Exam 2: Microbial Metabolism- Photosyntehsis

Question 1

. What is the most common anabolic process by which CO2 is converted into organic molecules?

Answer 1

Photosynthesis

Question 2

Do all organisms capable of photosynthesis possess chloroplasts? Explain.

Answer 2

No

Question 3

Describe the endosymbiotic origin of chloroplasts.

Answer 3

Cyanobacteria living inside eukaryotes.

Question 4

What part of a chloroplast corresponds to the ancestral bacterium’s cytoplasm?

Answer 4

Stroma

Question 5

What part of a chloroplast corresponds to the ancestral bacterium’s cell membrane?

Answer 5

inner membrane- very infolded, theses infolds are called Thylakoid membranes where photosynthetic pigments are embedded.

Question 6

Dissect the term photoautotroph. What does each root mean?

Answer 6

photo-energy from light
auto-carbon form CO2
troph- eat

Photoautorrophs are those organisms which derive their energy from light and use as their sole carbon source

Question 7

Aside from plants, what groups of organisms can perform photosynthesis?

Answer 7

Some bacteria, algae, cyanobacteria, and some protozoa.

Question 8

Photosynthesis can be divided into two main sets of reactions. List these reactions and describe each in a single sentence, showing the relationship between the two.

Answer 8

Light reactions and calvin cycle. Light harvested and stored as ATP and NADPH occurs within the thylakoid membrane. The calvin cycle uses the ATP and NADH to fuel the process of reducing CO2 to form sugardsm, occurs within the stroma.

Question 9

Which photosystem(s) is/are involved in cyclic electron flow?

Answer 9

Photosystem I

Question 10

Briefly describe the process of cyclic electron flow, including how any products of this process are formed.

Answer 10

Grouping of pigments of various types like chlorophyll which absorb light. Light is transferred to a central pair of chlorophyll A molecules. Electrons from these chlorophyll A molecules are bumped up to a higher energy state and grabbed by a primary acceptor. Electrons are moved back to their ground state in a controlled fashion through electron acceptors and returned back to ground state. As they grab electrons and pass them on they capture some of energy which is used to produce ATP.

Question 11

Which photosystem(s) is/are involved in non-cyclic electron flow?

Answer 11

Both photosystem I and II

Question 12

What is the role of water in non-cyclic electron flow? What is the role of oxygen?

Answer 12

pigments in photosystem 2 absorb light. electrons bumped to higher energy state and move through the electron transport chain. ATP is generated. the electrons end up in photo system 1 at the end so now photosystem 2 is missing electrons. Electrons removed from H2O to replace those electrons. O2 is a waste product.

Question 13

Describe the Calvin cycle in a single sentence, showing its relationship to the photosynthetic light reactions.

Answer 13

Calvin cycle turns CO2 into sugar while spending ATP and NADPH that was produced in the light reactions.

Question 14

List the three key steps of the Calvin cycle, and describe each one in a sentence or two.

Answer 14

1) Fixation of CO2 to RuBP- 3 CO2 attached to three ribulose bisphosphatases. The result will be a 6 carbon molecule which breaks apart into 6 3 carbon molecules.

2) Reduction to form G3P- spend ATP to add an additional phosphate to each of the 6 carbon molecules to form 6 G3P sugars.

3)Regeneration of RuBP- ⅚ G3P are modified by spending ATP to RuBP

Question 15

Why is the net production of the Calvin cycle only one G3P molecule when six G3P molecules are produced in a single turn of the Calvin cycle?

Answer 15

The other 5 are involved with regeneration of the initial tree RuBPs.

Question 16

List and briefly describe at least four specific ways in which metabolism is regulated by cells.

Answer 16

• Synthesis or degrade transport proteins- done at gene expression level, turn on genes= more synthesis. Example; lactose present genes are on, lactose not present genes are off.
• Synthesize catabolic enzymes only when the substrate is available- Lac operon has 3 genes one is transport other two are involved in breakdown of lactose. Regulated as a group and turned off when lactose is not available.
• Preferentially catabolize the most efficient energy source- Lac operon off when lactose is not around, turned on when lactose is present…but not always. If both glucose and lactose are available then its going to stay off because glucose is more efficient. When given the option, choose the most efficient option.
• Cease synthesis of metabolites available as nutrients- If something is available as a nutrient then no need to waste energy making it.
• Isolate certain enzymes within specific organelles
• Allosteric regulation- includes feedback inhibition. Concentration of product controls production of product. Enough product available no need for process to occur more product needed process is started.
• Regulate different processes using the same substrate via different coenzyme requirements.

Question 17

What are the two very general ways in which metabolism is regulated?

Answer 17

Control of gene expression or control metabolic expression

Control of gene expression: control the production of proteins.

Control metabolic expression: control the enzymes already produced.

Question 18

Describe three ways in which catabolic and anabolic reactions interact with each other.

Answer 18

• ATP produced in catabolism drives anabolism
• Precursor metabolites produced in catabolism are substrates for anabolic reactions.
• Most metabolic pathways are amphibolic (can go both directions product to reactions and reactants to products).

Question 19

From what amino acids are the nitrogenous bases formed? From what precursors are these amino acids formed?

Answer 19

Two different amino acids glutamine and aspartic acid. Precursors are krebs cycle intermediates, ribose-5-phosphate form pentose phosphate pathway, and folic acid.

Question 20

Briefly describe two different reactions by which the amino acid aspartic acid can be produced.

Answer 20

Krebs cycle intermediates and ribose-5-phosphate from the pentose phosphate pathway.

Question 21

How many essential amino acids do humans have? How about E. coli? How about Neisseria meningitidis?

Answer 21

Humans- 9
E.Coli- None
Neuserua nebugutudus- All of them

Question 22

What is the difference between an essential amino acid and a nonessential amino acid?

Answer 22

Essential amino acids are ones that an organism cannot produce and have to be obtained through diet. Nonessential amino acids can be synthesized within the organism.

Question 23

In three or fewer sentences, briefly describe the process by which a fat molecule is produced from precursor metabolites.

Answer 23

Fatty acids are covalently linked to glycerol
Glycerol is derived from glycolysis or the Calvin cycle
Fatty acids are produced by linking together acetyl-CoA molecules in a series of reactions
Effectively the reverse of beta-oxidation

Question 24

Compare the synthesis of a fatty acid to the catabolism of a fatty acid. Do you see any similarities? Explain.

Answer 24

hile fatty acid degradation occurs in the mitochondrion, biosynthesis occurs in the cytosol. The second big difference is that the carrier of these fatty acyl chains was CoA in the beta-oxidation pathway. The carrier is a protein called ACP (acyl carrier protein) in the synthesis pathway.

Question 25

Dissect the word gluconeogenesis into its roots: gluco-neo-genesis. What do these roots mean, and what is gluconeogenesis?

Answer 25

Gloc-glucose neo-new genesis- formation = production of new glucose molecues.

Synthesis of sugars from non-carbohydrate precursors. Occurs in humans during times of fasting or with a low-carbohydrate diet. Highly endergonic process.

Question 26

Most of the chemical reactions of glycolysis are amphibolic. What does this mean? How is this relevant to gluconeogenesis?

Answer 26

Amphibolic: reaction that can proceed in either direction. Example; towards catabolism or towards anabolism.

Most of the reactions are amphibolic, and use enzymes of glycolysis in reverse.

Question 27

How many of the numerous enzyme-catalyzed reactions of gluconeogenesis are not amphibolic?

Answer 27

4?

Question 28

What are precursor metabolites? In what key metabolic pathways are they formed?

Answer 28

Precursor metabolites are intermediate molecules in catabolic and anabolic pathways that can be either oxidized to generate ATP or can be used to synthesize macromolecular subunits such as amino acids, lipids, and nucleotides. Produced via glycolysis, krebs cycle, and pentose phosphate.

Question 29

Into what types of molecules can the precursor metabolites (as a group) be converted?

Answer 29

macromolecules

Question 30

Anoxygenic photosynthesis vs. oxygenic photosynthesis

Answer 30

Difference anoxygenic no O2 produced, cyclic, electron donors are H2S, H2, Fe2+, electrons not recycled, only photosystem I or II . Oxygenic phosphosites O2 produced, non-cyclic, electron acceptor NADP+, both photosystem I and II.

Question 31

Anoxygenic Photosynthesis

Answer 31

the phototrophic process where light energy is captured and converted to ATP, without the production of oxygen

Question 32

Viewing a detailed image of the various steps of glycolysis, find six different precursor metabolites.

Answer 32

• Glucose 6 phosphate
• Fructose 6-phosphate
• Glyceraldehyde 3-phosphate
• phosphoglyceric acid
• phosphoenolpyruvic acid (PEP)
• Pyruvic acid

Question 33

Viewing a detailed image of the various steps of the Krebs cycle, find four different precursor metabolites.

Answer 33

• Acetyl CoA
• α-ketoglutaric acid
• Succinyl -CoA
• Oxaloacetate

Question 34

Viewing a detailed image of the various steps of the pentose phosphate pathway, find two different precursor metabolites.

Answer 34

• Ribose 5-Phosphate
• Erythrose 4-Phosphate

Question 35

How does the bacterium E. coli compare to humans in the ability to produce precursor metabolites? Does this make you feel a little bit less special?

Question 36

What is the function of water in oxygenic photosynthesis? What is the product of the oxidation of this water?

Answer 36

water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons. This transforms the water into oxygen and the carbon dioxide into glucose

Question 37

How would photosynthesis differ if H2S was used in place of H2O? What if it used H2?