Sata Bio Exam 3

What is the chemical reaction for cellular respiration?

C6H1206 + 6O2 --> 6CO2 + 6H2O + energy

Overall, respiration is a (oxidative/reductive) and (exergonic/endergonic) process.

oxidative, exergonic

Approximately how many ATPs are created as a result of cellular respiration?

38

Which product of cellular respiration has been oxidized?

CO2

Which product of cellular respiration has been reduced?

H2O

Describe substrate level phosphorylation

A high energy phosphate group is removed from an intermediate substrate and added onto ADP to make ATP

What is the key enzyme of substrate level phosphorylation?

kinase

What are the two main electron carriers?

NAD+ and FAD

What do NAD+ and FAD turn into respectively once they've picked up two electrons?

NADH and FADH2

When a molecule loses an electron, it's been _____.

oxidized

When a molecule gains an electron, it's been _____.

reduced

Where does glycolysis occur?

in the cytoplasm (for eukaryotes and prokaryotes)

What are the net inputs and outputs of glycolysis?

inputs: glucose, NAD+, ADP, Pi

outputs: pyruvates, NADH, H+, ADP, (2) ATP

Describe glycolysis.

2 ATPs are used to break down glucose (which starts out as a 6-carbon molecule) into two 3-carbon pieces with Pi's (phosphate groups) attached to them. both pieces will ultimately turn into a 3-carbon pyruvate. in that process, each piece uses 2 ADPs and an NAD+ to produce 2 ATPs and an NADH. so between the two pieces that came from the original glucose molecule, there are 2 ATPs, 4 ADPs, 4 Pi's, and 2 NAD+s needed to produce 2 pyruvates, 2 ADPs, 4 ATPs, and 2 NADHs.

Describe glycolysis in shorter terms, bro.

glucose (6-C molecule) is broken into 2 (3-C molecule) pyruvates, NADH and ATP is made

What is the first committed step of glycolysis?

energy investment --> hexokinase phosphorylates glucose and turns it into glucose-6-phosphate

What is the key enzyme of the first committed step of glycolysis?

hexokinase

What is the rate limiting step of glycolysis?

phosphofructokinase phosphorylates fructose-6-phosphate and turns it into fructose-1,6-biphosphate

What is the key enzyme of the rate limiting step of glycolysis?

phosphofructokinase

What inhibits the rate limiting step of glycolysis?

(high levels of) ATP and citrate

What are the inputs and outputs of Acetyl CoA formation/pyruvate oxidation?

inputs: pyruvate (from glycolysis), CoA, NAD+

outputs: acetyl CoA, NADH, CO2

What enzyme performs Acetyl CoA formation?

pyruvate dehydrogenase

What are the regulators of Acetyl CoA formation?

Acetyl Coa, NADH, NAD+, GTP, GDP

Where is Acetyl CoA formation performed?

Eukaryotes: in the mitochondrial matrix

Prokaryotes: in the cytoplasm

Describe Acetyl CoA formation/pyruvate oxidation.

pyruvate (3-C molecule) is oxidized and converted into acetyl CoA (2-C molecule bound to coenzyme a), NADH is generated, CO2 is released

What are the steps of Acetyl CoA formation?

1. citrate synthase

2. isocitrate dehydrogenase

What are the inputs and outputs of the Krebs cycle?

inputs: acetyl CoA, NAD+, FAD, ADP, Pi, water

outputs: ATP, CO2, NADH, FADH2, H+, CoA

Where does the Krebs Cycle take place?

eukaryotes: in the mitochondrial matrix

prokaryotes: in the cytoplasm

Describe the Krebs Cycle.

Acetyl Co-A is combined with oxaloacetate (4-C molecule) to form citric acid. citric acid is broken down one carbon at a time (released as CO2) then rearranged to form the original oxaloacetate molecule

Because only 2 ATPs are produced per glucose (by glycolysis), what does most of the free energy from the Krebs Cycle do?

reduce NAD+ and FAD

What is the first committed step of the Krebs Cycle?

citrate synthase combines Acetyl CoA and oxaloacetate

What is the key enzyme in the first committed step of the Krebs Cycle?

citrate synthase

What induces the first committed step of the Krebs Cycle?

AMP

What inhibits the first committed step of the Krebs Cycle?

ATP

What is the rate limiting step of the Krebs Cycle?

oxidative decarboxylation of isocitrate

What is the key enzyme of the rate limiting step of the Krebs Cycle?

isocitrate dehydrogenase

What induces the rate limiting step of the Krebs Cycle?

ADP (enhances its affinity for substrates isocitrate and NAD+)

What inhibits the rate limiting step of the Krebs Cycle?

(high levels of) NADH and ATP

Where does oxidative phosphorylation take place?

eukaryotes: on the mitochondrial inner membrane

prokaryotes: on the plasma membrane

Describe oxidative phosphorylation.

NADH and FADH2 made in the other steps deposit their electrons in the ETC and turn back into NAD+ and FAD. as electrons move through the ETC, the energy produced pumps protons out of the matrix. protons follow their gradient back into the matrix by going through the enzyme ATP synthase which produces ATP yay! electrons are ultimately received by oxygen to make water

Between FADH2 and NADH, which donates electrons to the ETC at a lower energy level during oxidative phosphorylation?

FADH2 donates electrons to the ETC at a lower energy level than NADH (and therefore makes less ATP)

During oxidative phosphorylation, will the pH in the matrix of mitochondria will be higher or lower than that of the intermembrane space?

higher (more protons in the intermembrane space --> higher pH in the matrix)

Electrons moving through the ETC go from higher energy levels to low energy levels. What is the ultimate destination for these electrons?

oxygen (forms water; if the cell doesn't get enough oxygen, the ETC will stop running and no more ATP will be made through chemiosmosis in the mitochondria)

About how many ATPs are produced by oxidative phosphorylation for every molecule of glucose?

34 ATPs per glucose

Link the inputs/outputs of glycolysis, Acetyl CoA formation, the Krebs Cycle, and oxidative phosphorylation

- pyruvate from glycolysis goes to Acetyl CoA formation/pyruvate oxidation

- Acetyl CoA from Acetyl CoA formation/pyruvate oxidation or from fatty acid beta oxidation goes to the Krebs Cycle

- NADH and FADH2 from the Krebs Cycle goes to oxidative phosphorylation

- NAD+ and FAD from oxidative phosphorylation go back to the glycolysis, Acetyl CoA formation, and the Krebs Cycle

How do proton gradient uncouplers mess with cellular respiration?

they make the inner membrane of mitochondria leaky which eliminates the protein gradient

Give an example of a protein gradient uncoupler.

dinitrophenol (DNP)

How do ATP synthase inhibitors mess with cellular respiration?

they bind directly to ATP synthase which blocks protons from being able to come back into the inner matrix of the mitochondria

How do electron transport inhibitors mess with cellular respiration?

they block the electron transport chain which eliminates the proton gradient, and they keep oxygen from receiving electrons which means no regeneration of NAD+ or FAD which means no Krebs Cycle

Give an example of an ATP synthase inhibitor

oligomycin

Give an example of an electron transport inhibitor.

cyanide (CN-), carbon monoxide (CO), azide (N3-)

Why does fermentation occur?

if the cell doesn't have mitochondria or when there's no oxygen, there aren't any cells to receive the electrons from the ETC which means NAD+ can't be regenerated. in this context, ATP is made solely by glycolysis, and fermentation regenerates NAD+ to keep glycolysis going

Which organisms perform alcoholic fermentaiton?

yeasts and some bacteria

Which organisms perform lactic acid fermentation?

yogurt bacteria and human muscle cells

What are the inputs and outputs of lactic acid fermentation?

inputs: glucose, ADP, Pi

outputs: lactate, ATP

Describe lactic acid fermentation.

NADH (from glycolysis) gives its electrons to pyruvates which makes lactate and the NAD+ needed for glycolysis to continue

Pyruvate turning into lactate is a (reductive/oxidative) process.

reductive (because in the process, NAD+ turns into NADH which means NAD+ is oxidized and is therefore the reducing agent of pyruvate)

What are the inputs and outputs of alcoholic fermentation?

inputs: glucose, ADP, Pi

outputs: ethanol, CO2, ATP

Describe alcoholic fermentation.

pyruvates are decarboxylated by pyruvate decarboxylase which releases CO2 and ethanol. alcohol dehydrogenase uses the NADH from glycolysis as a reducing agent which generates the NAD+ needed for glycolysis to continue

Why is photosynthesis important?

it allows plants to make their own food, fixes atmospheric CO2 into carbs, and generates organic compounds from which all other organic molecules are made

What is the chemical reaction for photosynthesis?

6H2O + 6CO2 -(light)-> C6H12O6 + 6O2 + 6H2O

What is the mesophyll?

cells in the middle layer of the leaf tissue --> primary site of photosynthesis

What are stomata?

small pores found on the surface of leaves that allow CO2 to diffuse into the mesophyll layer and oxygen to diffuse out

What are thylakoids?

small, disk-like structures arranged in stacks (grana) inside chloroplasts --> their membranes contain chlorophyll pigments that absorb light

What is the stroma?

the fluid-filled space that surrounds the grana in chloroplasts

What is the thylakoid space?

the gel-filled space inside thylakoid disks

What is phloem?

vascular tissue that transports sugars and other soluble compounds from the green parts of the plant to the rest of it --> allows stuff to move in two directions

What is xylem?

vascular tissue that transports water and dissolved minerals from the roots to the rest of the plant --> things can only move in one direction

Where do light reactions take place?

inside the thylakoid

Describe light-dependent reactions.

photons excite electrons in the stroma and split water (photosystem II) and break down water. electrons move from photosystem II to the electron carriers in the thylakoid membrane which transport them through the ETC (photosystem I). as the electrons move through the ETC, the energy released pumps protons into the thylakoid. for the protons to go down their gradients back into the stroma, they have to go through ATP synthase which generates ATP.

electrons released from the ETC get transferred to NADP+ which forms NADPH.

During photophosphorylation, will the pH of the thylakoid space will be higher or lower than that of the stroma?

lower (more protons in the thylakoid space --> higher pH in the stroma)

What does Photosystem II do?

harvests light energy via chlorophyll and other pigments and splits water to make oxygen --> functions only in non-cyclic photophosphorylation

Around what wavelength does Photosystem II absorb best?

680 nm

What does Photosystem I do?

reduces NADP+ to make NADPH --> functions in cyclic and non-cyclic photophosphorylation

Around what wavelength does Photosystem I absorb best?

700 nm

Where does the Calvin Cycle take place?

in the stroma (of chloroplasts)

Does the Calvin Cycle need light to do its thang?

nope

What are the inputs and outputs of the Calvin Cycle?

inputs: CO2, ATP, NADPH

outputs: glucose, ADP, Pi, NADP+

Where do the inputs of the Calvin Cycle come from?

CO2 - from the atmosphere

ATP and NADPH - from light reactions

Where do the outputs of the Calvin Cycle go?

glucose - growth and storage

ADP, NADP+, Pi - to light reactions

Is the Calvin Cycle endergonic or exergonic?

endergonic (needs ATP to function)

Why does the Calvin Cycle need NADPH?

it's a reductive process

How many times does the Calvin Cycle need to run to make a single glucose molecule?

6 times

Describe the Calvin Cycle.

rubisco uses ATP and NADPH from light reactions to fix CO2 and O2 to produce 3-C sugars (glyceraldehyde-3-phosphate) which combine to form glucose

What are the three steps of the Calvin Cycle?

carbon fixation, reduction (of electron carriers as they donate electrons), regeneration of RuBP (to perform another cycle)

What is the key regulatory step of the Calvin Cycle?

rubisco combines CO2 and ribulose biphosphate to make 3-C-phosphoglycerate

What are the regulators of rubisco in the Calvin Cycle?

CO2, O2, Mg2+, NADPH, pH

What induces cyclic photophosphorylation?

(high levels of) NADPH

What are the inputs and outputs of cyclic photophosphorylation?

inputs: ADP, Pi, light

outputs: ATP

Which photosystem(s) feature cyclic photophosphorylation?

photosystem I

What are the inputs and outputs of non-cyclic photophosphorylation?

inputs: water, NADP+, ADP, Pi, light

outputs: O2, H+, ATP, NADPH

Which photosystem(s) feature non-cyclic photophosphorylation?

photosystem I and II

Where do electrons go after non-cyclic photophosphorylation?

they are transferred to NADP+ to make NADPH (they don't return to the reaction center)

How are electrons regenerated in non-cyclic photophosphorylation?

splitting water (creates O2 as a byproduct)

Chemiosmosis is an (exergonic/endergonic) process that directly helps the (exergonic/endergonic) process of ATP synthesis in oxidative phosphorylation.

exergonic, endergonic

Describe chemiosmosis in the mitochondria.

electrons fuel the ETC on the inner membrane to pump protons out of the inner matrix into the intermembrane space à in order for the protons travel down their gradient back into the inner matrix, they have to pass through the ATP synthase which produces ATP

Describe chemiosmosis the chloroplasts.

o electrons fuel ETC on the thylakoid membrane to pump protons from the stroma into the thylakoid space à in order for protons to travel down their gradient back into the stroma, they have to pass through the ATP synthase which produces ATP

What is photorespiration?

on hot, sunny, dry days, CO2 levels fall, O2 levels rise, and stomata close. rubisco fixes O2 into RuBP and releases CO2 --> results in the use of RuBP without making any sugars or ATP --> occurs until CO2 levels are back to normal

Rank C3, C4, and CAM plants in order from least energy efficient to most energy efficient.

CAM < C4 < C3

Rank C3, C4, and CAM plants in order from least water efficient to most water efficient.

C3 < C4 < CAM