biol 160 ch 5 vocab

activation energy

energy necessary for reactions to occur

active site

enzyme’s specific region to which the substrate binds

active transport

method of transporting material that requires energy

adenosine diphosphate (ADP)

nucleotide with two phosphates formed when ATP gives up a phosphate

adenosine triphosphate (ATP)

nucleotide with three phosphate groups that is the primary energy currency of the cell

allosteric inhibitor

inhibition by a binding event at a site different from the active site, which induces a conformational change and reduces the enzyme’s affinity for its substrate

amphipathic

molecule possessing a polar or charged area and a nonpolar or uncharged area capable of interacting with both hydrophilic and hydrophobic environments

aquaporin

channel protein that allows water through the membrane at a very high rate

carrier protein (transporter)

membrane protein that moves a substance across the plasma membrane by changing its own shape

channel protein

membrane protein that allows a substance to pass through its hollow core across the plasma membrane

coenzyme

small organic molecule, such as a vitamin or its derivative, which is required to enhance an enzyme’s activity

cofactor

inorganic ion, such as iron and magnesium ions, required for optimal enzyme activity regulation

competitive inhibition

type of inhibition in which the inhibitor competes with the substrate molecule by binding to the enzyme’s active site

concentration gradient

area of high concentration adjacent to an area of low concentration

diffusion

passive transport process of low-molecular weight material according to its concentration gradient

endergonic reaction

a chemical reaction that absorbs energy rather than releasing energy on balance

endocytosis

type of active transport that moves substances, including fluids and particles, into a cell

exergonic reaction

a reaction that releases free energy

exocytosis

process of passing bulk material out of a cell

facilitated diffusion

process by which material moves down a concentration gradient (from high to low concentration) using integral membrane proteins

feedback inhibition

a product’s effect of a reaction sequence to decrease its further production by inhibiting the first enzyme’s activity in the pathway that produces it

fluid mosaic model

describes the plasma membrane’s structure as a mosaic of components including phospholipids, cholesterol, proteins, glycoproteins, and glycolipids (sugar chains attached to proteins or lipids, respectively), resulting in a fluid character (fluidity)

glycolipid

combination of carbohydrates and lipids

glycoprotein

combination of carbohydrates and proteins

hydrophilic

molecule with the ability to bond with water; “water-loving”

hydrophobic

molecule that does not have the ability to bond with water; “water-hating”

hypertonic

situation in which extracellular fluid has a higher osmolarity than the fluid inside the cell, resulting in water moving out of the cell

hypotonic

situation in which extracellular fluid has a lower osmolarity than the fluid inside the cell, resulting in water moving into the cell

integral protein

protein integrated into the membrane structure that interacts extensively with the membrane lipids’ hydrocarbon chains and often spans the membrane

ion channel

protein that allows specific ions to diffuse across the membrane down their concentration gradient

isotonic

situation in which the extracellular fluid has the same osmolarity as the fluid inside the cell, resulting in no net water movement into or out of the cell

osmolarity

total amount of substances dissolved in a specific amount of solution

osmosis

transport of water through a semipermeable membrane according to the water’s concentration gradient across the membrane that results from the presence of solute that cannot pass through the membrane

passive transport

method of transporting material through a membrane that does not require energy

peripheral protein

protein at the plasma membrane’s surface either on its exterior or interior side

phagocytosis

process by which a cell takes in relatively large particles (type of endocytosis)

primary active transport

active transport that moves ions or small molecules across a membrane using ATP to drive substrates up their concentration gradient

pump

active transport mechanism that works against electrochemical gradients

secondary active transport

movement of a solute up its concentration gradient, powered by an energy source other than ATP

selectively permeable

membrane characteristic that allows some substances through

solute

substance dissolved in a liquid to form a solution

substrate

molecule on which the enzyme acts

tonicity

amount of impermeable solute in a solution