Chapter 8 Review Sheets - Microbial Metabolism

What are the three macromolecules? (Excluding Lipids)

The three macromolecules are Nucleic Acids, Proteins, and Carbohydrates

What is metabolism?

What is anabolism?

What is catabolism?

Provide an example of each.

Metabolism —> all of the chemical reactions inside of cells — both anabolic and catabolic pathways

Anabolism —> chemical reactions that convert simple molecules into more complex ones — Amino Acid + Amino Acid = Dipeptide

Catabolism —> chemical reactions that break down complex molecules into simpler ones — Cellular Respiration

What is ATP?

How is ATP involved in linking anabolic and catabolic reactions?

ATP is the energy currency of the cell

Energy released during catabolic reactions are used to drive anabolic reactions

What is an enzyme?

Enzymes are catalysts for biochemical reactions inside cells

How does an enzyme increase the rate of a reaction?

An enzyme increases the rate of a reaction by decreasing the Activation Energy of the reaction

What is the active site of an enzyme?

What binds to the active site?

The active site is the location within an enzyme in which a substrate(s) binds

What is a substrate?

What can a substrate be?

Substrates are things that interact with the active site of an enzyme and are converted into product

Substrates can be any kind of molecule

What are the key characteristics of a Catalyst?

The key characteristics of a Catalyst are:

1. Increases the rate of the reaction by decreasing the Activation Energy

2. Enzymes are specific (only interact with a select amount of molecules)

3. They are not changed by the reaction (can change DURING reaction, but the end product is identical to the beginning reactant)

4. In biological systems, usually is a Protein

5. Enzyme names usually end in “-ase”

What is the turnover number?

The turnover number is the amount of reactions that an enzyme can complete in a given amount of time

What is a cofactor?

Are cofactors proteins?

Cofactors are inorganic ions that help stabilize enzyme conformation and function

Cofactors are NOT proteins

How does temperature and pH influence enzyme activity?

Extreme temperatures can cause enzymes to denature

They can change the performance of the enzyme throughout a certain range

How does substrate concentration influence enzyme activity?

When substrate concentrations are higher, enzyme activity is increased until it reaches a saturation point (enzyme can bind no additional substrates)

What is an inhibitor?

How does a competitive inhibitor differ from a non-competitive inhibitor?

How are they similar?

Inhibitors are molecules that slow or block a chemical reaction

Competitive Inhibitor —> binds to the active site to prevent substrate binding

Non-Competitive Inhibitor —> bind to allosteric sites to induce conformational change and prevent enzyme function

What is feedback inhibition?

Feedback inhibition is when the product of a metabolic pathway noncompetitively binds to an enzyme early in the pathway so as to prevent the synthesis of a product

How does Glucose act as an energy source?

What is the energy currency of the cell?

Energy trapped in the bonds of the Glucose molecule are released when the bonds break and the energy is stored as ATP

ATP is the energy currency of the cell

What is an oxidation-reduction reaction?

What does it mean for one thing to become oxidized and for another thing to become reduced?

Oxidation is loss, Reduction is gain

An Oxidation-Reduction (Redox) reaction is a reaction that pairs an Oxidation with a Reduction

What types of molecules are good sources of energy?

Give some examples

Electron Carriers

Examples:

• NAD+ / NADH

• NADP+ / NADPH

• FAD / FADH

It ________ energy to generate ATP

When ATP is hydrolyzed, energy is ________

Requires

Released

What are the different ways that ATP can be generated?

There are two different ways to generate ATP:

1. Substrate-Level Phosphorylation

2. Oxidative Phosphorylation

How does a catabolic reaction work?

A catabolic reaction starts with a reduced compound, then electrons are removed from the compound and used to generate reduced electron carriers (NAD+ —> NADH + H+) and ATP energy

End product is an oxidized form of the energy source

What is the difference between Respiration and Fermentation?

Which provides the cell with more energy?

Respiration —> final electron acceptor is Oxygen, creates water, occurs in Mitochondria and Cytoplasm

Fermentation —> final electron acceptor is not Oxygen, does not create water, occurs in Cytoplasm

Respiration creates more energy

What is Glycolysis?

What is generated during Glycolysis?

Is Glycolysis an example of Substrate-Level Phosphorylation, Oxidative Phosphorylation, or Photophosphorylation?

Glycolysis is the breaking down of sugar

ATP is generated and the end product is Pyruvic Acid

Glycolysis is an example of Substrate-Level Phosphorylation

What are the alternative ways to breakdown Glucose, besides Glycolysis?

There are two alternative pathways to Glycolysis to break down Glucose:

1. Entner-Doudoroff (ED) Pathway —> used by many enteric bacteria due to abundance of Gluconate; generates less ATP

2. Pentose Phosphate Pathway (PPP) —> generates 5-carbon intermediates to be used for the synthesis of biomolecules

What is Aerobic Respiration? What is Anaerobic Respiration?

Aerobic Respiration —> uses O2 and produces CO2, H2O, and a lot of ATP

Anaerobic Respiration —> does not use O2 and produces Lactic Acid, Ethanol, and a little ATP

What happens to Glucose during Aerobic Respiration?

What does it become?

Glucose is oxidized and creates ATP, CO2, and water

What is the Citric Acid / Krebs Cycle?

What is the starting molecule for this cycle? Where does it come from?

What is generated?

Why is it referred to as a cycle?

The CA Cycle is a metabolic pathway used to release energy stored in the chemical bonds of Acetyl-CoA

The starting molecule is Acetyl-CoA

It comes from the conversion of Pyruvate

Generates 3 NADH, 1 FADH2, and 1 ATP (& CO2)

It is referred to as a cycle because the starting reactant is regenerated as a final product

What happens in the Electron Transport Chain?

Where do the electrons that feed the ETC come from?

During the ETC, electrons from NADH and FADH2 are passed from one ETC electron carrier to another

The electrons come from the breakdown of Glucose during Glycolysis

Where is most of the ATP generated during Aerobic Respiration?

How is this energy generated?

Most of the ATP in Aerobic Respiration is generated during the ETC

It is generated via Oxidative Phosphorylation

What powers the ATP Synthase?

Proton Motive Force

What if fermentation?

Why do organisms that grow via fermentation grow more slowly than those that respire aerobically?

Fermentation is the process of using an organic molecule as a final electron acceptor so as to regenerate NAD+ from NADH— this allow glycolysis to continue

They grow slower because they generate less energy available for use

Which method would a facultative organism use if present conditions could support either mode of metabolism — Aerobic or Fermentation?

The organism would use Aerobic Respiration because it produces more ATP

What determines the end products of Fermentation?

The end products of Fermentation are determined by the enzymes available during the process

What process do organisms get their energy from when they go through Fermentation?

Substrate-Level Phosphorylation

What are some sources of energy used by the cell other than glucose?

Would the same central metabolic pathways be used to gain energy from these sources?

Other sources include Lactic Acids, Fatty Acids, and Proteins

Similar, but not identical, pathways would be used

Define the following carbon-source organisms:

• Chemoheterotroph

• Chemoautotroph

• Photoheterotroph

• Photoautotroph

Chemoheterotroph —> uses organic molecules as its carbon source; AKA Organotroph

Chemoautotroph —> uses inorganic molecules as its carbon source; AKA Lithotroph

Photoheterotroph —> uses light energy, but cannot solely use CO2

Photoautotroph —> uses light energy and inorganic carbon sources

What determines if an organism can use a specific carbon source to generate energy?

Whether they have the enzymes necessary to break the sources down

How is a Triglyceride broken down?

How do the individual components feed into the central metabolic pathway?

Lipase helps hydrolyze the bond to allow the fatty acids to be released from the Glycerol

The Glycerol then can be used to create Glucose

What is the name of the process used to break down fatty acids?

Beta Oxidation

What is the name of the enzyme used to break down Triglycerides and other fats?

Lipase

Why does the cell need extracellular proteases?

What are two examples of extracellular proteases?

Cells need extracellular proteases because external proteins are too large to be transferred across the cell wall

Two examples include Caseinase and Gelatinase

What is the fate of smaller peptides?

How are they used for energy?

Small peptides are taken up into the cell to be further broken

They eventually enter the Transition reaction or the Krebs Cycle

How does carbon cycling work with Autotrophs and Heterotrophs?

Autotrophs fix CO2 into organic compounds

Heterotrophs consume those compounds and respirate the CO2 back out into the air

Explain the different parts of the Nitrogen Cycle

Nitrogen Fixation —> nitrogen is converted into Ammonia

Nitrification —> ammonia is converted into NItrate by the presence of bacteria in the soil

Assimilation

Ammonification —> dead organisms release nitrogen back into the soil and decomposers convert it back into Ammonium

Denitrification —> nitrogen compounds make their way back into the atmosphere by converting nitrate into nitrogen gas

What is the role of Cyanobacteria in Nitrogen Fixation?

What is a heterocyst?

What is a Nitrogenase?

Cyanobacteria fix inorganic Nitrogen into Ammonia

Heterocyst —> specialized nitrogen-fixing cells formed by some filamentous Cyanobacteria

Nitrogenase —> enzymes produced by certain bacteria that is used to reduce nitrogen into ammonia

Why can most organisms not fix nitrogen?

What group of organisms is the only group able to naturally fix nitrogen?

Most organisms cannot fix nitrogen cause it is not in a usable form

Bacteria are the only group of organisms able to naturally fix nitrogen

What is bioremediation?

Why might bioaugmentation be necessary?

Bioremediation —> use of microbes to remove xenobiotics or environmental pollutants

Bioaugmentation ensures that all contaminants degrade completely

Why might Xenobiotics be difficult for organisms to break down?

Synthetic compounds (Xenobiotics) are man-made, meaning that most normal biological processes have no natural way of properly degrading them