Fundamentals of Cells

Question 1

What is cell theory?

Answer 1

-Cells are the building blocks of life
-Smallest units that perform all vital physiological functions
-Come from the division of pre-existing cells

Question 2

What are the core functions of the human cell?

Answer 2

1. Cell division
2. Dna replication + protein synthesis
3. Cellular respiration
4. Cell migration
5. Cellular transport

Question 3

Prokaryotes vs Eukaryotes?

Answer 3

-Single closed compartment,
enclosed by the plasma membrane, Lacks a defined nucleus, very small
VS
-Surrounded by the plasma membrane, Contains a defined membrane-bound nucleus, Cell interior (cytoplasm) contains membrane enclosed organelles, bigger

Question 4

What are the 4 functions of the proteins at the plasma membrane?
Name 2 ways cells are joined together?

Answer 4

1. Transport: Membrane proteins form channels and transporters
2. Communication: send and receive information through ligands and receptors
3. Recognition: recognise other cells and pathogens through recognition receptors
4. Enzyme reactions: enzymes break down macromolecules

-. Cell junctions: cells are joined to one another through proteins called cell adhesion molecules (CAMs)
-. Cell-matrix adhesion: Cells are bound to the extracellular matrix by adhesion proteins called adhesion receptors or matrix receptors

Question 5

What are cytoskeleton proteins, What are the 3 types?

Answer 5

-cell’s skeleton, providing support and to maintain the shape of cells. It also allows movement of cells as well as the transportation of intracellular vesicles.

1. Microfilaments/Actin filaments: Involved in generating contractile forces and movement.
2. Intermediate filaments: Strengthen the cell and help maintain its shape.
3. Microtubules: Form the mitotic spindle for the separation of the duplicated chromosomes during mitosis.

Question 6

1. What is protein sorting?
2. What is a sorting signal?
3. What happens to proteins without a sorting signal?

Answer 6

1. biological mechanism by which proteins are transported to their appropriate destinations in the cell or outside it.
2. “address labels” or sorting signals that indicate which cellular compartment they are destined for. The sorting signals are part of the amino acid sequence of the proteins.
3. They remain in the cytosol

Question 7

What is the process of Protein synthesis?

Answer 7

1.Code for making the protein is transcribed into mRNA
2.mRNA dock onto ribosomes to be translated into polypeptides
3.Polylypeptides destined to be cytosolic proteins get folded and remain in the cytosol. For proteins which get localised to other organelles and the plasma membrane, the polypeptides need to go to the ER first.
4.In the ER, polypeptides get folded, move to the Golgi and then shipped out through vesicles

Question 8

What happens when proteins are misfolded?

Answer 8

> Mutations can change the amino acid sequence of polypeptides which leads to misfolding.

-Misfolded proteins are toxic and cause cell death/apoptosis.

-Cells have organelles dedicated for the disposal of misfolded proteins: the proteasome

-Cells first tag misfolded proteins with ubiquitin.

-This allows them to be delivered to the proteasome to be degraded.

Question 9

What is autophagy?

Answer 9

-Natural, regulated mechanism of the cell that removes waste or dysfunctional components of cells

Question 10

What is the process of cell degradation?
Give 4 examples of how cell degradation is a normal function?

Answer 10

1. Membrane receptor proteins which have activated signalling pathways need to be turned off and destroyed.
2. macromolecules like cholesterol need degrading to avoid excess build up.
3. Immune cells need to destroy bacteria which they engulf.
4. Damaged or worn out organelles need degrading too.

Question 11

What is the process of cell division to produce 2 identical daughter cells?

Answer 11

1. Interphase: Cells grows in size. DNA is replicated and checked.
2. Prophase: Chromosomes condense and become visible. Spidle fibres emerge from the centrosomes
3. Prometaphase: Nuclear envelope breaks down
   Kinetochores appear at the centromeres. Mitotic spindle fibres attach to kinetochores
4. Metaphase: Chromosomes are lined up at the equator of the spindle.
   Each sister chromatid is attached to a spindle fibre from opposite poles
5. Anaphase: Sister chromatids are pulled towards the pole it faces to form daughter chromosomes.
6. Telophase: Chromosomes arrive at opposite poles and begin to decondense.
   Mitotic spindle breaks down.
   Nuclear envelope reform.
7. Cytokineses: Lastly, the cytoplasm is divided in two. This is achieved by a contractile ring of actin and myosin filaments which pinches the cell in two.