Biology Energy Processes: Photosynthesis and Cellular Respiration

autotroph

An organism that makes its own food

heterotroph

organism that obtains energy from the foods it consumes; also called a consumer

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

photosynthesis

Conversion of light energy from the sun into chemical energy.

pigment

Light-absorbing molecule

chlorophyll

Green pigment in plants that absorbs light energy used to carry out photosynthesis

thylakoid

saclike photosynthetic membranes found in chloroplasts

photosystem

cluster of chlorophyll and proteins found in thylakoids

stroma

fluid portion of the chloroplast; outside of the thylakoids

NADP+

carrier molecule that transfers high-energy electrons from chlorophyll to other molecules

light-dependent reactions

first stage of photosynthesis where certain wavelengths of the visible light are absorbed to form two energy-carrying molecules (ATP and NADPH)

light-independent reactions

set of reactions in photosynthesis that do not require light; energy from ATP and NADPH is used to build high-energy compounds such as sugar; also called the Calvin cycle

ATP synthase

protein complex in the thylakoid membrane

Calvin Cycle

light-independent reactions of photosynthesis in which energy from ATP and NADPH is used to build high-energy compounds such as sugar

calorie

Amount of energy needed to raise temperature 1 gram of water 1 degree C

glycolysis

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

cellular respiration

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

NAD+

electron carrier involved in glycolysis

fermentation

Process by which cells release energy in the absence of oxygen

anaerobic

Process that does not require oxygen

aerobic

Process that requires oxygen

Krebs cycle

second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions

electron transport chain

series of electron carrier proteins that shuttle high-energy electrons during ATP-generating reactions

matrix

Innermost compartment of the mitochondrion