Unit 9: Cell Processes Flashcards
What is the role of NAD during cell respiration?
electron carriers = substances that are easily oxidised and reduced
NAD = nicotinamide adenine dinucleotide
REDOX occurs here
Describe the conversion of glucose to pyruvate by
stepwise reactions in glycolysis with a net yield of ATP and reduced NA
glycolysis = breaking apart a sugar
- anaerobic within cytoplasm, enzyme catalysed steps
PRODUCES
- 2 ATP
- 2 pyruvate molecules
- 2 reduced NAD
STEPS:
(see diagram on iPad, C1.2.8)
Describe the conversion of pyruvate to lactate as a
means of regenerating NAD in
anaerobic cell respiration
ADP and NAD must be available for glycolysis to occur. If O2 available, reduced NAD is converted back to NAD. If no O2…
pyruvate —–> lactate
to convert reduced NAD to NAD by donating oxygen to make lactate
Anaerobic respiration:
- Glycolysis = 2 reduced NAD and 2 ATP
- Lactate production uses 2 reduced NAD (oxidised to form NAD)
- Net total = 2 ATP
Discuss the anaerobic cell respiration in yeast and its use in brewing and baking
Alcoholic fermentation = 2 steps to regenerate NAD
if we want ethanol, no O2 allowed.
BREAD
1. aerobically respires (producing water and co2)
2. switches to anaerobic, but still co2 produced
3. co2 bubbles get trapped in bread dough (fluffy bread)
4. ethanol burns off during baking
ALCOHOL
1. sugar –> ethanol and co2
2. anaerobic
3. let off co2
4. alcohol content ↑ with sugar content
5. can be used for alcoholic drinks or bioethanol (renewable fuel)
Oxidation and decarboxylation of pyruvate as a link reaction in aerobic cell respiration (Krebs cycle)
See iPad C1.2.11
What are electron carriers?
proteins embedded in the inner membrane of the mitochondria that are easily reduced and oxidised (gain and donate e-)
explain the transfer of energy by reduced NAD to the electron transport chain in the mitochondrion
reduced NAD and reduced FAD donate e- to the chain
explain the generation of a proton gradient by flow of electrons along the electron transport chain
some energy from the e- is released at each pass along the chain
the energy is used to pump protons from matrix to intermembrane space
e- from reduced NAD = 10
e- from reduced FAD = 6
generates a high conc. gradient of protons in the intermembrane space
what is chemiosmosis & how does ATP synthesis work in the mitochondrion
movement of protons from high conc. to low conc. through ATP SYNTHASE in order to convert ADP to ATP
–> ATP synthase = channel protein for facilitated diffusion, catalyses the conversion of ADP to ATP through phosphorylation
–> as protons move through, the part of the ATP synthase that extends into the matrix rotates.
—-> causes conformational change in the protein, allowing ADP and a phosphate to bind
conc. gradient –> kinetic energy –> bonds
Reduced NAD: 2.5 ATP
Reduced FAD: 1.5 ATP
what is the role of oxygen as terminal electron acceptor in aerobic cell respiration
reduction happens when 1 molecule has a higher affinity for electrons than the molecule getting oxidised
oxygen has a high affinity for electrons
–> acts as the final electron acceptor
–> combines with H+ ions in the matrix to produce water
w/o oxygen, there is nothing to accept the electron, then all of the electron carriers stop accepting electrons
–> reduced NAD/FAD cannot donate electrons, so they remain reduced and then anaerobic respiration must take place to regenerate NAD –> yields less ATP
what are the differences between lipids and carbohydrates as respiratory substrates
CARBS
energy content: 4 cal/g
reason: lots of O
glycolysis?: yes
anaerobic possible?: yes
LIPIDS
energy content: 9 cal/g
reason: lots of C-H
glycolysis?: no
anaerobic possible?: no
what are photosystems and what types of photosystems are there
= arrays of pigment molecules that can generate and emit excited electrons
see iPad C1.3.9
photosystem II (wavelength 680) –> e- from photolysis of water
–> produces ATP
photosystem I (wavelength 700) –> e- from PS II
–> produces reduced NADP
what are the advantages of the structured array of different types of pigment molecules in a
photosystem
- lots of pigments = lots of photons can be absorbed
- increases range of wavelengths
- efficient energy transfer to the reaction center
what is photolysis?
splitting of water using energy from light
describe how oxygen is generated in photosystem II
photon enters the photosystem and bounces around the pigment molecules
then e- is lost (excitation)
water is split to replace e- from photosystem II
2H2O –> O2 + 4H+ + 4e-
this was what oxygenated the atmosphere and an increase in biodiversity after the evolution of early life forms
