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Lecture 6

BCH210H1 Lecture Notes - Lecture 6: Glut4, Citric Acid Cycle, Negative Number


Department
Biochemistry
Course Code
BCH210H1
Professor
Michael Baker
Lecture
6

Page:
of 2
Soon-yi
a marathon runner
20 years old
had been training for 4 years- her best time was 10 minutes slower than the requirement- needs
more training
97 lb (44 kg)
during her training
she did 4 marathons (each 42 km)
practice schedules involved 3 things:
extended runs (>10 km)
shorter runs (5-10 km)
rest days – to rebuild the body fuel reserves for energy
Today = training day-shorter run
6 am morning run along the beach
nothing to eat since last night 8 pm
ATP needed for muscle contraction
she has about 3mM ATP in muscle cells
but her exercises are quickly using up this energy source- ATP hydroylysis needed for
energy
ATP + H2O---ADP +Pi +H+
How to maintain the ATP reserves in order to continue on ATP hydrolysis?
Creatine phosphate (25mM) in muscles now used to sustain ATP levels at 3mM
this is performed by creating kinase (CK)- acts as a phosphate transfer group
PCr +ADP ----- ATP + Cr
recall this could be done only if the phosphate transfer group (PCr) has a greater
negative number for ⌂G than gamma phosphate of ATP
eventually PCr levels decrease as well
Soon-yi needs more energy for her activity- so fuels must be broken down to sustain ATP levels
Although she hasn't eaten since last night, she does have some blood glucose levels of 3.2
mM- not hypoglycemic -largely because of the liver glycogen
blood glucose enters her muscle cells by glucose transporters
they enter the cell by flowing down its concentration gradient through GLUT4 – glucose
transporter – well more like a channel (** shouldn't be called a transporter)- down its
concentration gradient
glucose coming from the blood can be used in the glycolysis process to provide the
muscle cells with ATP
Glucose as a fuel for Soon- yi's muscles
****GLYCOLYSIS DOES NOT REQUIRE OXYGEN RIGHT? NOT AEROBIC?
Overview:
1. Glycolysis (linear pathway) – cytoplasm- glucose split into two molecules of
pyruvate(3C each)
1. Net 2ATP and 2 NADH produced
2. Pyruvate enters muscle mitochondria-
Inner membrane is usually where the transport functions- outer
membrane has pores – not an effective barrier
pyruvate → acetyl CoA by the pyruvate dehydrogenase complex- multi
enzyme complex- like a bunch of grapes – lots of enzymes held
together
reactants = 2 pyruvate , 2 NAD+ , CoASH,
Products= 2 CO2, 2 acetyl coA, 2 NADH
3. Acetyl CoA enters the Krebs cycle:
2CO2 are lost
reduced coenzymes: 3 NADH and 1 FADH2 are made per Acetyl CoA
4. NADH and FADH2 are used in electron transport and oxidative
phosphorylation to
5. generate high yields of ATP
Overall: effectively glucose is turned into CO2 and energy release is conserved as
ATP
Glycolysis
energy conversion pathway
occurs in cytoplasm of most cells
10 enzymes (so 10 steps) which function to split glucose into 2 pyruvates
2 main parts :
ATP investment stage
ATP production stage
The first 5 enzyme steps =ATP investment stage
specfically 2 reactions where a phosphate group is transferred from ATP
to a sugar- sugar is phosphorylated – high energy bond?
like going to casino- need to invest money to buy chips before making more
glycolysis is an energy conversion pathway
Occurs in cytoplasm of most of the cells liver, muscle, spleen, etc
ends with 3C pyruvate
Step 1- Hexokinase
ATP investment stage
irreversible react that uses ATP to make glucose -6 phosphate from glucose
HK handles α-D-glucose, α-D-fructose and α-D-mannose
prefers aldohexoses as substrates