Microbiology (Chapter 10)

Metabolism

all chemical reactions and physical workings of the cell

Anabolism

biosynthesis; synthesis of cell molecules and structures, requiring energy input

Catabolism

process that breaks the bonds of larger molecules to yield energy

Enzymes

catalysts that speed up the rate of a chemical reaction without being consumed

Endoenzymes

enzymes that are retained intracellularly and function inside the cell

Exoenzymes

enzymes that are transported extracellularly to break down large food molecules or harmful chemicals

What is the role of cofactors in enzyme activity?

they assist enzymes in aligning substrates, activating enzymes, or participating in chemical reactions.

What are the 6 classes of enzymes?

1. Oxidoreductases

2. Transferases

3. Hydrolases

4. Lyases

5. Isomerases

6. Ligases

Competitive inhibition

a mimic occupies the active site, competing directly with the substrate

Noncompetitive inhibition

molecules bind to a separate regulatory site, altering enzyme conformation

What happens to enzymes under altered temperature or pH?

they can become denatured, breaking weak bonds, distorting shape, and preventing substrate attachment.

Lactase

it breaks lactose down into glucose and galactose

Penicillinase

it hydrolyzes the beta-lactam ring of penicillin

DNA polymerase

it synthesizes a DNA strand using complementary DNA nucleosides

Redox reactions

they involve the transfer of electrons between an electron donor and acceptor, crucial for energy transfer

Exergonic Reactions

Reactions that release energy as they proceed forward.

Endergonic Reactions

Reactions that require the input of energy to move forward.

Dehydrogenation

the removal of hydrogen atoms during redox reactions

Constitutive enzymes

enzymes that are always present in relatively constant amounts regardless of cellular environment.

Regulated enzymes

enzymes whose production is turned on or off in response to substrate concentrations.

Active site

a place on enzyme where the substrate binds; a three-dimensional crevice formed by folded amino acid chains

What is the importance of enzyme specificity?

Each enzyme has a unique shape and function, allowing it to catalyze specific reactions.

What is the function of metallic cofactors?

They assist with precise enzyme-substrate alignment and can activate enzymes.

Enzyme repression

suppression of enzyme synthesis by excess product

Enzyme induction

synthesis of enzymes that occurs only when suitable substrate is present

Krebs Cycle

a cyclic metabolic pathway involved in energy production

Electron carriers

molecular shuttles that transport electrons during metabolic processes

Most common electron carrier?

NAD+ (Nicotinamide adenine dinucleotide)

What is the structure of ATP?

Composed of adenine, ribose, and three phosphate groups.

What is substrate-level phosphorylation?

Direct transfer of a phosphate group from a phosphorylated substrate to ADP.

Oxidative phosphorylation

a series of redox reactions occurring during the final phase of respiratory pathways

Photophosphorylation

ATP formation through sunlight-driven reactions in photosynthetic organisms

What is the net ATP yield from glycolysis?

2 ATP

What does the Krebs cycle yield per turn?

3 NADH, 1 FADH2, 1 ATP, and 2 CO2

What is the final electron acceptor in aerobic respiration?

Molecular oxygen (O2)

How does anaerobic respiration differ from aerobic respiration?

Anaerobic respiration uses non-O2 inorganic compounds as final electron acceptors while aerobic respiration needs O2.

Fermentation

the incomplete oxidation of glucose in the absence of O2, producing alcohols or acids

What is the role of lipases in metabolism?

They break triglycerides into glycerol and fatty acids for energy production.

Amphibolism

the integration of catabolic and anabolic reactions to optimize cellular efficiency

Calvin cycle

an anabolic pathway that fixes CO2 into glucose using ATP and NADPH.

Light-dependent reactions

catabolic reactions that generate ATP and NADPH and release O2 in photosynthesis

Light-independent reactions?

anabolic reactions that utilize ATP and NADPH to synthesize glucose

What distinguishes oxygenic photosynthesis from anoxygenic photosynthesis?

Oxygenic photosynthesis uses H2O as an electron donor and releases O2, while anoxygenic does not.

Eelectron transport system (ETS)

system that pumps H+ ions across the membrane, creating a proton motive force for ATP synthesis

How many ATP can be produced from one glucose molecule in aerobic respiration?

36-38 ATP

Proteases

they break proteins into amino acids for energy production and biosynthesis

What is the maximum ATP yield from fermentation?

2 ATP

How does the Krebs cycle differ between bacteria and eukaryotes?

The Krebs cycle operates in the cytoplasm of bacteria VS in the mitochondria of eukaryotes.

What happens to pyruvic acid before entering the Krebs cycle?

It is converted to acetyl CoA, releasing CO2 and generating NADH.

What are precursor molecules in metabolism?

Organic compounds diverted from catabolism to serve as starting substrates for biosynthesis.

What is the role of G3P in metabolism?

It is diverted from glycolysis to synthesize amino acids, carbohydrates, and triglycerides.

What is the significance of chemiosmosis in ATP synthesis?

H+ ions diffuse back through ATP synthase, driving the phosphorylation of ADP to ATP.

Apoenzyme

the protein portion of a conjugated enzyme

Holoenzyme

includes both the apoenzyme and its cofactor