Bio 1080 Quiz 3

Front 1

Classification of Organism:

Back 1

Organisms can be classified based on how they obtain energy:
•Autotrophs
–Able to produce their own organic molecules through photosynthesis
•Heterotrophs
–Live on organic compounds produced by other organisms
•All organisms use cellular respiration to extract energy from organic molecules

Front 2

Cellular respiration:

Back 2

is a series of reactions

Front 3

Oxidations:

Back 3

–loss of electrons

Front 4

Dehydrogenations:

Back 4

lost electrons are accompanied by protons
–A hydrogen atom is lost (1 electron, 1 proton)

Front 5

During redox reactions

Back 5

electrons carry energy from one molecule to another
•Nicotinamide adenosine dinucleotide (NAD+)
–An electron carrier
–NAD+accepts 2 electrons and 1 proton to become NADH
–Reaction is reversible

Front 6

Redox Reaction:

Back 6

Front 7

Cellular Energy:

Back 7

harvest
–Dozens or redox reactions take place
–Number of electron acceptors including NAD+
•In the end, high-energy electrons from initial chemical bonds have lost much of their energy
•Transferred to a final electron acceptor

Front 8

Respiration:

Back 8

Aerobic respiration
–Final electron receptor is oxygen (O2)
•Anaerobic respiration
–Final electron acceptor is an inorganic molecule (not O2)
•Fermentation
–Final electron acceptor is an organic molecule

Front 9

Respiration:

Back 9

C6H12O6+ 6O26CO2+ 6H2OG = -686kcal/mol of glucose G can be even higher than this in a cell
•This large amount of energy must be released in small steps rather than all at once.

Front 10

Respiration:

Back 10

Front 11

Electron carriers:

Back 11

Many types of carriers used
–Soluble, membrane-bound, move within membrane
•All carriers can be easily oxidized and reduced
•Some carry just electrons, some electrons and protons
•NAD+ acquires 2 electrons and a proton to become NADH

Front 12

Electron Carriers:
Reduction & Oxidation

Back 12

Front 13

ATP:

Back 13

ATP( plays a central role in metabolism)
•Cells use ATP to drive endergonicreactions
–ΔG = -7.3 kcal/mol
•2 mechanisms for synthesis
1.Substrate-level phosphorylation
•Transfer phosphate group directly to ADP
•During glycolysis
2.Oxidative phosphorylation
•ATP synthaseuses energy from a proton gradient

Front 14

ATP:

Back 14

Front 15

Respiration(Oxidation of Glucose):

Back 15

The complete oxidation of glucose proceeds in stages:
1. Glycolysis
2. Pyruvate oxidation
3. Krebs cycle
4. Electron transport chain & chemiosmosis

Front 16

Respiration:

Back 16

Front 17

Glycolysis:

Back 17

Converts 1 glucose (6 carbons) to 2 pyruvate (3 carbons)
•10-step biochemical pathway
•Occurs in the cytoplasm
•Netproduction of 2 ATP molecules by substrate-level phosphorylation
•2 NADH produced by the reduction of NAD+

Front 18

Glycolysis:

Back 18

Front 19

NADH must be recycled:

Back 19

For glycolysis to continue, NADH must be recycled to NAD+by either:
1.Aerobic respiration
–Oxygen is available as the final electron acceptor
–Produces significant amount of ATP
2.Fermentation
–Occurs when oxygen is not available
–Organic molecule is the final electron acceptor

Front 20

Fate of pyruvate:

Back 20

Depends on oxygen availability.
–When oxygen is present, pyruvate is oxidized to acetyl-CoA which enters the Krebs cycle
•Aerobic respiration
–Without oxygen, pyruvate is reduced in order to oxidize NADH back to NAD+
•Fermentation

Front 21

Pyruvate:

Back 21

Front 22

PyruvateOxidation:

Back 22

In the presence of oxygen, pyruvate is oxidized
–Occurs in the mitochondria in eukaryotes
•multienzyme complex called pyruvate dehydrogenase catalyzes the reaction
–Occurs at the plasma membrane in prokaryotes

Front 23

Pyruvate dehydrogenase:

Back 23

?

Front 24

Products of pyruvate oxidation:

Back 24

For each 3 carbon pyruvate molecule:
–1 CO2
•Decarboxylation by pyruvate dehydrogenase
–1 NADH
–1 acetyl-CoA which consists of 2 carbons from pyruvate attached to coenzyme A
•Acetyl-CoA proceeds to the Krebs cycle

Front 25

Pyruvate Oxidation:

Back 25

Front 26

Krebs Cycle:

Back 26

•Oxidizes the acetyl group from pyruvate
•Occurs in the matrix of the mitochondria
•Biochemical pathway of 9 steps in three segments
1.Acetyl-CoA + oxaloacetate → citrate
2.Citrate rearrangement and decarboxylation
3.Regeneration of oxaloacetate

Front 27

Krebs Cycle:

Back 27

For each Acetyl-CoA entering:
–Release 2 molecules of CO2
–Reduce 3 NAD+to 3 NADH
–Reduce 1 FAD (electron carrier) to FADH2
–Produce 1 ATP
–Regenerate oxaloacetate

Front 28

Krebs Cycle:

Back 28

Front 29

At this point:

Back 29

•Glucose has been oxidized to:
–6 CO2
–4 ATP
–10 NADH
–2 FADH2
•Electron transfer has released 53kcal/mol of energy by gradual energy extraction
•Energy will be put to use to manufacture ATP

Front 30

Electron Transport Chain:

Back 30

ETC is a series of membrane-bound electron carriers
•Embedded in the inner mitochondrial membrane
•Electrons from NADH and FADH2are transferred to complexes of the ETC
•Each complex
–A proton pump creating proton gradient
–Transfers electrons to next carrier

Front 31

Electron Transport Chain

Back 31

Front 32

Chemiosmosis:

Back 32

Accumulation of protons in the intermembrane space drives protons into the matrix via diffusion
•Membrane relatively impermeable to ions
•Most protons can only reenter matrix through ATP synthase
–Uses energy of gradient to make ATP from ADP + Pi

Front 33

Chemiosis

Back 33

Front 34

Energy Yield of Respiration:

Back 34

•Theoretical energy yield
–38 ATP per glucose for bacteria
–36 ATP per glucose for eukaryotes
•Actual energy yield
–30 ATP per glucose for eukaryotes
–Reduced yield is due to
•“Leaky” inner membrane
•Use of the proton gradient

Front 35

Energy Yield of Respiration

Back 35

Front 36

Regulation of Respiration:

Back 36

•Example of feedback inhibition
•2 key control points
1.In glycolysis
•Phosphofructokinase is allosterically inhibited by ATP and/or citrate
2.In pyruvate oxidation
•Pyruvate dehydrogenase inhibited by high levels of NADH
•Citrate synthetase inhibited by high levels of ATP

Front 37

Respiration

Back 37

Front 38

Oxidation Without O2:

Back 38

1.Anaerobic respiration
–Use of inorganic molecules (other than O2) as final electron acceptor
–Many prokaryotes use sulfur, nitrate, carbon dioxide or even inorganic metals
2.Fermentation
–Use of organic molecules as final electron acceptor

Front 39

Anaerobic respiration:

Back 39

•Methanogens
–CO2is reduced to CH4(methane)
–Found in diverse organisms including cows
•Sulfur bacteria
–Inorganic sulphate (SO4) is reduced to hydrogen sulfide (H2S)
–Early sulfate reducers set the stage for evolution of photosynthesis

Front 40

Fermentation:

Back 40

Reduces organic molecules in order to regenerate NAD+
1.Ethanol fermentation occurs in yeast
–CO2, ethanol, and NAD+are produced
2.Lactic acid fermentation
–Occurs in animal cells (especially muscles)
–Electrons are transferred from NADH to pyruvate to produce lactic acid

Front 41

Fermentation

Back 41

Front 42

Catabolism of Protein:

Back 42

•Amino acids undergo deamination to remove the amino group
•Remainder of the amino acid is converted to a molecule that enters glycolysis or the Krebs cycle
–Alanine is converted to pyruvate
–Aspartate is converted to oxaloacetate

Front 43

Catabolism of Protein

Back 43

Front 44

Catabolism of Fat:

Back 44

Fats are broken down to fatty acids and glycerol
–Fatty acids are converted to acetyl groups by beta-oxidation
–Oxygen-dependent process
•The respiration of a 6-carbon fatty acid yields 20% more energy than 6-carbon glucose.

Front 45

Catabolism

Back 45

Front 46

Evolution of Metabolism:

Back 46

Hypothetical timeline:
1.Ability to store chemical energy in ATP
2.Evolution of glycolysis
•Pathway found in all living organisms
3.Anaerobic photosynthesis (using H2S)
4.Use of H2O in photosynthesis (not H2S)
•Begins permanent change in Earth’s atmosphere
5.Evolution of nitrogen fixation
6.Aerobic respiration evolved most recently

Front 47

Photosynthesis Overview:

Back 47

Energy for all life on Earth ultimately comes from photosynthesis
6CO2+ 12H2O C6H12O6+ 6H2O + 6O2
•Oxygenic photosynthesis is carried out by
–Cyanobacteria
–7 groups of algae
–All land plants –chloroplasts

Front 48

Chloroplast

Back 48

Thylakoid membrane –internal membrane
–Contains chlorophyll and other photosynthetic pigments
–Pigments clustered into photosystems
•Grana –stacks of flattened sacs of thylakoid membrane
•Stroma lamella –connect grana
•Stroma –semiliquid surrounding thylakoid membranes

Front 49

Stages:

Back 49

Light-dependent reactions
–Require light
1.Capture energy from sunlight
2.Make ATP and reduce NADP+to NADPH
•Carbon fixation reactions or light-independent reactions
–Does not require light
3.Use ATP and NADPH to synthesize organic molecules from CO2

Front 50

Discovery of Photosynthesis:

Back 50

Jan Baptista van Helmont (1580–1644)
–Demonstrated that the substance of the plant was not produced only from the soil
•Joseph Priestly (1733–1804)
–Living vegetation adds something to the air
•Jan Ingen-Housz (1730–1799)
–Proposed plants carry out a process that uses sunlight to split carbon dioxide into carbon and oxygen (O2gas)

Front 51

Discovery of Photosynthesis:

Back 51

F.F. Blackman (1866–1947)
–Came to the startling conclusion that photosynthesis is in fact a multistage process, only one portion of which uses light directly
–Light versus dark reactions
–Enzymes involved

Front 52

Discovery of Photosynthesis:

Back 52

•C. B. van Niel (1897–1985)
–Found purple sulfur bacteria do not release O2but accumulate sulfur
–Proposed general formula for photosynthesis
•CO2+ 2 H2A + light energy → (CH2O) + H2O + 2 A
–Later researchers found O2produced comes from water
•Robin Hill (1899–1991)
–Demonstrated Niel was right that light energy could be harvested and used in a reduction reaction

Front 53

Pigments

Back 53

Molecules that absorb light energy in the visible range
•Light is a form of energy
•Photon –particle of light
–Acts as a discrete bundle of energy
–Energy content of a photon is inversely proportional to the wavelength of the light
•Photoelectric effect –removal of an electron from a molecule by light

Front 54

Absorption spectrum

Back 54

When a photon strikes a molecule, its energy is either
–Lost as heat
–Absorbed by the electrons of the molecule
•Boosts electrons into higher energy level
•Absorption spectrum –range and efficiency of photons molecule is capable of absorbing

Front 55

Pigments

Back 55

Organisms have evolved a variety of different pigments
•Only two general types are used in green plant photosynthesis
–Chlorophylls
–Carotenoids
•In some organisms, other molecules also absorb light energy

Front 56

Chlorophylls

Back 56

Chlorophyll a
–Main pigment in plants and cyanobacteria
–Only pigment that can act directly to convert light energy to chemical energy
–Absorbs violet-blue and red light
•Chlorophyll b
–Accessory pigment or secondary pigment absorbing light wavelengths that chlorophyll adoes not absorb

Front 57

Bacterial Cell Division

Back 57

•Bacteria divide by binary fission
–No sexual life cycle
–Reproduction is clonal
•Single, circular bacterial chromosome is replicated
•Replication begins at the origin of replication and proceeds bidirectionally to site of termination
•New chromosomes are partitioned to opposite ends of the cell
•Septum forms to divide the cell into 2 cells

Front 58

Septation:

Back 58

–Production of septum separates cell’s other components
–Begins with formation of ring of FtsZ proteins
–Accumulation of other proteins follow
–Structure contracts radially to pinch cell in 2
–FtsZ protein found in most prokaryotes
–Shows a high degree of similarity to tubulin
•Role in binary fission different from tubulin in mitosis

Front 59

Eukaryotic Chromosomes

Back 59

•Every species has a different number of chromosomes
•Humans have 46 chromosomes in 23 nearly identical pairs
–Additional/missing chromosomes usually fatal