C1.2 - Cell Respiration Flashcards
What is cell respiration as a process?
Converting organic molecules to chemical energy of ATP
What are nucleotides?
Subunits of DNA, RNA. Made of 3 parts - nitrogenous base, sugar, phosphate groups
What is ATP?
Adenosine triphosphate, a nucleotide made of adenine base, 5-carbon ribose sugar, and 3 phosphate groups that are negatively charged in chain
What qualities of ATP make it good for being the ‘energy currency’?
- ATP is soluble in water
- 3rd phosphate group of ATP can be easily removed/replaced to make energy
- ATP doesn’t pass freely through phospholipid bilayer
What 3 processes do cells need the energy of ATP for?
- Making macromolecules
- Active transport
- Cell movements
Where can energy to change ADP to ATP come from?
- Cell respiration
- Photosynthesis
- Chemosynthesis
Are energy transfers from ATP-ADP and ADP-ATP completely efficient?
No - some energy changed to heat
What carbon compounds can be used in cell respiration?
Mainly glucose and fatty acids - but others can also be used
What is gas exchange?
When oxygen enters the cells and at the same time carbon dioxide exits the cells
Distinguish between gas exchange and cell respiration? (how are they connected to each other?)
Different processes but are interdependent.
- Without gas exchange, there would be too much co2 and not enough o2 for cell respiration to happen
- Without cell respiration, the concentration gradient of the gases wouldn’t form to let it diffuse in and ount
State 3 word equations to show the different types of cell respiration?
[animals, plants] 1. glucose + oxygen -> (adp-atp) -> co2 + water
[animals, some bacteria] 2. glucose -> (adp-atp) -> lactate
[yeast, fungi] 3. glucose -> (adp-atp) -> co2 + ethanol
Contrast anaerobic and aerobic cell respiration?
Anaerobic:
- Oxygen is not used
- Co2, ethanol, lactate waste products
- Low ATP yield (2 ATP/glucose)
- Reactions in cytoplasm only
Aerobic:
- Oxygen is used
- Co2 and H2O waste products
- High ATP yield (30 ATP/glucose)
- Reactions in cytoplasm + mitochondria
When is anaerobic respiration usually used in humans?
To maximize power of muscle contractions -> anaerobic releases ATP really fast. Historically used for prey/predator stuff, now used for exercise.
Describe the waste product of anaerobic respiration in human muscles?
Waste = lactate which has a max concentration that a human can tolerate so anaerobic respiration is limited
Describe the factors that limit rate of cell respiration?
- Temperature -> optimum temp 20-30
- Substrate Concentration (too much Co2 = bad, too less O2 = bad)
- Type of cell -> some cells need more so rate is faster
What is oxidation?
Loss of electrons from a substance
What is reduction?
A substance experiences gain of electrons
What are electron carriers? What is cell respiration’s electron carrier?
Substances that link the oxidation reactions and the reduction reactions. NAD (nicotinamide adenine dinucleotide) is cell respiration’s carrier
Describe the structure of NAD?
Two nucleotides - one has an adenine base, one has a nicotinamide base. Each base has a ribose sugar connected, the ribose sugars are connected to the phosphate groups which are connected which joins the two nucleotides
How is NAD reduced for cell respiration?
Through substances being oxidized to give NAAD 2 electrons and 1 proton
What does NAD reduction show about reduction/oxidation in general?
Reduction can happen by losing accepting hydrogen atoms and oxidation can happen by losing hydrogen atoms
Are there any examples of reduction/oxidation through loss/gain of oxygen atoms?
Oxygen can be used
Fewer examples, maybe b/c oxygen was scarce on primitive Earth.
Ex: Bacteria oxidizing hydrocarbons with oxygen
What is glycolysis? (Basic overview!)
Glycolysis is 1st step in aerobic cell respiration -> changes glucose into pyruvate to make ATP and reduced NAD. In cytoplasm.
What is the first stage of glycolysis?
Phosphorylation to make fructose 1,6 biphosphate
- Phosphate is added to glucose to make glucose 6 phosphate.
- Glucose 6 phosphate to split fructose 6 phosphate
- Phosphate is added to fructose 6 phosphate to make fructose 1,6 biphosphate
What is the second stage of glycolysis?
Lysis
- Fructose biphosphate is split into 2 molecules of triose phosphate
What is the third stage of glycolysis?
Oxidation
- Each triose phosphate is oxidized / looses electron
- The NAD’s are reduced by the electrons from triose getting oxidized
- Makes glycerate and 2 biphosphate molecules
What is the fourth / last stage of glycolysis?
ATP Formation
- Biphosphate molecules get phosphate groups transferred to ADP to make ATP
- Glycerate is also converted to pyruvate to make 2 (3C) pyruvates
What is yielded by glycolysis?
- 2 ATP molecules net yield (2 are used in first stage, 2 are produced, 4-2=2)
- Two 3-carbon pyruvate molecules
- Two reduced NAD molecules
How is NAD regenerated?
reduced NAD is oxidized / looses 2H atoms to make it into NAD
What else can NAD get regenerated by?
Converting pyruvate into ethanol and co2
What is the first step in NAD regeneration through pyruvate -> ethanol, co2?
Co2 is removed from pyruvate to make ethanal
What is the second step in NAD regeneration through pyruvate -> ethanol, co2?
2 H are removed from NAD and put to ethanal to make ethanol.
What is NAD regeneration through pyruvate -> ethanol, co2 called?
Ethanol / alcoholic fermentation -> used in brewing, baking…yeast carries it out
What is yeast?
Yeast is a unicellular fungus called a faculative anaerobe -> can do cell respiration aerobically and anaerobically
How is yeast used when making bread?
Yeast first respires aerobically and then switches to anaerobic.
The yeast makes Co2 that makes bubbles in the dough that make it rise
How is yeast used when brewing?
Yeast is used to produced ethanol in brewing -> yeasts quickly eat up all the oxygen and then respire anaerobically, ethanol produced is dissolved and co2 bubbles up to escape
How is yeast used in producing bioethanol?
Bioethanol = renewable energy source made of plant matter.
Yeast converts the sugars in sugar cane or corn into ethanol, and ethanol is distilled to purify bioethanol, which can be used as fuel etc.
What is the link reaction (basic)?
‘Link’ between glycolysis and Kreb’s cycle
Oxidizing pyruvate into a 2-carbon acetyl group
A three enzyme complex carries out the reactions
What is the first step of the link reaction?
Carbon dioxide is removed from pyruvate (decarboxylation) to make 3-carbon pyruvate into 2-carbon molecule
What is the second step of the link reaction?
Two electrons are removed from pyruvate (oxidation) -> NAD takes these electrons and becomes reduced NAD
What is the third step of the link reaction?
The acetyl group that was made from the first 2 steps gets bound to coenzyme A to make acetyl coenzyme A / acetyl CoA
Where does glycolysis take place?
In the cytoplasm
Where does the link reaction and Kreb’s cycle take place?
In the matrix
How is the pyruvate moved from the cytoplasm to the matrix (glycolysis -> link reaction)?
Transporter protein moves it
What are the membranes and compartments of the mitochondrion?
Outer membrane (very outside part), inner membrane (foldy part), matrix (fluid filled inside), inter-membrane space (between the outer and inner membrane) -> search up a pic to confirm
What is the Kreb’s cycle? (basic)
When the acetyl group from the link reaction is changed through oxidation reactions
What is the first step of the Kreb’s cycle?
Acetyl group join using coenzyme A with oxaloacetate (4C) to make citric acid (6C)
What is the next step?/describe general Krebs cycle
After citrate (6C) forms, it is converted into a 5C compound (through decarboxylation and oxidation), and then to a 4C compound (more decarboxylation and oxidation. When oxidation reactions occur, electrons are removed. These electrons reduce NAD or FAD, and that energy is used in the electron transport chain.
What is the net yields of the Kreb’s cycle?
- One acetyl group is consumed
- Three NADs are turned into three reduced NAD
- One FAD is turned into reduced FAD
- 2 molecules of Co2 are released
- 1 ADP turns into ATP
Sum up where NAD is reduced / carrying electrons?
Reduced NAD accepts and carrying electrons
- Glycolysis makes reduced NAD which goes into the mitochondria
- Reduced NAD is also made through link reaction, Kreb’s cycle
How does the electron transport chain start?
In the inner mitochondrial membrane, there are protein carriers that accept the electrons carried by reduced NAD, and the sequence of these carriers makes the electron protein chain.
Role of NAD and FAD in the electron transport chain?
The first carrier takes an electron pair from reduced NAD, which reduces the carrier, giving it chemical energy. FAD also gives a pair of electrons, but these electrons have less energy, so they get accepted by a high affinity carrier.
What do the electron carrier proteins in the chain do?
Proton pumps - use energy released from moving electrons along sequence to pump protons across the mitochondrial membrane
How many electrons do the carrier proteins pump?
First and second pump 4 each, third pumps 2, making 10 total by the first 3 -> these r the ones that get electrons from reduced NAD.
The ones that get electrons from reduced FAD have less energy and only pump 6 total.
What happens to the energy used to pump the protons?
It gets stored as a proton gradient. The stored energy in the proton gradient is used to make ATP.
What are cristae?
Foldings of the inner mitochondrial membrane
What is chemiosmosis (basic)?
When ATP synthase produces ATP, it phosphorylates ADP. The proton gradient gives this energy to phosphorylate.
Where do the protons move in the gradient in chemiosmosis?
Protons move down their concentration gradient, intermembrane space to matrix. When they move they release energy which is used in ADP-ATP phosphorylation.
Describe the parts of ATP synthase in reference/context of chemiosmosis? (basic part)
- Two main regions
- One region is made of subunits of transmembrane -> this part is embedded in the inner membrane. This region lets protons pass across to release energy.
- Second region is globular, projects onto matrix, has active sites that use the proton energy to make ATP
What is the last electron acceptor in the ETC chain?
Molecular oxygen - it accepts electrons from the previous electron carrier and hydrogen ions from the fluid in the matrix to make water
Why is it used as the last electron acceptor in the ETC chain?
Because each electron carrier in the chain has stronger and stronger affinity for electrons, so we need a substance with a high affinity for electrons
What is the significance of oxygen to the aerobic cell respiration?
It’s needed in all the stages except glycolysis
What happens when oxygen runs out?
- Electrons are not removed at the end of the ETC / no terminal electron acceptor
- Then, all the carriers in the ETC become reduced so there’s no one to take the initial reduced NAD so there’s a lot of reduced NAD, so the Kreb’s cycle and link reaction stop because they can’t oxidate
What does the formation of water at the end of the ETC do?
Helps maintain the proton gradient
Compare and contrast lipids and carbs as respiratory substrates?
Carbs:
- Anaerobic respiration
- Lower energy yield
Lipids:
- Aerobic respiration
- Higher energy yield
