Unit 2.1 Metabolism Flashcards
Describe the big picture of metabolism.
- Metabolism is the buildup and breakdown of nutrients within a cell
- “The sum of all chemical reactions that take place in an organism.”
- These chemical reactions provide energy and create substances that sustain life
Briefly define Catabolism
- breaks down complex molecules;
- harvests and stores energy
- provides energy and building blocks for anabolism;
- exergonic
Briefly define Anabolism
- uses energy and building blocks to build complex molecules;
- endergonic
Briefly define Metabolic pathways
are sequences of enzymatically catalyzed chemical reactions in a cell
Name the thing that determines a metabolic pathway.
The enzymes.
Where do the enzymes of a cell come from?
Enzymes are encoded by genes
How is energy lost during catabolism and anabolism.
Because they are inefficient, some energy is lost as heat.
Briefly describe catalyst.
speed up chemical reactions without being altered
Briefly define enzyme.
biological catalysts
Briefly describe how enzymes are a benefit to metabolism.
Enzymes act on a specific substrate and lower the activation energy (the energy required for a chemical reaction to occur)
Name two ways the environment can cause proteins to denature.
- High temperature
- extreme pH
Briefly describe the role of competitive inhibitors in metabolism.
they fill the active site of an enzyme and compete with the substrate, slowing catalysis.
Briefly describe the structure of a competitive inhibitor.
the substance is similar to the enzyme substrate (but does not react to form products).
When is a competitive inhibitor ineffective?
When concentration of the enzyme substrate is high, the substrate will out compete for the active site and catalysis will continue.
Briefly describe noncompetitive inhibitors.
interacts with another part of the enzyme (allosteric site) rather than the active site, rendering the enzyme nonfunctional
Name the process where a noncompetitive inhibitor reacts with an enzyme but not at its active site.
allosteric inhibition
Describe what happens during an allosteric inhibition?
The noncompetitive inhibitor indirectly changes the shape of the active site, rendering the enzyme nonfunctional
What is the effect of high substrate concentration in the presence of noncompetitive inhibitors?
no effect
Briefly describe the effect of oxidation.
removal of electrons
Briefly describe the effect of reduction.
gain of electrons
Briefly define a redox reaction.
an oxidation reaction paired with a reduction reaction
Name the word that best describe how oxidation occurs in biological systems.
Biological oxidations are often dehydrogenations
How are electrons transferred in biological systems?
In biological systems, electrons and protons are removed at the same time; equivalent to a hydrogen atom
Name the process of ATP generation from ADP.
ATP is generated by the phosphorylation of ADP with the input of energy.
Describe ATP generation with Substrate-Level Phosphorylation.
ATP is generated when high-energy PO4- is added to ADP
Where does Photophosphorylation occur?
only in photosynthetic cells with light-trapping pigments such as chlorophylls
What is the purpose of photophosphorylation?
Light energy is converted to chemical energy
Briefly describe what happens during photophosphorylation.
ATP is generated during the transfer of electrons (oxidation) from chlorophyll as they pass through a system of carrier molecules
What is the role of ATP in biological metabolism?
To chemically store energy.
Briefly describe the chemistry of Metabolic Pathways of Energy Production.
- Series of enzymatically catalyzed chemical reactions
Briefly describe the processes of Metabolic Pathways of Energy Production.
- Extracts energy from organic compounds and stores it in chemical form (ATP)
Briefly define chemiosmosis.
the process wherein ATP is generated from ADP using the energy derived from the electron transport chain.
Briefly describe what happens during glycolysis.
The oxidation of glucose
to pyruvic acid
produces ATP and NADH
Features of the preparatory stage of glycolysis.
- 2 ATP are used
- Glucose is split to form two molecules:
one glyceraldehyde 3-phosphate (g P),
one dihydroxyacetone phosphate (DHAP) - DHAP is readily converted to g P
Features of the energy-conserving stage of glycolysis.
- The two glyceraldehyde 3-phosphate molecules are oxidized to 2 pyruvic acid molecules
- 4 ATP are produced
- 2 NADH are produced
Name two Additional Pathways to Glycolysis.
Pentose phosphate pathway
Entner-Doudoroff pathway
Features of the Pentose phosphate pathway.
- Breaks down 5-carbon pentose sugars and/or glucose and produces NADPH
- Operates simultaneously with glycolysis
- Can provide intermediates for synthesis reactions
Features of the
Entner-Doudoroff pathway.
- Produces NADPH and ATP
- Does not involve glycolysis; operates independently
- Occurs in Pseudomonas, Rhizobium, and Agrobacterium
Features of cellular respiration.
- Oxidation of molecules liberates electrons to operate an electron transport chain
- Final electron acceptor comes from outside the cell and is inorganic
Aerobic respiration uses oxygen as the final electron acceptor
Anaerobic respiration uses a molecule other than oxygen as the final electron acceptor - ATP is generated by oxidative phosphorylation
Features of the Kreb cycle.
*Aerobic Respiration
* Pyruvic acid (from glycolysis) is oxidized and decarboxylation (loss of CO2) occurs
* The resulting 2-carbon compound attaches to coenzyme A, forming acetyl CoA and NADH
* Oxidation of acetyl CoA produces NADH, FADH2 and ATP, and liberates CO2 as waste
Features of the electron chain transport system
- Aerobic Respiration
- Occurs in the plasma membrane of prokaryotes; inner mitochondrial membrane of eukaryotes
- Series of carrier molecules (flavoproteins, cytochromes, and ubiquinones) are oxidized and reduced as electrons are passed down the chain
- Energy released is used to produce ATP by chemiosmosis
Features of Chemiosmosis.
- Electrons (from NADH) pass down the electron transport chain while protons are pumped across the membrane
Establishes proton gradient (proton motive force) - Protons in higher concentration on one side of the membrane diffuse through ATP synthase
Releases energy to synthesize ATP
Features of Carbohydrate Catabolism.
- Each NADH can be oxidized in the electron transport chain to produce 3 molecules of ATP
- Each FADH2 can produce 2 molecules of ATP
Features of Anaerobic Respiration.
- The final electron acceptor in the electron transport chain is NOT O2
- Yields less energy than aerobic respiration
Features of Fermentation.
- Releases energy from the oxidation of organic molecules
- Glucose is oxidized to pyruvic acid, which is then reduced by N A D H
- Does not require oxygen
- Does not use the Krebs cycle or E T C
- Uses an organic molecule as the final electron acceptor
- Produces only small amounts of A T P
Features of Lipid and Protein Catabolism.
- Proteins are degraded by extracellular proteases and peptidases into amino acids
- Amino acids cross plasma membranes
- Deaminated, decarboxylated, desulfurized to obtain molecules that can enter the Krebs cycle for further processing
describe Detecting Amino Acid Catabolizing Enzymes in the Lab
Bacteria are inoculated into tubes containing glucose, a pH indicator, and a specific amino acid.
(a) The pH indicator turns to yellow when bacteria produce acid from glucose.
(b) Alkaline products from decarboxylation turn the indicator to purple.
Briefly describe fermentation test.
bacteria that catabolize carbohydrate or protein produce acid, causing the pH indicator to change color
* Can also be used with a Durham tube to detect gas production during fermentation
What is the function of the Oxidase test.
identifies bacteria that have cytochrome c oxidase (e.g., Pseudomonas)
Briefly describe the Light-dependent (light) reactions of photosynthesis.
conversion of light energy into chemical energy (A T P and N A D P H)
Briefly describe the Light-independent (dark) reactions of photosynthesis.
A T P and N A D P H are used to reduce CO2 to sugar (carbon fixation) via the Calvin-Benson cycle
formula of the summary reaction of photosynthesis
6CO2 + 12H2O + light
—>
C6H12O6 + 6H2O + O2
Briefly define phototroph
organisms that use light as their energy source and carry out photosynthesis
Briefly define Photoheterotroph
phototroph that uses organic compounds (carbon source)
photoheterotrophs include what microorgansims?
green and purple nonsulfur bacteria
briefly contrast cyanobacteria from other photoautotrophs
source of reducing power is H2O
which photoautotrophs use sulfur?
green and purple sulfur bacteria
compare similarities between cyanobacteria and algae/plants
- chlorophyll a
- thylakoids
- reduces with H2O
- generates O2
contrast green and purple bacteria differences from cyanobacteria
- reducing power from other compounds (not H2O)
- does not make O2
- found in anerobic environments
steps of cyclic photophosphorylation
- light interacts with chlorophyll in photosystem I
- excited electrons move through the electron transport chain
- electrons moving through cytochromes creating a proton gradient
- proton gradient drives ATP synthase to produce ATP via chemiosmosis
- electrons return to photosystem I
another name for energy source in the energy production of cells
electron donors
name the energy sources for the energy production of cells
photosynthetic pigments + light
glucose, sulfur, ammonia, hydrogen gas
name the electron carriers in the energy production of cells
NADP+
NAD+
FAD
name the final electron acceptors in the energy production of cells
O2 (aerobic respiration)
NO3-, SO4^2- (anerobic)
organic compound (fermentation)
Briefly describe autotroph
organism that uses CO2 as carbon source
Briefly describe heterotroph
organism that uses organic compounds as carbon source
Briefly describe chemotroph
organisms that use chemicals as their energy source
Features of Chemoautotrophs
- Obtain energy from inorganic chemicals; use CO2 as carbon source
- Energy is used in the Calvin-Benson cycle to fix CO2
- Obtain energy A N D carbon from organic chemicals
- Medically and economically important
Briefly define Amphibolic pathways
metabolic pathways that function in both anabolism and catabolism
