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Ch 5 pt2
Terms in this set (58)
substances easily diffuse across a cell membrane.
polar or charged substances do not easily cross cell membranes.
How do transport Transport proteins contribute to a diffusion membrane's selective permeability?
Because they are specific for the solutes they transport, the numbers and kinds of transport proteins affect a membrane's permeability to various solutes.
• In ___ ___ t, a cell must expend energy to move solute against its ____ ___ .
active transport, concentration gradient.
The energy molecule ____ supplies the energy for most active transport.
Cells actively transport Ca2+ out of the cell. Is calcium more concentrated inside or outside of the cell? Explain.
Outside: Active transport moves calcium against its concentration gradient.
___ and ___ transport large molecules across membranes
• A cell uses two mechanisms to move large molecules across membranes those are?
is used to export bulky molecules, such as proteins or polysaccharides.
is used to take in large molecules.
In both cases, material to be transported is ____ within a vesicle that fuses with the membrane.
• There are two kinds of endocytosis.
Phagocytosis, Receptor-mediated endocytosis
is the engulfment of a particle by the cell wrapping cell membrane around it, forming a vacuole.
uses membrane receptors for specific solutes.
As a cell grows, its plasma membrane expands. Does this involve endocytosis or exocytosis?
Exocytosis: When a transport vesicle fuses with the plasma membrane, its contents are released and the vesicle membrane adds to the plasma membrane.
Cells transform __ and ___ as they perform work
is the energy of motion.
is energy stored in the location or structure matter and includes chemical energy.
law of energy conservation; the energy in the universe is constant. Energy can transfer and change form but cannot be created or destroyed.
First law of thermodynamics:
Some energy becomes unavailable to do work. It converted to ___ energy (random molecular motion measured as entropy or disorder) and released as ___
thermal , heat.
energy transfers or transformations increase disorder, or entropy, with some energy being lost as heat.
Second law of thermodynamics:
Q How does the second law of thermodynamics explain the diffusion of a solute across a membrane?
Diffusion across a membrane results in equal concentrations of solute, which is a more disordered arrangement (higher entropy) than a high concentration on one side and a low concentration on the other.
require energy to form chemical bond
· Each time the chemical bond is broken, energy is released (Hydrolysis).
Yield products rich in potential energy stored in chemical bonds (Dehydration).
encompasses all of a cell's chemical reactions.
Metabolism includes ___ and ___ reactions.
Remembering that energy must be conserved, what do you think becomes of the energy extracted from food during cellular respiration?
• Some of it is stored in ATP molecules; the rest is released as heat.
Chemical reactions either __ or ___ energy
___ drives cellular work by coupling exergonic and endergonic reactions
powers nearly all forms of cellular work.
• The transfer of a phosphate group from ___ is involved in chemical, transport, and mechanical work.
the addition of Phosphate, P.
Explain how ATP transfers energy from exergonic to endergonic processes in the cell.
• Exergonic processes dephosphorylate ATP to form ADP and P and release E. ATP transfers energy to endergonic processes by phosphorylating other molecules.
speed up the cell's chemical reactions by lowering energy barriers
are protein catalysts that decrease the activation energy needed to begin a reaction.
Many enzymes require NONPROTEIN helpers such as
Inorganic COFACTORS such as Zn, Fe and Cu ions. Organic COENZYMES such as vitamins like folic acid, and B vitamin.
such as Zn, Fe and Cu ions.
such as vitamins like folic acid, and B vitamin.
Q The graph illustrates a reaction with and without an enzyme. Which curve represents the enzyme-catalyzed reaction? What do lines a, b, and c represent?
• The red curve is the enzyme-catalyzed reaction. • Line a is the activation energy without enzyme; • Line b is the activation energy with enzyme; • Line c is the change in energy between reactants and products, which is the same for both the catalyzed and uncatalyzed reactions.
A specific enzyme catalyzes each ___ reaction
An enzyme's ___ fits specifically in its ___ site.
The process of catalytic cycle : first, formation of enzyme-substrate complex.
1 The enzyme is available with an empty active site 2 The substrate enters the active site, which enfolds the substrate with an induced fit
1 The enzyme is available with an empty active site 2 The substrate enters the active site, which enfolds the substrate with an induced fit 4 The products are released 3 The substrate is converted to products
Enzyme __ can regulate enzyme activity in a cell
competes with the substrate for the active site.
alters an enzyme's function by changing its shape.
Feedback inhibition in ___ pathways.
Many cellular reactions involved a series of steps, each ____ by specific enzyme.
• If a cell is producing more of the products than it needs, the product may act as inhibitor of one of the enzymes in a series. This is called
helps regulate metabolism.
Explain an advantage of feedback inhibition to a cell.
It prevents the cell from wasting valuable resources by synthesizing more of a particular product than is needed.
Many ___, ___ and ___ are enzyme inhibitors
drugs, pesticides, poisons
Many beneficial drugs act as enzyme inhibitors. Examples:
1) Ibuprofen 2) Blood pressure medications 3) Antidepressants 4) Antibiotics such as Penicillin.
are produced in response to injury that causes pain.
Ibuprofen is a pain reliever because it inhibits the enzyme that synthesizes ___.
What determines whether enzyme inhibition is reversible or irreversible?
If the inhibitor binds to the enzyme with covalent bonds, the inhibition is usually irreversible. When weak chemical interactions bind inhibitor and enzyme, the inhibition is reversible.
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