M104 T2 L2 Flashcards
What is the suffix of anabolic and catabolic reactions?
ana: -genesis (building up)
cata: -lysis (breaking down)
What is E required for?
Motion (muscle contraction)
Transport (of ions/molecules across membranes)
Biosynthesis of essential metabolites
Thermoregulation
Why can’t heat flow be used as a source of E for cells?
bc cells are isothermal systems - they maintain a constant temp
heat flow can only be used as a source of E when it passes from an area of higher to lower temp
What gives cells E?
sources of free E from nutrient molecules
What is the eq linking entropy, enthalpy and Gibbs free E?
{} G = {} H- T{}S
What is represented by the change in enthalpy?
the kinds and numbers of chemical bonds broken and formed
When is the change in enthalpy positive?
when E is absorbed by the reaction
What is represented by the change in entropy?
the formation of large complex molecules from smaller molecules or vice versa
When is the change in entropy positive?
when randomness increases (catabolic reactions)
What is the Gibbs free E change of a reaction?
the maximum E that can be obtained from a reaction at constant temperature and pressure
When is a reaction spontaneous / exergonic?
If the concentration of the products are greater than the concentration of the reactants at EQL
Is free E negative or positive in exergonic reactions?
negative values - under zero
release E
When is a reaction unfavourable / endergonic?
If the concentration of the reactants are greater than the concentration of the products at EQL
Is free E negative or positive in endergonic reactions?
positive values, greater than zero
needs E input
What is the relationship between the free E of products and reactants in exergonic reactions?
free E of reactants are much higher than those of the products
so products are more stable than the reactants
formation of product is “downhill”
this makes for a spontaneous / exergonic reaction
these are involved in catabolism
What is the relationship between the free E of products and reactants in endergonic reactions?
free E of products are much higher than those of the reactants
so reactants are more stable than the products
formation of product is “uphill”
this makes for a unfavourable / endergonic reaction
these are involved in anabolism
How do anabolic reactions start in cells if E input is required to start the reaction?
by the coupling of reactions
How does the coupling of reactions work?
by coupling an endergonic reaction with an exergonic reaction through a common intermediate to drive it in the forward direction
How is the coupling of reactions used in the body?
used to trigger unfavourable reactions in cells
What is a reaction that goes by the coupling of reactions?
the phosphorylation of glucose
the hydrolysis of ATP
How does the coupling of reactions work for ATP and glucose?
they both involve water and a phosphate
so these are crossed out
combine the reactions into reactants and products
use the two values of each reaction to calculate an overall gibbs free E change
In what form are ATP or ADP found in in cells?
as a complex with magnesium ions
How is ATP / ADP binding with magnesium ions in a complex useful?
the magnesium ions interact with the oxygens of the triphosphate chain
this makes the complex more susceptible to cleavage in the phosphoryl transfer reaction
What is the effect of a magnesium deficiency and why?
impairs virtually all metabolism
bc mg forms a complex with atp or adp
allows the phosphoryl transfer reaction to happen easier
What happens during the process of substrate-level phosphorylation?
a substrate donates a phosphate group
a molecule of ADP can receive this phosphate group to make a molecule of ATP
What is the difference between substrate-level phosphorylation and respiration linked phosphorylation?
they require different things to be involved and different conditions
What do substrate-level phosphorylations require?
soluble enzymes
chemical intermediates
What do respiration linked phosphorylations require?
membrane-bound enzymes
transmembrane gradients of protons
oxygen
What do enzymes NOT affect?
the gibbs free E change
What are the two most common types of enzyme?
oxidoreductases
transferases
What is the role of oxidoreductases?
they catalyse the transfer of electrons
redox reactions
What is the role of transferases?
they catalyse the transfer of functional groups
What are most coenzymes derived from?
vitamins
How do co factors participate in enzymatic reactions?
they cycle between oxidised and reduced forms
How do cosubstrates work?
they have a loose association with their enzyme
they diffuse between enzymes carrying electrons
What are the two types of cofactors?
metal ions
co enzymes
What are the two groups of coenzymes?
prosthetic groups
cosubstrates
What is the role of prosthetic groups?
they act as a temporary store for e- or intermediates
they stay attached to the substrate for the whole reaction
they aren’t released as part of the reaction
Which two co enzymes have central roles in metabolism?
Riboflavin (B2)
Niacin
What type of co-enzyme is Niacin?
NAD+
What type of co-enzyme is Riboflavin?
FAD or FMN
What type of co-enzyme class does Riboflavin come under?
it’s a prosthetic group
What type of co-enzyme class does Niacin come under?
Cosubstrate
What is the function of redox coenzymes and prosthetic groups?
to accept electrons and to transfer them to the respiratory chain in order to generate ATP
How is NAD+ reduced?
it accepted two electrons and one hydrogen
What is NAD+ reduced to?
NADH
How is FAD reduced?
it accepted two electrons and two hydrogens
What is FAD reduced to?
FADH2
What are the reduced forms of NAD+ and NADP+?
NADH
NADPH
by accepting pairs of electrons
What is the functional part of the NADP+ molecule?
the nicotinamide ring
What pathway is NADH used for?
ATP synthesis
What pathway is NADPH used for?
reductive biosynthesis
What happens to NADH and FADH2 in the mitochondria?
they are constantly being recycled to their oxidised form by transferring their electrons to the respiratory chain in the mitochondria
What reaction is the respiratory chain coupled with?
ATP synthesis
What two reactions make up oxidative phosphorylation?
ATP synthesis
respiratory chain reaction
Where does the first part of cellular respiration occur?
in the cytosol
What cellular respiration reactions occur in the cytosol?
glycolysis
What is the glycolysis reaction that occurs in the cytosol?
the breakdown of glucose into pyruvate
Where does the second part of cellular respiration occur?
in the mitochondria
What happens in the mitochondria during the second part of cellular respiration?
pyruvate < acetyl coA < (citric acid cycle) < (electron transport chain) < E
By what intermediataries does glucose (6C) turn into G3P?
6C glucose 3C x2 pyruvate G6P F6P FBP DHAP (or G3P) G3P
In the phophorylation of glucose into G3P by hexokinase, what is required?
ATP
it will turn into ADP
What catalyses G6P into F6P?
isomerase
What catalyses F6P into FBP?
PFK-1
requires ATP to turn into ADP
How does the committed step regulate glycolysis?
it controls the activity of PFK-1
which is responsible for turning F6P into FBP
What is the relationship between G3P and DHAP?
they are interchangeable
only DHAP continues into the next part of glycolysis
but eventually all G3P turns into DHAP
How is G3P or DHAP produced?
from FBP with the help of aldolase
In what order of reaction types does glycolysis occur?
priming reactions
payoff reactions
By what intermediataries does GTP turn into pyruvate?
GTP 1,3 BPG 3-phosphoglycerate 2-phosphoglycerate phosphoenylpyruvate pyruvate
How is 1,3 BPG produced?
from GTP
via GADPH
and NAD+ which turns into NADH
How is 3-phosphoglycerate produced?
from 1,3 BPG
via PGK
and ADP which turns into ATP
How is 2-phosphoglycerate produced?
from 3-phosphoglycerate
via mutase
How is phosphoenylpyruvate produced?
from phosphoenylpyruvate
via enolase
How is pyruvate produced from phosphoenylpyruvate?
via pyruvate kinase
and ADP which turns into ATP
Which steps of glycolysis come under substrate level phosphorylation steps?
from the production of 3-phosphoglycerate
to the production of pyruvate
Two cycles of payoff reactions (G3P to pyruvate) will produce what?
one metabolised molecule of glucose
What do the priming reactions cover?
the conversion of glucose into G3P
Why are they called priming reactions?
bc they require the investment of ATP at the hexokinase and PFK-1 reactions
What enzymes are involved in glycolysis?
Hexokinase Phosphoglucose isomerase PFK-1 Aldolase Triose phosphate isomerase
What is used and generated in the priming stage?
2 ATP mlcs are used
2 interconvertible C3 mlcs are produced (DHAP and GAP)
What is generated in the priming stage?
4 ATP
2 NADH
various intermediates
What happens when pyruvate is oxidised with oxygen?
produces co2 and water
What happens when pyruvate in hypoxic conditions?
reduced to lactate by the enzyme lactase dehydrogenase in a reversible reaction
so when o2 is present, oxidation
