Metabolism Flashcards
Cellular respiration/fermentation are catabolic or anabolic pathways? What does this mean?
Catabolic
They release energy b|c they break something down
Cell metabolism=
Catabolism (release of energy)
Anabolism (requires energy)
-breaking down; building up
What makes something a nucleotide?
Sugar, phosphate, nitrogenous bases
Which phosphate in atp has most energy
Third one; it’s the first to break off when ATP becomes ADP + Pi
ATP is a polymer of …. ?
Nucleotides
What is the general overview of cellular respiration?
Takes energy from food we eat and stores it in ATP. Refers to the oxidation of glucose as the fuel!!!!
Exergonic
release energy
Oxidation
partial or complet loss of electrons
What breaks down ATP into ADP+Pi?
Enzyme called ATPase
Phosphorylated
Compound is more reactive; still getting energy
ATP –> ADP+Pi+energy
The third phosphate enzymatically breaks off and phosphorylates (gives its energy) to another compound ex: muscle.
The Pi eventually falls off and can be used again to make ATP
REDOX Reactions
Release energy when electrons move closer to electronegative atoms.
A short reference to: oxidation-reduction reactions which involves the partial or complete transfer of electrons from on reactant to another.
Reduction
Partial or complete gain of electrons
electrons=negative so if you GAIN electrons, the charge is REDUCED
Every time an electron moves/is transferred…
It loses energy
What is oxygen’s role in terms of REDOX reactions?
It is really electronegative so it pulls electrons toward it which causes electrons to give off energy
What is the chemical formula for glucose?
C6H12O6
Do we always lose energy when we get it from something?
YES- transfer is never 100%
We give off lost energy in HEAT (that’s why body is warm)
Can REDOX reactions occur in bacteria?
Yes but they use Nitrogen gas from the air instead of oxygen
How does a GENERALIZED REDOX reaction work?
electron transfer between a donor and an acceptor so, when one is oxidized the other is reduced
Reducing agent
The substance being oxidized (giving up the electron) because it is REDUCING another substance by giving that electron to that other substance (which is being reduced)
Oxidizing agent
The substance being reduced (gaining the electron)
In REDOX reactions, why is there an electron transport chain?
Because electrons only give off energy when they’re moving (in humans they are moving toward O2 at the end of the chain)
Why do we die without oxygen?
Because there is nothing for electron to be attracted to so electron doesn’t move and doesn’t give off energy
Is the ETC a slow or fast way of burring energy?
Slow burn! That’s WHY we have an ETC. ETC is oxidation=breaking things down to get energy (catabolism)
What would happen without an ETC?
The cell wouldn’t have enough time to catch energy
What are good sources of energy (Carbs, protein, or fat) and why?
Carbs and fats because they have a lot of C-H bonds which both lose potential energy as they move closer to electroneg. atoms
What do enzymes do for the activation energy used to start chemical reactions? (ADP+Pi= ATP)
Enzymes lower the activation energy so that the oxidized glucose may pass through Glycolysis and the Krebs cycle in a stepwise fashion
In sugar burned (oxidized) slowly or quickly? WHY?
Slowly bc if it was quick we wouldn’t be able to catch the released energy
What are the three acts?
Act 1- Glycolysis
Act 2- Krebs (citric acid) cycle
Act 3- Electron transport cycle
Substrate
What enzymes work on
Are enzyme apart of the product?
NO! they are just match makers that speed up the RATE of a reaction
Where does Glycolysis occur?
In the cytoplasm/cytosol
Does Glycolysis require oxygen?
- NO oxygen required (fermentation/ANAEROBIC)
- Catabolic (yields energy)
How many ATP is produced from Glycolysis?
It makes 4 BUT the process requires to so we only get TWO ATP out of it
What does glyco- in glycolysis tell us but this act?
glyco= sugar
glycolysis is the first step in getting energy out of sugar; this stage splits the sugar in half as soon as it comes into the cell (cytoplasm).
What are the phases of glycolysis?
The formula for glucose= C6 H12 O6
PHASE 1: So, we start with 6 CARBONS and need TWO ATP (activation energy)
PHASE 2: don’t have to know
PHASE 3:
-Have 2 NAD+ (becomes NADH+H+ which is more energy-rich) and 2 ADP+Pi (makes 4 ATP)
-2 Piruvic acids are formed that go to the Krebs (citric acid) cycle
-Lactic acid may be produced during fermentation
NAD+(less energy) + 2H —–> NADH + H+ (energy-rich)
Go to ACE
NAD+
first molecule on ETC; co-enzyme
assists enzymes in electron transfer during metabolic REDOX reactions
In short, what does Glycolysis produce?
4 ATP (use 2) and NADH used to get more ATP in further acts
Partially oxidizes glucose (C6) into 2 pyruvate (3C) molecules
Are hydrogen atoms stripped from glucose transferred directly to oxygen?
NO! they get passed a the electron accepter NAD+ in the electron transport chain
Co-enzyme
A small non-protein molecule thats required for certain enzymes to function
Is carbon dioxide released as glucose is oxidized to pyruvate?
NO
All carbon in glucose can be accounted for in the 2 molecules of pyruvate
NAD+ as an oxidizing reagent
(being reduced)
NAD+ functions as an oxidizing reagent during glucose oxidation; it traps energy-rich electrons from glucose
Dehydrogenases
The enzymes that NAD+ assist
- They remove a pair (2) hydrogen atoms (2 protons, 2 electrons) from substrate
- deliver 2 electrons an done proton to NAD+ (becomes NADH + H+)
- release remaining proton into surrounding medium
NAD+ +2H ——-> NADH + H+
(neutral)
NAD+ vs. NADH
NAD+ Oxidized coenzyme (net positive charge since lost electron)
NADH Reduced coenzyme (electrically neutral bc gets one H)
FAD
Also a co-enzyme like NAD+
Substrate - level phosphorylation
the mechanism of producing ATP during Glycolysis and the Krebs cycle
(Remember: substrate means NAD+ was involved so we know glycolysis and krebs)
Oxidative - level phosphorylation
ATP production resulting from the movement of electrons down the electron transport chain (ETC)
Get the most ATP here
(Remember: Oxidative means REDOX reactions= ETC)
(Phosphorylation= ADP is getting a phosphate to make ATP)
Where does the Kreb’s (citric acid) cycle occur?
In the mitochondrial matrix
What is the junction between glycolysis and krebs?
The oxidation of pyruvate to acetyl CoA
Therefore, Krebs (aka citric acid) starts when citric acid is made
Where is most of the energy from glucose at the end of glycolysis?
Still stored in the 2 pyruvate molecules
What happens to the pyruvate when oxygen is present?
It enters the mitochondrion where it’s completely oxidized by a series of enzyme-controlled reactions (krebs)
What happens to each 3carbon pyruvate after glycolysis?
3c—-> 2c (Acetyl CoA)
CO2 comes off
thats how it becomes
2c
Acetyl CoA (2c) combines with Oxaloacetic Acid (4c) = 6c (Citric Acid)
CO2 comes off reducing it to 5c
(Alphaketoglutaric Acid)
CO2 comes off reducing it back to 4c (Oxaloacetic Acid)
Goes back to beginning when it combines with new acetyl CoA from new glucose molecule
This whole thing occurs TWICE for each pyruvate producing TWO ATP TOTAL in end
Acetyl Acid CoA
First acid in Kreb’s
2 Carbons
Oxaloacetic Acid
2nd acid in Kreb’s (standing by)
4 Carbons
Citric acid
3rd acid in Krebs (Acetyl + Oxaloacetic)
6 Carbons
Alphaketoglutaric Acid
4th acid in Krebs (formed by citric losing c as CO2)
5 Carbons
Is kreb’s exergonic or endergonic?
Exergonic- releases energy to reduce coenzymes (NAD+ and FAD) and phosphorylate ADP (substrate-level phosphorylation)
Where is most of the energy from glucose at the end of the Krebs?
In molecules of NADH and FADH2
What does NADH do for glycolysis AND krebs
NADH (reduced coenzymes) link glycolysis and krebs to electron transport chain to oxygen
Does Act 3 (ETC) make NADH?
No
Where does the ETC occur?
In the inner membrane of the mitochondrion (CRISTAE)
GENERALLY what does ETC do?
Accepts energized electrons from reduced coenzymes (NADH and FADH2) that are harvested in glycolysis and krebs
What is oxygens role in the ETC?
It pulls electrons down the ETC toward it where there’s lower energy
Makes 90% of ATP (oxidative phosphorylation)
What is the ETC composed of?
A series of electron-carrier molecules built in to the mitochondrial inner membrane (cristae)
What do the electron-carrier molecules in ETC do?
Accept energy-rich electrons from NADH and pass them along chain until they reach oxygen
What happens when the oxygen at the end of ETC gets the electrons?
It gets the electrons (2 hydrogen nuclei- dehydrogenation) to form water H2O (waste)
Is ETC exergonic or endergonic?
Exergonic bc energy is released along the way
Does Krebs use oxygen?
NO, not directly
BUT it does require aerobic conditions
ETC and oxidative phosphorylation ARE what USE oxygen as final acceptor
Chemiosmosis
The mechanism for coupling exergonic electron flow from the oxidation of food to the endergonic process of oxidative phosphorylation
Strict (obligate) aerobes
Organisms that REQUIRE oxygen as the final electron acceptor for growth
Strict (obligate) Anaerobes
Organisms that live ONLY in the ABSENCE of oxygen
Facultative anaerobes
Make their ATP by either fermentation OR respiration (facilitate either way)
Proteins and cellular respiration
Deamination if amino acids allows entry into cellular respiration
Fats and cellular respiration
3 fatty acids and glycerol
Products enter cellular respiration at the glycolysis level from glycerol OR as Acetyl CoA
ATP synthetase
protein complex containing enzyme which makes ATP using the proton gradient across the inner mitochondrial membrane (powers ATP synthesis)
Cytochromes
some of the carrier molecules that act as electron carriers in the ETC
Whats the first step of Fermentation
glycolysis
What is fermentation (under anaerobic conditions)
Doesnt use oxygen; pyruvate is reduced and NAD+ is regenerated . This prevents the cell from depleting (using up) the pool of NAD+, which is the oxidizing agent for glycolysis to continue. No additional ATP produced
Under aerobic conditions…
pyruvate is oxidized further and more ATP is made as NADH passes electrons removed from glucose to the ETC. NAD+ is regenerated in the process.
Is fermentation efficient?
Not really; far less ATP produced than by aerobic conditions
What is the final acceptor in fermentation?
An organic compound (ex: protein, fat, carb)
