual size

Make sure all units are the same.

Microscopy -

Why do we use stains in microscopy?

To highlight different structures in cells, to make them more visible under a microscope.

Cell specialisation -

What is meant by “cell differentiation”?

The process by which unspecialised cells develop → specialised cells w/ specific structures + functions.

Cell specialisation -

Give three examples of specialised animal cells + how their structure helps their function.

Sperm cell - long tail for mobility, mitochondria for energy, acrosome w/ enzymes to penetrate egg.

Nerve cell - Long to carry impulses over distances; branches for connections.

Muscle cell - Lots of mitochondria for energy; can contract to move.

Cell specialisation -

Give two examples of specialised plant cells.

Root hair cell - Large surface area for water/ mineral uptake.

Xylem cell - Hollow + strengthened w/ lignin for water transport.

Cell division & the cell cycle -

What is the purpose of mitosis?

To produce two genetically identical daughter cells for growth, repair, + asexual reproduction.

Cell division & the cell cycle -

What is the purpose of mitosis?

To produce two genetically identical daughter cells for growth, repair, + asexual reproduction.

Cell division & the cell cycle -

Describe the main stages of the cell cycle.

Growth phase - cell increases in size; organelles + DNA are duplicated.

Mitosis - nucleus divides

Cytokinesis - cytoplasm + cell divide into two

Cell division & the cell cycle -

Why is it important that the daughter cells produced by mitosis are identical?

To ensure genetic consistency for proper function in body tissues + organs.

Stem cells -

What are stem cells?

Undifferentiated cells that can divide to produce more stem cells / differentiate → specialised cells.

Stem cells -

Where are stem cells found in humans?

Embryonic stem cells - can become most cell types.

Adult stem cells - limited to certain cells like blood cells.

Stem cells -

How can stem cells be used in medicine?

To replace damaged cells. Stem cells may be grown into specific tissues for transplantation.

Stem cells -

What are some risks + ethical concerns of stem cell use?

Ethical - use of embryos destroys potential life.

Medical - risk of rejection, mutations, / infection.

Stem cells -

What are meristems + their role in plants?

Regions in plants that contain unspecialised cells that can divide + differentiate throughout the plant’s life.

Transport in cells -

Define diffusion + give one example in the human body.

The movement of particles from an area of high to low concentration. E.g. oxygen diffusing from alveoli into red blood cells.

Transport in cells -

What factors affect the rate of diffusion?

Concentration gradient, temperature, surface area, + diffusion distance.

Transport in cells -

Define osmosis.

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

Transport in cells -

Describe an example of osmosis in a plant cell.

Water moves into the plant cell, increasing turgor pressure + keeping the plant rigid.

Transport in cells -

What is active transport + how does it differ from diffusion?

Movement of substances against a concentration gradient using energy from respiration. Unlike diffusion, it requires ATP.

Transport in cells -

Give two examples of active transport.

• Absorption of minerals by root hair cells in plants

• Reabsorption of glucose in the kidney tubules in humans