Unit 4: Cellular Respiration Flashcards
Where does all the energy that we use on earth ultimately come from?
What do plants do with this energy?
The sun ☀️
Plants photosynthesize to produce glucose and oxygen
How are photosynthesis and cellular respiration related?
Both provide energy, both use some energy as heat
During energy conversions, some energy is lost as…
Heat 🔥♨️
What is the fundamental function of cellular respiration?
Generating ATP for cellular work
What is the balanced chemical equation for cellular respiration?
C6H12O6 + 6O2—6CO2 + 6H2O + ATP
Where is the energy available to a cell contained?
In the chemical bonds of food molecules
Where is the energy we get from glucose stored?
Chemical bonds
What is redox reaction?
Oxidation-reduction reaction the movement of electrons from one molecule to another
Oxidation vs. reduction
Why do oxidation and reduction always go together?
Oxidation: loss of electrons
Reduction: gain of electrons
Because electron transfer requires a donor and an acceptor
In cellular respiration, glucose is…and O2 is…
Glucose: oxidized
O2: reduced
What are the two key players in the process of oxidizing glucose? What does each do?
- Dehydrogenase: strips 2 hydrogen atoms from an organic molecule
- NAD+: made by cells to move electrons in redox reactions
When NAD+ picks up electrons that have been stripped from glucose, what does it become?
Is it the oxidized is reduced form?
Where does this molecule bring the electrons it has picked up?
NADH
It is reduced
It bring them to the Electron Transport Chain
What is the electron transport chain? What is it called?
O2 is found at the end of the ETC. It is called the final electron acceptor
What are the 3 main stages of cellular respiration and where do they occur in the cell?
- Glycolysis: occurs in cytoplasm
- Citric acid cycle: takes place in mitochondria
- Oxidative phosphorylation: occurs in ETC
What is reactant and final product of glycolysis?
Reactant: glucose
Product: 2 pyruvate
How does NAD+ become NADH during glycolysis?
Where does NADH go from there?
The cell reduces 2 molecules of NAD+
Goes to the ETC
How does ATP generated during glycolysis?
What is the net gain of ATP molecules from glycolysis?
Substrate level phosphorylation, an enzyme transfers a phosphate group from a substrate molecule directly to ATP which forms ATP
2 net ATP are gained for each glucose molecule that enters
Substrate level phosphorylation in glycolysis
An enzyme transfers a phosphate group from a substrate molecule durectly to ADP, forming ATP
Why is glucose the preferred molecule in cellular respiration?
It creates energy and is released in steps so not too much is released at once.
C-H bonds have lots of energy
How does glucose enter the cell?
Facilitated diffusion
How many ATP are invested in glycolysis?
2
What are the final products of glycolysis?
2 pyruvate, 2 net ATP and 2 NADH
How does pyruvate enter the mitochondrion?
Active transport
What is the acetyl CoA step? What happens in this step?
The intermediate step between glycolysis and the electron transport chain. Pyruvate is converted to the compound acetyl coenzyme A
What happens in substrate level phosphorylation?
Enzyme transfers a phosphate group from a substrate moleucle directly to ADP, forming ATP. This produces a small amount of ATP in glycolysis and the citric acid cycle
What are intermediates?
The products formed between the initial reactant glucose and the final product pyruvate
What has to happen to pyruvate before it enters the citric acid cycle?
It undergoes “chemical grooming”. A large multi enzyme complex catalyzes 3 reactions that forms acetyl co enzyme A
What is the function of Coenzyme A?
Helps the acetyl group enter the citric acid cycle, the it splits off and is recycled
After acetyl co-A enters the cycle, what happens?
Multiple steps occur that are each catalyzed by a specific enzyme found in the mitochondrial matrix or embedded in the inner membrane.
Acetyl joins a 4 carbon molecule to form a six carbon moleucle which is processed through a series of redox reactions. 2 carbon atoms are removed as CO2 and the 4 carbon molecule is regenerated
Does glycolysis or the citric acid cycle produce more energy?
Citric acid cycle
What are the four products of the citric acid cycle?
1 turn: 1 ATP, 3 NADH, 1 FADH2
In total: 2 ATP, 6 NADH, 2 FADH2
How many ATP, NADH and FADH2 does the citric acid cycle and glyocoysis produce?
10 NADH, 4 ATP, and 2 FADH2
What is the ETC?
Electron carriers built into the inner mebrane of the mitochondria making it possible for the mitochondrion to make it possible to use the chemical energy released by redox reactions to create a hydrogen ion gradient and drive the energy stored in the gradienr ro drive ATP synthase
Why is the cristae beneficial to the mitochondria?
They enlarge the surface area, providing more space for thousands of copies of the ETC and many ATP synthase complexes
How do electrons arrive at the ETC?
NADH and FADH2 move them through the ETC to oxygen, the final electron acceptor
How do electrons pass down the enegy staircase from one protein complex to the next?
Carriers bind and release electrons in redox reactions
Where do electrons go after the energy staircase?
They bind to O2, the final electron acceptor
How does H2o form?
Each oxygen atom accepts 2 electrons from the chain and picks up 2 hydrogen ions from the surrounding solution
How does the H+ gradient form in the inbtermembrane space of the mitochondria?
Protein complexes use energy released from electron transfers to actively transport H+ across the membrane from a low to high concentration. Hydrogen ions are transported from the matrix to the inner membrane space
What does the H+ gradient store?
Potential energy
How does the storing of potential energy in the H+ gradient help to generate ATP?
ATP synthases built into the inner membrane act like mini turbine. Hydrogen ions go across the membrane by their concentration gradient, but can only go through a channel in the ATP synthase. Hydrogen ions go through the ATP synthase, are spun, which activates catalytic site in the synthase that attach phosphate groups to ADP, creating ATP
Oxudative phosphorylation
Does it generate more or less ATP than substrate level phosphorylation?
Formation of ATP during ETC
Forms MORE
What are the poisons that block the ETC?
What is the result of them blocking the ETC?
Rotenone, cyanide, and carbon monoxide
They block the passage of electrons to oxygen, no H+ gradient is made, no ATP is made
What is a repiratory poison that inhibits ATP synthase?
Oligomycin
What do uncouplers do?
Why is this harmful?
Make the membrane of the mitochondria leaky to hydrogen ions
It is harmful because ATP can’t be made and cells consume oxygen at a higher rate
Chemiosmosis
Releasing chemical energy by redox reactions to create a H+ gradient
What is DNP?
Highly toxic uncoupler, produces an enormous increase in metabolic rate
How many ATP are made per glucose by substrate level phosphorylation?
At what stages does this occur?
4
glycolysis and citric acid cycle
How many total CO2, NADH, FADH2 and ATP are created?
6 CO2
10 NADH
2 FADH2
36-38 ATP
Anaerobic respiration
Breakdown of sugar without the use of oxygen, but without the use of oxygen
Fermentation
An anerobic process, because there is no oxygen, but is the partial degredation of sugar (no ETC and no Kreb cycle)
Lactic acid fermentation
Steps
When cells regenerate NAD+. NADH is oxidized to NAD+ as pyruvate is reduced to lactate.
- Glyoclysis
- Reduction of pyruvate to regenerate NAD+-creates lactic acid, 2 carbon
Alcohol fermentation
Steps
NADH is converted back to NAD+, while converting pyruvate to CO2 and ethanol
- Glycolysis: 2 pyruvate, 2 net ATP, 2 NADH
- Loss of CO2 for each pyruvate (total of 2 CO2 lost)
- Reduction of 2 carbon sugar to regenerate NAD+
- Final product is ethanol (2 carbon)
Obligate anaerobes
Organisms that only do fermentation
Facultative anaerobes
Organisms that can do cell respiration and fermentation
The metabolic pathway that generates ATP during fermentation is…
This step uses no…
ATP
Oxygen
What oxidizes glucose in glycolysis? What is is?
NAD+
Electron accpetor
