Unit 3

Metabolism

All the chemical reactions in an organism

Metabolic Pathway

Series of chemical reactions that either build or break complex molecules

Catabolic pathway

Releases energy by breaking down complex molecules into simpler molecules

• EG: Breaking down ATP

• Gain in energy (cation = positive)

Anabolic Pathway

Consumes energy to build complex molecules from simpler ones

• EG: Photosynthesis

• Loss of energy (anion = negative)

Free Energy

A concept that can determine the likelihood of reactions

• Is something energetically favorable?

• Determines whether reactions can occur spontaneously (ie: without enzymes)

Endothermic reaction

A reaction that absorbs energy

• Gibbs free energy > 0

• EG: Photosynthesis

• Also known as endergonic

Exothermic reaction

A reaction that gives off heat

• Gibbs free energy < 0

• EG: Cellular respiration

• Also known as exergonic

Mechanical Work

Type of work that is movement

• EG: Contraction of muscle cells

Transport Work

Type of work that is the pumping substances across membranes against spontaneous movement

Chemical Work

Type of work that is the synthesis of molecules

• IE: Building polymers from monomers

Phosphorylation

The process of the released phosphate group from ATP moving to another molecule to give energy.

Enzyme

Macromolecules that catalyze (speed up) reaction by lowering activation energy.

• Protein

• Not consumed in a reaction

Substrate

The reactant that the enzyme acts on.

• Whatever molecule is attaching itself to the enzyme

Active site

Area of the enzyme which the substrate binds to

Enzyme Catabolism

Process where enzymes help to break down complex molecules.

Enzyme Anabolism

Process where enzymes help to build up complex molecules.

Induced Fit

Enzymes will change the shape of their active site to allow the substrate to bind better.

Cofactor

Non-protein that assists in enzyme function

• Inorganic

• EG: Iron to hemoglobin

Coenzyme

Organic molecules that assist in enzyme function

• EG: Vitamins

Inhibitor

Reduces the activity of specific enzymes

• Permanent or reversible

Competitive Inhibitor

Reduces enzyme activity by blocking substrates from binding to the active site.

• Can be reversed by increased substrate activity

Noncompetitive Inhibitor

Binds to an area other than the active site, which will functionally change the shape of the protein

Allosteric enzyme

Enzymes with multiple binding sites

• Active site

• Allosteric site (which can stimulate or inhibit a protein).

Cooperativity

Substrate binds to one active site (on an enzyme w/ more than one) which stabilizes the active form.

• EG: Hemoglobin holds four molecules of iron and if one is let go, the enzyme destabilizes.

• The binding of one site changes the other sites.

Photosynthesis

The process where plants and some types of bacteria can convert light/solar energy to chemical energy.

Autotroph

Organisms who can produce their own food / energy.

• EG: Organisms who live in dark places that can produce food via fermentation.

Heterotroph

Organisms unable to make their own food, who instead need to eat external food to gain energy.

Mesophyll

The cells that make up the interior tissue of the leaf.

• This is where most chloroplasts will be present.

Stomata

Pores in the leaves that allow CO₂ in and O₂ out. 

Stroma

The aqueous internal fluid of a chloroplast

• Where the Calvin Cycle occurs

Thylakoid

Flattened membranes with pigments (primarily chlorophyll) that form stacks known as grana.

Oxidation

A process in which you lose electrons

Reduction

A process in which you gain electrons

• Remember: electrons are negatively charged

Pigments

Chemicals that are capable of storing visible light.