MICR 20 - LEC 6

What is metabolism?

The sum of all chemical reactions in an organism.

What is catabolism?

The breakdown of chemical bonds that releases energy.

What is anabolism (biosynthesis)?

The process of making chemical bonds that requires energy.

How are catabolism and anabolism related?

Catabolism provides the building blocks and energy needed for anabolism.

What are enzymes?

Biological catalysts that carry out specific chemical reactions without being used up.

What happens when a substrate enters an enzyme's active site?

A temporary enzyme-substrate union forms through induced fit, allowing the reaction to occur.

What happens to the product after an enzyme reaction?

The product is formed and released, while the enzyme remains available for another reaction.

What two factors can denature enzymes?

Temperature and pH.

What is a redox reaction?

A coupled reaction in which one substance loses electrons and another gains electrons.

What happens to a molecule that loses electrons?

It is oxidized.

What happens to a molecule that gains electrons?

It is reduced.

What are the two components of a redox pair?

An electron donor and an electron acceptor.

How can energy from redox reactions be captured?

It can be used to phosphorylate ADP or another compound.

How is ATP generated?

By phosphorylation of ADP.

What is substrate-level phosphorylation?

The direct transfer of a high-energy phosphate group to ADP to make ATP.

What is oxidative phosphorylation?

ATP synthesis from the oxidation of nutrients; it includes chemiosmosis driven by a proton gradient and ATP synthase.

What are the three main steps of carbohydrate catabolism?

Glycolysis, the Krebs cycle, and the electron transport chain.

Where does glycolysis occur?

In the cytoplasm.

What happens during glycolysis?

Glucose is catabolized into pyruvic acid.

What happens to pyruvic acid before the Krebs cycle?

It is catabolized to acetyl-CoA.

What enters the Krebs cycle?

Acetyl-CoA.

What is the purpose of the Krebs cycle?

A series of enzymatic reactions that further acquire energy from glucose.

What is the electron transport chain?

A chain of carrier molecules that transfers chemical energy from glucose breakdown to ATP synthase.

What does ATP synthase do?

Uses energy through chemiosmosis to produce ATP.

Where does the Krebs cycle occur in eukaryotic cells?

In the mitochondrial matrix.

Where does the Krebs cycle occur in prokaryotic cells?

In the cytoplasm.

Where does the electron transport chain occur in eukaryotic cells?

On the mitochondrial inner membrane.

Where does the electron transport chain occur in prokaryotic cells?

On the plasma membrane.

Where does glycolysis occur in both eukaryotes and prokaryotes?

In the cytoplasm.

What is cellular respiration?

The catabolism of molecules such as glucose that releases electrons and generates ATP through oxidative phosphorylation.

What is aerobic respiration?

Respiration in which molecular oxygen (O₂) is the final electron acceptor.

What is anaerobic respiration?

Respiration in which the final electron acceptor is not O₂.

Which produces more energy: aerobic or anaerobic respiration?

Aerobic respiration.

Why does anaerobic respiration produce less energy?

Only part of the Krebs cycle operates under anaerobic conditions according to the lecture.

What is fermentation?

A metabolic process that releases energy from an organic molecule without oxygen or an electron transport system and uses an organic molecule as the final electron acceptor.

What are the two common types of fermentation?

Lactic acid fermentation and ethanol fermentation.

What is the major difference between respiration and fermentation?

Respiration uses an electron transport chain, while fermentation does not.

How much ATP does aerobic respiration produce per glucose according to the lecture?

38 ATP.

How much ATP does fermentation produce per glucose according to the lecture?

2 ATP.

What are the three major nutritional classification factors shown in the lecture?

Energy source, carbon source, and final electron acceptor.

What is a photoautotroph?

An organism that uses light for energy and CO₂ as its carbon source.

What is a chemoheterotroph?

An organism that obtains energy and carbon from organic compounds.

What is an example of a photoautotroph?

Algae.

What is an example of a chemoheterotroph?

Humans.

What type of organism can be both chemoheterotrophic and anaerobic?

Fermenting bacteria.

What is a culture medium?

Nutrients prepared for microbial growth.

What does sterile mean?

Containing no living microbes.

What is an inoculum?

The introduction of microbes into a culture medium.

What is a culture?

Microbes growing in or on a culture medium.

What is carbon used for in microbial media?

Building structural organic molecules and providing an energy source.

What carbon source do chemoheterotrophs use?

Organic carbon such as carbohydrates.

What carbon source do autotrophs use?

Inorganic carbon such as CO₂.

Why do microbes need nitrogen?

Nitrogen is found in amino acids, proteins, and nucleic acid bases.

Why do microbes need sulfur?

Sulfur is found in amino acids, thiamine, and biotin.

Why do microbes need phosphorus?

Phosphorus is found in DNA, RNA, ATP, and membranes.

What are trace elements?

Inorganic elements required in small amounts, often serving as enzyme cofactors.

What are examples of trace elements?

Iron, copper, molybdenum, magnesium, and zinc.

What are organic growth factors?

Vitamins, amino acids, purines, and pyrimidines that some organisms cannot synthesize and must obtain from the environment.

What is agar?

A complex polysaccharide used as a solidifying agent for culture media.

At what temperature does agar liquefy and approximately solidify?

It liquefies at 100°C and solidifies at about 40°C.

What is a chemically defined medium?

A culture medium whose exact chemical composition is known.

What is a complex medium?

A culture medium containing extracts and digests from sources such as yeast, meat, or plants.