Chapter 7: Membrane Structure and Function Flashcards
What are saturated fatty acid tails about how do they affect membrane fluidity?
- Phospholipids
- They have a regular structure
- Single bonds between carbons
^ closely packed, therefore less fluid
If there’s more saturated fatty acid tails, the membrane is _____ fluid.
Less
What are unsaturated fatty acid tails about how do they affect membrane fluidity?
- Phospholipids
- They have kinks
- Double bonds between carbons
^ loosely packed, therefore more fluid
If there’s more unsaturated fatty acid tails, the membrane is _____ fluid.
More
What is the purpose of cholesterol in the membrane?
Helps maintain fluidity
How and when does cholesterol decrease fluidity?
At warm temperatures when the membrane is too fluid, cholesterol will get in the way of the fatty acid tails and they will bump into each other, decreasing the fluidity.
How and when does cholesterol increase fluidity?
At cold temperatures when the membrane is rigid, cholesterol gets in the way of phospholipids and prevents them from touching and becoming too rigid, increasing fluidity.
What is a transmembrane (integral) protein?
Large proteins that sit through the membrane
- have hydrophobic and hydrophilic regions
What are peripheral proteins?
Smaller proteins that either sit on the inside of the membrane (towards the cell) or the outside of the membrane (towards the outside).
(Never actually inside the membrane phospholipid bilayer)
- hydrophilic
What factors affect membrane fluidity?
- Concentration of unsaturated phospholipids
- Concentration of cholesterol
- Protein content
- more proteins = less fluid
- less proteins = more fluid
- Temperature
- high temp = more fluid
- low temp = less fluid
What characteristics do substances need to have in order to permeate through the membrane?
- small
- nonpolar / hydrophobic
- no charges
What is passive transport?
Solutes move from high to low
- Does not require energy
From:
•• |
•• | H2O
•• |
To:
• | •
• | •
• | •
Na+ ions flow directly across the plasma membrane faster than CO2
True or false
False
Na+ is polar.
Therefore, hydrophobic.
Therefore, it is problematic and will flow slower than CO2.
Why can’t water do passive transport? What does it do instead to cross the membrane?
Because water is polar, hydrophilic, and it had charges.
Therefore, it does Osmosis.
What is osmosis?
When water diffuses from the solution with lower concentration of solute to the solution with higher concentration of solute
Water moves from:
High conc. —> low conc.
What does it mean when the environment is hypotonic to the cell?
- more solute inside of cell
- water moves INTO the cell
- eventually will do lyses (burst)
What does it mean when the environment is isotonic to the cell?
There is equal amounts of water and solute inside and outside of the cell
- nothing happens
What does it mean when the environment is hypertonic to the cell?
- more solute outside of cell
- water moves OUT of the cell
- eventually will shrivel
What is active transport?
When solutes move against their concentration gradients.
(Low to high)
- Requires energy
From:
• | ••
• | ••
• | ••
To:
| •••
| •••
| •••
Describe the process of the Na+/K+ pumps in active transport.
- Inside the cell:
- low Na+
- high K+
- The protein opens and 3 Na+ go in
- ATP is required to rotate the protein to facing the outside of cell.
- Na+ leaves the protein. 2 K+ enters.
- ATP rotates the protein to face the inside of the cell.
- K+ leaves the protein and enters the cell.
- Inside the cell:
- high K+
- no Na+
Outside the cell: - high Na+
- no K+
After one cycle of a sodium and potassium active transport, would the inside of the cell be positive or negative?
Negative
There are 3 Na+ on the outside of the cell and 2 K+ on the inside (3:2). Therefore, the cell is considered to be less positive, which means negative.
What is cotransport?
When two solutes are simultaneously transported through the membrane by one protein.
Eg, Na+ and sugar will simultaneously bind to the protein from the outside of the cell and transport inside.
- to keep the inside of the cell negative, an Na+/K+ pump will transport Na+ back outside.
What does it mean when molecules diffuse down their concentration gradients?
High to low
Passive transport
What does it mean when molecules move against their concentration gradients?
Low to high
Active transport
When large proteins are trying to enter the cell, but they are too big for passive/active transport, what do they do instead?
Endocytosis
When large proteins are trying to exit the cell, but they are too big for passive/active transport, what do they do instead?
Exocytosis
Do endocytosis and exocytosis require energy?
Yes
What are the 3 types of endocytosis?
- Phagocytosis
- Pinocytosis
- Receptor-mediated Endocytosis
What is phagocytosis?
Food comes in contact with the Pseudopodium of the membrane and enters the cell
Taken to lysosome to be digested
What is pinocytosis?
Solute comes in contact with the membrane and proteins create a coat around the caved part of the membrane
The coat protein with the solute completely enters the cell and becomes a coated vesicle containing solute
What is receptor-mediated endocytosis?
Solute binds to receptors in the membrane
A protein coat vesicle will begin to form and cave in the membrane
The protein coated membrane cave breaks off as a vesicle and goes inside the cell
Cholesterol travels in the blood as _____.
LDL
How does cholesterol enter the cell?
Through receptor-mediated endocytosis
LDL binds to LDL receptors inside the caved protein coat
(The receptors tell the cell that the LDL is coming)
The protein coated membrane cave breaks off as a vesicle and goes inside the cell
An LDL receptor is a ________ biomolecule.
Protein
What would you expect would happen in a person whose LDL receptors are defective?
A. Cholesterol accumulates in the cell
B. Cholesterol accumulates in the blood
C. Cholesterol levels in the blood go down
D. The person needs to eat more cholesterol in their diet
B
LDL will not get taken in by the LDL receptors and it will accumulate in the blood
Why night receptors be defective?
- wrong shape
- not enough of them
- wrong location/orientation
