Movement Across Membranes Flashcards
What is diffusion?
Diffusion is the movement of molecules from higher concentration to a lower concentration
Does diffusion require energy?
No
What can affect the rate of diffusion?
Concentration gradient, distance moved, surface area, barriers, temperature
What is simple diffusion?
Molecules can move directly through the membrane without assistance
What are examples of molecules that use simple diffusion?
Oxygen diffuses into the blood and carbon dioxide diffuses out of the blood
What is facilitated diffusion?
Carrier proteins allow large lipid-insoluble molecules that cannot cross the membrane by simple be transported into the cell
What is an example of a molecule that requires facilitated diffusion?
The transport of glucose into red blood cells
Does facilitated diffusion require energy?
No
What is channel-mediated facilitated diffusion?
Channels (hydrophilic pores) in the membrane allow inorganic ions to pass through the membrane
What is an example of a molecule requiring channel-mediated facilitated diffusion?
Potassium ions exiting nerve cells to restore resting potential
What do simple diffusion, facilitated diffusion and channel-mediated facilitated diffusion have in common?
None require energy
What is active transport?
Active transport uses energy to transport molecules against their concentration gradient across a partially permeable membrane
Where does the energy required for active transport come from?
ATP
What does ATP stand for?
Adenosine Tri Phosphate
Why does active transport require energy?
Because molecules are being moved against their concentration gradient
What is the difference between primary and secondary active transport?
For primary active transport ATP is used directly whereas for secondary energy is stored in the concentration gradient
Is ATP directly used in secondary active transport?
No
What is the function of a cell wall?
Provides strength and a fixed shape
What structures make up the plasma membrane?
Phospholipids, proteins, cholesterol, glycoproteins, glycolipids
What are the functions of glycoproteins?
Play an important role in cellular recognition and immune responses. Helps stabilise the membrane structure
What is the function of glycolipids?
They act as surface receptors and stabilise the membrane. Also have the role in helping cells aggregate in the formation of tissues
Where are peripheral proteins located on the membrane?
Are stuck to the surface of the membrane
What is the function of cholesterol in the membrane?
Cholesterol disturbs the close packing of phospholipids and keeps the membrane more fluid
What is the plasma membrane made up of?
Phospholipid bilayer
Is the head of a phospholipid hydrophilic or hydrophobic?
hydrophilic
What is hydrophilic?
Water attracting
What is hydrophobic?
Water repelling
What is the tail of a phospholipid made up of?
Fatty acids
What is the head of a phospholipid made up of?
An alcohol and phosphate group
Are the two tails of a phospholipid hydrophilic or hydrophobic?
Hydrophobic
What are 4 functions of the plasma membrane?
- allows substances in and out of the cell
- cellular communication
- transports materials
- surround cell organelles
What if the function of integral proteins?
Helps to transport certain materials across the membrane
What are the two types of transport across membranes?
Passive or active
What is the difference between passive and active transport?
Passive transport does not require energy whereas active requires ATP to occur
What is passive transport?
The movement of particles from a high concentration to a low concentration. Movement is down the concentration gradient.
What are examples of passive transport?
Diffusion, facilitated diffusion, osmosis
What is active transport?
The movement of particles against the concentration gradient. This means from low to high concentration
What is an example of active transport?
Sodium pumps
When is equilibrium reached?
When the concentration of molecules on each side of the membrane are equal at this point net movement stops
What is osmosis?
Osmosis is the diffusion of water molecules across a partially permeable membrane from a region of higher to lower concentration of water molecules
What is osmotic potential?
The tendency for water to move across a membrane based on te solute concentration
Does osmosis require energy?
No
What is a solvent?
The substance that does the dissolving
What is the universal solvent?
Water
What is a solute?
The particles being dissolved eg. sugar, salt
What is solute concentrations?
The amount of solute in a given solution
What is an isotonic solution?
Two solutions containing the same concentrations of solutes
What is a hypotonic solution?
A solution with less concentration of solutes than the solution in the cell
What is a hypertonic solution?
A solution with more concentration of solutes than the solution in the cell
What happens to a hypotonic cell?
Swells
What happens to a hypertonic cell?
Shrinks
Why does active transport require energy?
Because the materials are moving against their concentration gradient
What is the function of transport proteins?
Harness the energy of ATP to pump molecules from a low to high concentration
What is exocytosis?
The movement of large amounts of materials to the outside of the cell
What is endocytosis?
The intake of large molecules by the cell
What are the two types of endocytosis?
Pinocytosis and phagocytosis
What is pinocytosis?
The intake of fluids
What is phagocytosis?
The intake of solids
Does endocytosis and exocytosis require energy?
Yes
What does a glycoprotein enable?
Cell to cell communication
