Cellular Metabolism Modulates Ion Channels That Regulate ...
Cellular metabolism
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Transcript of Cellular metabolism
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Slide 2.1
Human AnatomyHuman Anatomy
CELLULAR METABOLISMCELLULAR METABOLISM
Pavemedicine.comPavemedicine.com
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Slide 14.46
Processes of the Digestive SystemProcesses of the Digestive System
Figure 14.11
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Slide 14.47a
Control of Digestive ActivityControl of Digestive Activity
Mostly by reflexes via the parasympathetic division
Chemical and mechanical receptors trigger reflexes
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Slide 14.47b
Control of Digestive ActivityControl of Digestive Activity
Stimuli include: Stretch of the organ pH of the contents Presence of breakdown products
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Slide 14.47b
Control of Digestive ActivityControl of Digestive Activity
Reflexes include: Activation or inhibition of glandular
secretions Smooth muscle activity
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Slide 14.55
Digestion and Absorption in the Digestion and Absorption in the StomachStomach
Proteases act on:
Pepsin –protein digestion
Rennin –milk protein digestion
Absorption of:
Water, alcohol and aspirin
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Slide 14.57a
Digestion in the Small IntestineDigestion in the Small Intestine
Pancreatic enzymes provide… Complete digestion of starch
Amylase Other carbohydrases
About half protein digestion (trypsin, etc.)
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Slide 14.57b
Digestion in the Small IntestineDigestion in the Small Intestine
Pancreatic enzymes, cont…
Fat digestion (lipase)
Nucleic acid digestion (nucleases)
Alkaline content neutralizes acidic chyme
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Slide 14.58
Stimulation of the Release of Pancreatic Stimulation of the Release of Pancreatic JuiceJuice
Vagus nerve
Local hormones
Secretin
Cholecystokinin
Figure 14.15
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Slide 14.59
Absorption in the Small IntestineAbsorption in the Small Intestine
Water
Products of digestion
Most molecules absorbed by active transport
Lipids absorbed by diffusion
Nutrients transported to the liver
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Slide 14.63
NutritionNutrition Nutrient – substance used by the body
for growth, maintenance, and repair Categories of nutrients
Carbohydrates Lipids Proteins Vitamins Mineral Water
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Slide 14.67
Cellular MetabolismCellular Metabolism
“All the chemical reactions necessary to maintain life”
Anabolism: a constructive process during which larger molecules are built from smaller ones
Usually involves condensation
AKA dehydration synthesis
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Slide 14.67
Cellular Metabolism, con’t…Cellular Metabolism, con’t…
•Carbohydrates
•Monosaccharides = simple sugars
•Glucose, fructose
•Disaccharides = Combinations of monosaccharides, removal of water
•Sucrose, lactose, maltose
• Polysaccharides: usually polymers of glucose
•Starch, cellulose, chitin
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Slide 14.67
Cellular Metabolism, con’t…Cellular Metabolism, con’t…•Lipids
•1 glycerol + 3 fatty acids neutral fat + 3 H2O
•These are triglycerides
•Further modifications produce:
•Phospholipids (cell membrane)
•glycolipids (cell membrane)
•Lipoproteins (cell membrane, blood)
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Slide 14.67
Cellular Metabolism, con’t…Cellular Metabolism, con’t…•Proteins
•Two amino acids a dipeptide + H2O
•Covalent bond formed is a peptide bond
•Unique to proteins
•Polypeptides: 2-100 amino acids
•Protein: >100 amino acids
•Require additional modification to become functional
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Slide 14.67
Cellular Metabolism, con’t…Cellular Metabolism, con’t…•Proteins
•Modification occurs on four levels
•Primary: string of amino acids
•Secondary: helix or “pleat” structures
•Tertiary: 3-D folding
•Quarternary: two or more 3-D proteins that act as a functional unit
•i.e., hemoglobin, collagen
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Slide 14.67
Cellular Metabolism, con’t…Cellular Metabolism, con’t…•Proteins
•Recall from Chemistry: •Proteins each have a unique 3-D shape
•Shape determines function
•Loss of shape leads to loss of function
•“denaturing” proteins with heat, pH changes
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Slide 14.67
Cellular Metabolism, con’t…Cellular Metabolism, con’t…•Proteins
•May be structural or functional
•Structural:
•Play a role in cellular architecture
•Collagen, fibrin, actin, myosin, etc.
•Functional:
•Play a role in cell metabolism
•Enzymes, neurotransmitters, antibodies, etc.
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Slide 14.67
Cellular Metabolism, con’t…Cellular Metabolism, con’t…•Enzymes:
•Biological catalysts
•Highly specific for a substrate
•Substrate: substance upon which an enzyme acts
• i.e., peptidases act only on peptide bonds in small polypeptides
•Produced only in presence of substrate
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Slide 14.67
Cellular Metabolism, con’t…Cellular Metabolism, con’t…
•Enzymes:
•Huge protein molecules
•Alter shape to conform to shape of substrate (“wrap around” effect)
•Average 1500/cell (>5000 in liver cells)
•Most require co-enzymes
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Slide 14.67
Cellular Metabolism, con’t…Cellular Metabolism, con’t…•Enzymes:
•Recognize substrate by shape of binding site
•Serve to lower energy required for reaction to occur (activation energy)
•therefore speed up reactions
•Not changed or used up during reaction
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Slide 14.67
Cellular Metabolism, con’t…Cellular Metabolism, con’t…•Co-Enzymes:
•Required to activate enzymes
•Facilitate enzymatic reactions
•May be a metal ion (Zn++, Cu++, Fe++)
•May be a vitamin
•Vitamins are co-enzymes
•Only function if “their” enzyme is available
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Cellular Metabolism Catabolism: substances are broken down into molecules
“destructive” process
Large molecules broken down into smaller molecules
Usually by hydrolysis
“splitting with water”
Adds H2O back into molecule
Breaks covalent bonds
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Cellular Metabolism Catabolism
Energy is released when bonds break
Reverse of dehydration synthesis (condensation)
Hydrolysis = chemical digestion
Occurs simultaneously (and continuously) with anabolism
Processes controlled by enzymes
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Cellular Energy Cellular energy is chemical energy
Derived from breaking chemical bonds
~ ½ Energy is stored as ATP
~ ½ Energy is released as heat
Helps maintain body temperature
Enzymes control in the process
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Cellular EnergyAll nutrient molecules are ultimately
degraded or converted to glucoseOnly glucose can be used to make
ATPOxidation: cellular process of
chemically breaking apart a glucose molecule to release energy
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Cellular EnergyGlucose oxidation occurs in 2 phases
Anerobic metabolismOccurs in cytoplasmWithout oxygenAKA glycolysisSplits glucose into two 3-Carbon
molecules: pyruvate
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Cellular EnergyGlycolysis
Process also produces 2 ATPsIn yeast, plant cells:
Pyruvate can undergo alcoholic fermentation
In bacteria, animal cells:Pyruvate can produce lactic acid
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Cellular EnergyAerobic metabolism
Uses oxygenAKA Kreb’s Cycle or Citric Acid
cycle or Tricarboxylic Acid (TCA) Cycle
Occurs in mitochondriaMakes more ATP than anerobic
processes
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Cellular EnergyAerobic metabolism
CO2 and H2O are waste products
CO2:
Diffuses out of cellsDissolves in plasmaProduces HCO3
- in blood
Exhaled from lungs
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Cellular EnergyAerobic metabolism
H2O:
“metabolic” waterExhaled from lungs
Final products of glucose oxidation:CO2, H2O, ATP
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Cellular EnergyAerobic metabolism
For each molecule of glucose:2 ATP formed in glycolysis36 ATP formed in TCA cycleEnergy stored in phosphate
bondsA reversible reaction
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Metabolic Pathways“A particular sequence of enzymatic
reactions” Such as glycolysis, TCA cycle
Carbohydrate pathwaysCarbos should comprise most of
our diet (~ 50% complex carbs)Used as a primary energy sourceProduce 4kcal/gm
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Metabolic PathwaysCarbohydrate pathways
Excess carbs converted to energy storage formsGlycogen (muscle, liver)Adipose tissue (hips)Process is anabolism
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Metabolic PathwaysLipid pathways
Metabolism controlled by liverShould comprise <30% of calories
in dietGet 9 kcal/gm (more ATP!)Must be degraded into glycerol,
fatty acids, then pyruvateA reversible catabolic process
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Metabolic PathwaysProtein pathways
Proteins should comprise ~30% of diet
Get 4 kcal/gmCatabolism is more complex
Proteins contain nitrogen
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Metabolic PathwaysProtein pathways
Deamination: removal of nitrogen from amino acidsOccurs in liverNitrogen is converted to urea
A nitrogenous waste product
Sent to kidneys for excretion
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Metabolic PathwaysProtein pathways
After deamination: amino acid “skeleton” is
processed in TCA cycleMay produce CO2, H2O, ATP
May form glucose or fat
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Metabolic PathwaysProtein pathways
Glucose formed from amino acid skeletons may be re-converted to amino acids
“Essential” amino acids: Body cannot make theseMust obtain in the diet
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Regulation of Metabolic Pathways
Enzyme “saturation”Too much substrate for number of
enzyme moleculesReaction rate cannot increaseA single enzyme can control an
entire metabolic pathway“rate limiting” enzyme
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Slide 14.92b
Digestive System: DisordersDigestive System: Disorders
Ulcers: bacterial infection with H. pylori
Vomiting: controlled by center in medulla oblongata
Activity of tract slows in old age Fewer digestive juices Peristalsis slows Diverticulosis and cancer more common
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Slide 14.92b
Digestive System: DisordersDigestive System: Disorders
IBS: irritable bowel syndrome Crohn’s disease (autoimmune) Constipation Diarrhea Colitis Colon polyps/cancers