Transcript Document

Lecture 2- 19 September 2013
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-9th edition
Lecture 2- 19 September 2012
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 2
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
-the process of digestion-secretions and enzymes
required for nutrient digestion
-oral cavity
-esophagus
-stomach
-small intestine
-colon or large intestine
More detailed comments
a) Overview of Metabolism
-metabolism definition-sum total of all
chemical reactions that occur in living cells
- however the focus of this course in on
metabolism as it relates to nutrition
-consequently energy metabolism and its
regulation will be the focus of this course
-energy metabolism - how the body obtains
and uses energy-yielding nutrients after
they are absorbed
Energy metabolism
-eg glucose from carbohydrates, glycerol and fatty
acids from fat digestion and amino acids from
proteins
- is this really representative of energy
metabolism?
-catabolism-energy-producing reactions that occur
as the result of breakdown of energy yielding
nutrients-eg glucose from carbohydrates, glycerol
and fatty acids from fat digestion and amino acids
from protein
Energy metabolism
-anabolism-energy-using reactions that may be used
to build carbohydrates, lipids, proteins and
participates in the synthesis of a wide variety of
molecules in the body.-eg-glycogen synthesis from
glucose, triglyceride synthesis from fatty acids and
glycerol, protein synthesis from amino acids.
Energy metabolism
-metabolic regulation
-what is metabolic regulation?-orderly control
of metabolic processes so that molecules are
available for use when they are needed, in the form
they are needed, where they are needed, and in the
quantities they are needed
Catabolic rate =anabolic rate in healthy personscan you think of 2 exceptions to this equality?
Energy metabolism
why is regulation necessary? molecules would not
be available for use when they are needed, in the
form they are needed, and where they are needed
and in the quantities that are needed.
Catabolic rate = metabolic rate
-note that vitamins, minerals and water assist in
the regulation of energy metabolism. Water
and vitamins are metabolised as the result of
the metabolism of energy yielding nutrients.
Such metabolic results will not be the focus of
this course.
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
Cell components
-plasma membrane
-give cell shape and separate it from
extracellular environment
-protection for cellular contents
-allows for cellular stimulation, nourishment
and excretion of cellular wastes
-bag for cell contents
-membrane proteins act as pumps, gates,
receptors, energy transducers and
enzymes
-made up of lipids, proteins and
carbohydrates
Cell components
-cytoplasmic matrix or cytoplasm or cytoplast
-has microtrabecular lattice and fluid
environment
-site of glycolysis, hexose monophosphate
shunt, glycogenesis and glycogenolysis,
and fatty acid synthesis
Cell components
-mitochondrion(mitochondria)
-generation of most of adenosine triphosphate
(metabolic energy)
-oxidative metabolism(catabolism) of
carbohydrate, lipids and proteins
Cell components
-nucleus
-contains DNA-the brains of the operation
-DNA initiates and regulates most cellular
activities
Cell components
-endoplasmic reticulum-network of membranous
channels in cytoplast
-rough-has ribosomes
- protein synthesis
-smooth-no ribosomes
-lipid synthesis
-golgi apparatus-trafficking and sorting of proteins
Cell components
-lysosomes-digestion of lipids, proteins and
polysaccharides within the cell
-peroxisomes-fatty acid oxidation and amino acid
catabolism
Cell components
-cellular proteins
-receptors and intracellular signalling
eg insulin docks to its receptor and sets
up a series of intracellular signalling
processes by which glucose is
transported into the cell.
Cell components
-cellular proteins
-transport proteins-regulate flow of nutrients
into and out of cell
-can be carriers, pumps or pores
Cell components
-cellular proteins
-catalytic proteins
-enzymes that result in reactions taking
place more easily in the body
-are all enzymes contained in cells?
The cell
-apoptosis
-programmed cell death- certain enzymes
take the cell offline-implications for metabolism
and health?- why not just have cells live on forever
and reproduce forever?
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 day
metabolism of
carbohydrates not including fibre