Intro to Metabolism (Quiz 1) Flashcards
What is metabolism?
-the sum of all biochemical reactions that occur in living cells
-the product of one reaction is the substrate for the next reaction (pathways or metabolites)
-several thousand reactions occur simultaneously in cells, but both the internal and external environment of the cell remains constant
Do we store high energy electrons?
no
What enzymes can remove hydrogens/ electrons from food or within the body?
oxidases and dehydrogenases
What “catches” hydrogen and electrons?
coenzymes
What are the major goals of metabolism?
for the cell to maintain and replicate itself for:
-energy that will be synthesized as needed (ATP, NADH, NADPH)
-making precursors to synthesize large molecules
Where does ATP hold its energy?
between the phosphates, at the phosphoanhydride bond
What are catabolic pathways? Are they exergonic or endergonic?
-they degrade large compounds into smaller ones
-they are exergonic bc energy is being released, so delta G is negative
What are anabolic pathways? Are they exergonic or endergonic?
-they synthesize macromolecules from simple precursors
-they are endergonic, which means they need energy to build, so delta G is positive
What are amphibolic pathways?
they function as both catabolic and anabolic pathways
ex: TCA cycle oxidizes acetyl CoA to CO2 and also includes intermediates that serve as substrates for synthetic pathways
-oxygen is the driving force of TCA cycle
-2 carbons will change to 2CO2 per cycle and generate high energy electrons like NADH
-this is catabolic
-molecules within cycle will be used to make glucose, AA, or fat, which this is anabolic
-both of these happen separately within reaction so this is NOT coupling, but rather amphibolic
What is the driving force of TCA cycle?
oxygen
What does amphipathic mean?
hydrophilic + hydrophobic
What does energy coupling mean?
catabolic reaction drives anabolic reaction and they happen at the same time
What is oxidation?
-loss of electrons and hydrogens
What is reduction?
-gain of electrons and hydrogens
What biochemical reaction is digestion?
hydrolysis- uses water to breakdown food into smaller pieces
Energy containing nutrients are only what molecules?
organic containing molecules
What are the 3 energy containing nutrients?
carbs, fats, and proteins
Does water have energy?
no
What chemical energy can we use?
high energy electrons or high energy phosphate
Can you use the energy released during digestion?
no
What are the energy depleted end products after catabolism?
CO2, H2O, NH3 (ammonia)
Any energy that cannot be used will turn into….
heat
Creatine- P is a ________________ molecule
substrate phosphorylation
T/F: ATP can be transformed to NAD, FAD, or CoA
true
What is the base in ATP?
adenine
What is the sugar in ATP?
ribose
What shape does the sugar in ATP have?
furanose
In ATP, the energy is released by the hydrolysis of the 3rd phosphate group with the help of ___________. After this 3rd phosphate group is released, the resulting ADP can absorb energy and regain the group, thus regenerating an ATP molecule; this allows ATP to store energy like a rechargeable battery
ATP hydrolase
When ATP transitions to ADP, what is the delta G?
-7.3 Kcal/mol (note: the exergonic part (negative number) always has to be larger than the positive/endergonic part for the reaction to work)
What is the bond between the sugar and phosphate of ATP?
ester bond
How many high energy bonds does ATP have?
2
this is because theres 3 phosphates and the energy is held at the bond between phosphates (the phosphoanhydride bond)
Is substrate level phosphorylation rare/hard?
Yes only 4 molecules can do it
What is substrate level phosphorylation?
test q
formation of ATP by the direct transfer and donation of a phosphate group to ADP
ATP can be transformed by the 2nd messenger molecule cAMP by what enzyme?
adenylate cyclase
T/F: ATP is found in DNA and RNA
true
What is the delta G when ADP transitions into AMP?
-5 Kcal/mol (note: the exergonic part (negative number) always has to be larger than the positive/endergonic part for the reaction to work)
Does AMP provide energy if it is broken down?
no
T/F: ATP gets generated after breaking down food
true
ATP gets broken down anytime the body needs energy. For what reactions does this apply to?
any anabolic reactions
T/F: NADH is an electron carrier
false, NAD+ is the electron carrier in this case!
What does the N stand for in NAD+ or NADH?
nicotinamide/niacin/ vitamin B3
What is the difference between NAD+ and FAD in terms of structure?
The base
for NAD+ its nicotinamide/niacin/ vitamin B3
for FAD its riboflavin/ vitamin B2
What is the sugar in NAD+ and FAD?
ribose
What is the difference between NAD+ and NADP+ in terms of structure?
There would be a phosphate attached to C2 on one of the ribose sugars
What are the 4 major electron carriers in metabolism?
test q
1) NAD+
2) NADP+
3) FAD
4) FMN
NAD+ is used in ___________ reactions
oxidation/ catabolic (strip H away)
What is the major form- NAD+ or NADH?
NAD+
NADP+ is used in ____________ reactions
reduction/ anabolic (take in H)
What is the major form- NADP+ or NADPH?
NADPH
What is FMN?
riboflavin mononucleotide
-same thing as FAD but its only 1 nucleotide
NAD+ can be converted to….
NADH + H+
NADP+ can be converted to….
NADPH + H+
FAD can be converted to…
FADH2
FMN can be converted to…
FMNH2
Which electron carrier is found in the cytoplasm?
NADP+ (the other 3 electron carriers are found in mitochondria)
Coenzymes can be divided into 2 groups. What are they?
cosubstrates and prosthetic groups
What are the cosubstrates in metabolism?
-NAD+ + NADH
-NADPH + NADP+
What are the prosthetic groups in metabolism?
-FAD + FADH2
-FMN + FMNH2
What 2 enzymes strip electrons of a nutrient biomolecule and transfer them to electron carriers?
dehydrogenases and oxidoreductases
What 2 electron carriers are free to move from enzyme to enzyme and are usually associated with soluble dehydrogenases?
NAD+ and NADP+
Which 2 electron carriers are prosthetic groups of the dehydrogenases that are found embedded in the mitochondrial membrane?
FAD and FMN
Where does galactose usually come from (think food source)?
lactose in dairy
Where does fructose usually come from (think food source)?
sucrose (table sugar)
What are the 3 energy carriers in food?
carbs, proteins, and fats
How many carbons are in glucose?
6
Carbs break down into….
usually glucose (but can also breakdown to form galactose or fructose)
During glycolysis, one glucose makes how many pyruvate?
2 (because pyruvate is 3 carbons and glucose is 6C)
Glucose, galactose, and fructose are all _________ soluble and will go to liver
water
What happens to galactose and fructose in the liver?
they will be converted to glucose
Where does glucose go after the liver?
blood and tissues
What happens to glucose once it reaches tissue cells?
it will be converted to pyruvate (glycolysis)
What carbs does the liver not like?
fructose and sucrose
Glucose makes 2 pyruvate which will then make 2 acetyl CoA. 3 questions:
1) What is this step called?
2) What is the pyruvate to acetyl CoA rxn called?
3) What enzyme is used in this reaction?
step is called pyruvate oxidation (happens in mitochondria)
oxidative decarboxylation reaction
uses pyruvate dehydrogenase to convert pyruvate to acetyl CoA
Note: pyruvate is 3 carbons whereas acetyl CoA is only 2, the 3rd carbon makes CO2 and NADH/FADH2 will also be generated
What is the substrate for TCA cycle?
acetyl CoA
What is the product of TCA?
test q
2 CO2 and high energy electrons (3 NADH and 1 FADH2)
What is the product of ETC?
test q
ATP and water
What are the 2 ways to create ATP?
ETC (major way)
substrate level phosphorylation (minor way)
-can be done with creatine-P, 2 molecules within glycolysis, or one molecule in TCA (this will become more specific later…)
What are the other names for TCA cycle?
krebs cycle or citric acid cycle
Acetyl CoA enter the TCA cycle and will make….
2 CO2
3 NADH
1 FADH2
1 ATP
This is only one round (1 acetyl coa will go through one round, but if acetyl coa comes from glucose then there will be 2)
After TCA cycle, the high energy electrons NADH and FADH2 will go to ETC to transport electrons and make…
ATP (the H will change to water which is an oxidation reaction)
What processes/cycles need to occur for glucose to be completely oxidized?
test q
glycolysis> pyruvate oxidation> TCA cycle> ETC
which will result in ATP+ water + 6 CO2
Proteins get broken down into AAs for energy. How do AAs get processed and where do they go?
AAs will go to the liver and need to be processed
the amino group needs to be removed from the AA to be able to use AA for energy
the amino group of the AA will be cleaved and become urea
the remainder of the AA will become an alpha ketoacid
The AA is converted to an alpha ketoacid. What does it get converted to next?
pyruvate (and then will follow the same steps as glucose version, which is pyruvate> acetyl CoA undergoes TCA> electron carriers go to ETC)
Out of the 3 energy carriers in food what is the last resort?
fat
Fat gets broken down into FAs and then acetyl CoA. How?
triglycerides (TG) will break down into a MG and 2 FAs for digestive purposes
then will be converted back to a TG and go to the lymphatic system
eventually the TG will go to blood and become a FA
FA gets converted to acetyl CoA (THIS IS CALLED BETA OXIDATION)
-this is where the beta carbon of the FA will be oxidized and become a double bond which forces acetyl CoA to be cleaved off because carbon likes 4 bonds
now we have acetyl CoA (which will then undergo TCA make NADH and FADH2 which will go to ETC and make ATP and water)
What happens to the liver if theres excess glucose in the body and theres enough ATP in the tissues for energy?
the liver will store it as glycogen
Glucose that is in the blood will travel to tissue cells. What GLUT transporter is used? Is it passive or active?
GLUT4 is a passive transporter
Glucose> G6P> pyruvate
What is the pathway called that goes from G6P to pyruvate?
glycolysis
When does pyruvate get converted to lactate?
when theres no oxygen (anaerobic glycolysis)
Will lactate change to ATP?
no
If theres too much glucose it’ll change to pyruvate > acetyl coa > fatty acids. What is the pathway of acetyl coa to fatty acids called?
fatty acid synthesis
-theres too much glucose so the body will store it in adipose tissue as triglycerides or fatty acids
Glycogen breaks down to glucose when in _______ state
fasted
Excess AAs will turn to…
fat
Excess fatty acids will get stored as…
fat in adipose tissue
After glucose enters tissue cells it will immediately become _____________
glucose 6 phosphate (this traps glucose in the cells bc remember it travels through a passive GLUT4 transporter)
Glucose > G6P > pentose phosphates and NADPH
What is G6P to pentose phosphates and NADPH pathway called?
pentose phosphate pathway (PPP)
note: the pentose phosphate is usually ribose 5 phosphate which is used to create DNA and RNA, and the NADPH is used in reduction reactions and is an endogenous antioxidant bc it can provide H to reduce oxidative stress
Which AA can turn into pyruvate?
alanine
What is the gluconeogenesis pathway?
pyruvate > oxaloacetate (OAA) > G6P > glucose
gluconeogenesis means generate new glucose from non-carbs
glucose > G6P > pyruvate > __________ > cholesterol
acetyl coa
glucose > G6P > _________ > acetyl coa > ketones/ketone bodies
pyruvate
glucose > G6P > pyruvate > __________ > fatty acids
acetyl coa
Which 2 AAs can directly change to acetyl coa to create energy?
lysine and leucine (ketogenic AAs, they’re essential)
In a fed state what happens to insulin and glucagon?
insulin increases, glucagon decreases
Glucose gets completely oxidized by going through glycolysis, pyruvate oxidation, TCA cycle, and ETC. What is the end product?
ATP, water, and carbon dioxide
When theres enough energy in the body and glucose is still available what happens?
glucose gets converted to glycogen and will be stored in the liver and in the muscle
glycogen in liver can go back to blood as needed and is important for brain function to be able to think
glycogen in muscle tissues is important for muscular energy
Do we store unlimited amount of glycogen?
no only some, the rest will turn to fat if theres still enough energy, glucose, and glycogen everywhere within body
When theres enough energy and glucose, what happens if someone keeps eating?
glycogen has already reached its storage capacity, so the remainder of glucose intake will go straight to fat
T/F: glucose can be converted into non-essential AAs
true
When you eat AAs, what does it eventually become?
1) atp, water, carbon dioxide, and urea
2) tissue proteins
3) fats
When you eat fats like triglycerides what does it turn into?
FAs and then eventually ATP, water and carbon dioxide
What do FAs turn into if theres an excess?
fats
What happens to insulin and glucagon in fasting state?
insulin decreases, glucagon increases
In the fasting state, glycogen gets converted to glucose. This only lasts for 12 hours. What happens when the body starts to go into starvation mode?
muscles breakdown AAs and make glucose
TG > FA undergoes beta oxidation to make acetyl coa > atp
RBCs and the brain however, cannot use FAs for energy, so in this instance, TG > FA > acetyl coa > ketone bodies
Can FAs make AAs?
yes
Can FAs make carbs?
no
Can AAs make FAs?
no
Can AAs make carbs?
yes
Can carbs make FAs?
yes
Can carbs make AAs?
yes
What is the futile cycle?
pointless cycle of catabolic and anabolic events
ex: synthesizing FAs and breaking them down at the same time (same thing with glucose or any other molecule)
How do you prevent the futile cycle at the cellular level?
-target the rate limiting enzyme
-allosteric enzymes
-covalent modification
-alter enzyme conc. (create more enzyme)
Which hormones can create more enzymes?
lipid hormones
Can insulin and glucagon do allosteric regulation?
no, they’re too big, they cannot go into cell
Can insulin and glucagon do covalent modification (form a covalent bond)?
yes with a 2nd messenger
Which regulation mechanism is a feedback loop?
allosteric regulation
How do you prevent the futile cycle at the level of the whole organism?
-NS and endocrine system
-fine tuning of cellular regulation
What are the 6 enzyme classes?
1) oxidoreductase
2) transferase
3) hydrolase
4) isomerase
5) ligase
6) lyase
What 3 enzyme types are found under the oxidoreductase class?
1) oxidase
2) reductase
3) dehydrogenase
What is the function of oxidase?
remove H/ electrons (NAD+ can be used in this reaction)
What is the function of reductase?
add H/electrons (NADPH can be used in this reaction)
What is the function of dehydrogenase?
can add or remove H
ex: pyruvate will undergo an oxidative decarboxylation reaction with pyruvate dehydrogenase to make acetyl coa (this step is called pyruvate oxidation)
What vitamins are required for oxidoreductase enzymes?
vitamin B2 (riboflavin) and B3 (niacin/nicotinamide)
vit B2 is used with FAD and FMN
vit B3 is used with NAD and NADPH
What 3 enzyme types are under the transferase class?
1) kinase
2) phosphorylase
3) aminotransferase
What is the function of kinases?
add phosphate
ex: glucose undergoes reaction with glucokinase or hexokinase to make G6P
What is the function of phosphorylase?
breaks bond to transfer a phosphate (adds a phosphate)
ex: glycogen undergoes a reaction with glycogen phosphorylase to make glucose 1 phosphate (G1P)
What is the function of aminotransferase?
transfer an amino group
examples:
generally AAs can cleave amino group to make an alpha ketoacid
alanine can remove NH2 and make pyruvate
aspartate can cleave NH2 and make OAA
alanine + OAA with an alanine aminotransferase can make pyruvate + aspartate
What vitamin is required for aminotransferase reaction?
vitamin B6/ pyridoxine
What 2 enzyme types are under the hydrolase class (can do hydrolysis reaction- use water to break bond)?
1) digestive enzymes
2) phosphatase
What is the function of phosphatase?
remove phosphate with use of water to break bond (hydrolysis reaction)
ex: G6P will undergo a reaction with glucose 6 phosphatase to make glucose
What are the 2 types of enzymes under the isomerase class?
1) isomerase/mutase
2) isozymes
What are isomers? What is an example of an isomerase and mutase reaction?
isomers= same formula, different structure
G6P undergoes a reaction with phosphogluco-isomerase to make F6P
G6P undergoes a reaction with phosphogluco-mutase to make G1P (note: mutases will not change the entire structure like an isomerase, it’ll just change one piece like the location of the phosphate)
What are isozymes? what is an example of an isozyme?
enzymes that catalyze the same reaction
ex: glucokinase and hexokinase
What are the 3 enzyme types under the ligase class?
1) synthase
2) synthetase
3) carboxylase
What is the difference between synthase and synthetase?
synthase= no ATP directly in the reaction
synthetase= ATP is in reaction
What is the function of carboxylase?
add carbon
What vitamin is required for carboxylase/carboxylation reactions?
vitamin B7/ biotin
What are the 2 enzyme types under the lyase class?
1) lyase
2) decarboxylase
What is the function of a lyase?
break bond
What is the function of a decarboxylase?
remove carbon
What vitamin is required for decarboxylase/decarboxylation reactions?
vitamin B1/ thiamin
What vitamins are used in oxidation or reduction reactions?
B2 and B3
Which vitamin is required for any reaction with a “CoA” present?
vitamin B5
What vitamin is required for methyl donation?
vitamin B9
What do glucagon and epi add to an enzyme for regulation?
phosphate
Can fats become lactate?
no
Which vitamin is required for FA biosynthesis?
niacin /nicotinamide/ vit B3
Can pyruvate directly change to glucose?
no, but it can to lactate, acetyl coa, or alanine
What is the name for the pathway that breaks down glycogen?
glycogenolysis
What is the substrate in glycogenolysis?
glycogen
What is the rate limiting enzyme in glycogenolysis?
glycogen phosphorylase
What is the glycogenolysis pathway dependent on?
rate limiting enzyme, which is glycogen phosphorylase for this pathway
Which hormone inhibits glycogenolysis by inhibiting glycogen phosphorylase by dephosphorylating it?
insulin does this with a 2nd messenger! This is covalent modification
What is the active form of glycogen phosphorylase in the glycogenolysis pathway?
glycogen phosphorylase with phosphate attached
What activates glycogenolysis pathway?
glucagon adding a phosphate to glycogen phosphorylase
What happens to glycogenolysis if ATP goes up?
once theres enough ATP then the ATP will bind to glycogen phosphorylase as an allosteric inhibitor
What happens to glycogenolysis if ADP or AMP goes up?
ADP increases= ATP decreases
AMP increases= ATP decreases
So ADP and/or AMP are allosteric activators (pathway will start up again when more ATP is needed & the rate limiting enzyme is activated)
What do ATP, ADP, and AMP depend on in glycogenolysis?
enzyme concentration
What regulation mechanism is used as an on/off switch for glycogenolysis?
covalent modification
What regulation mechanism is used to “fine tune” glycogenolysis?
allosteric regulation
What are 2 protein hormones we talked about in class?
insulin and glucagon
When is glucagon secreted?
when you’re hungry
Where is glucagon made?
pancreatic alpha cells
What is the function of glucagon?
increase blood sugar (by breaking down glycogen to glucose so it can go to blood)
What effect does glucagon have on glycogen synthesis?
inhibits it in the LIVER
Where is glucagon found (think tissues)?
muscles and the liver
What effect does glucagon have on glycogen breakdown?
activates it (glycogen becomes glucose so that it can enter the blood and increase blood sugar)
What is the precursor for epi?
tyrosine
Which hormone increases sugar levels when you’re stressed and works with glucagon?
epinephrine
Where is epi made?
adrenal medulla
What is the function of epi?
mobilize energy reserves for fight or flight response
What effect does epi have on glycogen synthesis?
inhibits it in MUSCLES
What effect does epi have on glycogen breakdown?
activates it
When is insulin secreted?
after you eat
Where is insulin made?
pancreatic beta cells
What is the function of insulin?
decrease blood sugar (by pushing glucose into tissue cells)
What effect does insulin have on glycogen synthesis?
activates it
What effect does insulin have on glycogen breakdown?
inhibits it
T/F: ATP regulates the rate limiting enzyme by noncompetitive inhibition
false
What is the name of the pathway that synthesizes glycogen?
glycogenesis
What is the rate limiting enzyme in glycogenesis?
glycogen synthase
What hormone activates glycogenesis by removing a phosphate from glycogen synthase?
insulin does this with a second messenger (this is known as covalent modification)
What is the active form of glycogen synthase in glycogenesis?
glycogen synthase without phosphate
Which hormone inactivates glycogenesis?
glucagon
Which coenzyme is most likely used in FA biosynthesis?
NADPH
The reaction that converts a saturated FA to an unsaturated FA requires….
niacin
The delta G for substrate level phosphorylation is always positive or negative?
always negative
What is anaerobic glycolysis?
glucose to lactate
