unit 12 - carbohydrates metabolism

we classify carbohydrates into 2 types

• digestible

• non-digestible

digestible carbohydrates polyysaccharides are

starch

glycogen

digestible carbohydrate starch is a

polysaccharide

glucose stored in plants

digestible carbohydrate glycogen is a

polysaccharide

glucose stored in animal

digestible carbohydrate, are also disaccharides such as

sucrose

lactose

sucrose =

glucose + fructose

lactose

glucose + galactose

digestible carbohydrates - what type of bond

what bond is called a digestible bond

alpha bonds

digestible bond means what

we are able to produce energy from the bond

main function of digestible carbohydrates

production of ATP (energy)

nondigestible carbohydrates contain what type of polysaccharides

complex polysaccharides

nondigestible carbohydrates are complex polysaccharides such as

• cellulose

• inulin

• agar

what are the bonds in nondigestible carbohydrates

beta bonds

can we break beta bonds

no

if we have 1KG of cellulose how many ATPs are produced

0

from beta bonds can we produce energy

no atp production

nondigestible carbohydrates are also called

fibre

from the digestible carbohydrates we can spilt the process into 2

• degradation to monosaccharides

• absorption of monosaccharides by specific transportes at the intestinal level

step 1 of digestible carbohydrates

degradation

(to form monosaccharides)

step 2 of digestible carbohydrates

absorption of the monosaccharides

digestible carbohydrates - example with STARCH

step 1 what happens

starch is degraded into glucose (monosaccharide)

digestible carbohydrates - example with STARCH

step 2

glucose is absorbed

digestible carbohydrates - example with STARCH

why do we need to degrade starch?

we cannot absorb starch because its a polysaccharide

starch digestion full - read

done

glycolysis is the

degradation of glucose

Glycolysis is the degradation of glucose - what pathway is it?

catabolic pathway

glycolysis

is the …… way to get energy

fastest

glycolsis

fundamental way of producing energy for many tissues: (3)

• muscles with low O2

• red blood cells (no mitochondria)

• brain (glucose is the main fuel)

glycolysis

how many reactions are there in total

10

glycolysis

what is the total amount of ATP produced from the 10 reactions

2

glycolysis

if we produce 2 ATPs with 10 reactions how many ATPs is produced per 1 reaction

0.2

glycolysis

even though the system is fast is it efficient

no

(not the best way to produce ATP as you only get 2 )

glycolysis

from the 10 reactions they are divided into 2 phases - what are the 2 phases and which reactions in each

• Preparatory phase = reactions 1-5

• Payoff phase = reactions 6-10

glycolysis

where does glycolysis happen

cytoplasm (of the cell)

glycolysis

is it aerobic or anaerobic pathway?

it doesn’t matter because oxygen is not relevant (can be performed in both conditions)

glycolysis

out of the 10 reactions how many are are reversible and how many are irreversible

3 reactions are irreversible

7 are reversable

glycolysis

which 3 out of the 10 reactions are irreversible

• 1

• 3

• 10

glycolysis

which 7 reactions out of the 10 are reversable

• 2

• 4

• 5

• 6

• 7

• 8

• 9

glycolysis reactions 1-4 - READ

done

glycolysis

reaction 1

glucose —> glucose 6 phosphate

what is this reaction

any ATP consumes?

phosphorylation

1xATP consumes

glycolysis

reaction 2

glucose 6 phosphate → ← fructose- 6 phosphate

what is this reaction

any ATP consumes?

isomerisation

no ATP consumed

glycolysis

reaction 3

fructose- 6 phosphate → fructose 1.6 biphosphate

what is this reaction

any ATP consumes?

phosphorylation

ATP is consumed

glycolysis

reaction 4

fructose 1.6 biphosphate →← glyceraldehyde 3 phosphate and Dihydroxycetone phosphate

what is this reaction

any ATP consumes?

fructose 1.6 biphosphate is split into 2 × 3 carbons and 2 × 1 phosphate

to make 2 trioses phosphate

no atp is consumed

1-4 glycolysis read again

done

glycolysis

what is the goal of reaction 5

to get 2 identical triose phosphate

what is the balance of the Preparatory phase

• no ATPs produced

• 2 ATPs consumes

• = -2 ATPs

how many times is the payoff phase repeated

2

why is the payoff phase repeated twice

because we have 2 trioses phosphate

reactions 6-8 read

done

reactions 9 and 10 read - i’ve added the enzymes to the OG so read the paper

done

what is the balance of the payoff phase

• ATP PRODUCED = 4

• NADH PRODUCED = 2

• PYRUVATE PRODUCED = 2

what enzyme catalyses reaction 1

hexokinase

what enzyme catalyses reaction 3

phospho-fructokinase-1

what enzyme catalyses reaction 10

pyruvate kinase

what reactions have enzymes in glycolysis? why reactions 1, 3 and 10

• they are irreversible

what is the overall balance of glycolysis (preparatory phase and payoff phase)

full equation

glucose → 2 x pyruvate + 2 x ATP + 2 x NADH

if glucose comes from starch how many ATP is produced at the end of Glycolysis

2

if glucose comes from Glycogen how many ATPs are produced at the end of Glycolysis

3

what is the difference between starch and glycogen ?

in glycogen reaction 1 is not produced so its doesn’t consume that ATP

(glycogen has 9 reactions, starch has 10)

destinations of pyruvate

there are 3, what are they

• kreb cycle

• homolactic fermentation

• alcoholic fermentation

destinations of pyruvate

if perform the first process (kreb cycle) under aerobic conditions we would get

• energy

• co2

• h20

Kreb cycle takes place where

mitochondria

(which is why we need aerobic conditions)

destinations of pyruvate

in process 2 we get lactate what type of reaction is this

reversable

destinations of pyruvate

we get lactate through a reversable reaction because of

lactic fermentation

fermentation requirements

we don’t use oxygen

so use anaerobic conditions

from pyruvate to ethanol this is called

alcoholic fermentation

is the processes of getting ethanol from pyruvate via alcohol fermentation, irreversible or reversable

irreversible

can out cells perform Kreb cycle

yes

can out cells perform Lactic permentation

yes

can our cells perform alcoholic fermentation

no

which organisms can transform pyruvate into alcohol (ethanol)

yeast and bacteria

glycolysis regulation

reaction 1 = hexokinase

reaction 3 = phosphofructokinase-1

reaction 10 = pyruvate kinase

(irreversible reactions)

what type of enzymes are these

allosteric enzymes

glycolysis regulation

if they are allosteric enzymes the regulation is based off of

effectors

glycolysis regulation

we balance the speed of glycolysis according to

effectors that are bound to the 3 enzymes

glycolysis regulation

high energy compounds = ATP and Citrate

why is citrate a high energy compound

because it is part of kreb cycle

glycolysis regulation

high energy compounds = ATP and Citrate

if the level of ATP and Citrate is high do we need to continue performing glycolysis

no

glycolysis regulation

high energy compounds = ATP and Citrate

when the level of ATP and Citrate are HIGH both are

negative effectors

glycolysis regulation

high energy compounds = ATP and Citrate

when ATP and Citrate are high - this is a way to slow down Glycolysis? true or false

true

glycolysis regulation

Low energy compounds = ADP and AMP

if the level of ADP and AMP is high do we need to produce ATP?

yes

glycolysis regulation

Low energy compounds = ADP and AMP

if the level of ADP and AMP is high do we need to produce ATP? - yes

if we need to produce ATP we will perform glycolysis yes or no?

yes

glycolysis regulation

Low energy compounds = ADP and AMP

when the level of AMP and ADP are high they are both

positive effectors of glycolysis

high energy compounds vs low energy compounds and when

high energy compounds = negative effectors

low energy compounds = positive effectors

when the concentration is high

fructose 2,6-biohosphate is part of glycolysis - true of false

false

fructose 2,6-biohosphate is what

the most powerful activator of glycolysis

fructose 2,6-biohosphate

specifically activates which 2 enzymes

• phosphofructokinase-1 (reaction 3)

• pyruvate kinase (reaction 10)

the control/regulation provided by hormones

which hormones

insulin and glucagon

insulin and glucagon are produced where

pancreases

(islets of Langerhans)

insulin and glucagon control the level of

glucose

what is the function of insulin

to transfers glucose inside the cell

(reduces the level of glucose in blood)

what happens when one glucose is transferred into the cell by insulin

it is immediately phosphorylated and we get glucose-6 phosphate

(reaction 1 )

is insulin an activator of glycolysis

yes

glycogen function

increases the level of glucose in the blood stream

releases glucose from the liver cells (as glycogen)

if we release glucose to the blood stream - do we enhance glycolysis or stop glycolysis

stop glycolysis

(bc glucose is in the blood not cells)

is glucagon and activator or an inhibitor of glycolysis

inhibitor

read

done

read

done

gluconeogenesis

the production/synthesis of glucose

what pathway is gluconeogenesis

anabolic pathway

gluconeogenesis

is the production of glucose from

non-glucidic precursors

gluconeogenesis

we have 3 main molecules in our body to produce glucose and what are they

• glycerol - a lipid

• lactate - from fermentation

• 1 amino acid - alanine