glycolysis

Question 1

it is the first stage of glucose metabolism in organism

Answer 1

glycolysis
- center and the heart of carbs metabolism
- starts at the mouth, physical digestion (starts munching and chewing into smaller pieces)
- as well as chemical digestion, salivary amylase

Question 2

glycolysis process

Answer 2

index card

Question 3

how many steps are there in glycolysis

Answer 3

10

Question 4

what is the committed step in glycolysis

Answer 4

Fructose-1, 6-bisphoshate
- means u rlly have to go through the slide
- no turning back

Question 5

what are the reactant, products AND PROCESS of glycolysis

Answer 5

reactant:
1 molecule of glucose (6-C molecule)

product:
2 mol of pyruvate (3-C molecule)
2 mol of ATP
1 mol of NADH, Nicotinamide adenine dinucleotide

process:
oxidation
- each reaction in the pathway is catalyzed by an enzyme specific for that reaction

Question 6

what are the difference between anaerobic glycolysis, aerobic oxidation and anerobic alcoholic fermentation

Answer 6

requires oxygen:
aerobic oxidation
– produces the most ATP, takes place in mitochondria

does not require oxygen:
anaerobic glycolysis (when oxygen is limited)
anerobic alcoholic fermentation
- common in yeast and bacteria

Question 7

Pathway of conversion of glucose to lactate

Answer 7

Anaerobic glycolysis
Glucose → Pyruvate → Lactate
Occurs during intense exercise when muscles can’t get enough oxygen
The lactate buildup can cause muscle fatigue and soreness

Question 8

how can the lactate be converted back to glucose

Answer 8

in the liver when oxygen becomes available

Question 9

what is the first step of glycolysis

Answer 9

glucose is phosphorylated to give glucose-6-phosphate

endergonic reaction as it needs energy in the form of ATP

ATP
- serves as the energy source
- provide glucose the phosphate group hence the product of ATP is ADP
- one of the phosphate group from ATP is attached to the C6 of glucose

enzyme used:
hexokinase + co-factor of Mg2+

Question 10

second step of glycolysis

Answer 10

isomerization:
glucose-6-phosphate to fructose-6-phosphate

Question 11

third step of glycolysis

Answer 11

phosphorylation:
fructose-6-phosphate to
fructose-1,6-bisphosphate

enzyme used:
phosphofructokinase + MG2+

endergonic reaction to exergonic reaction
hence ATP needs to undergo hydrolysis

Question 12

Key allosteric control enzyme in glycolysis

Answer 12

Phosphofructokinase
- at least 1 subunit of the Phosphofructokinase should be activated in order to activate the other 3
- controls how fast glycolysis can occur which can prevent wasting glucose when energy isn’t needed

Slows down when ATP is high (cell has enough energy)
Speeds up when ATP is low (cell needs energy)

Question 13

step four of glycolysis

Answer 13

cleavage:
fructose-1, 6-bisphosphate to give 3-C fragments, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

enzyme:
aldolase

Question 14

Enzyme that catalyzes the reverse aldol condensation of fructose-1,6-bisphosphate

Answer 14

aldolase

*it has lysine residue and the thiol grp of cysteine

Question 15

step five of glycolysis

Answer 15

isomerization:
DHAP to G-3-P
dihydroxyacetone phosphate to glyceraldehyde-3-phosphate

enzyme: triphosphate isomerase

endergonic reaction
- reaction has a +deltaG value (+2.41 kJ mol-1 or +0.58kcal mol-1)
- overall process is negative

Question 16

step 6 to 10

Answer 16

index card

Question 17

why do we have to transfer a phosphate group from phosphoenolpyruvate, PEP to ADP to give pyruvate

Answer 17

Energy Levels:
PEP has very high energy (-61.9 kJ/mol)
ATP has lower energy (-30.5 kJ/mol)
PEP is like a “stretched rubber band” - unstable and wants to release energy

PEP is unstable due to high energy
Needs to transfer this energy somewhere

The Transfer Process:
PEP → transfers phosphate → to ADP

Results in:
More stable pyruvate
Useful ATP molecule
Like converting “unstable energy” to “usable energy”

Benefits:
Stabilizes the system
Creates useful energy currency (ATP)
Completes glycolysis efficiently
Cell can use the ATP later when needed

Question 18

it is the most the most important
pathway for the regeneration of NAD+ is reduction of pyruvate to lactate

Answer 18

anaerobic conditions

Question 19

under anaerobic conditions, why is important to regenerate NAD+

Answer 19

It’s Like a Reusable Shopping Bag:
NAD+ picks up electrons (becomes NADH)
NADH drops off electrons (becomes NAD+ again)
This cycle must keep going for glycolysis to continue

In Glycolysis:
NAD+ is needed in step 6 (making 1,3-bisphosphoglycerate)
Without NAD+, glycolysis stops

The Problem:
Limited supply of NAD+ in cells
Need to keep recycling it
Like having only a few shopping bags that must be reused

Solution in No-Oxygen Conditions:
–Lactate Formation–
Pyruvate + NADH → Lactate + NAD+
Regenerates NAD+
Allows glycolysis to continue

Question 20

similarities and differences between alcoholic fermentation and lactic acid fermentation

Answer 20

SIMILARITIES
Both start with glyceraldehyde-3-phosphate
Both use NAD+ and regenerate it
Both happen without oxygen
Both are ways to keep making energy when no oxygen is present

DIFFERENCES
–Final Products–
Alcoholic Fermentation → produces ethanol (alcohol)
Lactic Acid Fermentation → produces lactate (lactic acid)

STEPS
Alcoholic Fermentation:
Has an extra step (intermediate)
Pyruvate → Acetaldehyde → Ethanol
Uses enzyme alcohol dehydrogenase

Lactic Acid Fermentation:
Simpler process
Pyruvate → Lactate (direct)
Uses enzyme lactate dehydrogenase

WHERE IT HAPPENED
Alcoholic: In yeast (making bread/beer)
Lactic Acid: In human muscles during intense exercise

GOAL
Regenerate NAD+ to keep glycolysis running
Just do it in different ways with different end products

Question 21

briefly explain decarboxylation of pyruvate to acetaldehyde

Answer 21

Pyruvate, a product of glucose breakdown, loses a carbon dioxide molecule and turns into acetaldehyde.

enzyme:
pyruvate decarboxylase
cofactor:
Mg2+
TPP, thiamine pyrophosphate

Question 22

briefly explain reduction of acetaldehyde to ethanol

Answer 22

Acetaldehyde is then converted into ethanol by adding hydrogen

enzyme:
alcohol dehydrogenase

NADH gives up electrons turning into NAD+ which is needed to keep the fermentation process going

However, even though NADH and NAD⁺ are used in the reaction, they don’t show up in the final, simplified equation for alcoholic fermentation. Only ethanol and CO2 are shown

Question 23

briefly explain the energy production in glycolysis

Answer 23

glycolysis release energy:
by breaking down glucose into 2 molecules of pyruvate releases energy = exergonic reaction

the total amt of energy released:
abt -74 kJ for each mole of glucose
negative value means given off
released energy is used to power other reactions that need energy (endergonic reactions)

ATP:
as glycolysis happen, 2 ADP molecules are turned into ATP which is used for source of energy and metabolic processes

Question 24

briefly explain the control points in glycolysis

Answer 24

can be adjusted to either speed up or slow down glycolysis depending on the cell’s needs. this helps save energy if the cell doesn’t need more products right away.

1. Hexokinase (Glucose → G-6-P):

Controlled by ATP: ATP can activate this enzyme when energy is needed.

Controlled by G-6-P: If too much G-6-P builds up, it inhibits (or slows down) hexokinase, preventing more glucose from being used.

2.Production of fructose-1,6-bP:

This step is called the “committed step” because once it happens, glycolysis will continue to the end.

3.Pyruvate kinase (PEP → pyruvate):

Controlled by ATP: If ATP levels are high, this enzyme is inhibited, slowing down glycolysis since the cell doesn’t need more energy.

Controlled by alanine: If there’s plenty of alanine (a building block for proteins), this step is also slowed down, saving resources for other processes.