CELLULAR RESPIRATION
CHAPTER 7- CFE HIGHER HUMAN
BIOLOGY
CELLULAR RESPIRATION
• THIS IS A SERIES OF METABOLIC PATHWAYS THAT
BRING ABOUT THE RELEASE OF ENERGY FROM A
FOODSTUFF AND THE REGENERATION OF THE HIGHENERGY COMPOUND ADENOSINE TRIPHOSPHATE
(ATP)
ADENOSINE TRIPHOSPHATE (ATP)
A molecule of ATP is composed of adenosine and
three inorganic phosphate groups. Energy held in ATP
is released when the bond attaching the terminal
phosphate is broken by enzyme action. This results in
the formation of Adenosine diphosphate (ADP) and
inorganic phosphate (Pi). Energy is required to
regenerate ATP from ADP and inorganic phosphate.
TRANSFER OF ENERGY VIA ATP
FIXED QUANTITY OF ATP
THREE STAGES OF CELLULAR RESPIRATION
• 1. GLYCOLYSIS
• 2. CITRIC ACID CYCLE
• 3. ELECTRON TRANSFER CHAIN
The first stage of Cellular Respiration is called Glycolysis and occurs in the
cytoplasm.
In this stage glucose is ‘split’ to form Pyruvate.
Glycolysis consists of a series of enzyme-controlled steps.
Those in the first half of the chain make up the energy investment phase
where 2ATPs are needed to start the process off.
Those in the 2nd half of the chain make up the energy payoff phase
where 4ATPs are produced. By the time the original 2ATPs are paid back,
a net gain of 2ATPs are left.
Phosphorylation of intermediates occurs twice in the first phase, in step 1
and in step 3. Step 3 is catalysed by an enzyme phosphofructokinase.
Hydrogen ions are released from the substrate by an enzyme called
dehydrogenase. These hydrogen ions are added to a coenzyme called
NAD and becomes NADH.
The process of glycolysis does not need oxygen however the production of
further ATPs from NADH only occurs at the later stage in respiration if
oxygen is present. So far however only 2ATPs have been generated.
CARBOHYDRATES AS RESPIRATORY SUBSTRATES
FATS AS RESPIRATORY SUBSTRATES
PROTEINS AS RESPIRATORY SUBSTRATES
Proteins in the diet are broken down to
their component amino acids by the
action of digestive enzymes. Amino acids
in excess of the body’s requirements for
protein synthesis undergo deamination,
forming urea and respiratory pathway
intermediates as shown opposite. These
intermediates then enter the metabolic
pathway and act as respiratory
substrates regenerating ATP as before.
The third step in glycolysis can be regarded as
a key regulatory point as it can be controlled
by enzymes
When a cell contains more ATP than is needed
the high concentration of ATP has an
inhibitory effect on phosphofructokinase and
this slows down glycolysis. When ATP levels
drop again the phosphofructokinase is no
longer inhibited and glycolysis speeds up
again
When there is a high concentration of citrate
this also has an inhibitory effect on
phosphofructokinase and slows down
glycolysis
When citrate levels fall again glycolysis
speeds up again as there is no longer an
inhibitory effect on phosphofructokinase
CREATINE PHOSPHATE SYSTEM
CREATINE PHOSPHATE SYSTEM
Much of the energy
needed for repetitive
muscular contraction
comes from a chemical
creatine phosphate
CREATINE PHOSPHATE SYSTEM
CREATINE PHOSPHATE SYSTEM
LACTIC ACID METABOLISM
LACTIC ACID METABOLISM
OXYGEN DEBT
ATP TOTALS
TYPES OF SKELETAL MUSCLE FIBRE
MYOGLOBIN
DIFFERENT FIBRES FOR DIFFERENT EVENTS
DIFFERENT FIBRES FOR DIFFERENT EVENTS
• SKELETAL MUSCLES CONTAIN A GENETICALLY DETERMINED MIXTURE OF SLOWTWITCH AND FAST-TWITCH FIBRES. IN MOST MUSCLES, A FAIRLY EVEN BALANCE
EXISTS BETWEEN THE TWO BUT IN SOME MUSCLES, ONE TYPE PREDOMINATES
OVER THE OTHER.
• FOR EXAMPLE, THE MUSCLES IN THE BACK RESPONSIBLE FOR MAINTAINING
POSTURE CONTAIN MOSTLY SLOW-TWITCH FIBRES, WHEREAS THE MUSCLES THAT
MOVE THE EYEBALLS ARE MADE UP MAINLY OF FAST-TWITCH FIBRES.