cell biology

What are the major structural components of a eukaryotic cell?

Plasma membrane, cytoplasm/cytosol, cytoskeleton, nucleus, ribosomes, ER, Golgi body, mitochondria and lysosomes.

What is the function of the plasma membrane?

A phospholipid bilayer that acts as a selective barrier and supports membrane proteins such as receptors and enzymes.

What is the difference between cytoplasm and cytosol?

Cytoplasm = everything between the plasma membrane and nucleus.
Cytosol = fluid component containing water, ions and proteins.

What is the cytoskeleton and what are its functions?

Protein scaffolding that maintains cell shape, polarity, intracellular organisation and movement.

What are the three major cytoskeletal proteins?

Intermediate filaments, actin microfilaments and microtubules.

What is the function of ribosomes?

Protein synthesis by translating mRNA into amino acid chains.

What is the difference between free and fixed ribosomes?

Free ribosomes float in cytosol; fixed ribosomes attach to rough ER.

What is the function of rough endoplasmic reticulum (rER)?

Protein synthesis and transport.

What is the function of smooth endoplasmic reticulum (sER)?

Lipid/steroid synthesis and detoxification of drugs/toxins.

What is the function of the Golgi body?

Modifies, packages and exports proteins into vesicles.

What are mitochondria and their functions?

Organelles producing ATP via oxidative phosphorylation; also involved in apoptosis and signalling.

What are lysosomes?

Membrane-bound vesicles containing digestive enzymes that break down macromolecules and debris.

What is the function of the nucleus?

Stores DNA and controls cell activity.

What is the nucleolus?

Region within the nucleus responsible for ribosome production.

How is DNA packaged in cells?

DNA → nucleosomes → chromatin fibres → chromosomes during mitosis.

Why do cells undergo division?

For growth, repair and replacement of damaged cells.

What are the stages of mitosis?

Prophase, prometaphase, metaphase, anaphase and telophase.

What happens during metaphase and anaphase?

Metaphase: chromosomes align at the equator.
Anaphase: sister chromatids separate to opposite poles.

How is the cell cycle regulated?

Cyclin-dependent kinases (CDKs) tightly regulate growth and division.

What can happen if cell cycle regulation fails?

Uncontrolled proliferation and cancer (neoplasia).

What determines whether a molecule can cross the plasma membrane easily?

Small, non-polar molecules cross easily; larger or charged molecules require transport proteins.

What is passive transport?

Movement down a concentration gradient without energy

What is active transport?

Movement against a concentration gradient requiring ATP energy.

What is the difference between channel and transporter proteins?

Channels form pores for diffusion; transporters bind solutes and change shape to move them.

What is an example of primary active transport?

The Na⁺/K⁺ ATPase pump.

What functions do membrane proteins perform?

Cell signalling, adhesion, immune recognition and movement.

How are enterocytes adapted for absorption?

Microvilli increase surface area for nutrient absorption.

How are keratinocytes adapted for protection?

Strong cytoskeletal connections create durable protective barriers.

How are neurons adapted for communication?

Long processes and specialised membranes allow rapid signal transmission.

What is the relationship between cell structure and function?

Cells contain specialised structures and membrane adaptations that enable their specific functions.