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Lecture 2b- 11 January 2017
Lecture based largely on chapter 1 of
Advanced Nutrition and Human Metabolism
by Gropper et al -5th edition-on 2 hour reserve in
library
plus
Chapter 7 of Understanding Normal and Clinical
Nutrition-10th edition
Lecture 2ab- 9,11 January 2017
Main components of this lecture are:
a) overview of metabolism
b) the cell and how it works in metabolism
c) digestion and how it contributes to
metabolism
Outline of lecture 2ab
a) Overview of Metabolism
-definition
-catabolism
-anabolism
-metabolic regulation
- why is regulation necessary?
Metabolism cannot take place without the cell
b) The cell
-required as a location to house some metabolism
and to produce components for metabolism no
matter where such metabolism occurs
-specific aspects of metabolism occur at specific
points in the cell
-must know where metabolism occurs to
understand what is happening and why
The cell
- cell components
-plasma membrane
-cytoplasmic matrix
-mitochondrion
-nucleus
-endoplasmic reticulum
-golgi apparatus
-lysosomes and peroxisomes
The cell
-cellular proteins
-receptors and intracellular signalling
-transport proteins
-catalytic proteins
The cell
-apoptosis
-programmed cell death
-cellular enzymes that take the cell offlineimplications for disease
c) digestion and how it contributes to metabolism
-cells are essential for digestion
-overview of the structure of the digestive
tract
-structures of upper gastrointestinal tract
-structures of lower gastrointestinal tract
and accessory organs
-coordination and regulation of digestive processes
-regulatory peptides
-neural regulation
MORE DETAILED COMMENTS
-the process of digestion-secretions and enzymes
required for nutrient digestion
-oral cavity
-esophagus
-stomach
-small intestine
-colon or large intestine
c) Digestion and how it contributes to
metabolism
-cells are essential for digestionimpossible to have and regulate
digestion and therefore all other
metabolic processes without cells-note the use of cells-plural-why?
Overview of the structure of the digestive tract
-structures of upper gastrointestinal tract
-oral cavity- mouth and pharynx
-esophagus
-stomach
Overview of the structure of the digestive tract
-structures of lower gastrointestinal (gi) tract
and accessory organs
lower gi tract
-small intestine
-large intestine
accessory organs
-liver
-pancreas
-gall bladder
Coordination and regulation of digestive processes
-regulatory peptides
-gastrin-stimulates release of HCl
-cholecystokinin
-stimulates release of pancreatic juices
and enzymes
-stimulates bile release from gall bladder
Coordination and regulation of digestive processes
-regulatory peptides
-secretin-stimulates release of pancreatic
juices
-inhibits gut motility-why is this
important in conjunction with
stimulation of release of
pancreatic juices
Coordination and regulation of digestive processes
-regulatory peptides
-gastric inhibitory polypeptide
-inhibits gastric secretions and motility
-somatostatin
-inhibits release of gastrin, gastric
inhibitory peptide, secretin and
vasoactive intestinal peptide
Coordination and regulation of digestive processes
-regulatory peptides
-motilin
-causes contraction of smooth muscle in
intestinal wall
-vasoactive intestinal peptide
-stimulates intestinal secretions
-relaxes most gi sphincters
-inhibits gastric acid secretion
-stimulates pancreatic bicarbonate
secretion into the small intestine
Coordination and regulation of digestive processes
-regulatory peptides
-gastrin releasing peptide
-stimulates release of HCl, gastrin
and CCK
-neurotensin
-may mediate gastric emptying,
intestinal motility and gastric acid
secretion after fat ingestion
Coordination and regulation of digestive processes
-regulatory peptides
-substance P-increases blood flow to gi
tract, inhibits acid secretion,
inhibits small intestine motility
Coordination and regulation of digestive processes
-neural regulation
enteric nervous system-nervous
system of gastrointestinal tract
Coordination and regulation of digestive processes
-neural regulation
What is a plexus?
-myenteric plexus
controls peristaltic activity and/or
gastrointestinal motility
-submucosal plexus
controls mainly gastrointestinal
secretions and local blood flow
Coordination and regulation of digestive processes
-neural and hormonal regulation
why have both?
The process of digestion-secretions and enzymes
required for nutrient digestion
-oral cavity
-teeth-function in digestion
-saliva
-alpha amylase
-starch
-linguinal lipase
-triglycerides
-mucins
-lubricate food
The process of digestion-secretions and enzymes
required for nutrient digestion
-esophagus
-peristalsis
-lower esophageal sphincter
-regulates entry of food into
stomach
why have sphincters at all?
The process of digestion-secretions and enzymes
required for nutrient digestion
-stomach
-parietal cells
secrete HCl and intrinsic factor
-intrinsic factor essential to
absorption of vitamin B12
-chief cells
secrete precursors of pepsin used to
degrade protein
The process of digestion-secretions and enzymes
required for nutrient digestion
-stomach
-endocrine cells
secrete hormones related to
digestion eg gastrin
-pyloric valve
-controls dumping in duodenum
The process of digestion-secretions and enzymes
required for nutrient digestion
-small intestine
-involvement of liver, gall bladder and
pancreas
-lipases
-proteases
-carbohydrases
-absorption which ultimately leads to
transport within the bodysignificance for metabolism?
-ileocecal valve-controls dumping into colon
The process of digestion-secretions and enzymes
required for nutrient digestion
-colon or large intestine
-water retention-why not let the kidney
worry solely about this?
-bacterial digestion of certain nutrients
undigested prior to colon
-primarily dealing with carbohydrate
and to some extent proteins and
amino acids
The process of digestion-secretions and enzymes
required for nutrient digestion
-colon or large intestine
-short chain fatty acid absorption
2-4 carbon fatty acids produced by
bacterial fermentation of
carbohydrate
used for energy in the body
The process of digestion-secretions and enzymes
required for nutrient digestion
-colon or large intestine
-vitamin K(some bacterial production) and
biotin absorption
-sodium, chloride and potassium
absorption- again why not let the kidney
worry solely about ion retention?
Next 2 lectures
metabolism of
carbohydrates not including fibre