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Bio1MGC > Cellular Respiration > Flashcards

Cellular Respiration Flashcards

1
Q

catabolism / catabolic pathway

A

a metabolic pathway that releases energy by breaking down complex molecules to simpler compounds
Cellular respiration is a catabolic pathway

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2
Q

anabolic pathway (biosynthetic pathways)

A

metabolic pathway that consumes energy to build complicated molecules from simpler ones
Photosynthesis is an anabolic pathway

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3
Q

fermentation

A

breakdown of sugars or other organic fuel without oxygen

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4
Q

aerobic respiration

A

oxygen used to break down fuels

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5
Q

break down of sugars - chemical equation

A

C 6 H 12 O 6 + 6 O2 gives 6 CO2 + 6 H20 + Energy (ATP and heat)

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6
Q

how is energy created in pathways

A

transfer of electrons from one reactant to another
the relocation of electrons releases energy stored in organic molecules and this energy is ultimately used to synthesise ATP

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7
Q

redox reactions

A

chemical reaction that involve a transfer of one or more electrons from one reactant to another

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8
Q

oxidation

A

A redox reaction is one that involves the transfer of electrons from one reactant to another
Oxidation is when a substance loses electrons

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9
Q

reduction

A

Redox reactions involve the transfer of electrons from one substance to another
reduction is when electrons are added to another substance
adding electrons is called reduction - adding negatively charged electrons to an atom reduces the amount of positive charge of that atom

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10
Q

cellular respiration as a redox reaction

A

Glucose becomes oxidised to form carbon dioxide (loses the hydrogens)
the oxygen becomes reduced to form water (gains the hydrogens)
Hydrogen is transferred from glucose to oxygen

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11
Q

NAD / NADH

A

nicotinamide adenine dinucleotide (derivative of the vitamin niacin)
Electron carrier / electron shuttle
cycles between oxidised NAD to reduced NADH
functions in several of the redox steps during the breakdown of glucose

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12
Q

electron transport chain

A

the electron transport chain consists of a number of molecules, mostly proteins, built into the inner membrane of the mitochondria of eukaryotic cells.
Electrons removed from glucose are shuttled by NADH to the top higher energy end of the chain. At the bottom lower energy end oxygen captures these electrons along with hydrogen nuclei forming water

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13
Q

where is the electron transport chain located

A

in the inner membrane of the mitochondria of eukaryotic cells and the plasma membrane of respiring prokaryotes

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14
Q

how is energy released in the electron transport chain

A

multistep
electrons cascade down the chain from one carrier molecule to the next in a series of redox reactions, losing a small amount of energy with each step until they finally reach oxygen, the terminal electron acceptor

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15
Q

what is the role of oxygen in the electron transport chain

A

oxygen is very electronegative

oxygen pulls electrons down the chain

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16
Q

three stages of cellular respiration

A

glycolysis
pyruvate oxidation and the citric acid cycle (krebs)
oxidative phosphorylation - electron transport and chemiosmosis

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17
Q

where does glycolysis occur

A

in the cytosol

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18
Q

what processes occur in the mitochondria

A

pyruvate oxidation
citric acid cycle
oxidative phosphorylation - electron transport and chemiosmosis

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19
Q

how many molecules of ATP are created for each molecule of glucose

A

For each molecule of glucose degraded to carbon dioxide and water by respiration the cell makes up to 32 molecules of ATP

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20
Q

what are the two energy phases of glycolysis

A

glycolysis can be divided into two phases - the energy investment phase and the energy payoff phase
During the energy investment phase the cell spends ATP
This is paid off
The net energy yield from glycolysis, per glucose molecule, is 2 ATP plus 2 NADH

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21
Q

what happens to glucose during glycolysis

A

glucose, a six carbon sugar, is split into two three carbon sugars. these small sugars are oxidised and their remaining atoms rearranged to form two molecules of pyruvate

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22
Q

is oxygen required for glycolysis

A

glycolysis occurs whether or not oxygen is present

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23
Q

glycolysis outputs

A

2 pyruvates + 2 H20
2 ATP
2 NADH + 2H

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24
Q

how does the pyruvate enter the mitochondrion

A

pyruvate is a charged molecule so in eukaryotic cells it must enter the mitochondrion via active transport with the help of a transport protein

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25
Q

what happens when pyruvate enters the mitochondrion

A

pyruvate is oxidised (electrons lost) to a compound called acetyl coenzyme A or acetyl CoA which is further oxidised in the citric acid cycle

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26
Q

what gas is released during the change from pyruvate to acetyl CoA

A

carbon dioxide is released. this is the first step in which carbon dioxide is released during respiration

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27
Q

what is the yield from the citric acid cycle

A

6 NADH 2 FADH2 and 2ATP + 2 Carbon dioxide

the cycle generates 1ATP per turn but most of the chemical energy is transferred to NAD and FAD

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28
Q

NADH and FADH

A

Glycolysis and citric acid cycle produce only 4 ATP per glucose molecule
after the CAC the molecules of NADH and FADH account for most of the energy extracted from each glucose molecule

29
Q

structure of the electron transport chain

A

the ETC is a collection of molecules embedded in the inner membrane of the mitochondrion
the folding of the inner membrane to form cristae increases its surface area providing space for thousands of copies of each component of the electron transport chain in a mitochondrion
most components of the chain are proteins which exist in multiprotein complexes I to IV
Tightly bound to these proteins are prosthetic groups - cofactors and coenzymes

30
Q

how does the electron transport chain work

A

electron carriers alternate between reduced and oxidised states as they accept and then donate electrons

31
Q

what are some of the proteins involved in the electron transport chain

A 
flavoprotein
iron sulphur protein
ubiquinone
cytochromes - contains a haem group 
the electron transport chain has several types of cytochromes
32
Q

what happens at the end of the electron transport chain

A

the last protein (cytochrome) of the chain passes its electrons to oxygen which is very electronegative
Each oxygen atom also picks up a pair of hydrogen ions (protons) from the aqueous solution neutralising the -2 charge of the added electrons and forming water

33
Q

does the electron transport chain make ATP

A

the electron transport chain makes no ATP directly
instead it eases the fall of electrons from food to oxygen breaking the energy drom into a series of smaller steps that release energy in smaller more manageable amounts

34
Q

chemiosmosis

A

pumping hydrogen ions across a membrane to make ATP

35
Q

what is ATP synthase

A

an enzyme that makes ATP from ADP and inorganic phosphate
located in the inner membrane of the mitochondrion
a molecular mill - hydrogen ions enter from the intermembrane space and bind within a rotor that changes shape and spins
they hydrogen ion exits into the mitochondrial matrix
turning the rod of the rotor produces ATP from ADP and P

36
Q

Hydrogen gradient that drives ATP synthesis

A

As electrons move down the chain, energy is released and used to pump protons (hydrogen) out of the matrix, forming a gradient. Protons flow back into the matrix through an enzyme called ATP synthase, making ATP. At the end of the electron transport chain, oxygen accepts electrons and takes up protons to form water.

37
Q

what would happen in cellular respiration if oxygen was not available

A

without the electronegative oxygen to pull electrons down the transport chain oxidative phosphorylation would cease

38
Q

anaerobic respiration

A

certain prokaryotic organisms that live in environments without oxygen
have an electron transport chain but do not use oxygen as the final electron acceptor at the end of the chain
some sulphate reducing marine bacteria use sulphate

39
Q

fermentation

A

does not use oxygen or an electron transport chain

an extension of glycolysis that allows the continuous generation of ATP
glycolysis plus reactions that regenerate NAD by transferring electrons from NADH to pyruvate

40
Q

alcohol fermentation

A

carried out by many bacteria in anaerobic conditions
yeast ( a fungus) in addition to aerobic respiration also carries out alcohol fermentation (bread)
pyruvate is converted into acetaldehyde and then ethanol - carbon dioxide is released (beer)

41
Q

lactic acid fermentation

A

pyruvate reduced to form lactate
no carbon dioxide released
lactic acid fermentation by certain fungi and bacteria is used to make cheese and yoghurt
human muscle cells make ATP by lactic acid fermentation when oxygen is scarce

42
Q

how are fermentation, anaerobic respiration and aerobic respiration similar

A

all use glycolysis to oxidise glucose to pyruvate
with a net production of 2 ATP by substrate level phosphorylation
NAD is the oxidising agent that accepts electrons during glycolysis

43
Q

how much ATP is produced through fermentation

A

fermentation yields 2 molecules of ATP produced by substrate level phosphorylation
in the absence of an electron transport chain the energy stored in pyruvate is unavailable

(in cellular respiration pyruvate is completely oxidised (all electrons transferred) in the mitochondrion - 32 molecules of ATP

44
Q

what organisms photosynthesise

A

plants
algae - unicellular and multicellular e.g. kelp
certain unicellular eukaryotes - e.g. euglena
some prokaryotes - cyanobacteria other bacteria

45
Q

where does photosynthesis occur

A

chloroplasts in leaves (mesophyll)

1 mm squared of leaf = 500,000 chloroplasts

46
Q

stomata

A

microscopic pores in a leaf

carbon dioxide enters and oxygen leaves through stomata

47
Q

how many chloroplasts in a cell

A

30-40

48
Q

structure of a chloroplast

A

two membranes surround the dense fluid called stroma (inner and outer membrane)
third membrane system within the stroma called thylakoids
inside the thylakoids is the thylakoid space (separated from the stroma)
thylakoids can be stacked into grana
thylakoids contain chlorophyll
between the two outer membranes is the intermembrane space

49
Q

chlorophyll

A

light energy absorbed by chlorophyll drives the synthesis of organic molecules in the chloroplast

50
Q

where does the oxygen given off by plants during photosynthesis come from

A

derived from H2O not from CO2

the chloroplast splits water into hydrogen and water

51
Q

photosynthesis as a redox reaction

A

water is split and its electrons are transferred along with hydrogen ions from the water to the carbon dioxide reducing it to sugar

52
Q

is photosynthesis an endergonic or exergonic reaction

A

the process is endergonic - it requires energy

the energy for photosynthesis comes from light

53
Q

what are the two stages of photosynthesis

A 
light reactions  (photo) - occurs in the thylakoid membranes
Calvin cycle (synthesis) - occurs in the stroma
54
Q

why is the calvin cycle referred to as dark reactions (light independent)

A

do not require light

however do occur during the day because the reaction requires the NADPH and ATP made by the light reactions

55
Q

why do we see green when we look at a leaf

A

chlorophyll absorbs violet blue and red light and reflects green light

56
Q

photosystem

A

in the thylakoid membrane chlorophyll molecules are organised along with other small organic molecules and proteins into a complex called a photosystem
composed of a reaction centre complex and a light harvesting complex

57
Q

what are the two photosystems in the thylakoid membrane

A

photosystem II - P680

photosystem I - P 700

58
Q

what is the light harvesting complex

A

consists of various pigment molecules including chlorophyll a, chlorophyll b and multiple carotenoids bound to proteins
the range of chlorophylls and carotenoids enables the photosystem to harvest light from a broader spectrum

59
Q

what happens in the light harvesting complex

A

pigment molecule absorbs a photon
energy passed from pigment molecule to pigment molecule until it is passed to a chlorophyll a molecule in the reaction centre complex

60
Q

what happens when the electron from the light harvesting complex gets to the reaction centre complex

A

special pair of chlorophyll a molecules transfer one of their electrons to the primary electron acceptor

61
Q

why are the photosystems called P680 and P700

A

this is the wavelength they best absorb
P680 pigment is best at absorbing wavelength of 680nm (red)
P700 - far red
(different proteins in each account for slight differences in light absorbing properties

62
Q

path of electrons in light reactions - linear electron flow

A

photon strikes pigment molecule in light harvesting complex of PS II - boosts electron
electrons excite each other until one reaches P680 chlorophyll a molecules in the PSII reaction centre complex
transferred to primary electron acceptor
enters electron transport chain from PSII to PS I(this drives chemiosmosis)
the electron enters the reaction centre of P700 exciting chlorophyll a molecules there and they become electron acceptors
enter second electron transport chain through the protein ferredoxin
NADP is reduced to NADPH by NADP reductase

63
Q

chemiosmosis in photosynthesis

A

in Photosystem II an enzyme catalyses the splitting of water molecule into two electrons, two hydrogen ions and a oxygen atom
electrons feed into the primary electron acceptor
the oxygen is released and joins another oxygen to form O2 (released by leaf)
the hydrogen is released into the thylakoid space
(interior of the thylakoid)
as electrons flow down the electron transport chain energy is released that pumps protons (hydrogens) from the stroma into the thylakoid space
makes a proton gradient across the thylakoid membrane
Stroma low hydrogen concentration / thylakoid space high concentration
ATP is sythesised as hydrogen ions diffuse from the thylakoid space back to the stroma through ATP synthase complexes
ATP forms in the stroma where it is used to help drive sugar synthesis during the calvin cycle

64
Q

how are the citric acid cycle and the calvin cycle alike

A

they are both cycles

starting material is regenerated after some molecules enter and others exit the cycle

65
Q

how are the citric acid cycle and the calvin cycle different

A

citric acid cycle is catabolic - breaks down molecules

calvin cycle is anabolic - makes more complex molecules out of simpler ones - builds carbohydrates

66
Q

what occurs during the calvin cycle

A

carbon enters the cycle in the form of carbon dioxide and leaves as sugar
the cycle spends ATP as a energy source and consumes NADPH as a reducing power (to add electrons) for adding electrons to make the sugar

67
Q

what carbohydrate is released at the end of the calvin cycle

A

G3P - glyceraldehyde 3 phosphate

68
Q

how many molecules of carbon dioxide are needed to make one molecules of G3P

A

3

Bio1MGC (11 decks)

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