Chapter 5: Membranes: The Interface Between Cells and Their Environment Flashcards
What are the 2 primary components that make up membranes?
phospholipids and proteins
What is the key feature of the phospholipid bilayer ?
It’s amphipathic; hydrophilic heads face outward and hydrophobic tails face inward
TRUE OR FALSE: Lipids and proteins work against each other
FALSE, lipid and proteins work together to carry out various functions in a cell.
What is the main characteristic of a TRANSMEMBRANE PROTEIN?
A transmembrane protein spans to both layers (leaflets) of the phospholipid bilayer
Where is a lipid-anchored protein located ?
They are located in HYDROPHOBIC areas of the membrane; the amino acid of the protein is covalently attached to a lipid
Where are peripheral membrane proteins located ?
They are either non-covalently bonded to parts of other proteins or located in the hydrophilic(polar) regions of the phospholipid bilayer.
What are the two integral proteins ?
Transmembrane proteins and lipid-anchored proteins; they are integrated into a hydrophobic region of the phospholipid bilayer.
Is the structure of a membrane fluid?
It’s semifluid; lipids and proteins can move in 2 dimensions within the plane of the membrane
How does the length of non polar tails affect the fluidity of a membrane?
The shorter the tail, the less likely they are to interact thus creating a more fluid membrane
How does the presence of double bonds effect fluidity ?
Double bonds prevent phospholipids from packing tightly, making it more fluid.
Define SELECTIVE PERMEABILITY
Membranes allow some molecules and ions to pass but not all; allows cells to maintain a favorable internal environment.
How does simple diffusion move ?
down the gradient WITHOUT the use of a transport protein
How does facilitated diffusion move?
Down the gradient WITH the use of a transport protein
What makes active transport different from simple and facilitated diffusion ?
Substances move AGAINST the gradient, WITH aid of a transport protein AND requires energy
When is a gradient present?
When concentration solute is uneven from one side to the other.
Why do cells have gradients ?
to maintain internal and external environment
What is a solution called when it has the SAME concentration on both sides of the membrane ?
ISOTONIC
What is a solution called when it has HIGHER concentration on the outside than the inside of the membrane ?
HYPERTONIC
What kind of solution has LOWER concentration on the outside of the membrane ?
HYPOTONIC
What is the term for water diffusion across a membrane from high to low?
Osmosis
What are the two types of passageways for cells to interact ?
Channels and Transporters
What is the difference between channels and transporters ?
Transporters have specific binding sites for ions, and they go through structural changes.
What is the difference between PRIMARY active transport and SECONDARY active transport?
Primary active transport directly uses ATP while secondary uses stored ATP
What is the function of a gap junction? What about plasmodesmata?
Gap junctions (in animal cells) provide passageways for intercellular transport; plasmodesmata (in place cells) are channels that connect the cytoplasm of adjacent cells
An animal cell is placed in pure water (which contains no solutes). In what direction will water move?
Water will move into the cell from the outside because water moves from areas of high free water concentration to areas of lower water concentration.
What is this an image of? Label 1-9.
This is a close up of a phospholipid bilayer. 1) integral membrane protein, 2) glycoprotein, 3) glycolipid, 4) carbohydrate, 5) phospholipid bilayer, 6) extracellular leaflet, 7) cytosolic leaflet, 8) cholesterol, 9) peripheral membrane proteins
T or F: The two leaflets of a lipid bilayer are formed because the non polar phospholipid tails can interact with the polar interior and the exterior of the cell.
FALSE; the POLAR head groups of the phospholipids can interact with the polar interior and exterior of the cell
What is this an image of? Label 1-4.
This is a close up of the phospholipid bilayer. 1) transmembrane protein, 2) lipid, 3) lipid-anchored protein, 4) peripheral membrane protein
Cellular membranes play a role in which cell functions?
1) cell and nuclear division
2) cell signaling
3) anchoring the cytoskeleton
4) protein sorting
What are the three molecular components of cellular membranes?
carbohydrates, phospholipids, and proteins
The cell membrane is referred to as a mosaic because it is a mixture of what types of molecules?
carbohydrates, lipids, and proteins
Define exocytosis.
The process by which cells move materials from within the cell into the extracellular fluid, via vesicles
What are the three biochemical properties of phospholipids that affect fluidity?
1) length of non-polar tails
2) presence of double bonds
3) presence of cholesterol (in animal cells)
What is one way that solutes that cannot diffused across the membrane can still gain access to the interior of the cell?
transport proteins
This is a close up of the phospholipid bilayer in the cell membrane. Label 1-5.
1) fiber in the ECM, 2) plasma membrane, 3) cytoskeletal filament, 4) linker protein, 5) transmembrane protein
This is an image of three different types of diffusion. Label them, left to right.
Left: simple diffusion
Middle: facilitated diffusion
Right: active transport
The ability of solutes to cross the bilayer by simple diffusion depends on what?
size (small diffuse faster than large), polarity (non polar diffuses faster than polar), and charge (non-charged diffuse faster than charged)
Passive transport is energetically ______ and tends to _______ the magnitude of a pre-existing gradient.
favorable; decrease
The primary difference between endocytosis and exocytosis is?
the direction of transport
Label a-c.
a) isotonic
b) hypertonic
c) hypotonic
This is an image of different types of transporters. Label a-c.
a) uniporter
b) symporter
c) antiporter
This is an image of two types of active transport. Label them.
a) primary active transport
b) secondary active transport
There are four different types of anchoring junctions. This is an image of all four. Label a-d. Label 1-4.
a) adherens junctions
b) desmosomes
c) hemidesmosomes
d) focal adhesions
1) cadherins
2) intermediate filaments
3) linker proteins
4) actin filament
What is the function of an anchoring junction? What about a tight junction?
anchoring junctions link cells to each other and to the ECM; tight junctions form a tight seal between cells and prevent material from leaking between adjacent cells
1) Materials inside the cell are packaged into vesicles and excreted to the extracellular environment.
2)The plasma membrane invaginates to form a vesicle that brings substances into the cell.
Name these two processes.
1) exocytosis
2) endocytosis
During osmosis, what direction does water move across a plasma membrane?
Toward the side with a hypertonic concentration of solutes.
The sodium-potassium pump functions to pump?
sodium ions out of the cell and potassium ions into the cell
