Topic 2 Cell Physiology Flashcards
What are some types of extracellular molecules that receptor proteins can bind?
Hormones, neurotransmitters
Ligand
Molecules that bind to a receiving proteins
Describe the steps of glucose uptake in terms of receptor proteins
1- insulin binds to receptor on skel.muscle or adipose tissue
2- triggers movement of more glucose transporters to cell membrane
3-increase in glucose movement from blood into cells
Membrane proteins: enzymes
Control chemical reactions on outer or inner surface
What are 2 enzymes
1-acetylcholinesterase- breaks down Ach
2-Na+/K+-ATPase
Membrane proteins: Linker proteins
Anchor cell membrane to cytoskeleton or an adjacent cell
What do junctional proteins between cells form?
Desmosomes, tight junctions, gap junctions
How do linker proteins anchor in the ECF?
Through extra cellular fibres that are usually glycoproteins
Membrane proteins: identifying proteins
Example: Major Histocompatibility Complex proteins identify cell as part of the body and foreign. They’re present in all cells except rbcs
Membrane carbohydrates function
Allow cells to recognize type- sperm recognizes egg
Membrane carbohydrates are
Glycoproteins and glycolipids
Transport proteins includes
Channels and carrier proteins
Channels
Selectively permit channel-mediated facilitated diffusion of specific ions
Gated channels open and close how?
In response to stimuli
Non-gated channels are also called what?
Leakage channels
Carrier protein function
Bind solute and carry it across membrane
What type of transport happens with carrier proteins
Active transport and facilitated transport
What’s an example of a carrier protein
Glucose transporters
Phospholipid bilayer
Continuous layer across membrane that is a barrier to water soluble molecules and not to small or lipid soluble molecules
Membrane transport is?
The movement of material between the intra and extracellular fluid
Solute
Substance dissolved in a solution
Solvent
Substance solute is dissolved in-> water
What are the types of transport
Passive transport and Active transport
Does passive transport require energy?
No it doesn’t require ATP
Passive transport moves down its concentration gradient, in other terms?
It moves from high to low concentration
What are the types of Passive transport
Simple diffusion, facilitated diffusion, facilitated transport and Osmosis
Which type of passive transport involves the movement of a solvent?
Osmosis
Simple diffusion
Small lipid soluble (O2 and CO2) molecules cross through cell membrane bilayer
Facilitated diffusion
Ions diffuse through membrane through protein channels
Facilitated transport
Large charged or water soluble molecules move across membrane with the help of carrier proteins
What’s an example of facilitated transport
Glucose uptake into liver or skeletal muscle cells
Osmosis
Movement of H2O across a semipermeable membrane
In osmosis, water move where?
Down its concentration gradient via pores or directly across the membrane layer
Dilute solution
High H2O and low solute
Concentrated solution
Low H2O and high solute
Osmotic pressure
Pressure that must be applied to prevent movement of H2O from pure H2O solution across a semipermeable into another solution
If S2 has high salt concentration then H2O will move into it why?
Because s2 has low H2O concentration and H2O moves from high concentration low concentration
The greater the salt in a solution the greater the osmotic pressure that is?
Required to stop the water in S1 from moving into S2
What happens when S2 is also pure water
No P required to prevent H2O movement so OP=0
Tonicity depends on
Solute concentration and permeability of cell membrane to the solute
Isotonic solution
Cell neither swells no shrinks
In a red blood cell what is the solute concentration in ICF
0.9% saline NACL solution
Hypotonic solution
Cell swells and ECF has higher H2O concentration (so lower OP) than ICF.
Lysis
Swelling of cell in a hypotonic solution causes rupture
Hemolysis
Lysis of a red blood cell
Hypertopic solution
Cell shrinks due to H2O loss
Why does cell shrink in a hypertonic solution
Because if the ECF has lower H2O concentration and the ICF has higher water will move from high to low concentration
When is hypertonic solution used in medicine
To reduce brain edema (swelling) by injecting 10% sucrose solution will draw water into blood from tissues
What are the major body fluids ?
- Extracellular fluids such as blood plasma
2.Interstitial fluid
3.Intracellular fluid
Give an example of how osmosis regulates the concentration of a solute in our body in order to maintain body fluids within a narrow limit to prevent cells from dying?
When body loses water (such as sweat) the blood concentration will increase. Blood has higher OP cause blood is also a solute so when solute increases so does OP. Fluid will move from tissue into blood. The response will be thirst and a decrease in renal H2O which leads to decreased urine production.
What is bulk flow?
Movement of solvent + solutes due to hydrostatic pressure gradient
What is hydrostatic pressure?
P of a fluid pressing against surface e.g. cell membrane, blood vessel wall (=blood pressure)
Give an example of hydrostatic pressure in the body
e.g: capillary
-> if blood has higher pressure than ISF, fluid flows out of capillary= filtration
-> if ISF has higher pressure than blood, fluid flows from ISF into capillary = absorption
What are the active processes?
Active transport and vesicular transport
What’s active transport
Substances move against concentration gradient (low to high) and it is always protein carrier-mediated
What are the types of active transport
1-primary active transport
2-secondary active transport
Primary active transport
They are molecular pumps, ATP breakdown is a direct part of the transport process
So one protein breaks down ATP and also transports the solute
What’s an example of primary active transport
Na+/K+-ATPase that pumps 3Na+ out of the cell and 2K+ in per ATP
Secondary active transport
Co transport- meaning 2 proteins are involved and the use of ATP for the transport is indirect
Example of secondary active transport
Glucose entry at small intestine- two steps
1- Na+ gradient established by Na+/K+-ATPase
2- glucose & Na+ both must bind to carrier and are cotransported into cell
Vesicular transport
Substance is surround by a membrane within the cell (vesicle)
Types of vesicular transport
1- endocytosis movement into a cell
2-exocytosis movement out of cell
Phagocytosis
Large items into cell ( bacteria ) = cell eating
Pinocytosis
Fluids and dissolved substances = cell drinking
Exocytosis
Vesicles containing hormone, enzymes, nt
They tissue with cell membrane releasing contents into ECF- triggered by a rise of cytosolic Ca++
