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Honors Membrane Review
Terms in this set (50)
(adenosine triphosphate) main energy source that cells use for most of their work
composed of 3 negative phosphate groups forced together, creating high energy bonds that RELEASE energy when broken, unlike normal chemical bonds
The movement of a substance across a biological membrane against its concentration gradient, aided by specific transport proteins and requiring input of energy (often as ATP).
A transport protein in the plasma membrane of some plant or animal cells that facilitates the diffusion of water across the membrane (osmosis).Aquaporins: water channel - specifically facilititates osmosis - the diffusion of free water across the membrane
The aerobic harvesting of energy from food molecules; the energy-releasing chemical breakdown of food molecules, such as glucose, and the storage of potential energy in a form that cells can use to perform work; involves glycolysis, the citric acid cycle, and oxidative phosphorylation (the electron transport chain and chemiosmosis).
An increase or decrease in the density of a chemical substance in an area. Cells often maintain concentration gradients of ions across their membranes. When a gradient exists, substances tend to move from where they are more concentrated to where they are less concentrated.
moves: permeable molecules (non-polar and small) down their concentration gradient
requires: concentration gradient
The spontaneous tendency of a substance to move down its concentration gradient from where it is more concentrated to where it is less concentrated.
Cellular uptake of molecules or particles via formation of new vesicles from the plasma membrane. The cell takes in macromolecules and particles by forming new vesicles from the plasma membrane
Used to incorporate extracellular substances
process whereby the cellular membrane invaginates and engulfs material into thecell
The passage of a substance through a specific transport protein across a biological membrane down its concentration gradient. is similar to simple diffusion both involve movement of molecules down their concentration gradient, without energy.
Moves: impermeable particles down their concentration gradient
requires: protein channels; concentration gradient; requires no E
The movement of materials out of the cytoplasm of a cell by the fusion of vesicles with the plasma membrane. A transport vesicle buds from the Golgi apparatus and is moved by the cytoskeleton to the plasma membrane, where it fuses and the contents spill out
large material being expelled, e.g. neurotransmitter release (packets)
> both can also be used to rapidly change size of cell because cell uses membrane to make/absorb vesicles
Referring to a solution that, when surrounding a cell, will cause the cell to lose water.
Referring to a solution that, when surrounding a cell, will cause the cell to take up water.
A solution having the same solute concentration as another solution, thus having no effect on passage of water in or out of the cell.
Method by which organisms regulate solute concentrations and balance the gain and loss of water.
The diffusion of water across a selectively permeable membrane.
Moves: water down concentration gradient
The diffusion of a substance across a biological membrane, without any input of energy.
Cellular "eating"; a type of endocytosis whereby a cell engulfs macromolecules, other cells, or particles into its cytoplasm.
ingestion of large molecules
Cellular "drinking"; a type of endocytosis in which the cell takes fluid and dissolved solutes into small membranous vesicles.
endocytosis of fluids and small particles
A property of biological membranes that allows some substances to cross more easily than others and blocks the passage of other substances altogether.
a lipid made up of glycerol joined to two fatty acids and a phosphate group, giving the molecule a non-polar hydrophobic tail and a polar hydrophilic head. _______ form bilayer that function as biological membranes.
a protein that serves the function of moving other materials within an organism. ______are vital to the growth and life of all living things. Provide channel for the diffusion of a specific solute across a membrane. Provides hydrophilic channel that some molecules or ions use as a tunnel through the membrane. Another type of ________ binds its passenger, changes shape, and releases its passenger on the other side.
a membrane-enveloped cellular organelle, found in many microorganisms, that periodically expands, filling with water, and then contracts, expelling its contents to the cell exterior: thought to be important in maintaining hydrostatic equilibrium. pumps water back out of the cell in order to maintain osmotic equilibrium and avoid lysis.
How do aquaporins work?
Aquaporins selectively conduct water molecules in and out of the cell, while preventing the passage of ions and other solutes. Also known as water channels, aquaporins are integral membrane pore proteins. entry or exit of up to 3 billion H2O molecules / second. Water molecules traverse through the pore of the channel in single file. The presence of water channels increases membrane permeability to water.
Turgor pressure pushes the plasma membrane against the cell wall of plant, bacteria, and fungi cells as well as those protist cells which have cell walls. Turgidity, is caused by the osmotic flow of water from area of low solute concentration outside of the cell into the cell's vacuole, which has a higher solute concentration. To become turgid, a plant cell needs a net inflow of water. The pressure it exerts prevents the cell from taking in too much water and bursting.
Describe the properties of phospholipids and their arrangement in cellular membranes
- Phospholipids are amphipathic, have both hydrophobic regions and hydrophilic regions.
- the hydrophillic head on the exterior and the hydrophobic tail on in the interior
Describe how proteins and carbohydrates are spatially arranged in cell membranes and how they contribute to membrane function.
The proteins act as transport molecules to move material in and out of the cell (kind of like a tunnel). They are embedded in the membrane. These proteins are needed due to the phospholipid bilayer. The inside of the bilayer repels water, so this keeps all materials out of the cell unless it has been selected to be carried in by the proteins. The carbohydrates are located on the outside of the membrane. They recognize things the cell may need.
active transport v diffusion
active transport- requires the cell to expend its own metabolic energy, uses ATP energy, goes to less concentration to higher
diffusion = passive transport, no energy, down concentration gradient,
Distinguish between hypertonic, hypotonic and isotonic
hyper - more solute
hypo - less solute
iso - equal
Describe factors that affect selective permeability of membranes.
^Their hydrophobic interior is one reason for selective permeability. Hormones, temperature, electrical charge of membrane, sizeElectrical charge = charged ions can't pass freelyTemperature = increase temperature makes less transmittableSize = smaller means easier to cross
Depends on the discriminating barrier of the lipid bilayer and the specific transport proteins built into the membrane
1. Total number of channels available
2. Conductance - how well an ion passes through the channel
3. How long the channels are open
the membrane consists of
phospholipids: hydrophilic head, hydrophobic tail
proteins (carrier protein, ion channels)
cholesterol: membrane fluidity
provide the openings through which small, dissolved particles, especially ions, diffuse by passive transport
A concentration gradient is the concentration that exists between a two different areas.
Take osmosis for example. This is when water passes through a semi permeable membrane to another area. It tries to stay balanced between the two areas. So a concentration gradient is the concentration of water on each side on the semi permeable membrane.
the gradient will tell us whether this process will be passive or active
notice how the O in hypotonic looks like a swollen cell
(simple diffusion, facilitated diffusion, and osmosis) transfers solutes down their concentration gradients. No energy input is required. The energy has already been stored in the chemical gradient
fish moving from salt water (isotonic environment) to fresh water (hypotonic environment); water would rush in to fish cells
Cotransport is the name of a process in which two substances are simultaneously transported across a membrane by one protein, or protein complex which does not have ATPase activity.
different types pf co-transport:
>When both substances are transported in the same direction the transport protein is known as a symport .
>When the substances are transported in opposite directions the transport protein is known as an antiport.
6 things that affect diffusion rate
1) Diffusion path way, a short diffusion path way i.e one cell thick will speed up the rate of diffusion.
2) Surface area, a large surface area allows for faster diffusion.
3) Concentration gradient, the steeper the concentration gradient the faster the diffusion.
4) ATP availability has no effect as diffusion is a passive process so does not require energy.
5) There is a optimum temperature where the particles have sufficient kinetic energy to collide with the cell wall and diffuse quickly, before the temperature becomes too high and the cells denature.
6) pH would only have an effect if it was not at the optimum for the cell.
How are large molecules are transported across a cell membrane?
The process of exocytosis secretes large molecules by the fusion of vesicles with the plasma membrane.
compare pincocytosis and receptor-meidated endocytosis
Simliarity: All of these 3 involve taking in material from outside.
Pinocytosis is when a liquid material is absorbed/engulfed.
Rec. Med. endocytosis is a process by which cells engulf molecules (endocytosis) into a cell by the inward budding of plasma membrane vesicles containing proteins with receptor sites specific to the molecules being engulfed. So basically a substance is recognised before being engulfed
explain how transport proteins are similar to enzymes
Transport proteins have a specific shape, of which only one type of molecule can bind to it in order to be transported through the phospholipid membrane into the cell cytoplasm.
This is similar to an enzyme's active site, which again binds to only one type of molecule which fits the shape of the active site, hence enzymes catalyse specific biochemical reactions.
Both the shape of the enzyme and transport protein allows binding to specific molecules only.
distinguish following terms
Peripheral and integral membrane:
Channel and carrier proteins:
Channel proteins: have a hydrophilic channel that molecules use as a tunnel through the membrane
Carrier proteins: holds on to their passengers and changes their shape in a way that shuttles them across the membrane.
Sometimes a cell needs to move a solute against its concentration gradient. This process is called active transport, and it requires input of energy from ATP. For instance, most animal cells need to expel sodium ions (Na+) and take in potassium ions (K+), both against their concentration gradients. Here is how the sodium-potassium pump works: Sodium ions bind to a transport protein. ATP transfers a phosphate group to the protein, providing the energy that causes the protein to change shape and push the sodium ions across the membrane, where they are released outside the cell. Potassium ions now bind to the transport protein and the phosphate group is released. This causes the protein to return to its original shape, releasing the potassium ions inside the cell. The transport protein is now ready to repeat the process.
Explain how transport proteins facilitate diffusion.
Two types of transport proteins.
Channel proteins: simply provide corridors that allow specific molecules or ions to cross the membrane.
Carrier proteins: result in the net movement of a substance down its concentration gradient. No energy input is thus required. This is passive transport.
explain how active transport differs from diffusion
Diffusion: passive transfer of a substance across a semi-permeable membrane from an area of high concentration to an area of lower concentration.
Active transport is kind of the opposite to this. It is the transfer of a substance across a membrane which is against the diffusion gradient (so from low to high concentration) and therefore requires energy from the cell.
Active- against the flow of a river
regular diffusion- with the flow of a river
Explain what mechanisms can generate a membrane potential or electrochemical gradient.
Membrane potential = voltage across membranes
Electrochemical gradient = the chemical force (the ion's concentration gradient) and the electrical force (membrane potential) on the ion's movement across the cell membrane
1. The concentration gradient of an ion
2. Negatively charged proteins inside the cell
3. Plasma membrane's selective permeability to various ions
4. The Na - K pump
Define diffusion. Explain why diffusion is a passive and spontaneous process.
Diffusion: The movement of a substance down its concentration gradient due to random thermal motion.
Diffusion is a passive and spontaneous process because one solute is unaffected by the concentration gradients of other solutes and the cell does not expend energy when substances diffuse down their concentration gradient.
explain what regulates the rate of passive transport
the concentration gradient determines whether the solvent will move from a hypotonic solution to a hypertonic solution or not. The proteins also help stimulate hte rate (ie channel proteins, carrier proteins)
Explain why a concentration gradient of a substance across a membrane represents potential energy.
The concentration gradient of a substance across a membrane represents potential energy because it drives diffusion.
Define osmosis and predict the direction of water movement based on differences on solute concentrations.
Osmosis: The diffusion if water across a selectively permeable membrane.
The direction of water movement based on differences on solute concentrations depends on how the water diffuses down its own concentration.
describe how living cells with and without walls regulate the balance of water content
Cells without cell walls rely on tonicity (the ability of gain or lose water), isotonic cells result in no net movement as it is equal throughout, hypotonic cells will result in the entering of water, hypertonic will result in the loss of water. Cells with cell walls use their cell way to regulate the water balance, plant cells are turgid if it is very firm and normal water balance, if it is flaccid it has no net entrance for water, and if it is submerged in a hypertonic solution for a period of time, it will become plasmolyzed and most likely die.
Exchanges N+ and K+ across animal cell membranes, creating a higher concentration of potassium ions and lower concentrations of sodium ions within the cell.
How is cardiac muscle similar to skeletal muscle?
An example is when doing heavy resistance training: Transitioning of type IIx (fast glycolytic) to type IIa (fast oxidative glycolytic); High intensity resistance training and short-interval speed work transitions type I to type IIa
what are the requirements for spermatogenesis?
Steroid Hormones: Does it act as a ligand?
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