Transcript Digestion and Absorption of the Food Nutrients

Digestion and Absorption of the
Food Nutrients
Chapter 3
Nutrient Digestion and Absorption
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Hydrolysis reactions
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Catabolic
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Breakdown
Split of chemical bonds
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Separates water molecules into
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H+ - hydrogen ions
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OH- - hydroxyl ions
These ions then added to by-products of reaction
Hydrolysis
Nutrient Digestion and Absorption
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Hydrolysis reactions
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Examples:
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Polysaccharides (starches) to disaccharides
to monosaccharides
Proteins to amino acids
Lipids to glycerol and fatty acids
Nutrient Digestion and Absorption
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Condensation reactions
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Anabolic (building up)
Join H+ and OH- to form a water molecule
Source of metabolic water
Condensation
Enzymes
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Accelerate chemical reactions
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Reusable
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Specific protein catalyst
Reduce activation energy (energy input)
Enzymes don’t get changed during the
reaction
Substrate
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Any substance acted upon by an enzyme
Lock and Key Mechanism
Coenzymes
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Coenzymes
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Facilitate enzyme action
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Nonprotein
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Additional ions (minerals)
Smaller organic molecules (like B-vitamins)
Coenzymes
Coenzymes
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Temporary carrier
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NAD+
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NADH
Carry electrons and H+
This carrier allows the
enzymes of the
electron transport
chain to extract the
electrons and H+
Passive Transport
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Cell membranes
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Selectively permeable
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Maintain consistency in chemical composition
Passive Transport (4 types-does not require
energy input)
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Simple diffusion
Facilitated diffusion
Osmosis
Filtration
Simple Diffusion
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Continuous molecular
movement
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Higher to lower
concentration
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Until they are evenly
dispersed
Examples
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Almost all gases
Ex. Oxygen, Carbon
dioxide
Concentration
gradients allow
movement of gases
Facilitated Diffusion
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Membrane proteins
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Channels in cell
membrane
Open under specific
conditions
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Chemical
messenger
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Ions ( + or - )
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Neurotransmitter
Voltage gated
channels
Thus, they facilitate the
movement of molecules
Facilitated Diffusion
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Examples
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Glucose
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Lipid
insoluble
Uncharged
Binds to site
on
membrane
Structural
change
Osmosis
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Water moves based on differences in
solute concentration
It can move freely between these
compartments
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Intracellular
Extracellular
Plasma
Osmosis
Osmolality
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Concentration of dissolved particles in a solution
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Isotonic solution
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Hypertonic
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No gain or loss of water between cells and fluid surrounding
them
Higher solute concentration outside cell than inside (causes
cell to shrink)
Hypotonic
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Higher water concentration outside cell than inside (causes
cell to swell)
Osmolality
Filtration
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Hydrostatic pressure
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Pressure in blood stream is higher than
surrounding tissues
Causes flow of fluid from capillaries to
interstitial space
Higher protein content in plasma
Osmotic pressure causes absorption of
interstitial fluid back into capillaries
Filtration
Active Transport
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Requires energy (ATP)
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Ex. Sodium-Potassium Pump
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Moves ions against electrochemical gradients
Sodium-potassium ATPase
Sodium-Potassium Pump
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Na+ leak into cell
Action potential
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Depolarization
K+ moves out to reestablish charge
Sodium-potassium
pump “resets” cell
to resting gradients
Coupled Transport
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Linked, simultaneous transport
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Two substances
Across cell membrane
Same direction – symport
Opposite directions – antiport
Coupled Transport
Bulk Transport
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Movement of large particles and
molecules
Exocytosis
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Hormones, Neurotransmitters,
Secretions, wastes
ICF to ECF
Stages
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Enclosed in pouch
Pouch migrates to membrane
Contents ejected into ECF
Bulk Transport
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Endocytosis
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Water, lipids
Plasma membrane of cell surrounds
substance
Pinches away
Moves into cytoplasm
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Acid-Base Concentrations
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Acid: any substance that dissociates
(ionizes) in solution and releases
hydrogen ions (H+)
Base: any substance that picks up or
accepts H+ to form hydroxide ions (OH) in water solutions
pH: provides a quantitative measure of
the acidity or alkalinity (basicity) of a
liquid solution
Acid-Base Concentrations
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pH
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1.0 to 14.0
Examples
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HCl – 1.0 (acid)
Blood – 7.4
Lye – 14.0 (base)
Acid-Base Concentrations
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Enzymes
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Activated/inactivated by pH
Example
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Salivary amylase
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Mouth
Inactivated by stomach pH
Denatured
Acid-Base Concentrations
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Chemical buffers
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Use a base to “neutralize” an acid
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Acid + base → weaker acid → dissociates
into harmless or less harmful products
Acid-Base Concentrations
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Ventilatory buffer
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Increases or decreases in pulmonary
ventilation
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Lactic acid (Hla)
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H+ + LaH+ + HCO3- → H2CO3 → CO2 + H2O
Tissues
→ Lungs
Acid-Base Concentrations
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Renal buffer
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Kidneys excrete or conserve H+ to
maintain acid–base stability of body fluids