Cell and Molecular Biology Chapter 9

Define metabolism

the chemical processes that occur within a living organism in order to maintain life.

Define the anabolic pathway

The synthesis of macromolecules, requiring energy

Define the catabolic pathway

The breakdown of organic molecules to produce energy

Are catabolic reactions the exact reversal of anabolic reactions?

No, many reactions use different enzymes and have different intermediates.

What is aerobic catabolism?

Reactions carried out in the presence of oxygen.

What is anaerobic catabolism?

reactions carried out in the absence of oxygen

What is the most common energy molecule in cells?

ATP

What are other types of energy molecules in cells (besides ATP)?

GTP, creatine phosphate, NADH, NADPH

Which of the chemical bonds in ATP (phosphoanhydride bonds between phosphates, and phosphoester bonds between phosphate and ribose) contains higher energy?

Phosphoanhydride bonds

Why is ATP hydrolysis exergonic?

charge repulsion, resonance stabilization, increased entropy

Why is ATP important in cellular energy metabolism?

It occupies an intermediate position among energy-rich phosphorylated compounds in the cell: its dephosphorylated form (ADP) can receive phosphate from higher energy molecules, and ATP can serve as a phosphate donor to lower energy molecules. The ATP/ADP pair represents a reversible means of conserving, transferring, and releasing energy within the cell.

Why in many biological systems, are many enzymes catalyzing oxidation reactions called dehydrogenases?

Oxidation reactions involves both the removal of electrons and hydrogen atoms.

Is oxidation exergonic or endergonic?

Exergonic

Is reduction endergonic or exergonic?

Endergonic

Why do reduction and oxidation reactions occur simultaneously?

Each is a half reaction--one reactant is oxidized (electron donor), while the other is reduced (electron acceptor)

What is NAD+?

nicotinamide adenine dinucleotide is the most common coenzyme in biological systems for electron transfer: each NAD+ can accept two electrons and one hydrogen atom to become NADH and a proton.

What is the main energy source for most cells?

Glucose

What are the types of fermentation?

Lactate and alcoholic

What organisms use lactate fermentation?

Some animals and bacteria

What organisms use alcoholic fermentation?

yeasts, plants, and other microorganisms

Where do cells of chemotrophs get their glucose from?

Metabolizing carbohydrates such as glycogen and starch.

Why is glucose such a good source of energy?

one of the most important oxidizable substrates in energy metabolism; complete conversion of glucose to carbon dioxide and water produces -686 kcal/mol under standard conditions

What is the final electron acceptor for aerobic respiration?

Oxygen

What are the final electron acceptors for anaerobic respiration?

Organic molecules, S, H+, Fe 3+

What are the three types of organisms based on their need for oxygen?

Obligate aerobes, obligate anaerobes, and facultative organisms

What are the major characteristics of obligate aerobes?

Absolutely need oxygen (some bacteria, most fungi and algae, some animals)

What are the major characteristics of obligate anaerobes?

Cannot grow in the presence of oxygen, oxygen is toxic to them (some bacteria and fungi)

What are the major characteristics of facultative organisms?

Can function in aerobic or anaerobic conditions (some bacteria, some fungi, many invertebrates)

What are the major characteristics of glycolysis?

The metabolic pathway that converts glucose to pyruvate; is present in all organisms in the presence of oxygen, glycolysis leads to fermentation.

What are the major steps in glycolysis?

glucose—...—fructose-1,6-bisphosphate—twoglyceraldehyde-3-phosphate (G3P)—1,3-bisphosphoglyerate...— two pyruvate

What are the steps in glycolysis that involve ATP input?

glucose to glucose-6-phosphate, fructose-6-phosphate to fructose-1,6-bisphosphate

What are the steps in glycolysis that involve NADH generation?

G3P to 1,3-bisphosphoglyerate

What are the steps in glycolysis that involve ATP synthesis?

1,3-bisphosphoglycerate to 3-phosphoglycerate, and phosphoenolpyruvate to pyruvate

What is the overall reaction of glycolysis

glucose + 2NAD+ + 2ADP + 2 Pi 2pyruvate + 2NADH + 2H+ + 2ATP

What is the net ATP gain during glycolysis?

2ATP

What is substrate level phosphorylation?

Formation of ATP by directly transferring phosphate to ADP from a high-energy phosphorylated substrate.

What is the major purpose of fermentation?

regeneration of NAD+ so glycolysis can continue

What is the reaction for lactate fermentation?

2 pyruvate + 2NADH + 2H+ <--> 2 lactate + 2NAD+

What is the alcoholic fermentation reaction?

2 pyruvate + 2 NADH + 4H+ ----> 2 ethanol + 2NAD+ + 2CO2