Final Exam Flashcards
What is metabolism?
Metabolism is the overall process through which living systems acquire and use free energy to carry out their various functions, is traditionally divided into two parts:
Catabolism, how energy is gained from the break-down
Anabolism, how energy is used for biosynthesis
Metabolism are the reactions by which biomolecules are built and broken down
difference between catabolism and anabolism
Anabolism is the building of complex molecules from numerous simple ones. Think of protein synthesis.
Catabolism is the breakdown of complex molecules into numerous simple ones.
is catabolism exergonic or endergonic
In general, catabolic reactions carry out the exergonic oxidation of nutrient molecules. The free energy thereby released is used to drive such endergonic processes as anabolic reactions, the performance of mechanical work, and the active transport of molecules against concentration gradients.Exergonic and endergonic processes are often coupled through the intermediate synthesis of a “high-energy” compound such as ATP.
In an exergonic reaction, energy is released to the surroundings. The bonds being formed are stronger than the bonds being broken. In an endergonic reaction, energy is absorbed from the surroundings. The bonds being formed are weaker than the bonds being broken.
Many of the specific reactions of metabolism are common to all organisms, with variations due primarily to the sources of the free energy that supports them. What are the different metabolic sources of energy?
Autotrophs are organisms that can produce their own food from the substances available in their surroundings using light (photosynthesis) or chemical energy (chemosynthesis).
(a) plants, (b) algae, and (c) certain bacteria.
Heterotrophs cannot synthesize their own food and rely on other organisms — both plants and animals — for nutrition.
An autotroph is an organism that can synthesize their organic molecules from simple inorganic substances. They are producers. A heterotroph is a consumer and it obtains organic molecules from other organisms.
Organisms can be further classified by the identity of?
the oxidizing agent for nutrient breakdown/by their requirement for oxygen
the oxidizing agent for nutrient breakdown/by their requirement for oxygen
Obligate aerobes (which include animals) must use O2, whereas anaerobes employ oxidizing agents such as sulfate or nitrate. Facultative anaerobes, such as E. coli, can grow in either the presence or the absence of O2 . Obligate anaerobes, in contrast, are poisoned by the presence of O2
isozymes
An intriguing manifestation of specialization of tissues and subcellular compartments is the existence of _____, enzymes that catalyze the same reaction but are encoded by different genes and have different kinetic or regulatory properties.
A
isozymes
Different tissues often express different isozymes to match tissue function.
using different forms of the same enzyme to catalyze a given biochemical reaction. These different forms of the same enzyme are known as isozymes or isoenzymes. Isozymes arise from different genes, have different sequences of amino acids and a different structure yet catalyze the same reaction, have different properties and exhibit different enzymes kinetics and are usually controlled by different allosteric effectors.
Energy from oxidation of metabolic fuel is released stepwise. In what form is it stored and made available to drive endergonic processes?
ATP - the primary energy “currency” of the cell.
Why are phosphoanhydride bonds “high-energy”?
- Resonance stabilization of products larger than that of substrates.
- Mutual repulsion of negatively charged groups larger in substrates than in products.
- Smaller solvation energy of phosphoanhydride as compared to hydrolysis products.
Why is ATP so stable, despite the large amount of free energy released by its hydrolysis?
How can you drive an endergonic reaction?
Couple it with an exergonic reaction. Purpose of Coupled Reactions?
A
The hydrolysis of a “high-energy” compound, while releasing considerable free energy, is not in itself a useful reaction. However, the exergonic reactions of “high-energy” compounds can be coupled to endergonic processes to drive them to completion
Inorganic pyrophosphatase function
supply additional “driving force”.
Catalyzes Additional Phosphoanhydride Bond Cleavage by suppling additional “driving force”.
is an enzyme that catalyzes the conversion of one ion of pyrophosphate to two phosphate ions.[1] This is a highly exergonic reaction, and therefore can be coupled to unfavorable biochemical transformations in order to drive these transformations to completion.[2]
Explain how cellular ATP is replenished by phosphagens.
A
utilizes phosphocreatine and ADP to regenerate ATP in the cell when at rest (relies on concentration of substrate and products to determine if reaction should go forward or reverse)
What are thioesters?
“primitive” high-energy compounds
involved in substrate-level phosphorylation
acetyl-coenzyme A (acetyl-CoA)
Phosphocreatine function?
Phosphocreatine provides a “high-energy” reservoir for ATP formation (in muscles, nerves). How is phosphocreatine regenerated?
ATP + creatine –>ADP + phosphocreatine
most common source of energy in organisms? most common electron carriers?
OXIDATION-REDUCTION REACTIONS
“REDOX REACTIONS”
- NAD+ transfers 2 electrons
- FAD transfers one electron
- Fe2+/3+
They accept high energy electrons and carry them ultimately to the electron transport chain where they are used to synthesize ATP molecules
NAD + and FAD are not direct sources of energy, so what do they do?
A
When these electron carrier molecules accept the electrons, they are reduced into and form energy molecules NADH and FADH2
How do redox reactions occur? Loss of electrons is what? Gain of electrons is?
electrons are transferred from electron donor
(reducing agent) to electron acceptor (oxidizing agent)
loss of electrons = oxidation; gain of electrons = reduction
Slides 25-39 Glycolysis reactions
What is homolactic fermentation?
The process in which Under anaerobic conditions in muscle, pyruvate is reduced to lactate to regenerate NAD +
slide 41
What catalyzes the oxidation of NADH by pyruvate to yield NAD+ and lactate.
lactate dehydrogenase (LDH)
This reaction is often classified as Reaction 11 of glycolysis. The lactate dehydrogenase reaction is freely reversible, so pyruvate and lactate concentrations are readily equilibrated.
What is Alcoholic Fermentation?
Alcoholic Fermentation Converts Pyruvate to Ethanol and CO2
In yeast and certain other microorganisms, pyruvate is decarboxylated to yield CO 2 and acetaldehyde, which is then reduced by NADH to yield NAD +and ethanol.
the conversion of pyruvate to ethanol and CO2. to regenerate NAD+ FOR glycolysis
Yeast produces ethanol and CO 2 via what two consecutive reactions?
The decarboxylation of pyruvate to form acetaldehyde and CO 2 as catalyzed by pyruvate decarboxylase (an enzyme not present in animals).
The reduction of acetaldehyde to ethanol by NADH as catalyzed by alcohol dehydrogenase (Section 11-1C), thereby regenerating NAD + for use in the GAPDH reaction of glycolysis.
which needs a cofactor, Alcoholic Fermentation or Homolactic Fermentation?
Alcoholic Fermentation,
TPP Is an Essential Cofactor of Pyruvate Decarboxylase. Pyruvate decarboxylase contains the coenzyme thiamine
pyrophosphate
pyruvate is decarboxylated by a thiamine pyrophosphate (TPP)–dependent mechanism, and the resulting acetaldehyde is reduced to ethanol.
Compare the ATP yields and rates of ATP production for anaerobic and aerobic degradation of glucose.
he rate of ATP production by anaerobic glycolysis can be up to 100 times faster than that of oxidative phosphorylation
But Aerobic yields more ATP 32 per glucose and Fermentation is 2 ATP per glucose
Consequently, when tissues such as muscle are rapidly consuming ATP, they regenerate it almost entirely by anaerobic glycolysis.