Chapter 7 Flashcards
Why do cells need to move substances through their membrane?
To bring in nutrients, oxygen, and water and to release wastes, carbon dioxide, and excess water
What is a phospholipid?
A lipid made up of glycerol joined to two fatty acids and a phosphate group.
What chemical properties of the phospholipid are important to a plasma membrane?
The hydrocarbon chains of the fatty acids act as non-polar, hydrophobic tails while the rest of the molecule acts as a polar, hydrophilic head.
Why are phospholipids called amphipathic
They have both hydrophilic and hydrophobic parts.
What is a plasma membrane?
The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell’s chemical composition.
Name and describe the components of a phospholipid bilayer.
- Contains a phosphate group and two fatty acid chains.
- The phosphate heads are polar + hydrophilic and the tails are nonpolar + hydrophobic
How do phospholipids form the bilayer?
The heads face the water while the tails face each other, creating a bilayer.
In what kind of solvent does the process of phospholipids forming a bilayer occur?
Occurs in water
What’s the difference between a saturated and an unsaturated lipid?
Saturated lipids are solid at room temperature, while unsaturated lipids are not.
In what way is the phospholipid bilayer “fluid”?
unsaturated hydrocarbon tails cannot pack closely making the membrane more fluid.
What effect does cholesterol have on a membrane?
Cholesterol affects it by not allowing the phospholipids to rotate, flex or move around as efficiently.
What is meant by selective permeability?
a substance which allows only certain materials to pass through it.
What types of solutes pass easily across the lipid bilayer?
Small nonpolar molecules
Which cross the lipid bilayer only to a limited extent?
Small uncharged polar molecules
Which cannot cross the lipid bilayer at all?
Charged molecules
Can solutes enter a cell? If so, how?
Yes, through transport proteins
Osmosis
the diffusion (high to low concentration) of water across a selectively permeable membrane
Diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration.
Concentration gradient
the process of particles moving through a solution from an area of higher number of particles to an area of lower number of particles.
Equilibrium
A system in a steady state since forward reaction and backward reaction occur at the same rate.
In what direction does the net movement of water occur when a cell is placed in a hypertonic solution?
water moves out of the cell
In what direction does the net movement of water occur when a cell is placed in an isotonic solution?
no movement
In what direction does the net movement of water occur when a cell is placed in a hypotonic solution?
water moves into the cell (cell could burst)
How a hypertonic solution affects animal cells
it results in crenation where the shape of the cell becomes distorted and wrinkled and water leaves the cell.
