Cell Membranes And Transport - DSA Flashcards
Role of Cell Membranes
- Protective barrier
- selective permeability
- transport
Membrane composition
- Lipid Bilayer. Hydrophobic core hydrophilic surfaces
- Carbohydrates are covalently attached to some membrane lipids
- has lipds and proteins attached.
Phospholipids
- Most abundant lipids in biological membranes
Describe the two types of phospholipids and give examples of each.
- Glycerophospholipids: glycerol backbone + phosphate + 2 FA’s
- Phosphatidylserine, phosphatidylcholine. - Sphingolipids: sphingosine backbone + long chain FA + phosphorylcholine.
- Sphingomyelin
Function and products of sphingomyelinase
- cleaves sphingomyelin
- cleavage results in phosphorylcholine + Ceramide
Describe the structure of glycolipids. Where are they found?
- Sphingosine backbone with carbohydrate residues
- found in the outer leaflet
Location of Membrane Lipids. What is found in the inner sheet vs. outer sheet?
- Inner: phosphatidylinositol, phosphatidylserine, phosphatidylethanolamine.
- Outer: Phosphatidylcholine, sphingomyelin, glycolipids.
What are the three types of membrane proteins and how are they held to the membrane?
- Integral membrane proteins: hydrophobic interactions
- Peripheral proteins: electrostatic interactions w/ lipids or proteins
- Lipid-anchored proteins: covalently tethered to lipid.
What is the glycocalyx and what are its 3 functions?
Carbohydrate molecules covalently attached to proteins and lipids that face extracellular space
- Protection
- Cell adhesion
- Cell identification.
Factors that influence fluidity:
- Higher temperature = higher fluidity
- Saturated lipids decrease fluidity. Shorter chains increase fluidity
- Cholesterol: makes stiff membranes fluid and fluid membranes stiff.
Ion Gradients of Na, K, and Cl. Which is higher inside or outside of the cell?
- Na = higher outside cell
- K = higher inside cell
- Cl = higher outside of the cell
Types of Passive transport:
- Simple Diffusion = unaided. Small non-polar molecules diffuse freely across the membrane.
- Facilitated diffusion = needs a facilitator like channel or transporter
Types of Active Transport
- Primary: uses ATP directly
- Secondary: uses energy stored in concentration gradient.
Describe a P type ATPase
- Type of primary active transport.
- atp is hydrolyzed, protein gets phosphorylated
Describe ABC transporters
- atp is hydrolyzed, does NOT phosphorylate the transporter
Describe Secondary Active Transport
- energy dependent, moves molecules against concentration gradient.
- source of energy is not ATP hydrolysis.
- unfavorable flow of 1 species tied to favorable flow of another species.
- EX: SGLT, NCX
Describe Sodium Glucose Transporter 1
Location, function, molecule it moves
- located in epithelial cells of intestine and renal tubules
- mediates unidirectional movement of Na+ (favorable) and glucose (unfavorable) across small intestine and renal tubule.
- Na+ gradient is reset by Na+/K+-atpase.
- type of secondary active transport.
Na+/Ca+ exchanger (NCX) function, location,etc.
- Antiporter
- imports 3 Sodium down their gradient and exports 1 calcium against its gradient.
- Type of Secondary active transport
Describe transport of glucose from lumen of intestines to blood.
- Glucose & galactose move against their gradient with sodium into the enterocyte using SGLT1.
- Sodium is returned to blood via Na/KATPase
- glucose, galactose, and fructose (brought in by glut5 via facilitated diff) are transferred to blood via GLUT2 (facilitated diffusion)
