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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
Q

What is the structure of ATP synthase - How does this let it convert energy into ATP

A

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
Q

Where does chemiosmosis occur in prokaryotes and eukaryotes

A

prokaryotes - proton gradient across cell membrane

Eukaryotes - mitochondria and chloroplasts

27
Q

What is the role of O2 in cellular respiration

A

most ATP is formed by oxidative phosphorylation - reoxidation of NADH
O2 is reduced

28
Q

How is NADH reoxidised in anaerobic conditions

A

Fermentation (many different types)

29
Q

What is the difference in yield of ATP in aerobic vs anaerobic conditions

A

Aerobic - 32 ATP

Anaerobic - 2 (produced in glycolysis)

30
Q

What are 2 main types of fermentation

A

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
Q

Where does alcohol fermentation occur

A

Only in certain yeasts and some plants

32
Q

How are anabolic and catabolic pathways integrated

A

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
Q

What are common processes in catabolism

A
  • 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
Q

How are amounts of molecules maintained at fairly constant levels in the metabolic pool

A

regulation of enzymes via allosteric regulation and feedback inhibition (Fast) and also altering transcription of genes that encode enzymes (SLOWO

35
Q

How are catabolism, anabolism and photosynthesis linked

A

Cellular respiration linked by their reactants and products and b ATP and reduced coenzymes

36
Q

What is the equation for cellular respiration

A

Glucose + 6O2 -> 6CO2 + 6H2O + cellular energy

37
Q

What is the equation for photosynthesis

A

CO2 + H2O + Light energy -> Carbohydrates + O2

38
Q

What are the 2 pathways of photosynthesis

A

Light reaction - converts light into chemical energy (ATP and reduced electon carrier NADPH)
Carbon-fixation reaction - uses ATP and NADPH to produce carbohydrates

39
Q

How is the amount of light energy related to its wavelength

A

Inversely proportional energy to wavelength

40
Q

What are pigments

A

molecules that absorb wavelengths in the visible spectrum

41
Q

What is the absorption spectrum vs action spectrum

A

Absorption - Plot of light energy absorbed against wavelength
Action - Plot of biological activity of an organism against wavelength

42
Q

What pigments absorb light energy in plants

A

2 Chlorophylls - Chlorophyll a and chlorophyll b

- Also accessory pigment sthat absorb wavelength between red and blue and transfer some energy to chlorphylls

43
Q

How are pigment arranged?

A

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
Q

How is light energy converted into chemical energy?

A

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
Q

How is ATP produced from photosynthesis

A

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
Q

Plants have 2 photosystems - wha are the differences

A

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
Q

How is water oxidises by photosystem II

A

when electron is given up, Chl* is unstable and grabs an electron from H2O - splitting H-O-H bonds

48
Q

How is Chl* in photosystem I restabilized after giving up an electron

A

Grabs electron from the last carrie i the transport system of photosystem II
Reuces NADP+ to NADPH

49
Q

What is he cyclic electron transport

A

Uses only photosystem I and produces only ATP

Electron passed from Chl* through electron transport chain and recycled back to the same Chl

50
Q

What is the purpose of carbon fixation pathways

A

Require ATP

For energy storage as carbohydrates

51
Q

What is the Calvin cycle

A

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
Q

What are the 3 processes of the calvin cycle

A

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
Q

What is the difference between autotrophs and herterotrophs

A

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
Q

Where does almost all the energy on earth come from

A

the C-H bonds generated by the calvin cycle

Biological Systems (20 decks)

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