Exam 1: Lipids, membranes, and cells Flashcards
What is the polarity of lipids?
Non-polar
What are the three types of lipids?
Fats, Steroids, Phospholipids
How do lipids form?
Dehydration reactions (remove a water)
What is a fatty acid? What does it look like?
A simple lipid
Hydrocarbon chain bonded to polar carboxyl functional group (-COOH)
What is the difference between a saturated fatty acid and an unsaturated fatty acid?
Unsaturated fatty acids have double bonds
What is the effect of a double bond on the structure of a fatty acid?
There is a kink
Do saturated fatty acids or unsaturated fatty acids have a higher boiling point?
Saturated fatty acids
What is a glycerol?
3 carbon chain; each carbon bonded to a hydroxyl
What is the structure of a fat?
A glycerol linked to three fatty acids
How are fats formed?
Ester linkages; dehydration synthesis b/t hydroxyl group of GLYCEROL and carboxyl group of free FATTY ACID
What is the structure of steroids?
Four carbon rings with a hydroxyl group
What are steroids derived from?
Cholesterol
Why are steroids slightly soluble in water?
They have a hydroxyl group
What are the three components of a phospholipid?
Phosphate group, glycerol, two fatty acids
What makes up the polar (hydrophilic) head of a phospholipid?
Phosphate group
What makes up the nonpolar (hydrophobic) tail of a phospholipid?
Fatty acid
What are the two main components of the cell membrane?
Steroids and phospholipids
What are the three mechanisms of membrane transport?
- Diffusion
- Facilitated diffusion
- Active transport
Rank the four types of molecules in order of decreasing membrane permeability:
- Small, nonpolar molecules (O2, CO2)
- Small, uncharged, polar molecules (H2O, glycerol)
- Large, uncharged, polar molecules (glucose)
- Ions (Cl-)
What are four factors that affect membrane permeability?
- Number of double bonds on the fatty acids
- Length of the tail
- Number of cholesterol molecules (more cholesterol = less permeable
- Temperature
What is diffusion?
Molecules moving from high concentration to low concentration
Does diffusion move along or against the concentration gradient?
Along
What happens when equilibrium is reached?
Still movement of molecules, but no net change
If temperature is increased, what happens to diffusion rate through a membrane?
Increases
If molecular weight is increased, what happens to diffusion rate through a membrane?
Decreases
If the steepness of the concentration gradient increases, what happens to diffusion rate through a membrane?
Increases
If the membrane surface area increases (more gaps/spread out), what happens to diffusion rate through a membrane?
Increases
If membrane permeability increases, what happens to diffusion rate through a membrane?
Increases
What is osmosis?
Special case of diffusion in which water moves across selectively permeable membrane; can occur through lipid bilayer or aquaporins
Water moves from regions of _____ to regions ______
low solute concentration to high solute concentration
What is meant by isotonic?
Equal water and solute concentrations on either side of the membrane
What is meant by hypertonic?
Solute concentration is higher on one side of the membrane
What is meant by hypotonic?
Solute concentration is lower on one side of the membrane
If the inside solution is hypertonic to the outside, what happens?
Water flows to the inside causing the vesicle to burst
If the inside solution is hypotonic to the outside what happens?
Water flows to the outside causing the vesicle to shrink
Does passive transport require ATP? Active transport?
No. Yes.
Where are peripheral membrane proteins located?
One side of the membrane
Where are integral membrane proteins located?
In the membrane
What is another name for integral proteins?
Transmembrane proteins
What type of protein are transport proteins?
Integral proteins
What are the three classes of transport proteins?
- Channels
- Carrier proteins
- Pumps
How do ions cross the membrane?
Ion channels or pumps
What occurs when ions build up on one side of a plasma membrane?
Electrochemical gradients
What is an electrochemical gradient?
A combination of a concentration and charge gradient
What channel protein facilitates the movement of water through a membrane?
Aquaporin
What are gated channels?
Open or close in response to a signal
What is facilitated diffusion? How can it occur? (2 ways)
The passive transport of substances that would not otherwise cross the membrane
Can occur through channels or transporter/carrier proteins
What are the steps for facilitated diffusion via transporter/carrier proteins? (like GLUT-1)
- Unbound protein
- Desired molecule binds
- Protein undergoes conformational change
- Release of desired molecule
What is the sodium-potassium pump an example of?
Active transport
What are the 8 steps of the sodium potassium pump?
- Unbound pump
- 3 Sodium bind
- Pump undergoes shape change as P from ATP binds
- 3 Sodium released outside
- Unbound pump
- 2 Potassium bind
- P releases causing shape change
- 2 Potassium released
What do ATP driven ion pumps generate?
Ion electrochemical gradients
How does secondary active transport/cotransport work?
Pumps move materials against concentration gradient => sets up electrochemical gradient => electrochemical gradient provides potential energy to power movement of another molecule against its particular gradient
