B2.041 Metabolism and its Regulation Pt. 1

Question 1

what is caloric homeostasis?

Answer 1

in both the fed state and fasting, a healthy body keeps the same amount of “calories” available in the blood

Question 2

what are calories?

Answer 2

fuel that can be metabolized to do work

Question 3

what are the negative consequences of having too much fuel in the blood?

Answer 3

generation of too many electrons via oxidation that react with oxygen to produce ROS

Question 4

what types of fuel does the body utilize?

Answer 4

carbs (glucose, fructose, galactose)
fat (triacylglycerols, free fatty acids, ketone bodies)
protein (20 amino acids)

Question 5

where are fuels primarily stored?

Answer 5

liver (glycogen)

adipose (triacylglycerol and triglycerides)

Question 6

what drives the starve-feed cycle?

Answer 6

increase in ADP concentrations drives fuel oxidation and oxygen consumption (respiration)

Question 7

define glycolysis

Answer 7

conversion of glucose to pyruvate or lactate

Question 8

define glycogenesis

Answer 8

conversion of glucose to glycogen

Question 9

define lipogenesis

Answer 9

conversion of carbon of glucose and amino acids to fat

Question 10

what is the function of the pancreas in the well fed state?

Answer 10

pancreatic B cells produce insulin

Question 11

how does the liver process fuel in the well fed state?

Answer 11

liver is glycogenic, glycolytic, and lipogenic

Question 12

how does the muscle process fuel in a well fed state?

Answer 12

muscle is glycogenic

Question 13

how does adipose tissue process fuel in a well fed state?

Answer 13

adipose is lipogenic and stores TAG

Question 14

how do red blood cells derive energy?

Answer 14

need constant supply of glucose for anaerobic respiration, no mitochondria

Question 15

what is the function of the pentose phosphate pathway?

Answer 15

produces NADPH

NADPH is a reducing agent that keeps glutathione reduced and fights oxidative stress

Question 16

list the glucose transporters and their locations in the body

Answer 16

GLUT1- RBC
GLUT2- liver
GLUT3- brain tissue
GLUT4- adipose, muscle, heart

Question 17

how do blood glucose and liver glucose compare?

Answer 17

very similar bc all blood filtered through liver via portal vein

Question 18

what do glucuronides do?

Answer 18

solubilize insoluble compounds

Question 19

how does the body lower the amount of fuel in the blood during the well fed state?

Answer 19

synthesis and storage of glycogen in the muscle and liver

synthesis of fat in the liver, release of fat into the blood, uptake and storage of fat in the adipose tissue

Question 20

what state is the body locked in during obesity?

Answer 20

fed state

due to overconsumption of high energy fuels

Question 21

what is the relationship between insulin and glucagon in obesity?

Answer 21

insulin is very high
glucagon is very low
high I/G ratio
drives fat synthesis

Question 22

what is the rate limiting enzyme for fatty acid synthesis?

Answer 22

acetyl CoA carboxylase

Question 23

what is lipogenesis from glucose?

Answer 23

occurs in liver in well fed state

requires lots of glucose for glycolysis to produce pyruvate and for the pentose phosphate pathway to produce NADPH

Question 24

why does lipogenesis require mitochondria?

Answer 24

formation of citrate which carries acetyl groups from the mitochondrial matrix space to the cytosol for fatty acid synthesis

Question 25

for what tissues is glucose a primary fuel?

Answer 25

brain, RBCs, white muscle, kidney medulla, macrophages

Question 26

for what tissues are fatty acids an important fuel?

Answer 26

heart, skeletal muscle, liver, kidney

Question 27

why are ketone bodies important?

Answer 27

4 carbon compounds made from fatty acids water soluble fat calories important in heart, skeletal muscle, and kidney

Question 28

for what tissues are amino acids an important fuel?

Answer 28

liver and gut (glutamine)

Question 29

what is the distinction between heavy calories and light calories?

Answer 29

heavy calories: 1 lb of glycogen = 4 lbs total due to water uptake light calories: 1 lb of fat = 1 lb due to fat being dry and not taking up water

Question 30

when does hepatic gluconeogenesis become important during starvation?

Answer 30

increases before exhaustion of hepatic glycogen | begins rising at 4 hours and peaks at 2 days

Question 31

why does gluconeogenesis drop after 2 days of starvation?

Answer 31

increased production of ketone bodies by the liver and their use by other tissues

Question 32

what is the substrate most important for keeping someone alive during starvation?

Answer 32

ketone bodies

Question 33

define glycogenolysis

Answer 33

conversion of glycogen to glucose

Question 34

define gluconeogenesis

Answer 34

conversion of lactate, glycerol, and amino acids to glucose

Question 35

define ketogenesis

Answer 35

conversion of fatty acids to ketone bodies

Question 36

define proteolysis

Answer 36

conversion of proteins to amino acids

Question 37

define lipolysis

Answer 37

conversion of triacylglycerol to free fatty acids

Question 38

what does the pancreas do in the fasting state?

Answer 38

pancreatic a cells produce glucagon

Question 39

what does the liver do in the fasting state?

Answer 39

makes ketone bodies but can't use them

Question 40

what does the anterior pituitary do in the fasted state?

Answer 40

produces GH

Question 41

what does the brain do in the fasted state?

Answer 41

uses ketone bodies but not fatty acids

Question 42

how does adipose tissue function in the fasted state?

Answer 42

adipose is lipolytic

Question 43

how are counter regulatory hormones used in the fasted state?

Answer 43

adrenal cortex produces cortisol | medulla produces catecholamines

Question 44

how does muscle function in the fasted state?

Answer 44

muscle is proteolytic

Question 45

how does the liver function in the fasted state?

Answer 45

liver is glycogenolytic, gluconeogenic, ketogenic, and proteolytic

Question 46

when does ketoacidosis occur?

Answer 46

ketoacidosis occurs when the rate of B-hydroxybutyrate + H production by the liver exceed the rate of its uptake by other tissues

Question 47

how is excretion related to ketoacidosis?

Answer 47

excretion of B-hydroxybutyrate in urine with Na+ leaves H+ in blood, resulting in ketoacidosis

Question 48

what two reactions are coupled to convert palmitate to neutral compounds?

Answer 48

ketogenesis by liver palmitate to b-hydroxybutyrate and H+ ketolysis by other tissues b-hydroxybutyrate and H+ to CO2 and H2O

Question 49

what state is a DM1 patient locked in?

Answer 49

starved state

Question 50

what compounds accumulate in the starved state?

Answer 50

glucose, ketone bodies, fatty acids, triacylglycerols

Question 51

what does a glucose tolerance test demonstrate?

Answer 51

slow clearance = lack of insulin and/or insulin resistance | rapid clearance depends on stimulation of GLUT4

Question 52

what are the major differences between the DM1 state and starved state?

Answer 52

person w diabetes consumes food body does not transition to fed state with consumption of food ability to maintain caloric homeostasis is lost in DM1 in starved state, insulin levels are low but present, in DM1 there is no insulin

Question 53

how do DM1 and DM2 manifest differently in lab tests?

Answer 53

both have high blood glucose | DM1 also has a higher pH, HCO3, and urine glucose/ketones when DM2 is usually normal

Question 54

why is high glucose toxic?

Answer 54

causes oxidative stress (too much ROS) glycation increases increased hexosamine pathway

Question 55

what is glycation?

Answer 55

addition of sugar to proteins without an enzyme | produces advance glycation age end products (AGEs)