Transcript L25 HH Respiratory Substrates

Does it matter what
you eat for cellular
respiration?
• Examine the different substrates used for
respiration
• Investigate the affect on a model organism of
using different respiratory substrates
• Examine the effect of exercise or starvation
on respiratory substrates.
• How is the substrate route controlled?
• Creatine phosphate system as a booster for
maximum muscular
Carbohydrates
• Both starch/glycagon are chains of glucose
molecules.
• Broken down into glucose
• Disaccharides like sucrose or maltose also
broken down into glucose or used as
intermediates in glycolytic pathway.
Glycogen
Starch
Sucrose
Maltose
Glucose
Fructose
Pyruvate
Fats
• Broken down into glycerol
and fatty acids
• Glycerol converted glycolytic
intermediate
• Fatty acids are metabolised
and enter as acetyl
coenzyme A for use in citric
acid cycle.
FAT
Glucose
Intermediate
Pyruvate
Acetyl
Coenzyme A
Acetyl coenzyme A (2C)
Proteins
• Broken down into
amino acids
• Then used for
protein synthesis
• Excess undergo
deamination,
making urea and
intermediates,
and regenerating
ATP.
P
E I N
R O T
Amino acid
(eg alanine)
Glucose
urea
Pyruvate
urea
Amino acid
(eg leucine)
Amino acid
(eg aspartic
acid)
Acetyl Coenzyme A
urea
intermediate
Citrate
Citric Acid Cycle
Investigation / LO3
• Follow instructions will be examined
• p108-110
• Answer ALL questions (especially point 6
and 7!)
So what happens during exercise?
Burn baby burn .....
• Several minutes at the start of aerobic exercise
body burns carbohydrates.
• After 20-30 minutes of continued exercise
respiratory substrate shifts to 50%
carbohydrates/50% fat
• First hour of exercise less than 2% of
respiratory substrates are protein
• Prolonged exercise protein usage can reach 515% if prolonged exercise last 5 hours
(marathon running)
• Marathon running thus needs refreshments
throughout!
So what about this .....
Creatine Phosphate System
• ATP is immediate source, but
the ATP stored is only able to
do a few contractions.
• For repetitive muscular
contractions, creatine
phosphate donates it’s
phosphate for ATP synthesis.
During strenuous activity ......
creatine
ATP
Phosphorylation of ADP
creatine
phosphate
ADP
• ATP formed is used to sustain maximal muscular
contraction for a few more seconds.
• Helps for 100m sprint/golf swing and lifting/
lowering heavy weight.
Creatine Phosphate System
During rest period ......
creatine
ATP
Phosphorylation of creatine
creatine
phosphate
ADP
• During rest period ATP generates creatine
phosphate by phosphorylation.
• Creatine phosphate acts as a high-energy reserve
which is available for muscles during the next period
of strenuous activity.
Summary
Copy and complete the diagram below:
Creatine
ATP
Creatine
phosphate
• Phosphate and energy are being
transferred between molecules.
• This is a very fast way of producing ATP
for a short period of time.
So what happens during starvation?
Starving Marvin!
• Definition “body continously expends more energy
than it takes in as food”
• Early stages – uses up glycogen, mobiles fat
reserves
• Prolonged – liver cells continue to use fatty acids
for forming acetyl coenzyme A, forming ATP as
usual, some forms ketones which are transported
to the brain via the blood
• Tissue protein is used as source only during
prolongued stages when glycogen/fats exhausted
• Skeletal muscle and then other tissues are used
up, person emancipated and death soon follows.
So which path ......
• Controlled by regulation we examined earlier,
as carried out by enzymes
• Controls were?
•
•
•
•
•
Suitable temperature
Appropriate pH
Correct substrate
Adequate supply of substrate
Presence of an inhibitor (more next time)
In this case the third step is by phosphofructokinase,
an irreversible step thus a key regulatory point.
High concentrations of ATP inhibit
phosphofructokinase
Glucose (6C)
ATP
Phosphorylation at step 1
Other metabolic pathways
(eg. stored as glycogen)
ADP+ Pi
Intermediate 1
Intermediate 2
Irreversible step
ATP
ADP+ Pi
ATP & citric acid inhibit
phosphofructikinase! So
go back to intermediate 2
Phosphorylation at step 3 catalysed by
phosphofructokinase
Intermediate 3
Citric Acid Cycle & Electron
Transport Chain
• Prevents build up of intermediate is prevented
• ATP only produced from respiratory pathway as
required
• Resources con served
Question Tennis
Get in two rows, facing each other.
The first student asks the student opposite a question
about the lesson.
If they get it right the person sat next to them gets to
ask a question of the student opposite.
If they get it wrong, the first team continue asking the
questions.
Extension / Homework
Creatine supplements
Many athletes take creatine supplements.
Why do you think they do this?
What sort of sports would this be an advantage
in?
Answer…
When athletes take creatine in supplements it
is converted into creatine phosphate in the
muscles. Taking supplements maximises the
levels of creatine phosphate stored in the
muscles, therefore the amount of energy
stored is also maximised.
Creatine is not banned by major sporting
bodies. It may be of most use in activities
where short bursts of energy are required.
Can you think of any?
Assessment
Your task is to write an article on creatine
supplements for a sporting magazine.
Your article should include:
• a description of what creatine phosphate is
used for by the body
• a description of the role of creatine
supplements
• the type of activities that may benefit from
creatine supplements
• any other information you think is relevant.
Remember…
Most importantly your article should be easy to
follow and make sense.
Do not copy and paste text – put any research you
do into your own words.
The people reading a sporting magazine may not
be scientists. They have to be able to understand
the article.
SQA Arrangements p25
• Starch and glycogen are broken down to
glucose for use as a respiratory substrate.
Other sugar molecules can be converted to
glucose or glycolysis intermediates for use as
respiratory substrates. Proteins can be
broken down to amino acids and converted
to intermediates of glycolysis and the citric
acid cycle for use as respiratory substrates.
Fats can also be broken down to
intermediates of glycolysis and the citric acid
cycle.
p25
• Phosphofructokinase activity can be inhibited by
ATP and citric acid. These feedback mechanisms
help to synchronise the activity of glycolysis and
the citric acid cycle to ensure the cell conserves
its resources by only producing ATP from cellular
respiration when it is required.
SQA p26
• During strenuous activity muscle cells break down
ATP releasing ADP and phosphate, along with
energy. Creatine phosphate in the muscle cells
breaks down to provide energy and phosphate to
convert ADP to ATP by phosphorylation. This
system sustains maximal muscle contraction for a
short period of time, eg about a 100 metre sprint.
• When demand for energy in muscles is low ATP
produced by cellular respiration acts as a source of
phosphate for the phosphorylation of creatine into
creatine phosphate, which acts as a store of energy
for the muscle tissue.