Metabolic fate of nutrients Flashcards
Why is nutrition important?
Key to develop and maintain state of health
What is nutrition?
The process by which a living organism receives nutrients from its environment and uses them to promote its vital activities
What are Macromolecules?
Proteins
Fats
Carbohydrates
What are micromolecules
Minerals
Vitamins
What is the basal metabolic rate?
12 hours after eating
Number of calories needed at rest for normal body function
50-70% calories needed per day.
What is the thermic effect of food?
Energy required for the digestion and absorption of food
5-10% of energy expenditure
What are the main energy requirements in the body?
Basal metabolic rate
Thermal effect of food
Physical activity
Other factors - temperature changes, pregnancy, lactation
What is the preferential source of energy?
Glucose since it is readily available primary source of energy for the CNS and RBCs
How is glucose stored?
As glycogen by glycogenesis
How much ATP can come from 1 molecule of glucose in aerobic respiration?
36-38 ATP molecules
What is the main use of energy from fats?
Used in tissue activity and for the maintenance of body temperature
Why are fats important?
body structure - cell membranes Protection insulation Satiety Fat soluble vitamins Energy storage in adipose tissue
Why are fats a calorie dense nutrient?
Large amounts of O2 required to metabolise
Insoluble in water so difficult to access
How much ATP is produced from 1 mole of palmitic acid?
130 ATP molecules
Why are proteins important?
Amino acid pool Converted to other AAs Manufacture new proteins Build new tissue Oxidised to produce energy
What is Nitrogen balance?
Balance = N intake - N excreted
What are the results of a positive nitrogen balance?
Pregnancy
Growth
Recovery
What are the results of a negative nitrogen balance?
Starvation
Trauma/ infection/ sepsis
Tissue destruction
What are some non energy supplier nutrients?
Essential for life
Dietary fibre
Why are insoluble fibres important?
Provides bulk to the gut to prevent constipation
Why are soluble fibres important?
Absorbs water in the intestine to soften stool which helps waste move along colon
Lowers cholesterol
What are the water soluble vitamins?
B complexes
vitamin C
What are the fat soluble vitamins?
A,E,D,K
Why are water soluble vitamins important?
Anti-oxidants
enzyme cofactors
Why are fat soluble vitamins important?
Development of immune system
Calcium metabolism
Blood clotting
What are the main essential minerals?
Fe, Ca, Mg, Mn, Na, K, Zn
What are some vitamin deficiencies
Rickets (vitamin D deficiency)
Poor mineralisation of bone
Scurvy (chronic Vitamin C deficiency)
What causes pernicious anemia?
Vitamin B12 deficiency
How do we regulate body mass?
Energy intake = energy expended + energy stored
intake - expenditure = 0
What happens if energy intake > expenditure?
Positive balance, therefore add stored energy increasing body mass –> obesity
What happens if energy intake < expenditure?
Negative balance
Lose weight / starvation
What maintains consistent body weight?
neuroendocrine regulation of the process of feeding (appetite and satiety)
Appetite - Desire to eat food, felt as hunger
Satiety - Absence of hunger
How does the brain regulate hunger and satiety?
Controlled by hypothalamus
Glucostatic:
decrease glucose = hunger
Increase glucose = satiety
Adipostatic:
increased fat stored = satiety
What is the hormone that stimulates appetite?
Ghrelin
What hormones inhibit appetite?
Insulin
Leptin
stopping of Ghrelin release
What can change appetite perception?
Anemia
Cancer – colon, ovarian, stomach, pancreatic
Depression – although sometimes opposite effect
Intestinal disorders Intestinal parasites Liver disorders
Malabsorption syndrome
Mouth disorders
Taste loss – age, drugs
Stress, anxiety, Love
Altitude, cold
How is the majority of energy stored?
As adipose tissue (fats)
What is the preferred energy store to be used?
Glucose
What is the blood brain barrier?
Highly selective permeable barrier
Endothelial cells have tight junctions Separates blood - brain extracellular fluid CN
What is the disadvantage of using FAs over glucose?
ATP generated demands more O2
β-oxidation generates superoxide which can destroy cells
Rate ATP generation slower than glucose
What energy store is used for high intensity exercise?
Glucose due to Type 2 muscles being used and therefore requires anaerobic respiration and glycolysis of glucose
What energy store is used for low intensity exercise (marathon)?
Type 1 muscles used and therefore fats would be metabolised
What are the areas of the main stores of glycogen?
Liver
Muscles
What effect does insulin have on metabolism balance?
initiates anabolism (storage)
Fats -> adipose tissue
Glucose -> glycogen
AA -> New proteins
What effect does glucagon have on metabolism balance?
Initiates Catabolism (energy)
Fats -> FAs
Glycogen -> glucose
Proteins -> glucose (starvation)
What effect does insulin have on the liver?
Increased AA uptake
Increase Glycogenesis
Decreased Gluconeogenesis
Increased Lipogenesis
What effect does insulin have on the adipose tissue?
Increased Glucose Uptake
Increased Lipogenesis
Decrease Lipolysis
What effect does insulin have on the muscle tissue?
Increased Glucose uptake
Increased AA uptake
Increased Glycogen synthesis
What hormones promote lipolysis?
Glucagon
Adrenaline
Glucocorticoids
Insulin inhibits this
What are the origins of obesity?
Innate/Inherited: mutation of leptin
Acquired: inactivity overeating aging stress drugs
What are the two fates of Acetyl CoA in metabolism?
Either enter krebs cycle
or be converted into FAs and triglycerides (fats)
What is the problem with low fat diets?
They are instead high in fructose
Fructose is metabolised differently and does not stimulate insulin secretion.
No insulin secretion leads to food intake not being inhibited and therefore we eat more leading to over eating
What are some treatments to obesity?
Drugs altering appetite - Sibutramine (suppresses appetite)
Drugs altering absorption of calories - Orlistat
Restrict food intake - diets, gastric balloon, bariatric surgery.
Exercise
What is the origin of starvation?
Simple deprivation of calories (no genetic components)
What is starvation characterised by?
Mechanisms to preserve plasma glucose to maintain brain and spinal cord
What is starvation marked by?
Increased liver synthesis of glucose and ketone bodies.
Gluconeogenesis
Ketogenesis
What happens during starvation when glucose has been exhausted?
Rely on synthesis from endogenous sources such as AAs and Fats
How can muscle and fat be used as an energy source?
Breakdown of muscle to amino acids
Breakdown of fat to release glycerol
What is the disadvantage of using muscles and fats as energy sources?
Muscle performance declines
Finite resource
How are ketone bodies produced?
Produced from fatty acid (insoluble)
Ketone bodies - water soluble product
Diffuses via concentration gradient to blood
Taken up from blood (without need for transporters)
Cross blood brain barrier
**Source of Energy used by brain in starvation as well as in type 1 diabetes
What are the time stamps of glucose metabolism before starvation?
0-6hrs - glucose from blood used as main fuel for brain
6-16hrs - glycogen is broken down in liver to be used as glucose as fuel for the brain
16-72hrs - 1st metabolic shift as very low levels of glucose
Increased gluconeogenesis and lipolysis
2-3 days of fasting - increased lipolysis
liver converts FAs to ketone bodies
Decreased gluconeogenesis
> 24 days - relies on gluconeogenesis due to depletion of fat stores.
Rely on muscles wasting to provide energy.
46-70 days = death
