Biology 120: Exam 2

photosynthesis

process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches

pigments

molecules that absorb specific wavelengths of sunlight

activation energy

the minimum amount of energy required to start a chemical reaction

ATP

adenosine triphosphate, an organic molecule that acts as the main energy source for cell processes; composed of a adenine molecule, ribose, and three phosphate groups

Enzymes

proteins that act as biological catalysts speeding up reactions

enzyme pathway

a series of enzymes that work in sequence to convert a substrate molecule into specific end products.

enzyme complexes

the temporary intermediate compound formed when the substrates make contact with the active site on the surface of the enzyme

feedback inhibition

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

allosteric site

A site on an enzyme other than the active site, to which a specific substance binds, thereby changing the shape and activity of the enzyme.

active site

the site on an enzyme that attaches to a substrate

monosaccharide

a simple sugar that is the basic subunit of a carbohydrate

polysaccharide

any of a class of carbohydrates whose molecules contain chains of monosaccharide molecules

glycogen

polysaccharide that stores glucose in animals

amylose

starch or glucose storage molecule for plants

cellulose

a polysaccharide that is the chief constituent of all plant tissues and fibers, chemical compound made out of sugar; forms tangled fibers in the cell walls of many plants and provides structure and support

aerobic respiration

the process in which pyruvic acid is broken down and NADH is used to make a large amount of ATP; the part of respiration that is carried out in the presence of oxygen

substrate-level phosphorylation

The formation of ATP by an enzyme directly transferring a phosphate group to ADP from an intermediate substrate in catabolism; occurs during glycolysis and the Krebs cycle

oxidative phosphorylation

A process occurring in the mitochondria that results in the formation of ATP from the flow of electrons across the inner membrane to bind with oxygen; part of the electron transport chain

redox reaction

A chemical reaction involving the transfer of one or more electrons from one reactant to another; also called oxidation-reduction reaction

NADH

electron carrier that stores energy used to make ATP; most common electron carrier in cellular respiration

FADH2

electron carrier produced during the Krebs cycle; another main electron carrier in cellular respiration.

mitochondria

Powerhouse of the cell, organelle that is the site of ATP (energy) production

glycolysis

first step in releasing the energy of glucose, in which a molecule of glucose is broken into two molecules of pyruvic acid

pyruvate oxidation

2nd step in cellular respiration occurs on the way to the mitochondrial matrix. Pyruvate is oxidized into 1 CO2, 1 NADH, 1 acetyl-COA (2 carbons attached to coenzyme A), Conversion of pyruvate to acetyl CoA and CO2 that occurs in the mitochondrial matrix in the presence of O2.

krebs cycle

stage of cellular respiration that finishes the breakdown of pyruvic acid molecules to carbon dioxide, releasing energy, A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules to carbon dioxide; occurs within the mitochondrion

electron transport chain

a series of molecules, found in the inner membranes of mitochondria and chloroplasts, through which electrons pass in a process that causes protons to build up on one side of the membrane, a series of proteins in which the high-energy electrons from the Krebs cycle are used to convert ADP into ATP.

fermentation

process by which cells release energy in the absence of oxygen, anaerobic process by which ATP is produced by glycolysis

Priestley

discovered that plants released oxygen by placing a match and a sprig of mint under a jar, Placed mint in sealed place with candle. Candle relight itself. Therefore, plants produce oxygen.

photoelectric effect

effect that photons can dislodge electrons; taking what was light energy and converting it to electrical energy (or chemical energy)

chlorophyll a

main photosynthetic pigment in plants, absorbs violet-blue and red

chlorophyll b

An accessory photosynthetic pigment that transfers energy to chlorophyll a, absorbs blue and orange-red

accessory pigments

Pigment that absorbs light at different wavelengths and then pass energy onto chlorophyll a

carotenoids

An accessory pigment, either yellow or orange, in the chloroplasts of plants. By absorbing wavelengths of light that chlorophyll cannot, these can broaden the spectrum of colors that can drive photosynthesis.

photosystem

in the thylakoid membranes of chloroplasts, a cluster of chlorophyll and other pigment molecules that harvest light energy for the light reactions of photosynthesis; a group of proteins used to collect energy from the sun, made up of a whole bunch of chlorophyll molecules

reaction center chlorophyll

one molecule in the center of bunch that all the photons need to pass through, all photons need to funnel energy into one point

photosystem II

One of two light-capturing units in a chloroplast's thylakoid membrane; it has two molecules of P680 chlorophyll a at its reaction center.

photosystem I

One of two light-capturing units in a chloroplast's thylakoid membrane; it has two molecules of P700 chlorophyll a at its reaction center.

Calvin cycle

The second of two major stages in photosynthesis (following the light reactions), involving atmospheric CO2 fixation and reduction of the fixed carbon into carbohydrate., a biochemical pathway of photosynthesis in which carbon dioxide is converted into glucose using ATP

rubisco

Ribulose bisphosphate (RuBP) carboxylase, the enzyme that catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP).

photorespiration

a metabolic pathway that consumes oxygen, releases carbon dioxide, generates no ATP, and decreases photosynthetic output; generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide

C3 plants

A plant that uses the Calvin cycle for the initial steps incorporates CO2 into organic material, forming a three-carbon compound as the first stable intermediate, common plants- stoma close during dry weather- get CO2 directly from air- essentially stopping sugar production

C4 plants

A plant that prefaces the Calvin cycle with reactions that incorporate CO2 into four-carbon compounds, the end product of which supplies CO2 for the Calvin cycle., these plants adapt to dry weather by opening stoma at night

CAM plants

Store the organic acids made at night in vacuoles and use them for photosynthesis during the day when stomata are closed

chitin

structural polysaccharide found in fungi and arthopods

amylopectin

branching chain of polysaccharides found in plants

cyclic phosphorylation

replenishes ATP levels only-no NADPH is formed; occurs when the Calvin cycle (which requires enormus energy) uses up available ATP; electrons travel from PSII to PSI and back to PSII again

non-cyclic phosphorylation

or electron transport; both ATP and NADPH formed; electron energized by absorption of light and pass through electron transport chain to NADP+, When electrons from Photosystem II go through ETC and are added to NADP⁺ to make NADPH when light is limited.