week 2 Flashcards
module 1 topic 3 - digestion, absorption and metabolism
positive energy intake =
energy in is greater than energy out = increase weight
negative energy balance =
Energy out is greater than energy in = decrease weight
what are the digestive processes converting macromolecules to monomers
- carbohydrate to monosaccharides (glucose, fructose, galactose)
- lipids to fatty acids
- protein to amino acids
- micronutrients are freed from macromolecules
where does most absorption take place?
small intestine
Why is adequate digestion and absorption processes key for optimal nutrition?
food constituents do not contribute to energy for health until they are “inside” the body
steps of ATP production from glucose
- anaerobic respiration
one glucose molecule (glycolysis, to from pyruvate) has a net yield of 2 ATP - Aerobic respiration
one glucose molecule has a net yield of 32 ATP
describe post - prandial (fed state) energy metabolism
about anabolism
promotes up-regulation of relevant enzymes for:
- glycogen synthesis (glycogenesis)
- fat synthesis (lipogenesis)
- protein synthesis (gene expression -> mRNA translation into functional protein)
- Urea synthesis (from deamination of amino acid carbon skeleton use
inulin is the hormone primarily involved in the post-prandial state
mouth and salivary glands function (digestion)
- Prepare food for swallowing: chewing, moistening with saliva
- Detect taste molecules
- Start digestion of starch with amylase enzyme
- Start digestion of fat with lingual lipase
oesophagus function (digestion)
Moves food to stomach by peristaltic waves initiated by swallowing
The lower oesophageal sphincter prevents back flow (reflux) of stomach contents into the oesophagus
stomach function (digestion)
- Secretes gastric juice containing acid, enzymes, and hormones
- Mixes food with gastric juice, converting it to liquid chyme
- Starts digestion of protein and fat
- Kills microorganisms with acid
- Secretes intrinsic factor, a protein required for vitamin B12 absorption
- The pyloric sphincter controls the flow of stomach contents (chyme) into the small intestine
pancreas function (digestion)
Secretes pancreatic juice containing digestive enzymes and bicarbonate into the small intestine
The hepatopancreatic sphincter controls the flow of bile and pancreatic juice from the common bile duct and pancreatic duct into the small intestine.
liver function (digestion)
produces bile to aid fat digestion and absorption
gallbladder function (digestion)
Stores and concentrates bile and releases it to the small intestine
The hepatopancreatic sphincter controls the flow of bile and pancreatic juice from the common bile duct and pancreatic duct into the small intestine
small intestine function (digestion)
- Mixes chyme with bile and pancreatic juice to complete digestion
- Secretes hormones that help regulate digestive processes
- Secretes digestive enzymes
- Absorbs nutrients and other compounds in foods
- Transports remaining residue to large intestine
- The ileocecal valve prevents the contents of the large intestine from reentering the small intestine
large intestine function (digestion)
Absorbs water and electrolytes (sodium and potassium)
Forms and stores faeces
Houses most of the gut microbiota
what are the digestive secretions and their functions
saliva - Dissolves taste-forming compounds; contains compounds that aid swallowing, digestion, and protection of teeth
HCl - Promotes digestion of protein, destroys microorganisms, increases solubility of minerals
mucus - Protects GI tract cells, lubricate digesting food
Bicarbonate - Neutralises stomach acid when it reaches the small intestine
Bile - Aids in fat digestion (emulsifies fat)
enzymes - Break down carbohydrates, fats, and protein into form small enough for absorption
hormones - Regulate food intake, digestion and absorption
what are the gastrointestinal hormones?
Ghrelin, gastrin, CCK, secretin, motilin, GIP, Peptide YY
ghrelin function
Increases appetite and food intake. Released by the stomach
gastrin function
Triggers the stomach to release HCl and pepsinogen; stimulates gastric and intestinal motility. Released by the stomach and duodenum in response to food reaching the stomach.
CCK function
Stimulates release of pancreatic enzymes and bile from the gall bladder. Released by the small intestine in response to dietary fat in chyme
secretin function
Stimulates release of pancreatic bicarbonate. Released by the small intestine in response to acidic chyme.
motillin function
Regulates motility of the gastrointestinal tract. Released by the small intestine in response to gastric distension and dietary fat.
GIP function
Inhibits gastric acid secretion, stimulates insulin release. Released by the small intestine in response to glucose, amino acids and fat.
peptide YY function
Inhibits gastric and pancreatic secretions. Released by the ileum and large intestine in response to fat in the large intestine.
what are the 4 types of absorption
- passive
- moves down the concentration gradient
- substrate concentration dependant - facilitated
- requires a carrier protein; saturable
- moves down the concentration gradient - active
- requires energy (ATP)+ Na+
- can transport against the concentration gradient - endocytosis
- cell wall engulfs a substance by surrounding it with the cell membrane
define glycogenolysis
the breakdown of glycogen to glucose
define glycogenesis
the synthesis of glycogen from glucose
define glycolysis
the synthesis of glycogen to pyruvate
define gluconeogenesis
the synthesis of glucose from non-glucose sources
define lipolysis
the breakdown of triglycerides to glycerol and fatty acids
define esterification
the synthesis of triglycerides from fatty acids and glycerol
define beta-oxidation
the oxidation of fatty acids to acetyl-CoA
define lipogenesis
the synthesis of fatty acids from acetyl-CoA
define ketogenesis
the synthesis of ketone bodies from acetyl-CoA
define glucogenic amino acid oxidation
the oxidation of glucogenic amino acids to pyruvate
define non-glucogenic amino acid oxidation
the oxidation of ketogenic amino acids to acetyl-CoA
define protein catabolism
the breakdown of protein to amino acids
define protein synthesis
the synthesis of proteins from amino acids
in the first few hours of a fast, what is the primary fuel for the body
glycogen stored in the liver
