LECTURE 1 - ENERGY Flashcards
what are the dietary sugars and their structures/characteristics?
- starch
repeating glucose units
found in rice
moderately branched
O group bond always down - glycogen
found in meat
repeating glucose units
highly branched
really big - cellulose
found in veggies
makes up the cell wall
unbranched
O group alternates between up and down
(amylase can only digest the down)
(cows have bacteria in their gut that make enzymes which can digest both bonds)
sugar: sucrose (glucose+fructose) digested by sucrase
milk: lactose (glucose+galactose) digested by lactase (also known as beta galactosidase)
which bond is up which bond is down?
down=alpha
up=beta
what are the three ways of transport by which glucose is taken up in the blood?
active transport
passive transport
secondary active transport
how do those three forms of transport work to uptake glucose into the blood?
glucose enters the vili through Na+ glucose symport down the concentration gradient for Na+
inside there is an ATPase which pumps Na+ out and brings K+ in to keep Na+ low in the vili, so that Na+ can enter down the concentration gradient and bring glucose with it
after, the glucose gets to the capillaries through a glucose uniport, which opens without need of energy, down its concentration gradient
what is the basal blood glucose level? (between meals)
<5.5mM
what happens in pancreatic beta cells between meals?
- glucose enters through Glut2 (passive)
- there are base amounts of glycolysis, there is some pyruvate formed
- oxidative phosphorylation in the mitochondria releases ATP
- the K+ ATP channel is open, and there is membrane hyperpolarization
- K+ inhibits the transporter, so nothing happens
- there is no opening of the Ca2+ channel and vesicles containing insulin stay inside the cell
what happens in pancreatic beta cells after a meal?
- more glucose enters through Glut2, more glycolysis, more oxphos, more ATP formed
- ATP inhibits the K+ATP channel and there is membrane depolarization
- the ATP binds to a regulatory domain, the channel detaches from the cell and closes
- the Ca2+ channel is sensitive to depolarization, and it opens
- Ca2+ gets in, vesicles release insulin
which tissues are insulin responsive for their uptake of glucose and which are not?
insulin responsive: adipose tissue and muscle
NOT insulin responsive: the liver
what happens in the adipose tissue for glucose uptake?
insulin binds to the insulin receptor
Glut 4 (passive glucose transporter) is recruited to the surface
glucose enters the adipose tissue and there is lipogenesis
what happens in the muscle for glucose uptake?
insulin binds to the insulin receptor
Glut 4 (passive glucose transporter) is recruited to the surface
glucose enters the muscle and there is glycogen synthesis
what happens in the liver for glucose uptake?
glucose goes inside the liver through Glut2 which depends on the glucose concentration gradient (can go both ways)
insulin binds to the insulin receptor and that activates glycogenesis and lipogenesis
the liver either stores or provides glucose
what happens in the liver at the fed/fasted stage?
the liver keeps the blood glucose levels at 5.5mM
fed: stores glucose as glycogen
fasting: 1. breaks down glycogen
2. gluconeogenesis (make new glucose)
why are there so many glucose uptake transporters?
transport tailored to the needs of a tissue (some need more than others)
tissues often express more than one transporter for glucose, functions are controlled by level of expression
sugar specificity
for regulation=different feedbacks
what are the stages of energy expenditure in exercise?
- use the ATP already available
- P-creatine in cells
- anaerobic glycolysis
- aerobic glycolysis
- aerobic lipolysis
the shortage of ATP triggers this succession
what is the P-creatine reaction?
P-creatine+ ADP —-> creatine + ATP
the enzyme is creatine kinase
forward reaction is favored
