Lecture 12 - metabolic integration part 1 Flashcards
Metabolic integration of protein
intermediates with 3-6 carbons can be used to make glucose
once you form acetyl CoA you can no longer use the building blocks to make glucose
What must metabolic maintain?
- blood glucose between 60-100 mg/dL
- blood pH near neutrality (related to amino group handling)
Where is blood glucose required in the body?
- by red blood cells as an energy substrate (because they have no mitochondria)
- by the central nervous system (although gradual adaptation to ketones possible)
- to maintain an active Kreb’s cycle
In the fed state, what is the predominant source of blood glucose
dietary CHO (if high carb diet)
dietary protein (if high protein diet)
In the post-absorptive state, what is the predominant source of blood glucose?
glycogen from liver (glycogenolysis)
In the fasting (no glycogen) state, what is the predominant source of blood glucose?
gluconeogenesis from protein catabolism
In the starvation state, what is the predominant source of blood glucose?
gluconeogenesis from glycerol produced by TAG breakdown;some protein catabolism
What is the nature of the insulin hormone?
anabolic
What is the nature of the glucagon hormone?
catabolic
What is the nature of corticosteroids (cortisol)?
catabolic
What is the nature of catecholamines (epinephrine)?
catabolic
What is insulin produced by?
pancreas (beta cells)
What is glucagon produced by?
pancreas (alpha cells)
What are corticosteroids (cortisol) produced by?
adrenal cortex
What are catecholamines (epinephrine) produced by?
adrenal medulla
What are the main effects of insulin?
raise glucose and AA uptake in muscle and liver
raise glycogen and protein synthesis in muscle and liver
raise TAG synthesis and storage in adipose
What are the main effects of glucagon?
raise breakdown of glycogen, protein and fat
raise gluconeogenesis from AAs and glycerol
What are the main effects of corticosteroids (cortisol)?
raise muscle protein catabolism
raise gluconeogenesis from AAs
What are the main effects of catecholamines (epinephrine)?
raise glycogenolysis and lipolysis
What are some characteristics of the brain metabolism?
- constantly working
- brain cells need glucose
- low carb diet - brain cells aren’t getting what they need
What are the brains requirements for oxidative metabolism?
- high requirement - needed to support continuous electrical activity
- 100-120 g per day required
Why can’t the brain use FA’s for energy?
FA can’t cross the blood-brain barrier enough to provide sufficient energy
What are some characteristics of the energy requirements of adipose tissue?
- low energy requirements, therefore not a lot of oxidative fuel consumption
- mostly just storage
What is glucose used for in adipose tissue?
- for de novo lipogenesis and TAg synthesis
- to provide energy for FA uptake
What does the adipose tissue release?
non-esterified FA (NEFA), into circulation from lipolysis
How much of total body weight does skeletal muscle represent?
40%
What are the two regulators of muscle fuel consumption?
nutritional status and exercise
What are the two different fibres of the skeletal muscle?
slow twitch
- used for long duration activity slow concentration
- FA are the predominant source of energy
fast twitch
- used for short duration activity, quick contraction
- local glycogen stores provide energy
What are some characteristics of fed to starvation phase in the body?
- glucose is used quickly
- glycogen reserves are sufficient for 24 hrs and then depleted
- protein breakdown occurs initially releasing glucogenic AA
- this will then slow down to preserve protein function, but small amounts continue to be broken down to maintain the activity of the krebs cycle
- FA breakdown occurs to spare protein eventually used to make ketone bodies
What are the trends of energy source from fed to starvation?
glucose - decreases
glycogen - peaks 24 hrs and then is zero
AA (protein) - raises after 24 hrs and then slowly decreases
FA - raised after 24 hrs and maintains consistently high
ketones - raised after 3 days and maintains high
