Unit 4 Flashcards
Digestion
food into nutrients Challenges include - tasks of the mouth - diaphragm - steady movement - lubrication of food - digestive enzyme functions - management of waste
GI tract
begins in mouth
- long flexible and muscular
- ends in anus
- stomach juices rlly start digestion process
- known as chyme after stomach
- small intestine, duodenum, receives chyme from stomach
- then jejunum then to ileum which connects to large intestine
- absorption of final bile and others
- rectum muscles relax
Muscle
2 layers of muscle in digestive tract: longitudinal and diagonal
- stomach has 3 + circular
peristalsis and segmentation
- chyme secreted out of stomach into duodenum
- circular muscle tighten tube constricts, chyme pushed forward down long intestine
Sphincter Contracts
- upper esophageal sphincter (top of esophagus) opens bc of swallowing.
- lower sphincter prevents reflux of stomach contents
- bottom of stomach holds chyme in for it to be mixed with gastric juices and liquified which prevents intestines from backing up.
- ileocolic sphincter is the end of the intestine which allows for emptying into large intestine
secretion of digestion
- salivary amylase
- gastric juices and pancreatic amylase + trypsinogen
- enzymes allow for breakdown of bonds of macros
mouth
saliva (salivary amylase) not enough time in mouth to break anything down
stomach: gastric juices
enzymes to breakdown proteins - zymogen
- activated by another substance when it gets to location
stomach: gastric juices
enzymes to breakdown proteins - zymogen
- activated by another substance when it gets to location
stomach: parietal cells
parietal cells make gastric juices which denatures proteins
- chief cells release pepsinogen which helps with protein digestion
stomach: pepsinogen
turns to pepsin by gastric juice
stomach: pepsin
pepsin breaks down proteins
stomach: fovlear cells
secrete mucus and protect the stomach lining from acid
Pancreas: pancreatic juice
dueodenum
- contains lipase, amylase and trypsinogen, chymotrypsinogen, responsible for breaking down fluid
Pancreas: intestinal juice
enterpeptidase: intestinal cells -> typsinogen -> trypsin
bicarb: neutralizes stomach acid bc small int cant handle acid
sucrase, maltase and lactase: carb breakdown
Peptidase-> enzyme for protein digestion
lipase -> fat digestion
Liver
CCK secretes in response to chyme -> trigger to gallbladder & liver to release bile to allow fats to come into solution so fats can be broken down
- bile released into liver
carb digestion
begins in mouth with salivary amylase
- when enters stomach salivary amylase doesn’t function
- majority of digestion in intestines is due to pancreatic amylase
- 1-4 hrs after meal all sugars have been digested, only fibre left
- fibre becomes stool
lipid digestion
fats difficult to digest bc hydrophobic and enzymes are hydrophilic
- bile allowed fat into water substance to be broken down
- lingual lipase - hydrolyse fats
- CCK release into small intestine -> gall bladder relesae bile which brings fats to be broken down (malsifyer)
Digestion of proteins
HCL denatures proteins
- pepsin breaks to small polypeptides
absorption of nutrients
the body begins to absorb nutrients 3-4 hrs after eating
- most absorption takes place in small intestine
- requires a continuous amount of blood supply
- nutrients -> bloodstream -> liver -> other body parts
intestinal absorbing cells
- folds in intestine called villi, places that come off are microvilli - maximize absorption of small intestine
- contain enzymes at the end of digestion (monosac)
- membranes need to be transported across membrane
- fats absorbed into lymphatic system not bloodstream
3 ways of absorbing nutrients: 1
simple diffusion
- given compound on inside of cell, move across membrane with no help
- water and small lipids
3 ways of absorbing nutrients: 2
Facilitated diffusion
- water-soluble vitamins
- needs transport protein
3 ways of absorbing nutrients: 3
Active transport
- glucose and AA’s
- carrier proteins
- requires energy
hepatic portal circulation
heart and lungs: blood leaves RV and goes to lungs via pulmonary artery
- blood from digestive tract goes to liver first via hepatic portal vein
- liver detoxifies blood, keeps body healthy
- blood leaves liver and goes to heart via hepatic vein
Carbohydrate Absorption and Fate
- carbs can be absorbed in mouth (and go directly to blood stream) but majority absorbed in small intestine
- monosac absorbed from GI tract go to hepatic portal circulation to liver
- glucose and fructose turn into glucose
- liver gives glucose supply to others, muscle stores it
- glucose stored as glycogen
- when body needs carbs it breaks glycogen down
GLUT-1
normal glucose intake into muscles
GLUT-4
normally in muscle
- comes to muscle membrane when desperately needed
Lipid absorption
- monoglycerides & long chain fatty acids
- bile forms micelles & brings lipids into digestive juices so fatty acids release, forms lipids, droplets known as micelles
- micelle gets absorbed, monogly formed back into trigly and packaged into chlyomicrons to enter lymphatic system and transported into bloodstream @ thoracic duct
- drops off fats at the heart
Micelle
monoglyceride + long chain fatty acids + bile = micelle
- micelle diffuses across enterocyte membrane & repackage triglycerides
Lymphatic system
- 1-way route up to thoracic duct, route for fluid from tissue spaces to enter into the blood.
- no pump
- lymph circulates cells & collects into tiny vesicles
- collects into thoracic duct, enters bloodstream via subclavian vein
Lipid Transport
Lipoproteins - transport vehicles for fat called lipoproteins
Chylomicrons
large, least dense high triglyceride
- fat absorb
VLDL
very-low density lipoprotein
- good amount of triglyceride
- little bit of protein
LDL
low-density lipoprotein
- biggest cholesterol containing
- bad cholesterol
HDL
high-density lipoprotein
- small and most dense
- cholesterol made of protein
HDL pt 2
made by liver
- removed cholesterol from the cells and back to the liver for recycling and disposal
- anti-imflammatory properties
Factors that lower LDL and raise HDL
- weight control
- monounsat fat
- phytochemicals
- soluble dairy fibres
Pathway through liver: Step 1
- intestines: fat absorbed in chylomichrons and released into bloodstream at subclavian vein and circulate body
Pathway through liver: step 2
- different tissues try to take triglycerides, but as we remove triglycerides from chylomicrons they become chylomicron remnant and go to liver to be removed from blood
pathway through liver: step 3
liver takes that to form VLDL.
- they get released into blood and deliver lipids to body cells.
- triglycerides get removed and we get LDL
- LDL continues to circulate or go back to liver
- liver also synthesizes HDL, released into circulation and collects LDL
Lipoprotein and fat fate
- enzyme-activated by insulin
- hydrolyzes triglycerides from lipoproteins to glycerol & fatty acids
- FFA and glycerol enter cells, reassembled
- located on an endothelial lining the capillaries
- capillaries around muscle, adipose and heart
Protein absorption and fate
AA’s transported into intestinal cells
- specific carriers for AA’s and small peptides into erythrocytes
- Once AA’s are in enterocyte
- used for energy
- synthesis of other proteins - unused AA are sent to liver via bloodstream and then to other tissues to form new proteins
- deamination produces ammonia and urea
excess protein
- stored as fat
- converted to non-essential amino acids
Final Stage
- vitamin and mineral absoption
- undigested residues
- continue through GI tract
- exercise the GI muscles
- retain water
Large intestine
fibre fermentation by bacteria
- recyclable materials (water,salt)
Liver
- veins expand the entire GI tract, culminate at hepatic portal vein
- deliver to liver
- veins branch out again, to different areas in liver
- hepatic vein leaves liver and goes back to heart
- liver first to receive water-soluble nutrient to detoxify
Hepatic portal circulation
liver is first past clearance
- blood travels from digestive tract via hepatic portal vein
Liver function
- produces bile
- detoxifies substances
- stores nutrients
- produces hormones
- produces clotting factors - close cuts
- produces transferrin
- produces glucose and ketone bodies, allow body to get nutrients
- does not produce bicarb
Site of metabolic reactions: overview
energy metabolism is all ways body uses energy from food
- all cells in body, varies by cells type
Site of metabolic reactions: liver
- carb conversion to glucose, glycogen storage, glycogen breakdown into glucose
- can use glucose in liver
- make glucose, convert excess glucose to fat
Site of metabolic reactions: lipids
- involved in lipid breakdown, package extra into lipoproteins
- breaks down fatty acids for energy when needed
- packages extra fatty acids for energy when needed
- manufactors bile to send to the gallbladder for use in fat digestion
- makes ketone bodies when necessary
Site of metabolic reactions: proteins
- manufactures non EAA’s that are in short supply
- removed AA from circulation that are excess and converts them to other AA’s or deaminates them and converts them to glucose of fatty acids
- removes ammonia and turns it to urea
- makes other nitrogen-containing compounds the body needs
- makes many transports and blood proteins
Site of metabolic reactions: other
- detoxifies alcohol, drugs, poisons and prepared waste products for excretion
- helps dismantle old red blood cells and captures the iron for recycling
- stores most vitamins and minerals
- converts Vit D into intermediate metabolic form
storage form of carbs and fat
best: glycogen in liver and skeletal muscles
- after 90 mins exercise, carbs run out
- fat store: adipose tissue, liver
Roles of macronutrients
carbs and fat: energy Proteins: - growth/maitenence of muscle, skin, bone - hormones - enzymes - fluid balance - acid-base balance - transporter - antibodies - energy
Breaking down nutrients for energy
different paths lead to
- pyruvate
- 3C structure
- used to make glucose - Acetyl CoA
- 2C structure
- cannot make glucose - Final energy pathway
- TCA cycle
- electron transport chai
Acetyl CoA options
slide
Fed-post prandial
Carbs -> glucose -> liver (muscle glycogen) -> stored as fat -> fatty acid -> fat store -> store for energy use
Proteins -> AA’s -> produce body proteins -> some lost in urine -> excess stored as body fat
Post - Absorptive State
body draws on stores glucose used for brain, nervous system & red blood cells, then other cells
Fasting beyond glycogen depletion
- no carbs for brain
- body breaks down body protein -> AA’s -> glucose -> energy
- some AA’s break down into ketones, some used for energy
- fats absorbed into lymphatic not bloodstream
- skeletal muscle greatest storage for carbs in body
Zymogen
inactive form of protein
gastic juice
start the denaturing of proteins
- comes from parietal cells
- made of HCL acid
chief cells
release pepsinogen
- zymogen
- function: help w protein digestion when cleaved to pepsin (by gastric juice)
Pyloric Sphycter
bottom of stomach
- allows chyme to mix with gastric juices
