Ch 7 - Metabolism

What is central carbon catabolism?

The cellular process of breaking down food, a carbon source gets oxidized (e.g. glucose gets oxidized into CO2), energy is transferred to ATP and e- carriers

What is glycolysis?

The oxidation of a carbon source into pyruvate (e.g. glucose), can occur with or without oxygen

What inputs are required for glycolysis?

1 carbon source molecule (e.g. glucose) and 2 ATP

What outputs are yielded from glycolysis?

4 ATP (via substrate-level phosphorylation), 2 NADH, 2 pyruvates, and intermdediates

What are the 2 additional pathways to glycolysis?

Pentose phosphate pathway and the Entner-Doudoroff pathway

What is the pentose phosphate pathway?

A pathway that converts sugars into pentoses, yield can vary (2 NADPH and 1 ATP)

What is the Entner-Doudoroff pathway?

An alternative pathway to glycolysis that still generates pyruvate, yields 1 NADPH, 1 NADH, and 1 ATP

What is the preparatory/intermediate step?

The step where pyruvate gets turned into acetyl-CoA

What are the inputs for the preparatory/intermediate step?

2 molecules of pyruvate

What are the outputs yielded from the preparatory/intermediate step?

2 NADH, 2 CO2 (waste), 2 acetyl- CoA, and intermediates

What is the TCA/Krebs cycle?

A cycle that oxidizes acetyl-CoA into CO2, glucose gets fully oxidized by this point

What are the inputs for the TCA/Krebs cycle?

2 acetyl-CoA

What are the outputs yielded from the TCA/Krebs cycle?

4 CO2 (waste), 6 NADH, 2 FADH2, and 2 ATP (via substrate-level phosphorylation), and intermediates

Why are multi-step pathways beneficial for bacteria?

They are beneficial because they help the bacteria regulate those pathways and allow for intermediates to be redirected into other pathways depending on what the cell needs

What is the final expected yield of ATP from glycolysis?

38 (2 from glycolysis, 2 from TCA, 34 from ETC)

What is the electron transport chain?

A series of oxidoreductase enzymes that are part of the membrane-bound protein complexes, pass e- (via redox reactions) to stronger and stronger e- acceptors, released energy allows some complexes to pump protons (H+) across the cell membrane, generating a chemiosmotic gradient (proton motive force)

Where do the e- come from for the ETC?

They can come from NADH, FADH2, etc.

Where do the protons get pumped from the ETC?

They get pumped outside of the cell membrane into the periplasm

What are some variations of the ETC in bacteria?

Some bacteria have no mitochondria; therefore, the ETC occurs across the cell membrane instead of within the mitochondria, bacteria can have various numbers and arrangements of ETC complexes, they can have a different cytochrome C placement, they can have a different terminal complex

What are some similarities in bacterial respiration?

The general types of redox centers are the same, the goals is the same (to transfer e- to create a proton gradient), the need for a membrane, and the use of ATP synthase used in oxidative phosphorylation

What is chemiosmosis?

The process of pumping proton ions across a cell membrane to drive ATP synthesis

What is ATP synthase?

An enzyme that uses energy from the proton gradient to make ATP via oxidative phosphorylation

What is oxidative phosphorylation?

A metabolic pathway that oxidizes compounds (e.g. NADH and FADH2) to release energy provide e- for the ETC

What is anaerobic respiration?

The process of respiration without the presence of oxygen, cell will use a different final e- acceptor (often a small inorganic compound, will likely have a lower affinity for e- relative to O2), results in less energy than aerobic respiration but still enough to support growth

What is fermentation?

The partial catabolism of glucose (or another carbon source) to transfer e- energy to pyruvate (or a pyruvate derivative), results in the slowest growth

What is the goal of fermentation?

To regenerate NAD+

What are obligate fermentors?

Bacteria that do not have an ETC and therefore must ferment to survive

What is the final e- acceptor in fermentation?

Pyruvate

How much ATP is gained from fermentation?

2 ATP/glucose

What is lactic acid fermentation?

A type of fermentation where pyruvate is reduced to lactic acid (option for human muscles when oxygen is low)

What is alcohol fermentation?

A type of fermentation where pyruvate is converted to acetaldehyde and CO2 is released while acetaldehyde is reduced to ethanol (useful is brewing and breadmaking)

What are the benefits of fermentation?

It allows microbes to thrive in anaerobic environments, products can help feed other microbes (symbiotic relationships), it can act as a backup option when oxygen is low/not present

What are phototrophs?

Bacteria that use light for energy

What are photoautotrophs?

Bacteria that use light for energy and perform CO2 fixation as a source of carbon

What are photoheterotrophs?

Bacteria that use light for energy and organic compounds for a carbon source

What are chemotrophs?

Bacteria the use inorganic/organic compounds for energy

What are chemoorganotrophs/chemohetertrophs?

Bacteria that use organic compounds for energy and as a carbon source

What are chemolithotrophs/chemoautotrophs?

Bacteria that use inorganic compounds for energy and perform CO2 fixation as a source for carbon

What are mixotrophs?

Chemolithotrophs who can use organic carbon sources

How do chemolithotrophs/chemoautotrophs make up for their inefficient levels of ATP production?

They consume massive amount of inorganic substances and operate at a high turnover rate to compensate for their low energy/food molecule ratio

Only what type of bacteria can be chemolithotrophs?

ONLY prokaryotes can be chemolithotrophs

What is photophosphorylation?

The production of ATP from a light source, uses an ETC, PMF, chemiosmosis, and ATP synthase

Why do plants need water for photosynthesis?

They need it because the splitting of the molecule provides protons for the proton gradient

What does oxygenic mean?

It means that phototroph uses water and releases oxygen (algae and cyanobacteria), uses 2 photosystems with chlorophylls and thylakoid membranes

What does anoxygenic mean?

It means that phototroph uses an alternative molecule (e.g. H2, S2, etc.) other than water and DOES NOT release oxygen (green and purple bacteria), use 1 photosystem with bacteriochlorophylls and specialized membranes called chromatophores and chlorosomes

What are autotrophs?

Build their own carbon sources internally instead of pulling them from the environment, can be photo- or chemo-, use carbon fixation or energy and CO2 to synthesize organic carbon compounds (sugars)

Who performs the calvin cycle?

Phototrophs and chemolithoautotrophs