Weight Loss and Nitrogen Metabolism Flashcards
What happens to food energy
metabolic pool in body to internal/external work to thermal energy
and/or
energy stored
How is daily energy expenditure used
purposeful activity (25%)
non exercise activity (7%)
Thermic effect of food (8%)
Basal metabolic rate (60%)
what are the energy stores
Lipids (~85%)
Proteins (~15%)
Carbohydrates (~0.6%)
Where are the energy stores located
Liver - major glycogen reserve
Adipose tissue - stores lipids as triglycerides
Skeletal muscle - half of protein in the body and glycogen reserve
Neural tissue - reliable supply of glucose
Other peripheral tissue - metabolise substrates under endocrine control
What does low blood glucose cause
coma and death
What happens to energy stores during starvation
1) carbohydrates rapidly deplete
2) fat
3) protein
What is cachexia
muscle wasting with cancer
what is sarcopenia
muscle wasting with age
frailty
where is the major amino acid and nitrogen reserve in the body
muscle
Types of muscle wasting
-starvation
-injury/illness
-immobilisation (wasting of thigh muscle)
-nerve damage
-cancer
-AIDS
-sepsis
-renal failure
-sarcopenia
-spaceflight
What causes muscle wasting
difference between nitrogen input into the body (dietary) and nitrogen excretion mainly as urea
How are proteins degraded
Proteins converted to AA
AA turn into pyruvate
pyruvate enters TCA cycle/oxidative phosphorylation
What are the 2 proteins for proteolysis
1) lysosomes
2) proteasomes
proteases of degradation
aminopeptidases - dipeptidases
calpains - cleave contractile proteins
caspases - cell death regulatory e.g. apoptosis
Lysosome pathway
degrades extracellular and cell surface proteins via endosomes and most proteins via autophagosomes
(common in starvation)
ubiqutin proteasome pathway
degrades proteins from the cytoplasm, nucleus, ER
What are lysosomes
- membrane bound
- low pH
- proteases - Cathepsins
types of cathepsins
cysteine proteases
serine proteases
aspartate (aspartyl) proteases
protein degradation steps
1) Ubiquitin activating enzyme (E1)
2) Ubiquitin conjugating enzyme (E2) attaches to E1 protein
3) Ubiquitin ligase (E3) decides what is degraded
4) polyubiquitination
5) protein tagged for ubiquitination
6) enters 26S proteasome
7) proteases attack amino acid bonds of proteins into peptides
What happens to amino acids from proteolysis
-nucleic acid precursors
-urea
-fatty acids
-energy
-glycolysis
-TCA cycle
where does gluconeogenesis occur
liver and kidneys only
not skeletal muscle
normal protein content
25-30g
what occurs if meal contain excess amino acids
storage (skeletal muscle)
blood sugar
urea cycle
immune defence
ketogenesis
What is hyperammonemia
high ammonia in bloodstream
What is urea
small, neutral, non-toxic, water soluble
H2NCONH2
Why have urea
ammonium ions are toxic (>1mM) causes encephalpathy
How is urea processed
1) Aspartate formed via transamination of oxaloacetate
2) oxidative deamination of glutamate to alpha-ketoglutarate
