Membranes Flashcards
What are cell membranes formed from?
A phospholipid bilayer
What does the molecule have?
A head and tail
The head is hydrophilic which means it is what?
Water loving (phosphate part)
The tail is hydrophobic which means what?
Water fearing (lipid part)
The inside and outside of a cell is mostly water, so the phospholipid molecule take on what?
A specific orientation
What else does the membrane contain that spans the whole cross-section?
Proteins; transmembrane proteins
The membrane is what?
Not static, the molecules are not fixed in place
Because the molecules are not static, they are allowed to do what?
Freely slide and drift around and past one another
What does the cell membrane follow?
The fluid mosaic model
What is facilitated diffusion?
A type of passive transport
What is facilitated diffusion used for?
The movement of large molecules across the membrane with the help of transmembrane proteins
What are the two types of transmembrane proteins?
Carrier proteins and channel proteins
What are carrier proteins?
Act as a lock where a molecule is the key, only one type of molecule can work, the molecule fits in a shape specific region of the proteins which induces a conformational shift in the proteins, this transports the molecule across the membrane (no energy required)
What are channel proteins?
Essentially a tunnel that let ions and water through, stuff substance specific
What is active transport?
The opposite of passive transport
Where do molecules move in active transport?
From an area of low concentration to an area of high concentration
The movement of active transport is?
Against the concentration gradient
Is energy required for active transport?
Yes, ATP
What kind of molecules simply do active transport?
Small molecules (pumps)
Large molecules are transported across the membrane in what?
Vesicles (formed from the cell membrane pinching in or by the Golgi)
What is exocytosis for?
Secretion and waste removal; a vesicle moves toward the cell membrane, fuses with it and releases its contents
What is endocytosis for?
To move large substances into the cell; solids by phagocytosis (eating) and liquids by pinocytosis (drinking)
What is the function of the membrane?
Regulating the movement of substances into and out of a cell
What are cells?
Semi-permeable; some substances can move in + out while others cannot
What can slip directly between the phospholipid molecules?
Small molecules
Large molecules and water must use what to cross the membrane?
Transmembrane proteins
What is Brownian motion?
Particles are in constant random motion
What is the concentration gradient?
The difference in concentration between two areas
What is equilibrium?
When two areas have equal concentrations
What is passive transport?
When molecules move across the membrane from an area of high concentration to low concentration
What type of movement on the concentration gradient is passive transport?
Down the concentration gradient; doesn’t require energy
T or F; The way one type of substance undergoes passive transport is independent of other substances
True
What is diffusion?
Basic passive transport
What is osmosis?
A special term for the passive transport of water; through specialized transmembrane proteins called aquaporins
What are related terms?
Used to describe the relationship between the concentration of two areas
What does hypotonic mean?
An area with less concentration
What does isotonic mean?
When two areas have equal concentrations
What does hypertonic mean?
An area with greater concentration
What tends to happen to hypertonic areas?
They tend to gain water
What tends to happen to hypotonic areas?
They tend to lose water
What happens at equilibrium?
Molecular movement continues, it just means that the rates forward and back are equal
What can happen to cells in the extreme?
A cell could shrivel or burst
