Question

1. Using 3 nucleotides, adenine, guanine, and cytosine, illustrate why the sequence in DNA is read from 5’--------?3’. Draw the structures of the linked nucleotides to illustrate your answer.

2. Draw the structure of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoinositol. Using the drawing, illustrate the difference between saturated and unsaturated fatty acids: 16:0 and 18:1, n-9.

3. Discuss how the structure of the cell membrane regulates the passage of material in and out of the cell. To answer this question, list and draw the components of a phosphocholine molecule in the cell membrane. Hint, pay attention to polar head and nonpolar tails:

4. Discuss the function of the following organelles and cellular structures:

Smooth E.R.

Rough E.R.

Mitochondria

Golgi Apparatus

Vesicle

Nucleolus

Ribosomes

5. Define G-proteins and discuss the mechanism of their activation:

6. Discuss the function of an active adenylate cyclase and the mechanism of generation of cAMP:

7. Explain the activation process of mitogen-activated protein kinase kinase kinase (MAPKKK) that may be initiated by platelet-derived growth factor (PDGF):

8. Discuss the function of histone deacetylases in the gene transcription process.

Answer 1

4. Smooth ER - To make cellular products like hormones and lipids. It regulates and releases calcium ions and toxins.

Rough ER - Ribosomes for protein synthesis

Mitochondria - To produce energy of the cell, ATP through respiration and to regulate cellular metabolism.

Golgi apparatus -Transport of lipids around the cell. Produce lysosomes. Modifying and packaging of proteins for secretion.

Nucleolus - It stores DNA, It coordinates growth, protein synthesis, metabolism and reproduction.

Vesicles - Transporting substances within thecell and phagocytizing harmful materials in the cell.

Cellular vesicles are lysosomes are used to break down food particles.

Ribosomes - Translation occurs. It synthesize proteins.

5).G protein - Also known as Guanine nucleotide - binding proteins, involved in transmitting signals and function as molecular switches. Their activity is regulated by factors that control their ability to bind to and hydrolyze GTP to GDP. When they are bound to GTP, they are on and when they bound to GDP, they are off.There are 2 classes of G protein -

The first function as monomeric small GTPases.

The second function as heterotrimeric G protein complexes.It is made up of alpha, beta and gamma subunits.

Mechanism of activation -

When a ligand activates the G protein - coupled receptor, it induces a conformational change in the receptor that allows the receptor to function as a guanine nucleotide exchange factor(GEF) that exchanges GDP for GTP thus turning the GPCR on.The GTP is bound to the G alpha subunit. This exchange triggers the dissociation of the G alpha subunit from the G beta Gamma dimer and the receptor as a whole. Both G alpha - GTP and G beta Gamma can then activate different signalling cascades and effector proteins,while the receptor is able to activate the next G protein.