mastering biology chapter 5

fluid mosaic model

fluid mosaic model

-depicts the membrane as a mosaic of protein molecules suspended in a fluid phospholipid bilayer

-kinks in the unsaturated fatty acid tails of phospholipids keeps the membrane fluid

selective permeability

-allows membranes to regulate the passage of molecules across them

-small nonpolar molecules (O2, CO2) can move freely across the membrane

cholesterol

-stabilizes the structure of the plasma membrane

-prevents the close packing of phospholipids.

carrier protein

transport protein that releases molecules on the other side of the membrane by binding & changing shape

channel protein

transport protein that provides channels through which specific molecules/ions can diffuse

active transport protein

transport protein that uses ATP to pump molecules against their concentration gradient

receptor protein

-binds to signaling molecules outside of a cell to transmit messages into the cell

-activates other molecules within the cell

attachment protein

-provides support by connecting to the cytoskeleton & ECM

-can relay information about internal & external conditions

glycoprotein

-allows other membrane proteins to recognize its attached sugars (ID tags)

-composed of a carbohydrate & protein

junction protein

forms long-lasting connections between cells

aquaporin

transport protein that facilitates osmosis

enzyme

-protein that carries out sequential reactions within the membrane

-changes the rate of a chemical reaction without being consumed by it

-organic catalyst

protein pore

passageway for facilitated diffusion

Na/K pump

-Na+ binds to the transport protein so that it can be moved across the membrane against the concentration gradient

-K+ binds to the transport protein so that it can be moved into the membrane against the concentration gradient

-Phosphate group of ATP needs to be transferred to the protein so that it changes shape (active transport)

contractile vacuole

expels excess water from plant cells against the concentration gradient using ATP (active transport)

ligand

molecule that binds to a receptor protein

net movement

difference between the number of molecules moving in the direction of the force & the number of molecules moving in the opposite direction

concentration gradient

-region along which the density of a substance increases or decreases

-substances tend to move from higher concentration to lower concentration

passive transport

diffusion of a substance across a membrane down a concentration gradient with no expenditure of energy

active transport

diffusion of a substance across a membrane against a concentration gradient that requires an input of energy

diffusion

-movement of particles down a concentration gradient

-tendency of particles to spread out in its available space

facilitated diffusion

passage of a substance through a transport protein across a membrane down a concentration gradient

osmosis

diffusion of water across a selectively permeable membrane from high to low areas of concentration

osmoregulation

homeostatic maintenance of solute concentrations & water balance

exocytosis

movement of molecules out of a cell by the fusion of vesicles with the cell membrane

endocytosis

-movement of molecules into a cell via formation of new vesicles from the plasma membrane

-cell membrane pinches inward

phagocytosis

-endocytosis in which a cell engulfs macromolecules into its cytoplasm

-”cell eating”

pinocytosis

-endocytosis in which the cell engulfs extracellular fluid

-”cell drinking”

receptor-mediated endocytosis

movement of molecules into a cell by the infolding of protein-containing vesicles with receptor sites specific to the molecules being taken in

tonicity

the ability of a solution surrounding a cell to cause that cell to gain or lose water

isotonic

-no net movement of water

-equal concentration of solvent and solute

hypotonic

-net movement of water into the cell

-causes the cell to grow

-higher concentration of solvent

hypertonic

-net movement of water out of the cell

-causes the cell to shrink

-higher concentration of solute

lysing

bursting of an animal cell caused by the net movement of water into the cell (hypotonic environment)

turgid

firm, healthy state of plant cells in a hypertonic environment

turgor pressure

prevents a plant cell from taking in too much water & lysing

flaccid

limp plant cell caused by the loss of water in an isotonic environment

plasmolysis

-the pulling away of a plasma membrane from a cell wall

-caused by the loss of water in a hypertonic environment

-causes the plant to wilt

crenation

shrinking of an animal cell after exposure to a hypertonic environment

system

matter under study

surroundings

everything outside the system

thermodynamics

study of energy transformations that occurs in a collection of matter

first law of thermodynamics

Energy can be transferred and transformed, but not created nor destroyed.

second law of thermodynamics

Energy conversion reduces the order of the universe, increasing its entropy.

entropy

measure of disorder/randomness

exergonic reaction

-energy-releasing chemical reaction in which the reactants contain more potential energy than the products

-i.e. cellular respiration

endergonic reaction

-energy-requiring chemical reaction in which products yield more potential energy than the reactants

-i.e. photosynthesis

energy coupling

the use of energy released from an exergonic reaction to drive an endergonic reaction in cellular metabolism

metabolic pathway

series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds

cellular respiration

-aerobic harvesting of energy from food molecules

-stores potential energy in a form that cells use to perform work (ATP)

ATP (adenosine triphosphate)

-main energy source for cells

-releases energy when its phosphate bonds are hydrolyzed

-2 phosphoanhydride bonds

ADP

-1 phosphoanhydride bond

AMP

-0 phosphoanhydride bonds

phosphoanhydride bond

high-energy bonds that link phosphate groups to one another in ATP, ADP, AMP

phosphorylation

-transfer of a phosphate group to a molecule

-ADP (adenosine diphosphate) is phosphorylated to form ATP

activation energy

amount of energy that reactants must absorb before a chemical reaction will start

induced fit

-changes in the shape of an active site caused by the entry of the substrate so that it binds the substrate snugly

-may contort substrate bonds/place amino acids in position to catalyze the reaction

cofactor

nonprotein molecule/ion that is required for the proper functioning of an enzyme

coenzyme

organic molecule serving as a cofactor

competitive inhibitor

-substance that reduces the activity of an enzyme by entering the active site in place of the substrate

-structure mimics that of the enzyme’s substrate

noncompetitive inhibitor

-substance that reduces the activity of an enzyme by binding elsewhere on the enzyme

-changes that shape of the enzyme so that the active site no long catalyzes the conversion of substrate to product

feedback inhibition

metabolic control in which a product of the metabolic pathway acts as an inhibitor of an enzyme within that pathway