The Energy of Life
What is metabolism?
This is the sum total of an organism’s chemical reactions
What is an enzyme (or a catalyst)?
The term for a macromolecule that acts as a chemical agent to speed up the rate of a reaction without being consumed by the reaction
What is the cytosol?
The semifluid substance within the plasma membrane containing the organelles
What are amphipathic molecules?
This term describes molecules, like phospholipids, that have both hydrophobic and hydrophilic regions
What is diffusion?
The general tendency of molecules of any substance to spread out in the available space, down the concentration gradient
What is the first law of thermodynamics (or the principle of conservation of energy)
This law of thermodynamics states that energy can be transferred and transformed, but not created or destroyed
What is the substrate?
The specific molecule that an enzyme acts on
What is the nucleoid?
The structure where prokaryotic DNA is concentrated without a membrane separating it from the rest of the cell
What is the fluid mosaic model?
This describes the arrangement of phospholipids and proteins in biological membranes, where components drift laterally in the plane of the membrane
What is osmosis?
The diffusion of water across a selectively permeable membrane
What is entropy?
This property is a measure of disorder or randomness; every energy transfer or transformation increases this property of the universe
What is a noncompetitive inhibitor?
This type of inhibitor impedes enzymatic reactions by binding to another part of the molecule, causing the active site to change shape and become less effective
What is the Golgi apparatus?
This organelle, which is extensive in cells specialized for secretion, modifies products from the ER and sorts and packages materials into transport vesicles
What is cholesterol?
Wedged between phospholipids in animal cells, this steroid restrains phospholipid movement at warm temperatures and maintains fluidity at cool temperatures
What is hypotonic?
A solution with a lower concentration of solutes relative to the other solution
What is energy coupling?
This process, often mediated by ATP, involves using an exergonic reaction to drive an endergonic one in order to perform cellular work.
What is activation energy (or free energy of activation)?
This is the initial investment of energy, necessary to push the reactants over an energy barrier so the "downhill" part of the reaction can begin
What are mitochondria?
These are the organelles that convert energy to forms that cells can use for work and are the sites of cellular respiration
What are peripheral proteins?
These membrane proteins are loosely bound to the surface of the protein and are not embedded in the lipid bilayer
What is active transport?
This type of process requires the cell to expend metabolic energy to move solutes across membranes against their concentration gradient
What is an endergonic reaction?
This is a nonspontaneous reaction that absorbs free energy from its surroundings
What is saturated (or saturation)?
This is the state where all active sites on the enzymes are engaged, and the reaction rate is determined by the speed at which the active site converts substrate to product
What are lysosomes?
These membrane-bound sacs in animal cells contain hydrolytic enzymes and are responsible for digestion of macromolecules or the recycling of cell components via autophagy
What is intercellular joining?
This general function of membrane proteins allows two adjacent cells to attach together with gap or tight junctions
What are aquaporins?
Specific channel proteins, such as these, greatly facilitate the diffusion of water across the membrane