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