Topic 2: Cell Physiology Flashcards
1
Q
Phospholipid Bilayer
A
- Continuous layer around cell
- Barrier to water soluble substances - NOT to small molecules and/or lipid soluble molecules (e.g. O2 and CO@)
2
Q
Membrane Proteins
A
1) Transport Proteins
a) Channels
b) Carrier Proteins
2) Receptor Proteins
3) Enzymes
4) Joining Proteins
5) Identifying Proteins
3
Q
Channels (Transport Proteins) (Membrane Proteins)
A
- Form pore in membrane
- Selectively permit channel- mediated facilitated diffusion of specific ions
- Can be:
1) Gated: can open or close -in response to stimuli
2) Non-gated (= leakage channels): always open
4
Q
Carrier Proteins (Transport Proteins) (Membrane Proteins)
A
- Blind solute + carry it across membrane
- Allow protein carrier-mediated facilitated transport OR active transport
- E.g. glucose transporters
5
Q
Receptor Proteins (Membrane Proteins)
A
- Can bind specific extracellular molecules (=ligands) e.g. hormones, neurotransmitters (nt)
- e.g. glucose uptake:
1) insulin binds to receptor on skel. muscle or adipose tissue
2) triggers movement of more glucose transporters to cell membrane
3) Increased glucose movement from blood into cells
6
Q
Enzymes (Membrane Proteins)
A
- Control chemical reactions on outer or inner surface
- e.g. 1: acetylcholinesterase
e. g. 2: Na+/K+ - ATPase - all cells have this
7
Q
Joining Proteins (Membrane Proteins)
A
- Anchor cell membrane to cytoskeleton or an adjacent cell
1) Junctional proteins between cells forming: - Desmosomes, tight junctions, gap junctions
2) Extracellular fibres (usually glycoproteins)
8
Q
Identifying Proteins (Membrane Proteins)
A
- e.g. Major Histocompatibility Complex (MHC) proteins
- On surface of all cells except rbc
- Identify cell as “self” (part of the body” - not foreign
9
Q
Membrane Carbohydrates
A
- Glycoproteins and glycolipids
- Differ for every cell type - allow cells to recognize type e.g. sperm recognizes egg
10
Q
Membrane Transport
A
- Movement of material between the intra- and extracellular fluids
- Types of Transport:
1) Passive Transport
2) Active Transport
11
Q
Solute
A
Substance dissolved in a solution
12
Q
Solvent
A
Substance solute is dissolved in e.g. water
13
Q
Passive Transport
A
- No energy required (no ATP)
- Movement form high to low concentration (i.e. down its concentration gradient)
- The greater the difference in concentration = more and faster the molecules will move
14
Q
Types of Passive Transport
A
- Types:
1) Simple Diffusion (solute movement)
2) Facilitated Diffusion (solute movement)
3) Facilitated Transport (solute movement)
4) Osmosis (solvent movement)
5) Bulk Flow
15
Q
Simple Diffusion (solute movement)
A
- Solute crosses through the cell membrane bilayer - small, lipid soluble (O2, CO2, etc)
16
Q
Facilitated Diffusion (Solute movement)
A
- Ions diffuse through membrane via protein channels
17
Q
Facilitated Transport (solute movement)
A
- Large, charged or water-soluble molecules
- Move across membrane using a specific carrier protein - MUST BIND to protein to be transported
- e.g. glucose into liver or skull. muscle cells
18
Q
Osmosis (solvent movement)
A
- Movement of H2O across a semipermeable membrane (permeable to H20) due to [H2O] difference (water moves down its concentration gradient) via pores (channels) or across the membrane bilayer
19
Q
Osmosis Note
A
- High [H20] = low [solute] - dilute solution
- low [H2O] = high [solute] - concentrated solution
- [Solute] depends on the number of ions or molecules, not the type
20
Q
Osmotic Pressure (OP)
A
- Pressure that must be applied to prevent movement of H2O from pure H2O solution (S1) across a semipermeable membrane into another solution (S2)
21
Q
Osmotic Pressure Step 1
A
If S2 has high [salt] (low[H2O]) then H2O will move into it –> requires pressure to stop it moving into S2
- the greater [salt] in S2, the greater the OP and lower [H2O] –> more water will move in (down its gradient) –> more P needed to stop it moving
22
Q
Osmotic Pressure Step 2
A
If S2 also = pure H2O –> no required to prevent H2O movement (no gradient) - S2 OP = 0
- OP is used as a measure of the [solute] in a solution
- High OP = high [solute] (low [H2O]) + vice versa
23
Q
Tonicity
A
- Response of a cell immersed in a solution
- Depends on [solute] (and permeability of cell membrane to the solute)
- Classifications:
1) Isotonic Solution
2) Hypotonic Solution
3) Hypertonic Solution
24
Q
Isotonic Solution
A
- cell neither swells nor shrinks
- ECF and ICF have EQUAL OP
- rbc - [all solutes] in ICF = 0.9%
saline (NaCl) solution (= normal saline)
25
Hypotonic Solution
- Cell swells (takes in water)
- ECF has higher [H2O] (lower OP) than ICF (cytosol)
- <0.9% NaCl e.g. 0.1%
- Swelling can rupture cell = lysis
- if a red blood cell --> hemolysis
26
Hypertonic Solution
- Cell shrinks (loses H2O)
- ECF has lower [H2O] (higher OP) than ICF (cytosol)
- >0.9% NaCl e.g. 1.5%
- Uses:
- injecting 10% surges solution (hypertonic) will draw water into blood from tissues
- e.g. use to lower brain edema (swelling)
27
Osmosis Role in Regulation of [Solute]
- Concentration of solutes in body fluids must be maintained within narrow limits or cells will die
- Major body fluids:
1) Extracellular Fluids (ECFs):
- Blood Plasma
- Interstital Fluid (ICF)
2) Intracellular Fluid (ICF)
- E.g. if body loses H2O (sweat) => [blood] increases
- Blood OP increases = fluid moves from tissues into blood
- Response = thirst and lower renal H2O loss which leads to decreased urine production
28
Bulk Flow
- Movement of fluid (+solutes) due to pressure gradient (high pressure to low pressure)
- Hydrostatic pressure = P of a fluid pressing against a surface e.g. cell membrane, blood vessel wall (= blood pressure)
29
Example of Bulk Flow in Capillary
- If blood has higher pressure than ISF, fluid flows out of capillary (= FILTRATION)
- If ISF is higher pressure than blood, fluid flows from ISF into capillary (= ABSORPTION) (Flowing into)
30
Active Processes
- Require energy (ATP)
- Types:
1) Active Transport
a) Primary Active Transport
b) Secondary Active Transport
2) Vesicular Transport
31
Active Transport
- Substances move against concentration gradient (low to high)
- Always protein carrier-mediated
- Theres two different types
32
Primary Active Transport
- Molecular pumps - ATP breakdown is a direct part of transport process i.e. ONE protein breaks ATP and transports the solute(s)
- e.g. Na+/K+-ATPase - 3 Na+ out of cell and 2 K+ in per ATP
33
Secondary Active Transport
- Cotransport (2 proteins involved & use of ATP is indirect) i.e. one protein breaks down ATP (creating a Na+ gradient = stored energy) and another protein transport the solute(s)
- e.g. glucose entry at small intestine - 2 steps:
1) Na+ gradient established by Na+/K+-ATPase (=ATP-use step
2) Glucose & Na+ both must bind to carrier and are cotransported into the cell --> Na+ moving down its concentration gradient drives in glucose concentration gradient (= transport step) = glucose transport is active
34
Example of Secondary Active Transport
- e.g. glucose entry at small intestine - 2 steps:
1) Na+ gradient established by Na+/K+-ATPase (=ATP-use step
2) Glucose & Na+ both must bind to carrier and are cotransported into the cell --> Na+ moving down its concentration gradient drives in glucose concentration gradient (= transport step) = glucose transport is active
35
Vesicular Transport
- Substance is surrounded by a membrane within a cell (a vesicle)
- types:
1) Endocytosis
i) Phagocytosis
ii) Pinocytosis
2) Exocytosis
36
Endocytosis
```
Endocytosis - movement into a cell
i) Phagocytosis
- large items into cell (e.g. bacteria)
= "cell eating"
ii) Pinocytosis
- Fluids (+ dissolved substances)
"cell drinking"
```
37
Exocytosis
Exocytosis - movement out of cell
- Vesicles containing hormone, enzymes, neurotransmitter etc.
- Fuse with cell membrane, releasing contents into ECF (triggered by a rise in cytosolic Ca2+)
