Week 3- Organelles, Cell Growth and Cytoskeleton Flashcards
1
Q
What is the structure of the plasma membrane
A
- Lipid Bilayer
- Glycoproteins
- Transmembrane structural proteins
- transmembrane channels
2
Q
Functions of Plasma membrane
A
- Compartmentalization - continuous enclosure for specific activities
- Barrier - protects cellular components but is permeable
- Transport - machinery for two-way traffic of substances
- Response - receptors linked signaling cascade in response to external stimuli
3
Q
Membrane
A
- Lipid- protein assembly held by noncovalent bonds
- Transmembrane structural protein
- Membrane lipid are polarized bilayer
4
Q
Composition of plasma membrane
A
- Provides compromise between rigid structure and fluid liquid
- Allows movement of membrane proteins for specific activities
- Allows growth of membrane with new components
- Allows coordinated movement of cells
5
Q
What is the Lipid Bilayer
A
- flexible and tolerate to changes in shape (movement and cell division)
- able to self assemble (liposome and delivery)
6
Q
What are peripheral membrane proteins
A
- non-covalently attached to hydrophilic lipid ends or integral protein ends
- those found on cytosolic membrane surface function as membrane skeleton or signaling molecules
- those found on the external surface are part of extracellular matrix
7
Q
Movement across the plasma membrane
A
- diffusion whereby substance binds specifically to membrane-spanning protein and diffuses through it
- the membrane spanning protein is a facilitative transporter
- there is no release of energy in facilitated diffusion as compared to active transport
- binding is possible on both sides of transporter
8
Q
Plasma membrane- active transport against gradient
A
- ions gradients are needed and maintained by pumps in active transport
- pumps are energy driven
- 1st, Na+ binds to transporter from cytoplasmic side and triggers its phosphorylation
- 2nd, phosphorylation changes transporter’s conformation, allows exit of Na+
- 3rd, K+ bind to outside of transporter, which is then dephosphorylated, leading to release of K+ inside the cell
9
Q
Mitochondria
A
- Center of oxidative metabolism
- Oxidative metabolism incorporates O2 into metabolism to oxidize cellular compounds into CO2 and H2O
- Oxidative metabolism generates energy needed for cellular activities and stores them as ATP
10
Q
Endoplasmic reticulum
A
- Ribosome attached
- Protein secreting
- Site of biosynthesis
11
Q
Endomembrane system
A
- Consist of endoplasmic reticulum, Golgi complex, endosomes, lysosomes, vacuoles
- transport vesicles to move materials in cells
- biosynthetic pathways = secretion
- endocytic pathways = uptake
12
Q
Golgi Complex
A
- flattened, disc-like morphology
- Golgi complex is polarized: cis facing ER, trans closer to the plasma membrane
- vesicles budding at trans side
- assembly of glycoprotein and glycolipids
13
Q
Vesicle transport
A
- transport vesicle covered with protein coat
- protein coat select components for transport
- three types of protein coat
1. COPII coated vesciles: ER to Golgi
2. COPI coated vesciles: Golgi to ER
3. Clathrin-coated vesicles; trans golgi to endosome/lysosome, plasma membrane to endosome
14
Q
Endosomes
A
- Uptake of molecules too large for transport through plasma membrane
- Two main mechanisms:
1. phagocytosis: uptake of pathogens
2. endocytosis: uptake of proteins and hormones (growth factors)
15
Q
Lysosomes
A
- Targeting of lysosomal enzymes
1. Lysosomal enzymes synthesized in RER
2. Lysosomal enzymes are glycosylated and phosphorylated (in CGN), to form mannose-6-phosphate side chain
3. Modified lysosomal enzymes are recognised by mannose-6-phosphate receptors (MPR), with a coat protein and adaptor protein, at TGN and form vesicles
4. Coat protein and adaptor dissociate from vesicle, lysosomal enzymes delivered to endosome and vesicle with MPR
5. MPR returned to TGN to start the cycle
6. MPR can also be present at plasma membrane, to capture secreted lysosomal enzymes to direct them to lysosomes
