Cell biology

What are cells?

The structural and functional units of all living organisms.

What is the difference between prokaryotic and eukaryotic cells?

Prokaryotes (bacteria) lack a nucleus and membrane-bound organelles.
Eukaryotes (animal/plant cells) contain a nucleus and specialised organelles.

What are the major structural components of a eukaryotic cell?

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

What are the two main functions of the plasma membrane?

Acts as a selective barrier and provides a structural base for membrane proteins such as enzymes and receptors

What is the cytoplasm and cytosol?

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

What is the cytoskeleton and what does it do?

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

What are the three major cytoskeletal components?

Intermediate filaments, actin microfilaments and microtubules.

What is the function of ribosomes?

What is the difference between free and fixed ribosomes?

What is the difference between free and fixed ribosomes?

Free ribosomes float in cytosol; fixed ribosomes are attached to rough ER.

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

Protein synthesis and processing.

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

Lipid, steroid and carbohydrate synthesis plus detoxification of drugs/toxins.

What is the function of the Golgi body?

Processes, packages and exports proteins into vesicles.

What are mitochondria and their main functions?

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

What are lysosomes?

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

What is the main function of the nucleus?

Stores genetic information (DNA) and regulates cell activity.

What is the nucleolus?

Dense region within the nucleus involved in ribosome production.

How is DNA packaged in cells?

DNA → nucleosomes → chromatin fibres → chromosomes during cell division.

Why do cells divide?

For growth, repair, replacement and increased functional demand.

What is mitosis?

Division of a eukaryotic cell into two genetically identical daughter cells

What are the stages of mitosis?

Prophase, prometaphase, metaphase, anaphase and telophase.

What happens during metaphase?

Chromosomes align at the cell equator before separation.

What happens during anaphase?

Sister chromatids separate and move to opposite poles.

How is the cell cycle regulated?

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

What can happen if the cell cycle is dysregulated?

Uncontrolled proliferation and cancer (neoplasia).

What is passive transport?

Movement of substances down their concentration gradient without energy.

What is active transport?

Movement of substances against their concentration gradient requiring energy (ATP).

What is the difference between channels and transporter proteins?

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

What is an example of primary active transport?

Na⁺/K⁺ ATPase pump using ATP hydrolysis.

What functions do membrane proteins perform?

Cell adhesion, communication, immune recognition, signalling and cell movement.

How are cell structures adapted to specialised functions?

• Keratinocytes: strength/barrier function

• Enterocytes with microvilli: increased absorption surface area

• Neurons/Purkinje cells: communication and signal transmission