Studied by 8 people
What does the plasma membrane do?
regulates what enters and exits the cell
What makes up the phospholipid bilayer?
hydrophilic polar heads & hydrophobic non polar tails made up of two fatty acids
hydrophobic nonpolar tails are made of
two fatty acids
What does cholesterol do in plasma membrane?
stabilizes the interactions between the phospholipids and prevents the membrane from getting too fluid or too flexible
What does hydrophilic mean?
water-loving
What does hydrophobic mean?
water-fearing
What are two types of membrane proteins?
peripheral and integral
Where are peripheral proteins found?
only on one side of the membrane
Where are integral proteins found?
found on one or both sides of the membrane
Which membrane protein can move laterally?
integral proteins
How is it possible for molecules to get through the phospholipid bilayer?
membrane is semipermeable
What are 3 factors that determine how a substance will be transported across the membrane?
size, polarity, charge
What is a concentration gradient?
the region along which the density of a substance increases or decreases
What does "going down" a concentration gradient mean?
going from an area of high to low concentration
What does "going up" a concentration gradient mean?
going from an area of low to high concentration
Does going up (low to high) a concentration gradient require energy?
yes
What types of molecules move freely across the membrane?
water
small molecules
noncharged molecules
What other method will water use to cross the membrane?
aquaporins
Other molecules use what 3 methods to cross the membrane?
channel proteins, carrier proteins, vesicles
What two specific methods to vesicles use?
endocytosis and exocytosis
What is diffusion?
movement of molecules from area of higher to lower concentration
In a solution what two things are present?
a solute (solid) and a solvent (liquid)
Can gases also diffuse across a membrane?
yes
Give an example of diffusion of gases in the body.
oxygen and carbon dioxide exchange in the lungs
List four factors that influence the rate of diffusion.
concentration gradient, membrane permeability, temperature, and pressure
Electrical currents
movements of ions across cell membrane that are driven by electrochemical gradients
Molecular size
As temperature increases does the rate of diffusion increase or decrease?
increase
What is osmosis?
diffusion of water across a semipermeable membrane
In diffusion what is always the direction the concentration will go?
from higher to lower concentration
What is osmotic pressure?
pressure that develops in a system due to osmosis
The greater the osmotic pressure the more likely or less likely water will diffuse in that direction?
more likely
What is an isotonic solution?
solute concentration equal inside and out cell
What is a hypotonic solution?
a solution that has lower solute concentration than inside the cell
What is a hypertonic solution?
a solution that has a higher solute concentration inside the cell
In a hypotonic solution a cell may ____?
lysis (burst)
In a hypertonic solution a cell may _____?
crenate (shrivel)
Are carrier proteins specific or nonspecific?
specific
How do carrier proteins transport a molecule across the membrane?
carrier proteins combine with a molecule
What two methods are carrier proteins required for?
facilitated transport and active transport
What types of molecules are associated with facilitated transport?
small molecules that are not lipid-soluble
What is a concentration gradient?
the region along which the density of a substance increases or decreases
Is energy required in facilitated transport?
no
What happens in active transport?
molecules combine with carrier protein which uses energy to move against their concentration gradient
What are these carrier proteins called in active transport?
pumps
What is the function of vesicle formation?
membrane-assisted transport
Why is a vesicle required to transport macromolecules?
to keep it contained
What do vesicles transport?
macromolecules
Does vesicle formation require energy?
yes
What are two types of vesicle transport?
exocytosis and endocytosis
What happens in exocytosis?
vesicle fuses with plasma membrane and secretion occurs
What happens in endocytosis?
a process by which cells take in substances from outside the cell, such as macromolecules, particles, and other cells, to inside the cell
What happens to the membrane of the vesicle when it fuses with the plasma membrane?
it becomes part of the plasma membrane
What are there types of endocytosis?
phagocytosis, pinocytosis, and receptor mediated endocytosis
When is phagocytosis used?
when you have large separate matter
When is pinocytosis used?
when you have liquids or small particles dissolved in liquid
What is receptor mediated endocytosis?
a form of endocytosis in which receptor proteins on the cell surface are used to capture a specific target molecule
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