Cell Physiology Part 2

Question 1

Name some characteristics of the plasma membrane.

Answer 1

Bilayer of phospholipids with embedded proteins
-Glycolipids and glycoproteins help sensor pressure on the membrane
Semipermeable; selective- Transportation and Homeostasis
Signal transduction-receptors, cell-cell communication
Bioelectricity-Ion channels/pumps, membrane potential

Question 2

What is the most common structure in the membranes?

Answer 2

Phospholipids are the most common structure

• 2 parts: polar head and Nonpolar tail
• can be straight or kinked (double or triple bond)

Question 3

Name some other membrane lipids.

Answer 3

Cholesterol: is a Nonpolar molecule that stabilizes the packing of lipids and decreases membranes fluidity
Glycolipids: are lipids conjugated with carbohydrates, which provides a unique surface chemistry to the membrane

Question 4

What is the job of membrane carbohydrates?

Answer 4

Recognition of self
Cell to cell communication
-cells join together to form tissues which is important in embryonic growth
-important for tissue growth
–cells do not invade other tissues (healthy cells)
some cell adhesions have carbohydrates
-for cell adhesions

Question 5

What does fluidity mean in relation to a plasma membrane? What is FRAP?

Answer 5

That the lipids and proteins can “float” in the membrane via diffusion.
FRAP is a technique for detecting interactions between membrane proteins.
-Steps: label a protein w/ fluorescence, bleach the area, what he how the proteins interact
eventually the proteins will be back in the original spot

Question 6

What are the three classes of membrane proteins?

Answer 6

1) Transmembrane proteins
- have an extracellular domain (sugars always face out)
- Transmembrane domain
- intracellular domain
2) Lipid-anchored membrane proteins
- outside: covalently linked to a glycophospholipid
- Inside: covalently linked to fatty acid
3) Peripheral membrane proteins
- specific interaction between IMP and MPM
- or could bind to specific lipid heads

Question 7

What can a detergent do to membrane proteins?

Answer 7

Separate them from the membrane

Question 8

What are membrane microdomains and what are some characteristics of them?

Answer 8

Specialized PM domains: Enriched with cholesterol, sphingomyelin, glycophospatidinositol anchored.
Flask/omega shaped structures, detergent insoluble
Detergent insoluble: Lipid-rafts are linear and caveolae are invagination a of rafts with associated caveolin proteins
Micro compartments for localizing receptors,signaling proteins
-signaling platforms/compartment
Adipolytes,vascular endothelial cells, smooth muscle cells, neurons, glial cells, blood cells

Question 9

Do you understand cell to cell adhesions? Really tell me about them.

Answer 9

Cells are held together by:
Cell adhesions
Specialized cell junctions
Extracellular Matrix

Question 10

What are the Extracellular Matrix proteins?

Answer 10

Collagen
-Forms strong cables or sheets that provide tensile strength
-Disrupted in scurvy
Elastin
-Rubber like protein easy to stretch
-Found in tissues exposed to stretching and recoiling
Fibronectin
-Promotes cell adhesions
-holds cells in position via integrins
-reduced amount has been found in cancer tissues
fibronectin plays an important role in signaling

Question 11

Hey look at you your doing great, so tell me what the three types of specialized cell junctions.

Answer 11

Desmosomes (adhering junctions)
Tight junctions (impermeable junctions)
Gap junctions (communicating junctions)

Question 12

Describe Desmosomes.

Answer 12

Formed by plaque and glycoproteins
In contact with cytoskeleton
Protects against over stretching 
Functional syncytium/symplasm 
Mutations in desmonsomal proteins-Arrythmogenic right ventricular cardiomyopathy (ARVC)

Question 13

Talk about tight junctions.

Answer 13

Impermeable and forms a barrier
Formed by fusion of junction all proteins
Materials must be transported
-Transcellular pathway
-preserves endo/exocytosis in cells
Maintain cell polarity-preventing lateral diffusion of luminal and basho lateral membrane proteins
Found primarily in epithelial sheets, bile ducts, liver, intestine
Diarrhea: breaks on of intestinal tight junctions due to infection

Question 14

Gap junctions

Answer 14

Connexons form tunnels connecting adjacent so cells-electrical synapses
Low resistance pathway for charge-carrying ions and small molecules-connect cytoplasm of two cells
Spread the wave of excitation in the heart, smooth muscles, neuron, glia
Mutations-hearing impairment, visual deficit, mostly during developmental stages

Question 15

Let’s talk about communication baby. Intercellular communication use……

Answer 15

Gap Junctions
Cell-cell signaling
Chemical Messengers
-paracrines
-hormones
-NT
-Neurohormones

Question 16

Go through the process of transaction of a chemical Message.

Use G protein example

Answer 16

1. Receptor activation causes the release of the alpha subunit of the G protein complex
2. The alpha subunit diffuses to activate adenylate cyclase to form cAMP
3. cAMP activates protein kinase A (PKA)
4. PKA mediates phosphorylation of target protein
   - protein function is altered to produce desired result

Question 17

What does signal Amplification do?

Answer 17

Cascades of signals result in an amplification of downstream events