micro exam 3

what is metabolism?

the sum of all chemical reactions in the cell

what is catabolism?

a chemical reaction that breaks down a compound, often endergonic and reductive

what is anabolism?

a chemical reaction that builds up a compound, often exergonic and oxidative

what is intermediary metabolism?

a chemical reaction that converts one small molecule to another, usually no change in energy or redox

what’s an example of intermediary metabolism?

GTP/ATP exchange

what is the equation for GTP/ADP exchange?

GTP + ADP → ATP + GDP

what are the goals of energy-yielding metabolism?

trap energy in high-energy phosphate compounds and produce useful intermediates

why does energy-yielding metabolism occur in many small steps?

capture as much energy as possible, provide many opportunities for control, and provide a variety of intermediates for synthesis

what are the most important energy-yielding processes?

glycolysis, Krebs cycle, Pentose phosphate pathway, Beta oxidation of fatty acids

what are glycolysis and the Krebs cycle linked to in respiratory organisms? why?

electron transport, to provide additional energy

what is the purpose of glycolysis?

Primarily for energy harvest from carbohydrates, but many other molecules
can feed into it.

What’s the most common type of pathway for glycolysis?

the Embden Meyerhof pathway

Where does glycolysis occur?

the cytoplasm

what’s a constitutive process?

a process that is happening at all times

what’s the net equation for glycolysis?

glucose + 2NADox + 2Pi + 2ADP→ 2 pyruvate + 2NADred + 2ATP

examples of constitutive process

glycolysis

summarize the Emden-Meyerhof pathway

Energy from two ATPs is used to rearrange the glucose molecule and split it in half. These two halves contain phosphates from the ATP

what is a kinase?

an enzyme that catalyzes exchange of phosphate between a nucleotide and another organic molecule

what is a dehydrogenase?

an enzyme that catalyzes exchange of electrons (or H) between organic molecule and coenzyme

what’s the net product of glycolysis?

2 ATP

what happens to glucose after it’s split in half?

the two halves are oxidized and phosphorylated at the same time. Electrons from oxidation are transferred to coenzyme (NADox)

How is ATP made in glycolysis?

one phosphate is transferred from each half of glucose to ADP to make ATP

what part of respiration do non-respiratory organisms participate in?

glycolysis

how do respiratory organisms recover NADox?

they send NADred to electron transport to “dump off” electrons

how do non-respiratory organisms recover oxidized NAD?

they use fermentation

what is fermentation?

oxidation of organic energy source using endogenous terminal electron acceptor

what are the two most important types of fermentation?

(homo)lactic acid fermentation, ethanolic fermentation

equation for homolactic acid fermentation

pyruvate + NADred → lactate + NADox, catalyzed by lactate dehydrogenase

is lactate a reduction or oxidation product?

reduction

equation for 1st step of ethanolic fermentation

pyruvate → acetaldehyde + CO2, catalyzed by pyruvate decarboxylase

equation for 2nd step of ethanolic fermentation

acetaldehyde + NADred → NADox + ethanol, catalyzed by alcohol dehydrogenase

what is respiration?

Oxidation of an organic energy source employing substrate level and oxidative phosphorylation,and usually an exogenous terminal electron acceptor.

whats the most common exogenous terminal electron acceptor in respiration?

oxygen

what reaction links glycolysis and the Krebs cycle?

the pyruvate dehydrogenase reaction

where does the pyruvate dehydrogenase reaction occur?

cytoplasm in prokaryotes, mitochondrial matrix in eukaryotes

what’s the equation for the pyruvate dehydrogenase reaction?

pyruvate + NADox+ coenzymeA → acetylCoA +NADred + CO2, catalyzed by pyruvate dehydrogenase complex

the pyruvate dehydrogenase reaction is an example of what?

oxidative decarboxylation

where does the Krebs cycle occur?

cytoplasm and plasma membrane in prokaryotes, mitochondria in eukaryotes

equation for the first reaction in the Krebs cycle

Acetyl CoA + oxaloacetate → citrate + CoA, catalyzed by citrate synthase

what enzyme intersects between the Krebs cycle and electron transport?

succinate dehydrogenase

description of succinate dehydrogenase

flavoprotein, membrane-bound enzyme

what is a flavoprotein?

an enzyme with FAD covalently bound to it

which coenzyme works free in solution?

NAD

what are the products per turn of Krebs cycle?

2CO2, 3NADred, 1 FADred, 1GTP

how many turns for the Krebs cycle are necessary to break down a molecule of glucose?

two turns

whats the purpose of electron transport?

generation of ATP

what cell types use electron transport to generate ATP?

respiratory chemoheterotrophs, chemoautotrophs, phototrophs

what do chemotrophs use for electron transport?

oxidative phosphorylation

what do phototrophs use for electron transport?

cyclic or noncyclic photophosphorylation

what are some common features of all electron transport systems?

a chain of oxidation/reduction reactions to transfer energy to ATP, movement of protons at right angle to movement of electrons, membrane-bound, creation of proton gradient as energy source

why are all electron transport systems membrane-bound?

need a barrier of some sort to establish gradient, some processes function best when molecules are held in certain orientations

what does ATP production depend on?

ATP synthase

what types of molecules are found in all electron transport systems?

cytochromes, iron-sulfur centers, quinones, flavoproteins, dehydrogenases and other enzymes

what is a cytochrome?

small, heme-containing proteins

what are iron-sulfur centers?

large proteins containing iron bound to sulfur

what are quinones?

lipids structurally related to vitamin A

example of cytochromes?

cytochrome C

example of iron-sulfur centers

ferredoxin

example of quinone

ubiquinone

examples of dehydrogenases

NADH dehydrogenase, cytochrome oxidase

function of NADH dehydrogenase

accepts electrons from NADred

function of cytochrome oxidase

transfer electrons to oxygen

what molecules accept electrons in respiratory electron transport systems?

NADred and FADred

is NAD or FAD more electropositive?

NAD

is the oxidation of NADred or FADred more exergonic?

NADred

whats the theoretical ATP production from oxidating NADred?

3 ATP

whats the theoretical ATP production from oxidating FADred?

2 ATP

is anaerobic respiration ever as good as aerobic respiration?

no

what is always the terminal electron acceptor in anerobic respiration?

a highly oxidized molecule ex. NO3-, SO42-, CO2

examples of other important processes in central metabolism

The Entner-Doudoroff pathway, The pentose-phosphate pathway, beta-oxidation of fatty acids, gluconeogenesis

where is the Entner-Doudoroff pathway seen?

in Pseudomonas and relatives

describe the pentose-phosphate pathway

universal to prokaryotes and eukaryotes, runs parallel to glycolysis, produces NADPred and 4-5 carbon compounds

describe beta-oxidation of fatty acids

converts fatty acids into acetyl CoA, which then goes to Krebs
cycle. every two carbon unit of the fatty acid produces reduced coenzymes for electron transport and GTP by substrate level phosphorylation

describe gluconeogenesis

the synthesis of glucose from small organic molecules

what is autotrophy?

a metabolic lifestyle in which an organism derives all of its carbon needs from carbon dioxide

how is carbon dioxide brought in from the environment?

by the Calvin-Benson cycle

examples of autotrophs

the plant Kingdom, algae, some bacteria

what is phototrophy?

a metabolic life style in which the organism relies upon light as a source of
energy

how is energy captured from light?

pigments have electrons that can interact with photons of light, and those electrons are promoted to higher energy states

what happens to the electrons in pigments after they’re promoted to higher energy status?

they’re sent to electron transport chains

how do electron transport chains in phototrophs trap some energy as ATP?

chemiosmosis

how is ATP synthesized via electron transport chain?

protons move through the core of ATP synthase, the enzyme captures energy in order to phosphorylate ADP

what special vesicle houses the photosynthetic apparatus in some bacteria?

chlorosomes

what pigment do Halobacterium and relatives use?

bacteriorhodopsin

what kind of phototrophy do Halobacterium and relatives use?

photoheterotrophy

how does bacteriorhodopsin function?

when energized by light, protons within the molecule are pumped across the membrane. this creates a proton gradient that flows through ATP synthase

describe photoheterotrophy

organisms cannot redcuce CO2 and are fully reliant on organic sources of carbon

describe photoautotrophy

organisms use light energy to make ATP + transfer electrons from a donor to a coenzyme

why are photoautotrophs important?

they fix carbon dioxide

describe carbon dioxide fixing

using ATP and reductive power to convert CO2 into organic compounds

describe chemoautotrophy

bacteria use inorganic chemical reactions as energy sources to make ATP

how do chemoautotrophs make ATP?

with chemiosmosis or chemoheterotrophic respiration with an inorganic energy source instead of glucose

what energy source do the majority of carbon dioxide fixers use?

light

where did photosynthesis evolve from?

in the anaerobic conditions of the early earth, from bacteria

is photosyntheis aerobic or anaerobic?

anaerobic

what kind of photosynthesis is only seen in bacteria?

anoxygenic photosynthesis

what does anoxygenic photosynthesis commonly use as a source of electrons?

hydrogen sulfide

whats a common waste product of anoxygenic photosynthesis?

elemental sulfur

photosynethsis is ???-dependent

membrane

describe photosystems

physical units within the photosynthetic membrane which contain all the components necessary to trap light energy and direct the synthesis of ATP and sometimes reduced coenzyme