Digestion Flashcards
What is digestion
The breaking down of ingested food into useable nutrient molecules that can enter the vascular (within our blood) or lymphatic systems (within lymph)
What does the digestive system consist of?
- Gasterointestinal tract (GI)
- The accessory digestive organs
What is the gastrointestinal tract?
a tube from mouth to anus that breaks down the food and absorbs it.- breaks down proteins to a.a etc.
What are the accessory digestive organs?
Teeth (breaks food), tongue, liver, pancreas
What is the purpose of the accessory digestive organs?
help breakdown by mechanical( churning) or chemical means (HCL in stomach)
another term for GI TRACT?
Alimentary canal
What does the liver do?
produce bile salts- which are essential for the breaking down of lipids
What does the pancreas do?
through exocrine secretion,
-Panceratic enzymes are secreted into the digestive tract to help break down
What does the digestive process consist of?
- Ingestion
- Propulsion- smooth muscle contraction which send food particles down tube
- Mechanical breakdown- with teeth and churning in stomach
- Digestion- enzymes breaking food molecules
- Absorption
- Defecation- faeces
What is the summary of digestion of 3 main foodstuffs?
Carbohydrates
Proteins
Fats
What are carbohydrates structures?
-Either monosaccharides (e.g glucose), disaccharides (e.g. lactose) or polysaccharides (glycogen, starch)
What needs to happen to the disaccharides and polysaccharides before they can get absorbed?
need to be broken down into monosaccharides to be absorbed by the epithelial cells that line our small intestines.
How does the digestion of carbohydrates occur?
- Starts digestion in mouth
- Amylase from the salivary glands begins the breakdown of starch in the mouth, forming shorter oligosaccharides.
- This process is completed by amylase from the pancreas.
- These shorter chain sugar molecules are then converted to monosaccharides by the brush border enzymes in the small intestine, where they are absorbed.
What enzyme do you have in the small intestine?
pancreatic amylase
-releases more amylase so carbohydrates can be broken down more into smaller units.
What happens to remaining dissachardies that haven’t broken down?
- Epithelial cells that line the small intestine have enzymes embedded on their [l;asma membrane (integral proteins).
- Can break down into monosaccharides
- referred to brush border enzymes
How are the monosaccharides absorbed?
- easily via across brush border cell layer
- from lumen to cells by a process of facilitated diffusion or active transport
- Intergral proteins which acts as gates on plasma membrane
- releasing monosaccharides into blood supply where needed
What are proteins?
chains of amino acids
What happens in the digestion of proteins?
proteins need to be converted into dipeptides or single amino acids before they can be absorbed.
What is the process of breaking down proteins?
- No protein breakdown in the mouth
- Start the digestion in the stomach
- pepsin enzymes (HCL + pepsinogen) in the stomach breaks proteins into polypeptides and free amino acids.
- Pancreatic enzymes continue this breakdown
- Which is completed by brush border enzymes in the small intestine.
What happens when proteins are remaining?
they break down in the small intestine
- Enzymes on the brush border cells (integral proteins in the plasma membrane of the brush border)
- Absorbed pass the cell.
- enter blood supply
What are fats?
-most ingested fats are triglycerides that need to be broken down into monoglycerides and fatty acids.
How are fats digested?
- There is limited digestion of the fats in the mouth and stomach
- As fat is not solute in water would form big globules in water that could not be digested by enzymes
- therefore it is emulsified (broken into smaller bits) by bile salts
- bile salt emulsifies lipids- allow easier access to enzymes to the thiglycerides to break them down,
- These small fat spheres are split into monoglycerides and fatty acids by pancreatic lipase, which form ‘micelles’ that are absorbed.
- Fatty acids in micelles are in lymphs
- Micelles pass through brush border cells which are then transported to your lacteal which has lymph running through it and goes through lymphatic vessels to then around the body.
What is a triglyceride?
3 fatty acids bound together to a 1 glycerol molecule.
What else are micelles called?
chylomicron
Why is the digestion of proteins and carbs different to fats?
because they are pumped through the blood into the capillaries and to the rest of the body.
Compared to fats which go through lacteal, lymphatic vessels then blood.
What are the micronutrients?
- Vitamins
- Minerals.
How many essential nutrients are needed from our diet?
40 different as our bodies cannot synthesise them fast enough.
What does the body require (nutrients wise)?
- even though there are 40 essential nutrients needed, our body requires 100s.
- Therefore we can use these 40 nutrients and convert them to the many molecule types that we need
How does the body convert the nutrients?
-Liver- which is one of the main chemical factories.- as the blood from GI tract runs through the portal system in the liver.
How are carbohydrates mostly obtained?
from plant products
What are the 2 forms of carbs?
:Simple- monosaccharide and disaccharides- sugars
:Complex- polysaccharides- starch, fibre
What happens with the absorbed monosaccharides that are not glucose?
they can be converted to glucose by the liver.
Why is glucose important?
- feeds straight into cellular metabolism
- Harness a lot of energy need for the cellular processes for glucose.
What do you use carbohydrates in the body?
- Glucose main carb used as fuel
- Neurons and RBC are almost entirely reliant upon glucose to harness energy in ATP to use as an energy for cell function.
- Excess glucose can be converted into glycogen or fatty acids and stored later
what is a good store for glycogen?
liver
What happens if we max out the store for glucose?
- Excess glucose can be stored by converting to glycogen
- Can then store glycogen in liver
What happens if we have excess glycogen?
- convert excess glucose into fatty acids
- They can be stored in lipid inclusions - adipocytes or fat cells
- Store additional reservoirs
- Keep stores of energy
What is another function of carbohydrates apart from being broken down just to release energy?
- Release monosaccharides which can be used to build other things in the body
- An example can take in pentose sugars which are used to make new nucleic acids (in deoxyribose sugars or ribose sugar)
- Oligosaccharides and polysaccharides can be used in a cells glycocalyx- which stick out on cells
- Can secrete into extraceullar matrix (outside cell)- like GAGS-
what are the dietary requirements for carbohydrates?
- Inuits: low carbohydrate
- Far East populations: high carbohydrate
-Recommend in UK is 45-65% total calorie intake is recommended
What are the main dietary lipids?
triglycerides
What are the fats you can get in lipids?
Saturated and non-saturated
What are some examples of saturated fat?
animal products
cocounts
hydrogenated oils (trans fats) such as margarine
What are some examples of unsaturated fats?
seeds
nuts
vegetable oils
What is another category of lipid?
-Cholesterol
What are the foods which are in cholesterol?
- Egg yolks
- Meats
- Milk products
How is cholesterol produced ?
liver produces 85% of cholesterol regardless of dietary intake
What are fatty acids converted into?
readily converted into other fatty acids by the liver
What are the essential fatty acids in the body needed to take in through diet?
- Linoleic acid(omega 6 fatty acid)
- Linolenic acid (omega 3 fatty acid)
what do we use lipids for in body?
- fatty acids can be stored as triglycerides- by joining them
- They can be stored in inclusions in adipocytes, in adipose tissue around the body
- can be act as protective cushion against mechanical shock
- thermal insulation
- concentrated energy store
- Phospholipids- plasma membrane of every cell, myelin sheaths
- Use cholesterol- stabilises plasma membranes (fluid mosaic) , precursor of bile salts (digestions) and hormones (steroid)
- Fats help your body absorb fat soluble vitamins (A, D,E,K)
What are the dietary requirements for lipids?
-fats should represent 20-35% of total calorie intake
What lipid is not required in the diet?
-cholestrol because our bodies can synthesises all that they need
and majority of cholesterol can be produces via liver
What are the structure of proteins?
chains of amino acids
What are the types of proteins?
- complete proteins
- nutrionally incomplete proteins
What are complete proteins?
- contain all of a.a that we require to make all the proteins in the body
- found in animal products: eggs, meat, fish, milk and soya bean
What are nutrionally incomplete proteins?
- When broken down release a.a we require but not essential a.a
- Hence could become deficient
- things like legumes, nuts,cereal not all protein
What are the products with the highest quality protein?
animal product: those with the optimal ratio of all essential amino acids for humans.
What are the uses of protein in the body?
- Important structural materials of the body such as keratin (skin), collagen and elastin (connective tissue), muscle proteins
- Function protein- enzyme, hormones
- Growth hormone preserves protein mass in adults,
-glucocorticoids enhance protein breakdown and conversion to glucose.
Can essential amino acids be stored?
No
What is the all or none rule?
determines if all a.a are present when. protein is ready to be made then it can be made
-However if you don’t have one fo the a.a required to make the protein , it will not be created from your cells
What happens to the additional amino acids ?
- They are oxidised for energy or converted to carbohydrates or fats for energy storage.
- If there is insufficient deitary intake of calories, proteins can be used for ATP production
What are the dietary requirement for proteins?
- 8 per kg of body weight
- Supply of essential a.a which can also be converted into non essential amino acids by your body.
What is the requirement of minerals in our bodies?
- require small amount of 7 minerals
- and some trace amounts of 12 others
What are those minerals?
calcium phophorus potassium sulphur sodium- blood electrolytes chlorine- blood electrolytes magnesium
What are the trace amounts of minerals?
iron- haemoglobin
zinc- cell replication
copper - binds to enzymes
fluorine
How much does minerals make of body?
4% of total body mass
3% is calcium and phosphorus as bone salts
what is the purpose of the minerals ?
- Not fuel sources
- work with other nutrient to improve function e.g incorporating mineral calcium, phosphorous and magnesium into bone and teeth to make them stronger.
How are minerals found?
ionised in body fluids
-bound to phospholipids, hormones or proteins
Where foods are mineral found in?
- legumes
-veg
-milk
meats
What are vitamins?
organic compounds needed in minute amount for healthy growth and repair
What is the purpose of vitamins?
- Not energy source
-Essential in using lipids, proteins and carbs from our diet thought
-
What are the function of vitamins?
-as Co-Enzymes
What are co-enzymes as vitamins?
- they will bind to a protein complex and facilities the function of the protein for further celluar processes
- example - B vitamins are coenzymes in the process of glucose oxidation for energy tranfer to ATP.
How are most vitamins received?
ingested- except for vitamin D as it can be synthesised by the skin and small amounts of B and K vitamins which synthesised by intestinal bacteria and can be absorbed
- ingest beta carotene (provitamin) can be converted to vit A.
Where are vitamins found?>
in all food groups
What are the 2 types of vitamins?
water or fat soluble
What are the water soluble ones?
B vitamins and C- taken up with water from GI tract- the exception in vitamins b12 which binds intrinsic factor (a glycoprotein)
-Excess is excepted in urine 1 hr after ingested- (as excess can’t be stored)
What are the fat soluble vitamins?
- Can be stored
- Vitamins A,D,E,k- absorbed with lipids from GI tract- need lipids in diet to absorb these vitamins
- Except vit K (can’t be stored)
- Over consumption can be toxic.
What do the vitamins act as?
antioxidants
What do antioxidants do?
- Metabolism uses oxygens
- free radical are formed as byproduct
- they are reactive molecules due to the unpaired electron which have the ability to rip apart other molecules.- this can cause tissue damage.
-Vitamins A,C,E are good antioxidants , along with mineral selenium as they react with the free radical and neutralises them.
What else can act as antioxidants (eye)?
Lutein and zeaxanthin
-Accumulate and concentrate around fovea in your retina
How do you get these antioxidants in the eye?
taken through diet
so can form yellow spot in fovea to have protection .
what do macular pigment do?
absorb
