BRS CELL PHYSIOLOGY EXAM QUESTIONS AND VERIFIED CORRECT ANSWERS 100% GUARANTEED PASS
What is phospholipid made of?
Phospholipids are made of a glycerol backbone (hydrophilic) and two fatty acid chains (hydrophobic)
What are examples of lipid-soluble substances?
Oxygen
Carbon dioxide
Steroid...
What is phospholipid made of?
Phospholipids are made of a glycerol backbone (hydrophilic) and two fatty acid chains
(hydrophobic)
What are examples of lipid-soluble substances?
Oxygen
Carbon dioxide
Steroid hormones
Can lipid-soluble substances cross cell membranes?
Yes, because lipid-soluble substances can dissolve in the hydrophobic lipid bilayer.
Fat-loving
What are examples of water-soluble substances?
Sodium
Chloride
Glucose
Water
Can water-soluble substances dissolve in the lipid of the membrane?
No, water-soluble substances cannot dissolve but may cross through water-filled
channels or pores or transported by carriers.
Water-loving
What are integral proteins?
Integral proteins are anchored to and imbedded in the cell membrane through
hydrophobic interactions.
It can span cell membrane.
How are integral proteins anchored to and imbedded in the cell membrane?
through hydrophobic interactions
What are examples of integral proteins?
,Ion channels
Transport proteins
Receptos
Guanosine 5'-triphosphate (GTP)-binding proteins
What are peripheral proteins?
Peripheral proteins are NOT imbedded in the cell membrane, NOT covalently bound to
membrane components, and are LOOSELY attached to the cell membrane by
electrostatic interactions.
How are peripheral proteins loosely attached to the cell membrane?
by electrostatic interactions
What are tight junctions or zonula occludens?
Tight junctions are attachments between cells (e.g. epithelial cells)
What is the function of tight junctions?
may be an intercellular pathway for solutes, depending on the size, charge, and
characteristics of the tight junction
Where is tight junctions may be tight or impermeable?
in the renal distal tubule
Where is tight junctions may be leaky or permeable?
in the renal proximal tubule and gallbladder
What are gap junctions?
Gap junctions are attachments between cells that permit intercellular communication.
Where can gap junctions be seen?
Gap junctions permit current flow and electrical coupling between myocardial cells
What are the different types pf transport across cell membranes?
DOWNHILL
- simple diffusion
- carrier-mediated diffusion
UPHILL
- primary active transport
,- cotransport
- countertransport
What are the characteristics of simple diffusion?
SIMPLE DIFFUSION
- not carrier-mediated
- occurs DOWN an electrochemical gradient
- does not require metabolic energy
- it is passive
What is the equation for diffusion?
J = - PA (C1-C2)
flux/flow (mmol/sec) = - (permeability in cm/s)(area in cm2) (concentration1 -
concentration2 in mmol/L)
What is permeability?
Permeability
- describes the ease with which a solute diffuses through a membrane
- depends on the characteristics of the solute and the membrane
What are the factors that increase permeability?
Factors that increase permeability:
1) increase oil/water partition coefficient of the solute > increase solubility of lipid
membrane
2) decrease radius (size) of the solute > increase diffusio coefficient and speed of
diffusion
3) decrease membrane thickness > decreases diffusion distance
What are examples of small hydrophobic solutes?
Oxygen and Carbon dioxide
- highest permeabilities in lipid membranes (smallest = highest)
What are examples of hydrophilic solutes?
Sodium and Potassium
- cross cell membranes through water-filled channels or pores or via transporters
- if solute is an ion (charged), flow depends on the concentration difference and
potential difference across the membrane
, What is carrier-mediated transport?
CARRIER-MEDIATED TRANSPORT
it includes facilitated diffusion and primary and secondary active transport
What are the characteristics of carrier-mediated transport?
CARRIER-MEDIATED TRANSPORT
- Stereospecificity - isomers can be distinguished
- Saturation - saturated carriers can increase transport rate causing increase in solute
- Competition - structurally related solutes compete for transport sites on carrier
molecules (e.g. Galactose is a competitive inhibitor of glucose transport in the small
intestine)
What are the characteristics of facilitated diffusion?
FACILITATED DIFFUSION
- occurs down the electrochemical gradient
- passive
- more rapid than simple diffusion
- carrier-mediated and exhibits stereospecificity, saturation, and competition
What is an example of facilitated diffusion?
Glucose transport in muscle and adipose cells > downhill, carrier-mediated, and
inhibited by galactose
- In DM, glucose uptake by muscles and adipose cells is impaired because the carriers
of facilitated diffusion of glucose require INSULIN
What are the characteristics of primary active transport?
PRIMARY ACTIVIE TRANSPORT
- occurs AGAINST electrochemical gradient
- requires ATP
- active
- carrier-mediated and exhibits stereospecificity, saturation, and competition
What are the examples of primary active transport?
1) Na/K-ATPase (Na-K pump)
2) Ca-ATPase (Ca pump)
3) H/K-ATPase (proton pump)
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