Review of digestion and metabolism Flashcards
atoms form molecules which make up:
proteins and lipids that form cells and tissues and the glucose that is used for energy
how do humans get atoms?
Since we cant make atoms or create energy we have to get them from other sources
what does the GI tract consist of?
mouth, pharynx, esophagus, stomach, small and large intestine and the anus
what body processes take place in the GI tract?
Digestion, absorption and excretion
what is transit time?
The amount of time it takes food to pass the length of the GI tract
what do feces consist of?
waste including unabsorbed food residue, bacteria and dead cells that leave the body
when does digestion begin?
as soon as the food enters the mouth
what does saliva do in digestion?
lubricates food with the enzyme amylase which breaks down carbs in the mouth
in the stomach, gastric juice is released which contains:
- HCL (acidifying the stomach)
- Pepsinogen, inactive form of the enzyme pepsin
Once activated by HCL pepsin begins breaking down proteins
in children, what enzyme is released and what does it do?
renin
- helps digest milk
what churns the stomach content aiding in digestion?
powerful stomach muscles
when does chyme leave the stomach?
After 2-6 hours and enters the small intestine
in the small intestine, the pancreas releases:
- Bicarbonate (neutralizes acidic chyme)
- Enzymes that further break down carbs, proteins and lipids
what does the gallbladder release?
bile salts
what does the gall bladder do in the digestion process?
Emulsify lipids, separating them into smaller fat droplets which are more soluble and accessible to enzymes
where does most absorption occur?
small intestine
how long is the small intestine?
6 metres
what 2 things increase there SA of the small intestine?
Villi and microvilli
Single sugars, amino acids and short chain fatty acids enter where?
portal vein and go to the liver
where do Long chain fatty acids enter?
lymphatic system and go directly into the bloodstream
how long does it take chyme to move through the small intestine?
3-5 hours
where do unabsorbed materials enter (since they do not go in small intestine)?
large intestine
does the large or small intestine contain gut microbiome (large bacterial population)?
large
gut bacteria break down unabsorbed food and can produce:
beneficial compounds for the body
Biological material will stay in the large intestine for how many hours before being excreted?
24-36
the GI tract acts as a barrier to what?
the outside world, inside your body
The immune system is interconnected within the GI tract to prevent pathogens from entering body (phagocytes such as macrophages and lymphocytes such as B cells and T cells are present below the mucosa). T or F
T
how does a food allergy occur?
when the immune system reacts to a protein in our food and triggers an immune response
what percentage of Canadians have a food allergy?
7%
Celiac disease is an example of a food allergy due to an immune response to what?
wheat protein gluten
what is the benefit of commensal bacterial in the gut?
help fight pathogens by competing for nutrients
The human gut contains an entire ecosystem of microorganisms. T or F
T
what diseases have been been linked with gut microbiota?
Obesity, cancer, inflammation, CVD, liver disease
what’s the difference in the microbiome a baby has being born vaginally and C section?
vaginally:
- have an initial microbiome that resembles the mothers vaginal microbiome
C section:
- have a microbiome that resembles the mothers skin microbiome
what people would have greater quantity and variation in gut bacteria?
those who are lean
what people harbour more pro inflammatory species?
Those with lower bacterial numbers (and higher BMI)
what is lactase?
enzyme found in the small intestine that can break down lactose
when is lactase highly expressed?
during infancy but typically decreases as child transitions to solid foods
If the amount of lactase in the small intestine is insufficient to handle the lactose in the diet, some lactose will escape and enter where?
large intestine where bacteria will use it for energy
what contributes to the autoimmune response in T1D?
A bacterial protein has a similar sequence to the human insulin epitope
This bacteria may contribute an immune response to insulin and T1D onset
when we eat, what enters the blood supply from the intestines? And what organ do they get to first?
glucose, fatty acids and amino acids
- liver bc of portal vein
nutrients are used in 3 different ways:
- Broken down for energy (catabolism)
- Used to make new molecules (anabolism)
- Stored for later use
The energy obtained from breaking down glucose amino acids and fatty acids is converted to what?
ATP
ATP contains high energy bonds that when broken down, release energy that can be used to:
- Synthesize new molecules
- Fuel cellular and bodily functions
Glucose is used in 3 diff ways:
- Oxidized for energy
- Stored for later energy use as glycogen (carbs) or triglyceride (lipid)
- Used to make new molecules
what is the most important energy source?
glucose
- brain an RBC use glucose for energy
amino acids (protein) are used in 3 diff ways:
- Oxidized for energy
- Used to make new proteins or molecules
- Cannot be stored, all protein is functional
fats are used in 3 diff ways:
- Oxidized for energy
- Stored for later energy use as Triglyceride (lipid) in adipose tissue
- Used to make new molecules
once in the cells, nutrients are converted to what?
energy
what is Acetyl-CoA?
is the hub of energy production in the cell
Oxidation of macronutrients produces _________ which is exhaled by the lungs
carbon dioxide
Deamination of amino acids produces ammonium, nitrogenous waste is filtered out by the kidneys and excreted in the urine. T or F
T
glucose levels in the blood must remain ______ to keep body processes functioning by supplying energy to the brain and RBCs
near constant
Substances are metabolized differently depending on:
how long it has been since a meal
in the fasting state, are blood glucose levels high or low?
low
glucagon is released from the pancreas in response to what?
low blood glucose levels and insulin is decreased
how is energy supply maintained?
Fatty acids are broken down, providing energy to tissues that do not rely on glucose
what is Glycogenolysis?
Liver stores of glycogen are converted to glucose but are limited
This supply is used first
what is Gluconeogenesis?
The use of non carbohydrate sources to produce glucose, this process ramps up as glycogen stores are being depleted
what can be used as precursors for glucose?
Glycerol, lactate and amino acids
Proteins are broken down and instead of being remade, what are used for energy?
amino acids
what are ketone bodies produced by?
the liver from fatty acids as an alternative energy source for some tissues
in what individuals is an intermittent fasting diet beneficial?
individuals with metablic syndrome
During a prolonged fasted state, are blood glucose levels low or high?
remain low, glycogen has been depleted an there is limited excess protein to break down
what is the goal for the body in the starvation period?
maintain an energy supply for essential tissues, the brain and RBCs
why do ketone bodies build up in the blood?
from the breakdown of fatty acids
- once concentration gets high enough, the brain will begin using them for energy in addition to the limited glucose available
when does death occur from starvation?
When about 40% of body weight is lost
- BMI women=11
- BMI men=13
30-50% protein loss, 70-95% of fat depleted
how is the metabolic state of an individual determined?
Blood and urine levels of the different substances are used
