Cell biology pt 2 Flashcards
metabolism
all the chemical reactions that occur within the human body
what do metabolic pathways involve?
the building up and breaking down of molecules
what do anabolic pathways require?
energy
what are anabolic pathways?
biosynthetic (building up) processes
catabolic pathways release…?
energy
what do catabolic pathways involve?
the breakdowns of molecules e.g the breakdown of glucose in glycolysis
are the steps of metabolic pathways reversible?
metabolic pathways have both reversible and in-reversible steps
what is activation energy?
the energy needed to break chemical bonds in the reactant chemicals is called activation energy
how does activation energy work?
the bonds break when the molecules of the reactant have been absorbed enough energy to make them unstable (this is called the transition state) and the reaction can occur
what is the rate of chemical reaction indicated by?
the quantity of chemical change that occurs per unit time
what is an enzyme?
an enzyme is a biological catalyst which lowers the activation energy required by the reactants to form the transition state and speeds up the rate of reaction. it also is made of proteins
what factors affect enzyme activation?
temperature
pH
substrate concentration
enzyme concentration
what affect do inhibitors have on the rate of enzyme controlled reactions?
they may slow them down or bring them to a halt
what is an active site?
an enzyme contains an active site which is a specific shape (due to the structure and bonding of the amino acids in the polypeptide chain) it is also where a substrate molecule binds and undergoes a chemical reaction
why do enzyme’s only act on one substrate?
an enzyme only acts on one substrate because the enzyme is specific to its substrate and the molecules of the substrate are complementary to the enzymes active site for which they show on affinity (chemical attraction)
what happens to the products after enzyme reaction?
the products have low affinity for the active site and are released leaving the enzymes free to repeat this process with new molecules of the substrates
is the active site of an enzyme a rigid structure?
the active site of an enzyme is not a rigid structure it is instead flexible and dynamic
what happens when a molecule of a substrate enters the active site of an enzyme?
the shape of the enzyme molecule and the active site change slightly making the active site fit very closely round the substrate molecule, this is called induced fit
what happens if there is more than one substrate involved in a reaction?
the shape of the site determines the orientation if the reactions. this ensures that they are held together in such a way that the reaction can take place
what are metabolic pathways controlled by?
the presence and absence of an enzyme
what is a competitive inhibitor?
it is a substance which has a similar molecular structure to the substrate and competes with the substrate for the active site on the enzyme, it blocks the active site preventing the substrate from binding so the rate of reaction decreases
how are competitive inhibitors reversed?
by increasing the substrate concentration
qualities of a non-competitive inhibitor?
- does not have similar molecular structure
- does not combine directly with the active site
- attaches to a non-active (allosteric) site and changes the shape of the enzyme molecule
- indirectly altering the shape of the active site so the substrate cannot bind and rate of reaction decreases
when does feedback inhibition happen?
it occurs when the end product in the metabolic pathway reaches a critical concentration
what does feedback inhibition prevent?
a waste of resources by preventing further synthesis of the end product
what happens when the concentration of the end product decreases in feedback inhibition?
less of the earlier enzyme is affected and the pathway resumes this pathway is kept finely tuned control called negative feedback
what is cellular respiration?
cellular respiration is a series of metabolic pathways that releases energy from food and generates a high energy compound called adenosine triphosphate (ATP)
what is ATP composed of?
ATP is composed of adenosine and three inorganic phosphate (Pi) groups
when and how is energy released from ATP?
energy is released from ATP when the bond attached to the terminal phosphate is broken by enzyme action
what forms when ATP releases energy?
ATP releases energy and breaks down to form Adenosine diphosphate (ADP) and inorganic phosphate (Pi)
what is the reaction known as phosphorylation?
ADP + Pi –> ATP
why is ATP important?
it acts as the link between catabolic energy releasing reactions (e.g. respiration) and anabolic energy-consuming reactions (e.g protein synthesis)
what is there a rapid turnover of in a cell?
ATP
do humans have a vast store of ATP?
ATP is continuously used up so it is being continuously produced so there is no need for humans to have a vast store of ATP
what is phosphorylation?
an enzyme controlled process by which a phosphate group is added to a molecule
when does phosphorylation happen?
it occurs when the phosphate and energy are transferred from the ATP to the molecules of a reactant in the metabolic pathway, making them more reactive
steps of cellular respiration
step one - glycolysis
step two - citric acid cycle
step three - electron transport chain
where does glycolysis occur?
in the cytoplasm of a cell
where does the citric acid cycle happen?
in the central matrix of the mitochondria
where does the electron transport chain happen?
occurs in the inner membrane of mitochondria
what is glycolysis?
the breakdown of glucose to pyruvate under the control of enzymes in the cytoplasm
steps of glycolysis
- energy investment phase
- 2 ATP are required for the phosphorylation of glucose
and intermediates - energy payoff phase
- ATP are produced during the breakdown of the final
intermediate into pyruvate
- ATP are produced during the breakdown of the final
- net gain of 2 ATP per molecule of glucose
- dehydrogenase enzymes remove
hydrogen ions and electrons and pass them to the coenzyme NAD forming NADH
is oxygen required for glycosis?
no
steps of the formation of citrate
CAC
*this stage only happens in aerobic conditions (aerobic respiration)
stage 1 - pyruvate is broken down to an acetyl group that combines with coenzyme A which then carries acetyl to the citric acid cycle
stage 2. Acetyl Coenzyme A + `Oxaloacetate —> citrate
acetyl with coenzyme A forms with Oxaloacetate to become citrate.
stage 3 - CAC involves many enzyme controlled steps which results in ;
- release of CO2
- generation of a small amount of ATP
- Dehydrogenase enzymes remove H+ ions and electrons and pass them to NAD to make NADH
- regeneration of oxaloacetate
Electron transport chain
- the hydrogen ions and electrons from NADH are passed to the electron transport chain
- the electron transport chains is a series of carrier proteins attached to the inner membrane of the mitochondria which allows ATP synthesis
- electrons are passed along the electron transport chain releasing energy
- this energy is used to pump hydrogen ions across the inner mitochondrial membrane
- these ions then pass back through the membrane protein ATP synthase synthesising ATP
- oxygen combines with hydrogen ions and electrons to form water
dehydrogenase enzymes function
they remove hydrogen ions and electrons and pass them to the coenzyme NAD forming NADH
net gain
overall gain of ATP during gycolysis
matrix
central cavity of a mitochondrion in which the CAC occurs
NAD
coenzyme which carries hydrogen and electrons from glycolysis and the CAC to the electron transport chain
why does fermentation occur?
because the cells lack oxygen
what stage of respiration happens in fermentation
glycolysis
how does glycolysis in fermentation work
glucose —> pyruvate —-> lactate
what does the conversion during glycolysis in fermentation involve?
involves the transfer of hydrogen from NADH to produce lactate
what happens during vigorous exercise?
the muscle cells do not receive sufficient oxygen to support the electron transport chain. under these conditions pyruvate is converted into lactate
where does lactate gather and what does this cause?
lactate gathers in muscle cells and causes fatigue and an oxygen debt builds up
what does it mean if NAD is regenerated?
that ATP production through glycolysis can continue
how does the oxygen debt in fermentation get repaid?
when exercise comes to a halt and energy mode from Aerobic respiration is used to convert lactate back to pyruvic acid and glucose in the liver
myoglobin
is an oxygen strong protein present in muscle cells and has a stronger affinity to oxygen than haemoglobin
what are body movements brought about by?
the action of skeletal muscle fibres
what do skeletal muscles contain?
a genetically determined mixture of slow-twitch fibres.
why is there always a fixed quantity of ATP?
because of how ATP is manufactured the same time it is used up therefore there isnt any need for a living organism to possess a vast store of ATP.
what are skeletal muscles connected to the skeleton by?
skeletal muscles are connected to the skeleton by tendons and contracts to cause movement during exercise.
what are the two types of skeletal muscles?
slow twitch and fast twitch
what are qualities of skeletal muscles?
they contract relatively slowly but can sustain contractions for longer. they are used for endurance activities such as long distance running.
what do slow twitch muscles rely on?
slow twitch muscles rely on aerobic respiration to generate ATP and have many mitochondria, a good supply with a dense capillary network and a high concentration.of the oxygen strong protein called myoglobin.
why do slow twitch muscle fibres take up more oxygen and sustain activity for longer?
by using stored fats as a main energy source
qualities of fast twitch muscle fibres?
they contract relatively quickly over short periods and are useful for activities such as sprinting. they contract more quickly and powerfully but fatigue very quickly, sustaining only short bursts of activity before muscle contraction becomes painful.
why does muscle contraction become painful after short bursts of activity?
due to lactate build up
what is the storage fuel for fast twitch fibres?
the major storage fuel of fast twitch muscle fibres of glycogen
How do fast twitch muscle fibres generate ATP?
through glycolysis only
What do fast twitch muscle fibres have fewer of than slow twitch muscle fibres?
mitochondria, blood vessels and myoglobin
what is the substance which builds up in muscle cells as they become fatigued?
lactate
when does oxygen debt build up?
builds up during fermentation in muscle cells
what is lactate produced by?
fermentation of pyruvate in mammalian muscle cells
what is affinity?
attraction between the activate site of an enzyme and its substrate
what is the definition of glycolysis?
the breakdown of pyruvate in the cytoplasm
what is ATP?
ATP is a substrate that is involved in the transfer of chemical energy in cells.
what is ATP built up from?
ATP is regenerated from ADP and inorganic phosphate using the energy released from cellular respiration.
what is respiration?
respiration is a catabolic pathway which converts the chemical energy stored in glucose into chemical energy stored in ATP
what is ATP used for?
ATP is used to transfer the chemical energy from cellular respiration to anabolic synthesis pathways and other cellular processes where energy is required. For example, DNA replication.
how is the energy in ATP released?
it is released when ATP is broken down into ADP
where does aerobic respiration start and end?
aerobic respiration starts in the cytoplasm and ends in the mitochondria
what is glucose converted into?
pyruvate (2 ATP are made)
what is pyruvate broken down into?
carbon dioxide and water using oxygen
what is ATP required in?
any cell process that requires energy. the majority of anabolic reactions needs ATP
what happens when ATP releases energy?
makes ADP and Pi
phosphorylation
the addition of phosphate to the molecule
what happens when ADP is phosphorylated?
ATP is formed
what is dephosphorylation?
removal of phosphate group from a molecule
what is the role of ATP during the energy investment phase?
to phosphorylate glucose and its intermediates
what do you gain from investing 2 ATP?
you get 4 back meaning that you gain 2 ATP
where does CAC happen?
the matrix of the mitochondria
what is CAC controlled by?
enzymes
what is CoA?
coenzyme A
what happens to acetyl when it enters the CAC?
it combines with oxaloacetate to form citrate
during CAC why is CO2 lost?
because of loss of carbons is lost in the form of CO2
where does the electron transport chain happen?
inner membrane of the mitochondria
what is the final acceptor of hydrogen?
oxygen
how much ATP is made from CAC?
a small amount
how much ATP is made from ETC?
a large amount
what are the raw materials used in CAC?
pyruvate/acetyl
what are the raw materials used in glycolysis
glucose
what are the raw materials used in ETC?
hydrogen ions, electrons and oxygen.
