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Biological Systems > Chapter 6 Chemical Pathways > Flashcards

Chapter 6 Chemical Pathways Flashcards

1
Q

How is energy stored and released in cells?

A

Stored in chemical bonds

Released and transformed by metabolic pathways

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2
Q

What is free energy

A

energy available to do work

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3
Q

What 5 principles govern metabolic pathways

A

1) chemical transformation occurs in a series of intermediate reactions that form metabolic pathways
2) Each reaction is catalyzed by a specific enzyme
3) Most metabolic pathways are similar in all organisms
4) In eukaryotes, many metabolic pathways occur inside specific organelles
5) Each metabolic pathway is controlled by enzymes that can be inhibited or activated

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4
Q

What does it meant that energy-transforming reactions are often coupled?

A

Energy releasing reaction is coupled with an energy requiring reaction

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5
Q

Give the equation for hydrolysis of ATP and how much free energy is released

A

ATP + H2O -> ADP + Pi + free energy (about -7.3 kcal/mol)

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6
Q

What is a method of releasing energy other than ATP hydrolysis?

A

REDOX reactions (transfer of H atoms)

  • the more reduced a molecule is, the more energy is stored in bonds (H bonds)
  • Energy is transfered from reducing agent to reduced product
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7
Q

What enzyme is a key electron carrier in redox reactions?

A

NAD+ and NADH (oxidised and reduced forms)

Reduction is endergonic, Oxidation is exergonic

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8
Q

What is a catabolic reaction

A

releases energy by oxidation - to drive chemical reactions

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9
Q

What is an anabolic reaction

A

simpler substances are combined to form more complex molecules (usually requiring energy/ATP)

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10
Q

How is energy transfered from NADH to ATP and why is this important?

A

Energy transfered by oxidativ phosphorylation

Important because exergonic reactions produce NADH and endergonic reactions require ATP

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11
Q

What is cellular respiration

A

Set of metabilic reactions used by cells to harvest energy from food
- Involves energy released when molecules with many C-C and C-H bonds are oxidised to CO2

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12
Q

About how much of energy released in cellular respiration is harvested

A

34%

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13
Q

What are the 3 pathways of catabolism of glucose under aerobic conditions (Presence of O2)

A

3 linked biochemical pathways

  • Glycolysis - glucose converted to pyruvate
  • Pyruvate oxidation - Pyruvate oxidised into acetyl CoA and CO2
  • Citric acid cycle - acetyl CoA oxidised to CO2
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14
Q

Where does glycolysis occur

A

Cytosol

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15
Q

What are the products of glycolysis

A

2 Pyruvate (Pyruvic acid)
2 ATP
2 NADH

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16
Q

Step 6 an 7 of glycolyis occur repeatedly in metabolic pathways - what are they and their products

A

6) Redox - exergonic - glyceraldehyde 3-phosphate is oxidised and NAD+ is reduced - produces NADH
7) Substate level phosphorylation - exergonic - energy released transfers phosphate from 1,3 biphosphogycerate to ADP - produced ATP

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17
Q

Where does pyruvate oxidatio occur

A

mitochondria in eukaryotes

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18
Q

What does pyruvate oxidation produce?

A

Acetyl CoA

NADH

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19
Q

Where does the cytric acid cycle occur?

A

Mitochondria in eukaryotes

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20
Q

How many times does the cytric acid cycle occur for every glucose molecule that enters glycolysis

A

twice

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21
Q

What are the products of the cytric acid cycle

A

A CoA is oxidised to 2 CO2

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22
Q

What is electron transport in the Cellular respiration process and its purpose

A

Electrons form the oxidation of NADH and HADH2 pass from one carrier to the next in the chain - create a proton gradient
Electron transport carriers are in inner mitrochonrrial membane and contain enzyme ATP synthase - use proton gradient to drive ATP production by chemiosmosis

23
Q

Define chemiosmosis

A

the movement of ions across aa semipermeable barrier from a region of higher concentration to lower concentration

24
Q

What does ATP synthase do?

A

converts potential energy of concentration gradient into chemical energy in ATP

25
What is the structure of ATP synthase - How does this let it convert energy into ATP
molecular motor with 2 subunits - F0 - transmembrane domain(H+ channel) - F1 - 6 subunits. F0 rotates when H passess through, causing F1 to rotate ADP and Pi bind to active sites that become exposed on the F1 unit as it rotates -> ATP formed
26
Where does chemiosmosis occur in prokaryotes and eukaryotes
prokaryotes - proton gradient across cell membrane | Eukaryotes - mitochondria and chloroplasts
27
What is the role of O2 in cellular respiration
most ATP is formed by oxidative phosphorylation - reoxidation of NADH O2 is reduced
28
How is NADH reoxidised in anaerobic conditions
Fermentation (many different types)
29
What is the difference in yield of ATP in aerobic vs anaerobic conditions
Aerobic - 32 ATP | Anaerobic - 2 (produced in glycolysis)
30
What are 2 main types of fermentation
Lactic acid - produce lactate - Pyruvate reduced to lactic acid, NADH oxidised to NAD+ Alchoholic - produces ethanol - Pyruvate converted to acedaldehyde and CO2 released, NADH reduces acedaldehyde to ethanol and regenerates NAD+
31
Where does alcohol fermentation occur
Only in certain yeasts and some plants
32
How are anabolic and catabolic pathways integrated
Both required for maintaining energy balance Anabolic pathways use energy to produce molecules and Catabolic pathways breakdown molecules to produce energy Anabolic pathways can simply be catabolic pathways in reverse
33
What are common processes in catabolism
- Polysaccharides hydrolyzed to glucose (enters glycolysis) - Lipids -> fatty acids and glycerol. Can be convered into Acetyl CoA - Proteins hydrolyzed into amino acids - can feed into glycolysis of citric acid cycle
34
How are amounts of molecules maintained at fairly constant levels in the metabolic pool
regulation of enzymes via allosteric regulation and feedback inhibition (Fast) and also altering transcription of genes that encode enzymes (SLOWO
35
How are catabolism, anabolism and photosynthesis linked
Cellular respiration linked by their reactants and products and b ATP and reduced coenzymes
36
What is the equation for cellular respiration
Glucose + 6O2 -> 6CO2 + 6H2O + cellular energy
37
What is the equation for photosynthesis
CO2 + H2O + Light energy -> Carbohydrates + O2
38
What are the 2 pathways of photosynthesis
Light reaction - converts light into chemical energy (ATP and reduced electon carrier NADPH) Carbon-fixation reaction - uses ATP and NADPH to produce carbohydrates
39
How is the amount of light energy related to its wavelength
Inversely proportional energy to wavelength
40
What are pigments
molecules that absorb wavelengths in the visible spectrum
41
What is the absorption spectrum vs action spectrum
Absorption - Plot of light energy absorbed against wavelength Action - Plot of biological activity of an organism against wavelength
42
What pigments absorb light energy in plants
2 Chlorophylls - Chlorophyll a and chlorophyll b | - Also accessory pigment sthat absorb wavelength between red and blue and transfer some energy to chlorphylls
43
How are pigment arranged?
in light-harvesting complexes or antenna systems Photosystem spans the thylakoid membrane in the chloroplast consists of multiple antenna systems surrounding a reaction centre
44
How is light energy converted into chemical energy?
Chlorophyll absorbs light - enters excited state - rapidly returns to ground state releasing an excited electron - electron is given to acceptor molecule which is reduced (becoming chemical energy in H bond)
45
How is ATP produced from photosynthesis
Excited electron is accepted by the fist carrier in the electron transport system Final acceptor is NADP+ which is reduced ATP is produced Chemiosmotically (proton gradient) during electron transport
46
Plants have 2 photosystems - wha are the differences
Photosystem I - absorbs ligth energy at 700nm and passes and excited electron to NADP+ - reduces to NADPH Photosystem II - absorbs light at 680 nm, oxidises water and initiates ATP production
47
How is water oxidises by photosystem II
when electron is given up, Chl* is unstable and grabs an electron from H2O - splitting H-O-H bonds
48
How is Chl* in photosystem I restabilized after giving up an electron
Grabs electron from the last carrie i the transport system of photosystem II Reuces NADP+ to NADPH
49
What is he cyclic electron transport
Uses only photosystem I and produces only ATP | Electron passed from Chl* through electron transport chain and recycled back to the same Chl
50
What is the purpose of carbon fixation pathways
Require ATP | For energy storage as carbohydrates
51
What is the Calvin cycle
Energy in ATP and NADPH is used to 'fix' CO2 in reduced form in carbohydrates occurs in stroma of chloroplast Each reaction is catalyzed by a specific enzyme
52
What are the 3 processes of the calvin cycle
1) fixation of CO2 Co2 added to Ribuluse 1,5 biphosphate (RuBP) -> 6-carbon molecules result -> split into two 3-carbon molecules 3-phosphoglycerate (3PG) 2) 3PG is reduced to form glyceraldehyde 3 phosphate 3) CO2 Acceptor RuBP is regenerated form G3P
53
What is the difference between autotrophs and herterotrophs
Autotrophs (photosynthetic organisms) use most of energy provided by photosynthesis to support their growth and reproduction Heterotrophs cannot photosynthesize and depend on autotrophs for chemical energy.
54
Where does almost all the energy on earth come from
the C-H bonds generated by the calvin cycle

Biological Systems (20 decks)

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