phase 1 week 9 Flashcards
Describe what is recommended from the “eat well” plate
plenty of fruits and vegetables
plenty of starchy foods such as bread, rice, potatoes and pasta
some meat, fish, eggs, beans and other non-dairy sources of protein
some milk and dairy foods
just a small amount of foods or drinks that are high in fat or sugar
What is metabolism?
the sum of all chemical reactions in which energy is made available and consumed in the body
Give some uses of energy in the body
Contraction of muscle and hence for all movement
accumulation of ions and other molecules against concentration gradients
biosynthesis and hence for the building of tissues
waste disposal and hence for getting rid of the end products of bodily function
generation of heat and hence maintenance of body temperature
Describe ATP
It is often stated that ATP is the energy currency of living organisms, since hydrolysis to give ADP and Pi liberates large amounts of energy
In metabolism, ATP is continually made and broken down
How is glucose converted into Acetyl CoA?
glycolysis
How are fatty acids converted into Acetyl CoA?
beta oxidation
How are amino acids converted into Acetyl CoA?
transamination, oxidative deamination
What are the major common pathways that are the main producers of ATP?
TCA (Krebs) cycle
oxidative phosphorylation
Describe glycolysis
glucose is turned into 2 pyruvate
occurs in cytosol
ATP investment and ATP generation stages
Describe what happens to pyruvate in anaerobic conditions
pyruvate is converted into lactate, this regenerates NAD+ to keep glycolysis going
overall glucose + 2ADP +2Pi > 2lactate + 2 ATP
Describe what happens to pyruvate in aerobic conditions
pyruvate is transported to the mitochondria and converted to acetyl CoA by the action of pyruvate dehydrogenase
NADH produced
Describe the breakdown of fatty acids
released from triglyceride stores in adipose tissue via the action of lipase enzymes
transported in the blood as a complex with albumin and are taken up by cells for oxidation
They are then attached to CoA, driven by ATP and catalysed by acyl CoA synthase
Acyl groups are joined to carntitine which allows them to translocate into the mitochondria
In each reaction of the cycle the fatty acid is shortened by 2 carbon atoms, with NADH and FADH2 and acetyl CoA being produced.
Acetyl CoA enters the TCA cycle and NADH and FADH2 enter the election transport chain
What is the ATP yield from the TCA cycle and electron transport chain?
In the TCA cycle 1 GTP, 3NADH and 1FADH2 are produced
NADH yields 2.5 ATP and FADH2 yields 1.5 ATP
Total yield per acetyl CoA is 10ATP
How is glycolysis regulated?
high levels of citrate and ATP inhibit phosphofructokinase which is an important enzyme in glycolysis
Describe protein metabolism
9 amino acids are essential and must be obtained from the diet
transamination - 1 amino acid is converted to another
oxidative deamination - the amino acid of an amino acid is lost as ammonia, which can enter the urea cycle
Describe energy requirements
Basal energy expenditure (BEE) / basal metabolic rate (BMR) represent the energy required to maintain basic functions when a person is lying down, relaxed, in a normal ambient temperature
What is BMI?
Body mass index
weight/height squared
What are the ranges for BMI?
30 obese
Describe anorexia
self induced weight loss
low body weight
body image distortion
endocrine disorder
Describe the psychological presentations of anorexia
overvalued idea re weight
dysphoria
abnormal behaviours - food fads, odd eating, drink in excess or too little, secretiveness, avoidance of social eating
Describe some compensatory behaviours in anorexia
excess exercise to burn energy
use laxatives, induce vomiting
Describe some of the personality traits involved in anorexia
premorbid perfectionism introversion poor peer relationships low self esteem "perfect" child becomes angry, deceptive, manipulative, withdrawn
Describe the treatment for anorexia
inpatient / outpatient psychological intervention physical monitoring diet plan SSRIs when clear obsessional component
Describe bulimia
cravings binge eating counteractive behaviour body image symptoms physical effects to purging also malnourished can be overweight
Describe the management of bulimia
outpatient based self help resources CBT - 16-20 sessions high dose SSRI periodic biochemistry monitoring
Describe the 2 groups of organs in the alimentary system
digestive tract
accessory organs - salivary glands, gallbladder, liver, pancreas
Describe the structure of the GI system
mucosa
submucosa
muscularis propria
adventitia
What is in the mucosa?
epithelium, lamina propria, mucularis mucosae
What is in the muscularis mucosa?
inner circular, outer longitudinal
Describe the pharynx
muscular tube
conducts air
muscles direct food to oesophagus
3 parts - nasopharynx, oropharynx and larynnopharynx
Describe the oesophagus
muscular tube - pharynx to stomach lies in neck, thorax and abdomen posterior to the trachea and heart pierces diaphragm sphincters
Describe the stomach
found ion the left hypochondriac / epigastric region
endocrine cells produce gastrin
parietal cells produce HCl and intrinsic factor
chief cells produce pepsinogen
Describe the small intestine
Comprises duodenum, jejunum and ileum
primary site for digestion and absorption
describe the deodenum
receives chyme short length contains Brunner's glands - alkaline secretion receives common bile duct (sphincter of Oddi) major duodenal papilla bile pancreatic "juice" Ends a deodenojejunal junction
deserve the pancreas
Dual purpose
exocrine gland - 99%
endocrine gland - islets of Langerhans
What does the exocrine portion of the pancreas produce?
many digestive enzyme
bicarbonate ions
What does the endocrine portion of the pancreas produce?
hormones - insulin, glucagon, somatostatin
Describe the liver
metabolism - storage of glycogen and release of glucose protein synthesis inactivation of hormones, drugs excretion of waste produces bile
Describe the large intestine
Caecum - appendix
Colon - ascending, transverse, descending, sigmoid
rectum
What is the blood supply to the GI tract?
3 vessels all arising from the abdominal aorta
coeliac trunk
superior mesenteric artery
inferior mesenteric artery
Describe the divisions of the abdomen
Right and left hypochondriac, epigastric
right and left lumbar, umbilical
Right and left iliac, suprapubic
What nervous system influences digestive processes?
enteric
What does the myenteric plexus do?
GI motility
What does the submucous plexus do?
sensing environment in the lumen
regulating GI blood flow
controlling epithelial cell function
Describe the mouth, pharynx and salivary glands
start digestion by physically chewing food and breaking it down with saliva
What are the functions of saliva?
Maintaining healthy oral tissues - contain thiocyanate ions, proteolytic enzymes and antibodies
starts digestion of carbohydrates
contributes to digestion of fats
its absence provides the urge to drink
provides mucous
keeps mouth moist for speech, oral comfort, chewing and swallowing
Describe salivary amylase
produced by acini glands
pH optimum 6.9
activity continues for 15-30 minutes in mouth and stomach
breaks down alpha 1,4 glucosidic bonds
starch, glycogen > maltose, maltotriose and alpha limit dextrins
Describe the functions of the stomach
storage of food
churn and mix with gastric secretions
acid and pepsin secretions
slow emptying of digestive contents into small intestine
What are the gastric secretions?
mucous secreting cells
acid secretion
chief cells produce pepsinogen
intrinsic factor
Why is mucous important in the stomach?
protects stomach from damage by gastric acids
What do acid secretions in the stomach do?
breakdown of connective tissue, activates pepsin, solubilises calcium and iron, acts as a barrier to microbes
What does pepsinogen do?
converted into pepsin, digests proteins
What is intrinsic factor important for?
absorption of vitamin B12
Describe pancreatic juice
made of aqueous and enzymatic component alkali - contains bicarbonate buffers acidic secretion of stomach protects mucosa enters small intestine provides right pH for proteolytic enzymes
What are the two types of pancreatic secretions?
proteolytic and non-proteolytic
Give examples of proteolytic enzymes
trypsin yhromotrypsin carboxypeptidase elastase phospholipase secreted by acinar cells as zymogens
Give examples of non-proteolytic enzymes
amylase lipase ribonuclease deoxyribonuclease released in active form
Describe pancreatic amylase
endoamylase, similar to salivary
digests alpha 1-4 glucose bonds
digests starch and glycogen to maltose maltotriose and dextrins
Describe pancreatic lipase
acts of water insoluble triglycerides
releases fatty acids and 2-monoglycerides
Describe liver bile
synthesised in the hepatocyte
stored in the gall bladder
released into duodenum after meal
What is bile composed of?
bile acids phospholipid cholesterol bilirubin electrolytes detoxified drugs
What are the functions of bile?
emulsification of fat particles
helps in absorption of fats by forming complexes called micelles
What is the function of the duodenum?
mixing secretions from pancreas, liver and its own with food, neutralising the acid, further digestion, absorption
What is the function of the jejunum?
completing breakdown, nutrient absorption
What is the function of the ileum?
nutrient absorption
What is chylomicron formation?
if a fatty acid has more than 12 carbons, then triglyceride reformed in a cell coated protein, phospholipid and cholesterol enclosed in vesicles
What do the absorptive cells of the small intestine release?
digestive enzymes
What do goblet cells in the small intestine produce?
mucous
What do granular cells in the small intestine produce?
enzymes
what do endocrine cells in the small intestine produce?
hormones
Give examples of brush border enzymes
peptidases
lactase
lucrase
maltase
Describe protein digesition
starts in the stomach - pepsin
continues in small intestine - trypsin, chymotrypsin, carboxypeptidase
continues at brush border amino peptidases
amino acids and peptides absorbed by active transport vis 7 sodium linked carriers
Describe the digestion of fats
pancreatic lipase, collapse
mixed with emulsified fat and bile acid
triglyceride > 2-monoglyceride and fatty acids
Describe fatty acid absorption
at brush border lower pH at mucosa reduces solubility of lipid in micelles
fatty acids are absorbed by micelles
