Slides/AP Videos 3.1-3.7

Metabolism

Metabolism

The sum of all chemical reactions occurring in a cell or organism

Metabolic pathway

A series of reactions that begins with a specific molecule and ends with a product, with each step catalyzed by an enzyme (the way in which cells perform work)

within a chemical pathway, the product of one reaction can serve as a reactant in a subsequent reaction → the sequential reactions allow for a more controlled and efficient transfer of energy

Catabolic

pathways that release energy by breaking down complex molecules into simpler compounds

ex: cellular respiration, the breaking down of glucose in the presence of oxygen

Anabolic (noun: anabolism)

pathways that consume energy to build complex molecules from simpler ones

ex: synthesis of a protein from an amino acid

Enzyme

A catalytic protein that speeds up biochemical reactions, often named based on the substrate or reaction involved (often end in -ase)

not chemically changed by the reaction

→ can facilitate synthesis or digestion reactions

cells typically maintain a certain concentration

→ catalyze reactions by lowering the E_A barrier

*structure is specific resulting in each, only facilitating one type of reaction

ex: hydrolysis of sucrose by sucrase

Catalyst

A chemical agent that speeds up a reaction without being consumed by the reaction

Substrate

The reactant that an enzyme acts on (binds to), forming an enzyme-_____ complex.

Active site

The region on the enzyme where the substrate binds, with a unique physical and chemical properties to fit its respective substrate

Activation energy

The initial energy needed to start a chemical reaction.

induced fit

brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction (with their respective substrate)

**The substrate must have a complementary shape/conformation and charge to its respective enzyme for the reaction to be facilitated

substrate concentration

the more substrates there are, the faster the reaction rate, up to a certain point at which no further increase occurs (substrate saturation)

• initial increase raises chances of collisions

* increased product concentration = decrease opportunity for addition of substrate (matter takes up space, lowers enzyme-substrate collisions, slows reaction rate)

enzyme concentration

the less of an enzyme there is, the slower the activation rate since there is less opportunity for substrates to collide with active sites (vise-versa)

activation energy (E_A)

the initial energy needed to start a chemical reaction

→ typically reactions resulting in a net release of energy require less compared to reactions resulting in net absorption of energy

(often supplied in the form of thermal energy that the reactant molecules absorb from their surroundings)

endergonic

chemical reactions that require a net input of energy

exergonic

chemical reactions that have a net loss of energy

denaturation

changes in the conformational shape of proteins (and enzymes)

• ____ proteins are biologically inactive, and for enzymes this means they will not catalyze chemical reactions

• occasionally reversible

pH and temperature

the two main factors that effect enzyme denaturation

optimal temperature

the range of temp in which enzyme-mediated reactions occur fastest

• environmental increase in temp - initially increases reaction rate

  • increased speed of molecular movement by adding more kinetic energy (results in increased enzyme-substrate collisions)

temp increases outside of range result in enzyme denaturation (although lower temps do not denature enzymes)

negative feedback

where the product of the pathway inhibits the process responsible for its production

→ allows the cell to avoid wasting energy and resources

optimal pH

the range in concentration of hydrogen ions in a solution that an enzyme can function in - range in which enzyme-mediated reactions occur the fastest

• changes in hydrogen ion (proton) concentration can disrupt hydrogen bond interactions that help maintain enzyme structure

  • loses secondary and tertiary structures (because of altered H-bonds)

→ measured on a logarithmic scale (small shifts equate to large changes in # of hydrogen ions)

denaturation may occur outside of range (changes outside of range will slow/stop enzyme activity)

competitive inhibitors

bind to the active site of an enzyme, competing with the substrate

• can be reversible/irreversible

if ___ concentrations exceed substrate concentrations, reactions are slowed (if considerably lower, then reaction proceed like normal)

noncompetitive inhibitors

(allosteric regulation) bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

→ bind to allosteric sight

*increasing substrate cannot prevent effects

allosteric regulation

occurs when a regulatory molecule binds to a protein at one site and affects the protein’s function at another site

→ may either inhibit or stimulate an enzyme’s activity

allosteric site

a region enzymes may have (other than the active site) to which molecules can bind

ATP

Adenosine triphosphate, the cell's energy currency, composed of ribose (a sugar), adenine (a nitrogenous base), and three phosphate groups.

• regenerated by addition of a phosphate group to adenosine diphosphate (ADP)

bonds between the phosphate groups can be broken via hydrolysis

→ energy released when terminal phosphate bond is broken

first law of thermodynamics

Energy can be transferred and transformed, but it cannot be created or destroyed

aka principle of conservation of energy

second law of thermodynamics

Every energy transfer or transformation increases the entropy (disorder) of the universe

→ During every energy transfer or transformation, some energy is unusable, and is often lost as heat

catabolic pathway

when, in a cell, larger molecules are broken down to release energy → releases free energy in a series of reactions

transport, mechanical, chemical

the three types of cellular work

energy coupling

the use of an exergonic process to drive an endergonic one

cells manage energy resource to do work

most ___ ___ in cells is mediated by ATP

cellular respiration

includes anaerobic and aerobic processes, but is often used to refer to aerobic respiration

a characteristic of all life forms

Anaerobic Respiration

A process that uses a different final electron acceptor, such as sulfate, when oxygen is unavailable.

Fermentation

A metabolic process that regenerates NAD+ to allow glycolysis to continue in the absence of oxygen.

a characteristic of all life forms

Alcohol Fermentation

A type of fermentation by yeast that produces alcohol, used in making wine, beer, and bread.

Lactic Acid Fermentation

A type of fermentation where pyruvate is reduced to form lactate without releasing CO2.

Photosynthesis

The process that converts solar energy into chemical energy in plants, algae, and some prokaryotes.

Autotrophs

Organisms that produce organic molecules from CO2 and inorganic molecules, sustaining themselves without consuming other organisms.

Heterotrophs

Organisms that obtain organic material from other organisms and are the consumers of the biosphere.

Chlorophyll

The green pigment within chloroplasts that absorbs light energy for photosynthesis.

ATP Synthase

An enzyme that produces ATP as protons pass through it during chemiosmosis.

Calvin Cycle

A series of reactions in photosynthesis that uses ATP and NADPH to reduce CO2 to sugar, involving carbon fixation, reduction, and regeneration phases.