Animal Cells (Part One) Flashcards
Phospholipids are amphiphatic.
What does this mean?
A molecule that possesses both a hydrophilic and hydrophobic region.
Describe how cholesterol influences membrane fluidity.
- Reduces membrane fluidity at moderate temperature
- Avoids solidification at low temperatures
Cholesterol is the source of two sex hormones.
Name these hormones.
- Estradiol
- Testosterone
What are lipid rafts?
Membrane regions that assemble specialised lipids and proteins to perform a certain task
Name the protein responsible for the closing over of a bleached area during FRAP.
Sso1
Give 6 potential roles of a protein embedded in the plasma membrane of a cell.
- Transporters
- Enzymes
- Receptors
- Cell-cell recognition
- Intracellular joining
- Attachment to extracellular matrix and intracellular cytoskeleton
Name the four kinds of gated channels.
- voltage gated
- mechanically gated
- temperature gated
- ligand-gated (chemical)
What is the function of a Tight Junction?
- Acts as a diffusion barrier
- Holds cells together
What do Tight Junctions consist of?
Plasma-membrane proteins, claudin and occuldin, that interact
Name the two proteins that compose an Adherens Junction.
What is the role of each protein?
- Cadherins; bridge between the cells.
- Catenins; link to the actin cytoskeleton.
What is the function of an Adherens Junction?
Involved in controlling actin organisation in epithelial cells.
What are the connecting channels of a Gap Junction made of?
Connexins
What is the function of a Gap Junction?
- Allows passage of ions and small molecules (1-2nm in diameter)
- Supports exchange between cytoplasm of adjacent cells.
Name the proteins found in Desmosomes.
What is the role of this protein?
Catherin proteins; interact with each other and intermediate filaments.
What is the function of a Desmosome?
Resists shear force in the epithelia and in muscle.
Name the main protein found in a Hemidesmosome, and state its function.
Integrins; interacts with the extracellular matrix.
Where in the body are Hemidesmosomes found?
In skin epithelial cells
What is the function of the Hemidesmosome?
- Anchors the epithelia to the basal lamina
- Signalling
Name the 5 cell-cell contacts.
- Gap Junctions
- Tight Junctions
- Adherens Junctions
- Desmosomes
- Hemidesmosomes
Name the three secreted proteins in the extracellular matrix.
- Collagen
- Matrix proteins
- Glycoproteins
What are the roles of the extracellular matrix?
- holds tissue together
- provides strength
- directs cell migration
Name the two major intracellular signalling mechanisms.
- Phosphorylation of proteins
- Signalling by GTP-binding proteins
What are G-proteins?
Molecular switches
What are G-proteins
a) activated by?
b) deactivated by?
a) G-proteins are activated by a Guanine nucleotide exchange factor (GEF)
b) G-proteins are deactivated by a GTPase-activaitng protein
