ch 11 catabolism: energy release and conservation

Question 1

heterotroph

Answer 1

organisms that use organic molecules as their carbon source for growth

Question 2

autotrophs

Answer 2

organisms that use carbon dioxide as their sole or principal carbon source

Question 3

phototroph

Answer 3

use light as their energy source

Question 4

chemotroph

Answer 4

obtain energy from the oxidation of chemical compounds

Question 5

lithotrophs

Answer 5

rock eaters
use reduced inorganic substances as their electron source

Question 6

organotrophs

Answer 6

extract electrons from reduced organic compounds

Question 7

fueling reactions

Answer 7

the energy, electrons, and carbon that an organism obtains from its environment are used is chemical reactions
- ATP
- reducing power
- precursor metabolites

Question 8

chemolithoautotrophs

Answer 8

oxidize inorganic compounds such as iron, nitrogen, or sulfur containing molecules to derive both energy and electrons for biosynthesis, and use carbon dioxide as their carbon source
use respiration and fermentation

Question 9

respiration

Answer 9

an energy-yielding process in which the energy substrate is oxidized using an exogenous or externally derived electron acceptor
- in aerobic respiration the final electron acceptor is oxygen
- in anaerobic respiration the final electron acceptor is a different oxidized molecule such as NO3-, SO42-, Fe3+

Question 10

fermentation

Answer 10

does not use ETC
an energy-yielding process in which an organic molecule is oxidized without an exogenous electron acceptor. usually pyruvate or a pyruvate derivative serves as the electron acceptor

Question 11

3 pathways that catabolize glucose to pyruvate in the cytosol

Answer 11

1 Embden-Meyerhof pathway
2 Entner-Doudoroff pathway
3 pentose phosphate pathway

Question 12

Embden-Meyerhof pathway (EMP)

Answer 12

most common pathway for glucose degradation to pyruvate
found in all major groups of microorganisms, plants and animals, and functions in the presence or absence of O2
provides NADH, ATP
glucose + 2ADP + 2Pi + 2NAD+ -> 2 pyruvate + 2ATP + 2NADH + 2H+

Question 13

Entner-Doudoroff pathway (EDP)

Answer 13

used by some gram-negative bacteria, especially those found in soil
EDP: glucose + ATP + NADP+ -> pyruvate + glyceraldehyde 3-phosphate + ADP + NADPH + H+
EMP: glyceraldehyde 3-phosphate + 2ADP + NAD+ -> pyruvate + 2ATP + NADH + H+

Question 14

pentose phosphate pathway

Answer 14

used aerobically or anaerobically
oxidizes glucose 6-phosphate to ribulose 5-phosphate and then converts it to a variety of three to seven carbon sugars
glucose 6-phosphate + 12NADP+ + 6H2O -> 6CO2 + 12NADPH + 12H+ + Pi

Question 15

tricarboxylic acid cycle

Answer 15

citric cycle/krebs cycle
cycle must turn twice to completely oxidize one molecule of glucose
common in aerobic bacteria, archaea, free-living protists, and fungi
major role is to produce precursor metabolites used in biosynthesis

Question 16

mitochondrial electron transport chain

Answer 16

a series of electron carriers, operating together to transfer electrons from NADH and FADH2 to a terminal electron acceptor O2
- electrons flow from carriers with more negative reduction potentials to carriers with more positive reduction potentials

Question 17

two kinds of electron carrier proteins

Answer 17

• flavin: redox active, part of the molecule reduced when electron is accepted and then oxidized when that electron is donated; carry both electron and proton
• quinones (coenzyme Q): no prosthetic group, can directly be reduced and oxidized; carry both electron and proton
• cytochromes and iron sulfur proteins: can only carry protons

Question 18

bacterial and archaeal ETC aspects

Answer 18

flexible - change components of their ETCs to respond to different environmental conditions; electron carriers can be replaced or different terminal oxidases may be used

Question 19

bacterial chain ETC

Answer 19

• P. denitrificans
  can use one-carbon molecules (methanol) instead of glucose as a source of energy and electrons
• E. coli
  two branches; one for when oxygen is available, other when oxygen is limited

Question 20

oxidative phosphorylation

Answer 20

process by which ATP is synthesized using the energy from electron transport, which in turn is driven by the oxidation of a chemical energy source

Question 21

proton motive force

Answer 21

the combined chemical and electrical potential differences
used to perform work when protons flow back across the membrane, down the conc and charge gradients, and into the cytoplasm
flow is exergonic
also used by many secondary active transport mechanisms

Question 22

ATP synthase

Answer 22

an enzyme that catalyzes synthesis of ATP from ADP and Pi using energy derived from the proton motive force

Question 23

anaerobic respiration

Answer 23

chemoorganotrophic process whereby a terminal electron acceptor other than O2 is used for electron transport (nitrate, sulfate, CO2, metals, organic molecules)
generally yields less ATP than aerobic

Question 24

dissimilatory nitrate reduction

Answer 24

use of nitrate as terminal electron acceptor, making it unavailable to cell for assimilation or uptake

Question 25

denitrification

Answer 25

reduction of nitrate to nitrogen gas

Question 26

fermentation

Answer 26

does not require ETC
oxygen not needed
ATP formed by substrate-level phosphorylation

Question 27

homolactic fermenters

Answer 27

use the EMP and directly reduce almost all their pyruvate to lactate with the enzyme lactate dehydrogenase
- cheese, yoghurt, kimchi

Question 28

heterolactic fermenters

Answer 28

form products other than lactate (ethanol, CO2)

Question 29

alcoholic fermentation

Answer 29

fermentation of sugars to ethanol and CO2
pyruvate is decarboxylated to acetaldehyde which is then reduced to ethanol by alcohol dehydrogenase with NADH as the electron donor
- beer, wine

Question 30

mixed acid fermentation

Answer 30

results in the excretion of a mixture of acids (acetic, lactic, succinic, formic acids) and ethanol

Question 31

butanediol fermentation

Answer 31

butanediol is the major end product

Question 32

catabolism of carbs

Answer 32

goal is to convert the carb into a monomer that can be fed into a glycolytic pathway

Question 33

catabolism of lipids

Answer 33

triglycerides are common energy sources
hydrolyzed to glycerol and fatty acids by lipases, glycerol degraded via glycolytic pathway
fatty acids from triacylglycerols and other lipids can be oxidized in the beta-oxidation pathway after being linked to coenzyme A

Question 34

protease

Answer 34

hydrolyzes proteins to amino acids

Question 35

deamination

Answer 35

removal of amino group from amino acid

Question 36

catabolism of protein and amino acid

Answer 36

deamination accomplished by transamination
resulting organic acids converted to pyruvate, acetyl-coA, or TCA cycle intermediate

Question 37

chemolithotroph

Answer 37

rock eaters
carried out by certain bacteria and archaea
obtain electrons by oxidizing inorganic molecules
terminal electron acceptor is usually O2
to grow and reproduce, must oxidize a large quantity of inorganic material

Question 38

three major groups of chemolithotrophs

Answer 38

• oxidize hydrogen
• oxidize nitrogen
• oxidize sulfur

Question 39

nitrifying bacteria

Answer 39

soil and aquatic bacteria that carry out nitrification - the oxidation of ammonia to nitrate

Question 40

sulfur-oxidizing bacteria

Answer 40

flexible metabolism depending on environment
ATP can be synthesized by both oxidative phosphorylation and substrate-level phosphorylation

Question 41

flavin-based electron bifurcation (FBEB)

Answer 41

the conservation of energy by linking an unfavourable endothermic reaction with a favourable exothermic reaction

Question 42

two parts of photosynthesis

Answer 42

light reaction - light energy is trapped and converted to chemical energy
dark reaction - energy produced in the light reactions is used to reduce CO2 and synthesize cell constituents

Question 43

oxygenic photosynthesis

Answer 43

oxygen is generated and released when water is reduced
carried out by cyanobacteria and photosynthetic eukaryotes that contain chloroplasts

Question 44

chlorophyll

Answer 44

large planar molecules composed of four pyrrole rings with a central magnesium atom coordinated to the four nitrogen atoms of the pyrrole rings
major light-absorbing pigments - red and blue absobed

Question 45

accessory pigments

Answer 45

carotenoids and phycobiliproteins
help chlorophylls harvest light energy but they cannot harvest energy directly

Question 46

anoxygenic photosynthesis

Answer 46

molecules other than water are used as an electron source and therefore O2 is not produced
different pigments are used
only one photosystem used
different mechanisms used to generate reducing power
carried out by phototrophic green bacteria, phototrophic purple bacteria, heliobacteria

Question 47

rhodopsin-based phototrophy

Answer 47

microbes that use this live in nutrient depleted environments where organic carbon is limited
uses archaerhodopsin - a deep purple pigment, function as a light-driven proton pump