Biochemistry Exam II Flashcards
Secreted by B-cells of pancreas
Insulin
Secreted by a-cells of pancreas
Glucagon
Insulin receptors
autophosphorylate themselves
Brings Glu into the cell
GLUT 4
Insulin-dependent gucose entry into cell is mediated by _____ which controls glucose uptake in _____ and _____
glucose transporters (GLUT4)
skeletal muscle
adipocytes
Most GLUT 4 reside
intracellularly (<10% on PM)
_____ Increases the expression of GLUT 4 independently of insulin
muscular contraction
____ decrease the expression of GLUT4 in the muscle
Fatty acids
Main contribution to type 2 diabetes
–Insulin resistance
Inadequate synthesis
Secretion
Unable to exert normal effect (most common)
Main cause of insulin resistance
defect in signaling -receptor binding -mutation in receptor gene -anti-receptor autoantibodies Signaling defects -IRS-phosphoiniositol kinase pathway
Anti-insulin hormone
Glucagon
Mobilizes glucose
Increases blood glucose
stimulates catabolism
Suppresses anabolism
Glucagon–breaks down glycogen (catabolic)
Catecholamine
- secreted by AG
- Inhibits glycolysis and lipogenesis
- Stimulates gluconeogenesis
Epinephrine
Effect of Epinephrine
decrease glycolysis and lipogenesis
stimulate gluconeogenesis
Controlled by changes in plasma ratios of glucagon and insuin
Feed-Fast cycle
High insulin/low glucagon
fed state
Low insulin/high glucagon
fasting between 6-12 hours state
____ low insulin/high glucagon occurs during fasting of ___ or more hours, known as ____
Chronic
12
Starvation
Tissues affected in Fed (absorptive state)
Liver Muscle Adipose --Storage tissues Glucose utilization in brain = unaffected
Decrease in glycogen synthesis
Increase in glycogenolysis
Liver switches from glucose usage to glucose production
Fasting (postabsorptive) state
Gluconeogenesis key substrates
Lactate, alanine, glycerol
During fasting ___% taken up by insulin-dependent tissues
__% glucose goes to brain
Remaining is divided among ____ _____ and ____
80
50
RBC, Muscle, Adipose
after 12 hrs.
___% glucose comes from glycogen
Glucose contribution from ____ increases as it continues
-More ketone bodies present in this stage
Prolonged fasting (starvation)
During prolonged fasting, ___ help by releasing ____ which goes to liver
Muscles
Lactate
In liver, lactate—>
Glucose released goes to muscle =
pyruvate for gluconeogensis
Cori cycle
In this stage:
Free fatty acids are major energy substrate
Oxaloacetate decreases in mito to fuel gluconeogenesis–limiting TCA activity
Acetyl CoA accumulates–used for ketogenesis causing inc. plasma ketone body levels
Prolonged fasting (starvation)
During starvation, gluconeogensis occurs in
kidney and liver
During starvation, muscle proteolysis increases, releasing
Alanine and Gln
Anti-insuiln hormones
Epinephrine
Glucagon
Cortisol
Metabolism is effected during stress:
Gluconeogenesis?
Glycogen breakdown?
Ketone body production?
Increases gluconeogenesis
Increases glycogen breakdown (glycogenolysis)
Increases ketone production by ketogenesis
—Stress response preserves glucose supply
—leaves more for brain utilization
Stress induces insulin resistance
Cortisol decreases Glu4 expression
Cortisol induces expression of Glc-6-Pase and PEP carboxylase carrboxykinase genes which facilitate gluconeogenesis
Insulin-independent glu uptake increases
Outcomes of Stress Response
develops before age 35
destruction of B-cells
Viral infection,toxins, food
Autoantibodies to insulin, glutamic acid decarboxylase and protein tyrosine phosphatase
Type I Diabetes
Over age 40
Insulin resistance
Ketoacidosis rare
Obesity
normal glucose levels, hyper insulinemia
can be reversed with weighloss and exercise
Type 2 diabetes
