Digestion Flashcards
What are the 7 classes of nutrients required by the animal body?
carbohydrates
lipids
proteins
vitamins
minerals
ions
water
What is required for animals to use these nutrients?
digestion - both mechanical and chemical
How does food provide sustenance for life?
food provides the structural and functional building blocks for materials, energy and heat
What are the 2 processes involved in digestion?
assimilation
egestion
What is assimilation?
processes involved in nutrient acquisition, digestion, and absorption
What is egestion?
the excretion of undigested food
Where does assimilation occur?
in the GI tract
What 4 types of cells are in the GI tract?
secretory cells
absorptive cells
muscle cells
neurons
Are nutrients reduced or oxidized from food to generate energy?
oxidized
What determines the amount of energy needed from food for an animal?
the metabolic requirements of the animal
What affects metabolic rates?
body size
activity
growth rate
reproductive state
environmental stress
What is the caloric equivalent?
the energy content per gram of a specific macromolecule
What is the caloric equivalent of proteins and carbs?
4 kcal/g
What is the caloric equivalent of fats?
9 kcal/g
What are vitamins?
a class of nutrients composed of unrelated molecules with diverse functions
What do most vitamins function in?
catalysis as cofactors for enzymes
some are antioxidants
How are most vitamins categorized?
solubility - in water or fat
Which vitamins are fat-soluble?
A
D
E
K
Which vitamins are water-soluble?
B
C
How are vitamins acquired in the body?
in diet or bacteria in the GI tract
What are minerals?
a class of nutrients composed of metallic elements involved in physiology and structure
What are 5 minerals involved in physiology?
calcium
phosphorous
iron
copper
zinc
Why is calcium important in animal bodies?
involved in intracellular cell signalling
bone structure
muscle contraction
neurotransmission
What is phosphorous important for in animal bodies?
bone structure
ATP
phospholipids
How is iron involved in animal physiology?
it is the metal ion contained in hemoglobin (respiratory pigments)
How is copper involved in animal physiology?
contained in cytochrome c oxidase in oxidative phosphorylation = production of ATP
How is zinc involved in animal physiology?
zinc has a functional role in enzymes and transcription factors
Where are most minerals absorbed in the body?
along the GI tract by specific transporters
What is the function of digestive enzymes?
they convert macromolecules into forms that can be absorbed and processed by the body
What are 4 classes of digestive enzymes?
lipases
proteases
amylases
nucleases
what are lipases
enzymes that break down (lipids) triglycerides and phospholipids into fatty acids
What are proteases?
enzymes that break down proteins into smaller polypeptides
What are 3 types of proteases?
trypsin
chymotrypsin
carboxypeptidase
What do peptidases do?
enzymes that cleave amino acids in succession
What do amylases do?
enzymes that break down (carbohydrates) polysaccharides into oligosaccharides
what are 3 types of disaccharidases?
maltase
sucrase
lactase
What are nucleases?
enzymes that break down DNA into nucleotides
Where does most enzymatic digestion occur?
extracellularly in the lumen of the GI tract
What usually aids animal digestion?
symbiotic organisms (ex. bacteria, fungi, photosynthetic organisms)
What are the 3 types of symbionts in digestion?
enterosymbionts
exosymbionts
endosymbionts
What are enterosymbionts?
symbionts that live in the lumen of GI tract - usually in the cecum
Where are enterosymbionts usually located?
within the lumen of the cecum of the GI tract
What are exosymbionts? what’s an example?
symbionts that are outside the body
ex. leaf cutter ants that cut down leaves from trees for fungi to digest the leaves so that nutrients are available to the ants
What are endosymbionts?
symbionts that live in the interstitial spaces or within host cells
What are examples of endosymbionts?
zoochlorellae (green algae) in sponges, cnidarians, and molluscs that produce the carbon skeleton, glucose, and maltose
What are the main types of carbohydrates consumed by animals?
polysaccharides (ex. glycogen, starch, cellulose, chitin) and disaccharides (ex. sucrose, lactose, maltose)
What are the 4 polysaccharides?
glycogen
starch
cellulose
chitin
What are the 3 types of disaccharides?
sucrose
lactose
maltose
What are 3 types of monosaccharides?
glucose
fructose
galactose
What are the main types of carbohydrates that can be absorbed by animals?
monosaccharides (ex. glucose, fructose, galactose)
How are monosaccharides absorbed by animals?
absorbed by the epithelial cells in the intestine (enterocytes) via secondary active transport and facilitated diffusion
What are enterocytes?
epithelial cells in the intestine
What transportation is involved in absorption of monosaccharides?
secondary active transport
facilitated diffusion
What is glycogen?
the storage form of carbohydrates in mammalian muscle and liver cells
What is starch?
the storage form of carbohydrates in plants
What is cellulose?
a form of carbohydrate found in plant cell walls that cannot be digested by human enzymes
How do herbivores digest cellulose?
the enterosymbionts in their guts
what is chitin?
the carbohydrate form that exists in exoskeletons of arthropods and in plankton
What is maltose?
a disaccharide of 2x glucose monomers
found in malt in beer
What is lactose?
a disaccharide of glucose and galactose monomers
carbs found in milk
What is sucrose?
a disaccharide of glucose and fructose monomers
found in sweeteners
What are the two types of starch?
amylose and amylopectin
describe the structure of starch vs glycogen
starches are less branched than glycogen
all composed of glucose polymers
Describe the steps of carbohydrate digestion
polysaccharides (glycogen and starch) are broken down by salivary amylase in the mouth into glycogen, oligosaccharides
pancreatic amylases digest glycogen, oligosaccharides and starch in the small intestine into disaccharides
disaccharidases breakdown disaccharides into monosaccharides in the small intestine
Where does most of carbohydrate digestion occur?
in the small intestineW
What enzymes are involved carbohydrate breakdown? where?
salivary amylases in the mouth
pancreatic amylases in the small intestine break down polysaccharides into disaccharides
disaccharidases in the small intestine break down disaccharides into monosaccharides
T or F: glucose and amino acids can diffuse across plasma membranes
false
what are the specific protein transporters involved in transporting carbohydrate monomers across membranes?
GLUT-2 and GLUT-5
What absorbs monosaccharides?
enterocytes of the small intestine
What does GLUT-5 do?
imports fructose into cells
What is SGLT-1? what does it do?
Na+ glucose cotransporter 1
transports glucose and galactose into enterocytes
What does GLUT-2 do?
when high [glucose], GLUT-2 transports glucose, galactose and fructose
What is the apical membrane?
the membrane of an enterocyte that has microvilli and closest to the lumen
What is the basolateral membrane?
the membrane of an enterocyte that does not have microvilli and is closest to the interstitial fluid
Which membrane(s) of an enterocyte have microvilli?
only the apical membrane
Which enterocyte membrane interacts with the lumen of the small intestine?
apical
Which enterocyte membrane interacts with the interstitial fluid?
basolateral
How many amino acids are there?
20
What are amino acids used for?
they’re the building blocks of proteins
What is an essential amino acid?
the amino acids that cannot be produced by the body and must be obtained through diet
T or F: most amino acids are essential
false, only 9/20 are essential and need to be obtained from diet
What happens to an animal if essential amino acids are not acquired in amounts needed?
developmental defects and reduced growth
What is protein quality?
the amino acid profile of proteins obtained from the diet
Does animal or plant tissue provide higher protein quality?
animal tissue
Why are plant and animal based diets good?
animal tissues supply the AA requirements and when combined with plants, all AA requirements can be fulfilled
What breaks down proteins into large polypeptides?
gastric pepsin
Where does protein digestion begin?
aside from the mechanical and salivary break down in the mouth to move food down esophagus
in the stomach
Where is gastric pepsin?
in the stomach
What happens after proteins are digested into large polypeptides?
polypeptides move to the small intestine where they are broken down into dipeptides and further into AAs
What breaks down polypeptides in the small intestine? What does it break down into?
trypsin
chymotrypsin
carboxypeptidase
break down polypeptides into dipeptides
What breaks down dipeptides in the small intestine? into what?
dipeptidases break down dipeptides into amino acids in the small intestine
In what form(s) can proteins be absorbed in?
dipeptides, tripeptides, and AAs
What organ releases the 3 proteases that break down polypeptides in the small intestine?
the pancreas
What enzymes liberate free AAs, dipeptides, and tripeptides?
peptidases: aminopeptidase, dipeptidylaminopeptidase, tripeptidase
In the pancreatic duct, what form do the pancreatic proteases take when not digesting?
inactive
procarboxypeptidase
chymotrypsinogen
trypsinogen
Why are the pancreatic proteases inactive in the pancreatic duct?
to prevent digesting the pancreas
What happens when the inactive proteases are released by the pancreas?
- the pancreas secretes inactive trypsinogen into the small intestine and binds to membrane-bound enterokinase which cleaves trypsinogen into active trypsin
- active trypsin cleaves inactive chymotrypsinogen released by pancreas into active chymotrypsin
- chymotrypsin cleaves inactive procarboxypeptidase into active carboxypeptidase
Where are the pancreatic proteases activated?
in the duodenum of the small intestine
What activates trypsonigen?
it binds to membrane-bound enterokinase on the small intestine membrane which cleaves trypsonigen into active trypsin
What activates chymotrypsinogen?
trypsin cleaving it into chymotrypsin in the small intestine
What activates procarboxypeptidase?
chymotrypsin cleaves it into carboxypeptidase in the small intestine
What are the products of protein digestion?
peptides (di and tri) and amino acids
Where are peptides and amino acids absorbed?
the enterocytes of the small intestine
How are peptides and AAs absorbed into enterocytes? is it the same system for both?
both are transported across the apical membrane but the transport systems are different
What transporters move peptides across the apical membrane of enterocytes?
PEPT1 transport di and tripeptides with the support of a proton transporter
How are most amino acids transported across the apical membrane of enterocytes?
amino acid-Na+ cotransporters
What process can directly digest proteins without digestion into peptides and AAs?
some proteins can be absorbed by endocytosis (ex. antibodies)
What are simple lipids?
fatty acids
triacylglycerol
sterols (cholesterol)
What are compound lipids?
phospholipids
lipoproteins
What are saturated fatty acids?
fatty acids without C=C
the fatty acid is saturated with H+
What are unsaturated fatty acids?
fatty acids with C=C
can be mono or poly
Describe the trans configuration of an unsaturated fatty acid
the fatty acid will remain linear
the Cs in the double bond are on opposite sides
Describe the cis configuration of an unsaturated fatty acid
the Cs of the double bond are on the same side
this introduces a kink in the chain
What is the hydrophobic component of a fatty acid?
the hydrocarbon chain
What is the hydrophilic component of a fatty acid?
the carboxylic end
HO-C=O
T or F: animals can make almost all fatty acids from acetyl CoA
true
What material can animals make most fatty acids from?
acetyl CoA
Which fatty acids can animals not produce from acetyl CoA?
omega-3
omega-6
both are unsaturated fatty acids
How is omega 6 ingested?
as gamma-linoleic acid
What food stuff contains omega 6 FA?
plant seeds
poultry
eggs
nuts
What type of fatty acid is omega 6? omega 3?
they’re both unsaturated
How is omega-3 ingested?
as alpha-linolenic acid
What foodstuff is omega-3 FA found in?
cold water fish
Why is it called omega 3? or omega 6?
the number refers to the C number where the first double bond is from the omega start (opposite end to the carboxylic acid)
omega 6 - first double bond is located at C6
omega 3 - first double bond is at C3
How many carbons are in omega-6? how many double bonds?
18:2
How many carbons are in omega-3? how many double bonds?
18:3
What is the omega?
C1 when starting counting from the methyl end of the carbon chain/opposite of the carboxylic end
How is most body fat stored?
in the form of triacylglycerols (TAGs)
What breaks down FAs?
lipases
Describe the structure of a triacylglycerol
a glycerol backbone (3Cs) attached to 3 FA chains via an ester bond (-O-CO-FA)
How are triacylglycerols broken down?
from glycerol by lipases
Describe glycerol
H
|
H-C-OH
|
H-C-OH
|
H-C-OH
|
H
What binds glycerol with fatty acids to make TAGs?
ester bonds
What is an ester bond?
O
||
glycerol-O-C-FA
What type of lipid dominates biological membranes?
phospholipids
What are the 2 classes of phospholipids in animal cells?
phosphoglycerides
sphingolipids
Describe phosphoglyceride
a class of phospholipid in animal cell membranes made from diacylglycerol (glycerol + 2 FAs)and has a polar group on the third glycerol carbon (usually phosphate + choline)
Describe sphingolipids
a class of phospholipids in animal cell membranes containing a sphingosine backbone + 1 FA chain
usually has a polar group (phosphate + choline)
What breaks down phospholipids?
phospholipases
Are saturated fats more common in solid animal fats or liquid fats?
solid animal fats
Are unsaturated fats more common in solid animal fats or liquid fats?
liquid fats
the kinks make it harder to solidify
What breaks down sphingolipids?
sphingolipases
Is cholesterol hydrophobic or philic?
phobic
What is cholesterol a precursor to?
steroid hormones like glucacorticoids, mineralocorticoids and sex hormones
What makes digestion and absorption of lipids challenging?
lipids are hydrophobic
Where does digestion of lipids occur?
in the duodenum of the small intestine
Describe the steps of lipid digestion
in the lumen of the duodenum:
1.a lipase breaks down a fat globule into monoacylglycerides and FAs
- FAs, mono and glycerol are broken down by the bile secreted by the gall bladder into fat droplets (micelles)
- micelles of FAs, glycerol, and tri, mono, and cholesterol diffuse across cell membrane into an enterocyte
- FA + glycerol diffuse directly into the bloodstream
- tri, mono, and cholesterol are packaged into the smooth ER and Golgi and are then released into the lymphatic system and then into the circulatory system
What are micelles?
small droplets of fat produced when bile from the gall bladder breaks down lipids
What breaks down dietary fats? What do they break down into?
lipases break down dietary fats into fatty acids, glycerol and monoglycerides
What secretes lipases?
the pancreas
What type of cell do lipids diffuse into?
enterocytes of the small intestine
Once in the enterocyte, what happens to fatty acids and glycerol? why?
they diffuse directly into the blood vessels
they are short and medium chain lengths - easy to diffuse
Once in the enterocyte, what happens to longer chained fatty acids, monoglycerides, triglycerides and cholesterol?
they are packaged in protein coats (lipoproteins) in the smooth ER and Golgi and are then transported into the
lymphatic system and then into the circulatory system
lipoprotein lipase breaks down triglycerides to be used by tissues
What are chylomicrons?
the type of lipoprotein that forms the protein coat on the longer chain FAs, monoacylglycerides, triglycerides and cholesterol that enter the enterocyte
this occurs in the smooth ER and the Golgi
What happens to chylomicrons?
they are transported into the lymphatic system and then the circulatory system
What breaks down triglycerides once in the circulatory system?
lipoprotein lipases
Which lipids do not directly enter the circulatory system from the enterocyte?
longer chain fatty acids
monoacylglycerides
triglycerides
cholesterol
What direction does food flow through the GI tract of mammals (unidirectional, bidirectional)?
one way
Where does mechanical digestion occur in the GI tract of mammals?
mouth
pharynx
esophagus
What is the acidic compartment of the GI tract of mammals?
the stomach
Where does the major digestion and absorption of nutrients and water occur in the GI tract of mammals?
upper or small intestines
What occurs in the large intestines of mammals?
water absorption
Where is waste released from the mammalian digestive tract?
through the anus
Describe the regions of the GI tract of mammals from mouth onwards
mouth
esophagus
stomach
small intestine (duodenum, jejunum, ileum)
large intestine (cecum, colon, rectum)
anus
What are the regions of the small intestine?
duodenum
jejunum
ileum
What are the regions of the large intestine?
cecum
colon
rectum
What feature ensures unidirectional flow of food?
sphincters
What is the gut derived from?
the endoderm
What are the 3 major regions of the gut?
foregut
midgut
hindgut
What is included in the foregut?
esophagus
stomach
anterior part of duodenum
What organs form from the foregut during development?
the pancreas and liver
What is included in the midgut?
posterior end of the duodenum
jejunum
ileum
cecum
2/3 of the colon
What is included in the hindgut?
the last 1/3 of the colon
rectum
How do the liver, gall bladder, and pancreas interact with the small intestine?
the liver produces bile and secretes it into the gall bladder for storage
the gall bladder releases bile through the bile duct into the duodenum
the pancreas releases digestive enzymes through the pancreatic duct into the duodenum
How do the liver, gall bladder, and pancreas aid in digestion?
the liver produces and sends bile to the gall bladder
the gall bladder releases bile into the duodenum of the small intestine
the pancreas releases digestive enzymes into the duodenum of the small intestine
What major anatomical feature is involved in mammalian mechanical digestion?
teeth
What are the 4 types of teeth?
incisors
canines
premolars
molars
How can teeth be used to infer diet?
shape
incisors and canines are sharp and pointed for tearing and piercing flesh
premolars and molars are short and flat for grinding and chewing
What are the 3 layers of teeth?
enamel (outer)
dentin (mid)
pulp (blood vessels and nerves)
What aids teeth in the breakdown of food in the mouth to prepare for swallowing?
salivary glands
What are the 4 salivary glands in mammals?
orbital
sublingual
mandibular
parotid
What are salivary glands?
multicellular exocrine glands with ducts that open into the mouth to secrete saliva
What is saliva? what is its purpose?
produced by the exocrine salivary glands and released into the mouth to
lubricate and dissolve food
clean mouth - antimicrobial
contains enzymes = initiates digestion
What initiates digestion?
saliva
What controls saliva production?
nerve signals of the
PNS = stimulates
SNS = inhibits
How does saliva protect the GI tract?
it is antimicrobial = cleans the mouth
Where are most nutrients chemically broken down in mammals?
in the lumen of the GI tract
What absorbs nutrients in the GI tract?
enterocytes lining the small intestine
How is nutrient uptake improved?
by increasing surface area:
increased gut length
increased surface undulations (circular folds, villi, microvilli)
What are the 2 ways surface area of the GI tract can be increased?
increased gut length
increased surface undulations
What are 3 ways the surface undulations of the GI tract is increased?
circular folds in the lining
villi on the folds
microvilli on the enterocytes
How have ruminant mammals (ex. ungulates) evolved to digest complex plant materials like cellulose?
with the specialized compartments in their stomach
rumen
reticulum
omasum
abomasum
Where does the breakdown of cellulose occur in ruminants?
in the rumen compartment of their stomach
T or F; humans can break down cellulose
false, we don’t have specialized structures or symbiotic relationships to do that
What type of cells line the surface of the stomach?
columnar epithelial cells
What are the 5 specialized cells in the stomach?
tight junctions
mucous neck cells
parietal cells
chief cells
enteroendocrine cells
what is the purpose of the tight junctions in the stomach?
they prevent acid from leaking across the epithelium
what is the purpose of the mucous neck cells in the stomach?
they protect the stomach lining from the acidity by secreting mucus and bicarbonate
what is the purpose of the parietal cells in the stomach?
they create the acidic (low pH) environment of the stomach by secreting hydrochloric acid (HCl)
what is the purpose of the chief cells in the stomach?
they secrete pepsinogen (inactive) a digestive enzyme that when activated by low pH environment cleaves pepsin
what is the purpose of the enteroendocrine cells in the stomach?
they secrete hormones into the blood like gastrin
What muscle type lines the entire GI tract?
smooth muscle
What are the 4 main layers of the small intestine?
mucosa
submucosa (blood, lymphatic vessels, nerves)
circular smooth muscle
longitudinal smooth muscle
what 5 cell types make up the villi of the small intestine?
all mucosal cells
enterocytes
goblet cells
enteroendocrine cells
paneth cells
crypt of Lieberkuhn
What is the purpose of enterocytes of the villi?
they are the cells that absorb nutrients and are coated with microvilli
What is the purpose of goblet cells of the villi?
they protect food coming from the stomach by secreting mucus
What is the purpose of enteroendocrine cellsof the villi?
they secrete hormones
What is the purpose of paneth cells of the villi?
they secrete antimicrobial molecules called lysozyme
What is the purpose of the crypt of Lieberkuhn of the villi?
it secretes digestive enzymes
sucrase, maltase, lactase, peptidase
What exocrine cells of the pancreas secrete enzymes into the intestine?
acinar cells
What 5 types of enzymes do acinar cells of the pancreas secreted into the intestine?
proteases to break down proteins (secreted as proenzymes / inactive)
amylases to break down carbohydrates
lipases to break down fats (TAGs)
nucleases to break down nucleic acids
phospholipases to break down phospholipids
What is bile?
a solution of digestive chemicals and liver waste products that is produced in the liver and stored in the gall bladder
What are the 3 major constituents of bile? what are their functions?
phospholipids to help uptake lipids
bile salts to break down fats
cholesterol
How does bile enter the small intestine?
via a bile duct from the gall bladder into the duodenum
How does food move down the GI tract?
by smooth muscle contractions
What regulates the smooth muscle contractions of the GI tract?
nerves and hormones
What is the optimal speed of food along the GI tract?
a speed that is fast enough to minimize indigestible material but slow enough to allow for digestion and absorpiton
this depends on diet
What are the 2 layers of the smooth muscle cells in the gut?
longitudinal
circular
What do longitudinal smooth muscles cells do in the GI tract?
they control peristalsis (the wavelike rhythmic contractions)
What do circular smooth muscles cells do in the GI tract?
they help with peristalsis and control the diameter and segmentation of the GI tract
Is smooth muscle contraction in the GI tract myogenic or neurogenic?
both
What is the myenteric plexus?
the nerve network layer between the circular and longitudinal smooth muscle layers that is innervated by the SNS and PNS
Describe the steps involved in the control of gastric secretions when sight/taste/smell are the stimuli
stimuli: sight/taste/smell triggers activity of parasympathetic neurons to activate
a) G Cells
b) parietal cells
G cells produce Gastrin
Gastrin targets:
a) ECF cells
b) Chief cells
ECF releases histamine, both histamine
histamine and parasympathetic neurons directly activate parietal cells
parietal cells release acid
Chief cells activate pepsinogen
Describe the steps for control of gastric secretions when ingestion is the stimuli
chemo and mechanoreceptors sense the stimulus
activate
a) parasympathetic neurons
b) G cells
c) enteric nerves
the parasympathetic neurons and G cells follow the same pathway as described for taste/sight/smell
enteric nerves stimulate G cells which then release gastrin
gastrin targets ECF and Chief cells
ECF cells release histamine to target parietal cells which release acid
chief cells target pepsinogen
What neurons receive taste/sight/smell stimuli?
parasympathetic neurons
What neurons receive ingestion stimuli?
chemo and mechanoreceptors
What cells do the parasympathetic neurons target when sight/taste/smell stimuli is received or when chemo/mechanoreceptors send signals about ingestion?
G cells
Parietal cells
What cells do the chemo/mechanoreceptors target when there’s ingestion stimuli (not signals to PNS)?
enteric nerves
G cells
What do G cells release when stimulated?
gastrin
What cells do G cells target with gastrin?
ECF and chief cells
What do ECF cells release when stimulated?
histamine
What does histamine target?
parietal cells
What do chief cells target?
pepsinogen
What do parietal cells secrete?
acid
What are the 2 products of stimuli for sight/smell/taste and ingestion?
either acid or pepsinogen
What happens to acid in the control of intestinal secretion?
when acid is secreted it targets enteroendocrine cells
enteroendocrine cells release VIP or Secretin
VIP targets the pancreas and causes the release of bicarbonate (HCO3-)
Secretin targets the liver and causes the release of bile
When acid is produced, what 2 substances do the enteroendocrine cells produce?
VIP
Secretin
What organ does VIP target?
the pancreas
What does VIP stimulating the pancreas cause?
the release of bicarbonate in the intestine
What organ does secretin target?
the liver
What does stimulation of the liver by secretin cause?
the release of bile in the intestine
What are the steps following digestive products in the intestine regarding acidic gastric fluids?
enteroendocrine cells are stimulated to release CCK
CCK targets the
a) gall bladder to release bile
b) pancreas to release digestive enzymes (ex. amylase, protease, lipase)
What do enteroendocrine cells release in response to digestive products in the intestine?
CCK
What organs does CCK target?
gall bladder and pancreas
What does the stimulation of the gall bladder by CCK cause?
the secretion of bile into the intestine
What does the stimulation of the pancreas by CCK cause?
the secretion of digestive enzymes into the intestine
What is VIP?
Vasoactive Intestinal Peptide
What is CCK?
Cholecystokinin
What is body mass controlled by?
energy balance
food intake - food expenditure
What controls satiety and hunger?
the hypothalamus (CNS)
How does the hypothalamus control and regulate hunger, appetite, and satiety?
the CNS receives information from adipose tissues (fat) and from the gut on energy reserves
What 3 hormones control appetite?
leptin
ghrelin
peptide YY
CCK
What is leptin?
an appetite-suppressing hormone in adipose tissue
What is ghrelin?
an appetite-stimulating hormone released from gastric cells when the stomach is empty
What is peptide YY?
an appetite-reducing hormone released from enteroendocrine cells when colon is full
What hormones are released between meals (short term regulation of energy stores)?
ghrelin
PYY
CCK
vagus nerve is stimulated
What hormones are released during long term regulation of body energy stores?
leptin
tells the brain you’ve just eaten, you’re satiated, and can survive not eating until breakfast for ex.
Describe the set up of the mouse study and obesity, diabetes, body mass
mice with mutations for obesity and diabetes had their circulatory systems surgically connected to wild type mice or to another mouse with a condition (parabiosis)
What was the mutation that caused mice to be obese? diabetic?
the obese and diabetic mice lacked or had damage to the genes that encoded for the production of hormones that tell the hypothalamus they are satiated (ex. leptin)
what happened when the obese mouse was connected to the WT mouse? why?
the obese mouse lost weight
WT mouse remained same weight
the obese mouse was receiving signals from the circulatory system of the WT mouse for satiation and stopped feeding
what happened when the diabetic mouse was connected to the WT mouse? why?
the diabetic mouse stayed obese
the WT mouse lost weight
the diabetic mouse did not stop feeding as a result of the hormone production by the WT mouse - the diabetic mouse must have damage or lack the receptors for satiation hormones
the WT mouse overproduced satiation hormones to stop the diabetic mouse from eating but just prevented itself from eating cause diabetic had no receptors
what happened when the obese mouse was connected to the diabetic mouse? why?
the obese mouse lost weight
the diabetic mouse stayed the same weight
diabetic mouse must be able to produce the satiation hormones and circulate to the obese mouse with intact receptors
but the diabetic mouse must have damage to or lack the receptors for the satiation hormones
Which hormone was the obese mouse unable to produce?
leptin (satiating hormone)
Which receptor did the diabetic mouse lack?
leptin receptor
Why did the diabetic mouse not lose weight in any of the studies?
it was able to produce leptin (satiating) but was not able to receive it so it continued eating
Where are the receptors for hormones that control appetite?
in the hypothalamus
What secretes leptin? when? what is its main function?
white adipose tissues when lipid content is high (reached enough energy content)
to suppress appetite
What secretes ghrelin? when? what is its main function?
the stomach when it is empty
stimulates appetite
What secretes PYY? when? what is its main function?
the colon when it is full
suppresses appetite
What secretes CCK? when? what is its main function?
the duodenum when full
suppresses appetite
Which of the 4 appetite hormones suppress appetite?
leptin (white adipose tissue)
PYY (colon)
Which of the 4 appetite hormones stimulate appetite?
ghrelin (stomach)
CCK (duodenum)
What part of the hypothalamus has the receptors for appetite control hormones?
arcurate nucleus
What happens when the arcurate nucleus of the hypothalamus receives hormones from the gut or adipose tissues?
hypothalamic neurons release neurotransmitters to stimulate or inhibit appetite
What hypothalamic neurons stimulate appetite?
neuropeptide Y (NPY)
What hypothalamic neurons inhibit appetite?
pro-opiomelanocrotin (POMC)
How is the vagus nerve related to digestion?
the vagus nerve innervates the stomach muscles causing them to churn food for digestion and release digestive enzymes and hormones
T or F: gut microbiota is related to obesity
true, study suggests that there were different microbiota in obese vs. WT mice
What is the response to short term starvation (over night, between meals)?
in adipose tissues:
- Triglycerides broken down into FAs
- FAs converted into CO2 (used for energy)
FAs from adipose tissues can be transported to the liver or muscles
in the liver:
a) triglycerides are broken down into FAs
or FAs from adipose tissues
both are converted into CO2 (used for energy)
b) glycogen is broken down into glucose which is transported to the brain and byproduct of energy production releases CO2
Which organs are involved in the starvation responses?
adipose tissues
liver
muscles
brain
What stores of energy are used in response to SHORT term starvation?
energy stored in triglycerides (lipids) and in glycogen (carbohydrates)
What stores of energy are used in response to LONG term starvation?
triglycerides (lipids)
Amino acids
What happens in the adipose tissue during short term starvation?
energy stored in triglycerides is broken down into fatty acids
energy production releases CO2
fatty acids can be sent to liver or muscles
What happens in the liver during short term starvation?
energy stored in TGs broken down to FAs releases CO2 in energy production
energy stored in glycogen is broken down into glucose (releases CO2)
glucose is transported to the brain
What happens in the muscle during short term starvation?
TGs broken down to FAs - release CO2
glycogen broken down directly to CO2 (no glucose sent to brain)
What happens in the brain during short term starvation?
glucose is received from the liver and metabolized into CO2
What happens in the adipose tissue during long term starvation?
TGs broken down into FAs and metabolized into CO2 or sent to liver
What happens in the liver during long term starvation?
TG broken down into FAs or FAs received from adipose tissues metabolized into CO2 or ketone bodies
Amino acids in the liver or sent from muscles broken down into CO2 and ketone bodies
ketones sent to brain
What happens in the muscle during long term starvation?
amino acids in muscles are either sent to liver to be metabolized into ketones OR
are metabolized directly in the muscle to CO2
What happens in the brain during long term starvation?
ketones from the liver are metabolized into CO2
What is the energy source for the brain during short term starvation vs long term?
short term = glucose
long term = ketones
What produces and sends the energy source to the brain during short term vs. long term starvation?
short term: liver produces glucose and sends to brain
long term: liver produces ketones (from AAs, TGs -> FAs) and sends to brain
What energy stores does the liver use to produce the energy sent to the brain during short vs long term starvation?
short: liver uses glycogen stored IN the liver to produce glucose to send to brain
long: liver uses AAs stored in the liver or sent from muscles to produce ketones to send to brain
or liver uses TGs stored in liver or FAs sent from adipose tissues to produce ketones
What happens when the body enters long term starvation?
the glycogen stores in the liver and muscles have been used up
the liver now has to use amino acids and TGs to produce ketones to send to the brain for energy
basically a reorganization of metabolism
How does the body reorganize metabolism for survival during long term starvation?
glucose stores are conserved to protect glucose-dependent tissues (nerves)
muscles start to use lipid metabolism
after lipid and glucose stores are depleted
liver converts AAs, FAs, lipids into ketones
muscular atrophy and structural degradation begins to occur as protein stores are depleted
