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Semester 2 BMA 1912 > Sem 2 Module 5 - Digestion and Metabolism > Flashcards

Sem 2 Module 5 - Digestion and Metabolism Flashcards

1
Q

What are the digestion major processes?

A
  1. Ingestion
  2. Propulsion
  3. Mechanical digestion
  4. Chemical digestion
  5. Absorption
  6. Defecation
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2
Q

What happens in ingestion?

A
  • Taking food into the digestive tract

- Involves the oral cavity - lips and tongue

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3
Q

What happens in propulsion?

A
  • Moving food through the digestive tract
  • Swallowing (initiated voluntarily)
  • Peristalsis - alternate waves of muscle contraction and relaxation (involuntary)
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4
Q

What happens in mechanical digestion?

A
  • Breaking the food up into small fragments so it can be chemically digested
  • Mouth –> chewing and mixing food with saliva
  • Stomach –> churning and mixing with gastric juice
  • Small intestine - segmentation –> mixes food with digestive juices and ads in nutrient absorption
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5
Q

What happens in chemical digestion?

A
  • Enzymes break down complex food molecules into chemical building blocks
  • Begins in the mouth and ends in the small intestine
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6
Q

What happens in absorption?

A
  • Passage of digested end products from the digestive tract lumen into the blood or lymph via passive or active transport
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7
Q

What happens in defecation?

A
  • Elimination of indigestible substances, in the form or faeces, from the body via the anus
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8
Q

What are the fours layers of the alimentary canal?

A
  1. Mucosa
  2. Sub mucosa
  3. Muscularis externa
  4. Serosa
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9
Q

What is the mucosa?

A
  • Inner most layer
    Three sub-layers:
    1. A lining epithelium (simple columnar cells)
    2. A lamina propria
      - loose connective tissue containing capillaries, and lymphoid follicles
    3. A Muscularis mucosae
      - Thin layer of smooth muscle that moves the mucosa
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10
Q

What are the major functions of the mucosa?

A
  1. Epithelium
    - Secretes mucus –> protects the mucosa, helps move food along
    - Secretes digestive enzymes –> chemical digestion
    - Secretes hormones –> control motility and secretion of digestive juices
    - Absorbs nutrients
  2. Lumina propria contains
    - Capillaries –> absorption of the end products of digestion, nourishes epithelium
    - Lymphoid tissue –> Protection against infectious disease
  3. Muscularis mucosa
    - Produces folds in the mucosa of the small intestine to increase the surface areas for absorption
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11
Q

What is the sub mucosa?

A
  • External to the mucosa
  • Loose connective tissue with elastic tissue –> allows stretch and recoil

Rich supply of:

  • Blood vessels – nutrient absorption
  • lymphatic vessels – transports lipids
  • Lymphoid tissue – immune function
  • Nerves – parasympathetic –> raises motility and secretion
    - - Sympathetic –> Lowers motility and secretion
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12
Q

What is the Muscularis externa?

A
  • Surrounds the sub mucosa
  • Responsible for peristalsis (propulsion) and segmentation (mechanically digestion)
    Two smooth layers:
    • inner circular
    • outer longitudinal
  • The circular muscle can form sphincters
    –> act as valves to control the passage of food
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13
Q

What is the serosa?

A
  • Outer most layer
  • Connective tissue covered with a thin layer f squamous epithelium
    Functions:
    • Protection of the alimentary canal
    • Anchors the alimentary tissue within the peritoneal cavity
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14
Q

What are the digestive functions of the oral cavity (mouth)?

A

Digestive functions of the oral cavity (mouth):

  1. Ingestion
  2. Mastication (chewing) ——– bolus formation
  3. Mixing food with saliva ——- bolus formation
  4. Taste sensation
  5. Initiating chemical digestion
  6. Propulsion - swallowing food (deglutition)
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15
Q

What is the digestive function of the pharynx and oesophagus?

A
  1. Propulsion of food to the stomach
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16
Q

What does the oral cavity include?

A

Lined by stratified, squamous epithelium
- continually replaced due to abrasion
- produces antimicrobial peptides called defensins
Components include
- Lips and cheeks –> ingestion & positioning of the food for mechanical digestion
- Tongue
-> mixes food with saliva to form a bolus
-> bears gustatory receptors
-> initiates swallowing reflex
- Teeth –> mechanical digestion
- Salivary glands –> multiple functions
- Tonsils –> immune defence

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17
Q

What are the salivary glands

A
  • Extrinsic glands –> outside oral cavity
  • Intrinsic glands –> within oral mucosa
  • Parasympathetic control (CN VII & IX)
  • Produce 1- 1.5L of saliva per day
    - Water (97-99.5%)
    - Mucin protein –> mucus (lubricant)
    - Enzymes (salivary amylase, lingual lipase)
    - Antimicrobial proteins (antibodies, lysozyme, defensins)
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18
Q

What are the functions of saliva?

A
  • Moistens and lubricates food –> aids in bolus formation
  • Dissolves food chemicals and facilitate taste
  • Contains enzymes that begin chemical digestion (carbohydrates and lipids)
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19
Q

What are the functions of the stomach?

A
  1. Mechanical digestion - mixing food with gastric juice
  2. Disinfection of food
  3. Chemical digestion (proteins)
  4. Absorption (fat-soluble substances, e.g. alcohol)
  5. Storage of food
  6. Propulsion - to small intestine
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20
Q

What is the gross anatomy of the stomach?

A
  • Upper left quadrant of the abdominopelvic cavity
  • Empty volume - 50ml, internal folds expand to 4 L when full
  • Muscularis externa (modified)
    • Circular & longitudinal - mix, churn and propel food
      Oblique muscle —-> pummels food and rams it into the small intestine
      Mixing with gastric juices — > liquefies food to facilitates chemical digestion, disinfects the food (stomach acid)
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21
Q

What is the stomachs microscopic anatomy?

A

Stomach mucosa:

  • Lining of simple columnar epithelium –> produces an alkaline mucous, dotted with:
    • Gastric pits –> Produce mucous and lead to
    • Gastric glands –> produce 3L of gastric juice per day, includes
    • > Chef cells - secrete pepsinogen
    • > Parietal secrete HCI
    • > Enter endocrine - secrete hormones that control gut motility and secretion
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22
Q

Microscopic anatomy continued…

A

Parietal cells —> secrete HCI

  • denatures proteins –> unfold (aids degradation)
  • disinfects food, kills many, but not all, microbes
  • activates pepsin and provides optimal pH for function

Chief cells —> secrete pepsinogen, a precursor of pepsin

 - pepsin = a protease enzyme which initiates protein digestion 
 - activated by HCI 
 - Optimal activity occurs at pH 2
 - Hydrolyses 10-15% of ingested proteins to polypeptides
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23
Q

What is the mucosal barrier?

A

Gastric juice create creates a harsh environment

  • HCI is corrosive
  • Proteases can digest the stomach wall

The mucous barrier has three parts

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24
Q

What are the three parts of the mucous barrier?

A
  1. Bicarbonate-rich mucus on the stomach wall
    - - surface layer of vicious, insoluble mucus that traps an underlying bicarbonate-rich fluid that can neutralise stomach acid
  2. Mucosal epithelial cells joined by tight junctions
  3. Damaged mucosal epithelial cells shed and quickly replaced
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25
Q

What are ulcers in the stomach?

A
  • A breach of the mucous layer –> gastritis

- Persistent damage –> erosion of the stomach wall - gastric ulcer (–> perforation –> peritonitis)

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26
Q

What are the symptoms of a stomach ulcer?

A

Epigastria pain 1-3 hours after eating

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27
Q

What are the causes of stomach ulcers?

A 
Helicobacter pylori (90%) 
   - Toxin --> damage epithelium 
   - Proteins that 
         - Disrupt tight junctions 
         - Attract inflammatory cells 
Long- term use of NSAIDS (10%)
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28
Q

What are the four digestive functions of the small intestine?

A
  1. Propulsion
  2. Mechanical digestion
  3. Chemical digestion
  4. Nutrient absorption
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29
Q

What is the small intestines gross anatomy?

A
  • 2.4m long with muscle tone (6-7m without muscle tone)
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30
Q

What are the three divisions of the small intestine?

A
  1. Duodenum
    - 25cm long, cults around the pancreas
    - Receives bile and pancreatic juice for chemical digestion
  2. Jejunum
    - Major site of mechanical and chemical digestion and absorption
  3. Ileum
    - Ends at the large intestine
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31
Q

What is the microscopic anatomy of the small intestine?

A

The small intestine is highly adapted for nutrient absorption

  • Length provides huge surface area
  • Three structural modifications of the mucosa/sub mucosa further increase surface area
    • Circular folds
    • Villi
    • Microvilli
  • —> surface area increased more than 600 times
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32
Q

What are the circular folds?

A

Circular folds

  • Deep, permanent folds of the mucosa and sub mucosa
  • 1cm tall
  • Slow the movement of chime, thus increasing time for nutrient absorption
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33
Q

What are the villi?

A
  • 1mm high finer-like projections of the mucosa
  • Epithelial cells are mainly absorptive columnar cells bound by tight junctions —> nutrient and electrolyte absorption
  • Core contains a capillary bed and a wide lymph capillary
  • Goblet cells—> produce mucous
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34
Q

What are the microvilli?

A
  • Very small, densely packed villi on the surface of individual absorptive epithelial cells —> forma the “brush border”
  • Plasma membrane bears enzymes that complete carbohydrate, protein and nucleic acid digestion (“brush border enzyme”)
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35
Q

What are intestinal crypts in the small intestine?

A
  • Tubular glands, located in pits between the villi
  • Epithelial cells secrete slightly alkaline intestinal juice
  • Enter endocrine cells
    - hormones –> stimulate secretion of bile and pancreatic juice
  • Lymphoid tissue –> defence
  • Stem cells that give rise to the various epithelial cells as they migrate from the crypts and up the villi
36
Q

What are the small intestine digestive processes?

A
  1. Chemical digestion
    - Chyme
    - Segmentation
  2. Absorption
37
Q

What is chemical digestion?

A
  • Chyme delivered slowly, in small doses from the stomach
  • Segmentation (mechanical digestion) breaks up the chyme into even smaller portions
  • Alkaline intestinal mucus and pancreatic juice help to neutralise acidic chyme
  • Chyme is missed with digestive juices from the pancreas and gall bladder
  • Lipids and nucleic acids partially digested carbohydrates and proteins are digested carbohydrates and proteins are digested
  • Brush-border enzymes complete carbohydrate, protein and nucleic acid digestion
  • Transmit time of 3-6 hours
38
Q

What happens in absorption?

A
  • 90% of nutrient absorption occurs in the small intestine
  • The end products of digestion plus water, vitamins and electrolytes are absorbed across the single epithelial cell layer of the mucosa and into the capillaries or lymphatic circulation within the villi
    • Nutrients (water soluble) absorbed into blood travel in the hepatic portal vein to the liver
    • Nutrients (lipid soluble) absorbed into the lymphatic circulation enter the blood at the thoracic duct
39
Q

What is the livers gross anatomy?

A
  • Numerous metabolic and hematologic regulatory roles
  • ONE digestive function: production of bile for fat digestion
  • Largest gland - 1.5kg
  • 2 primary lobes and 2 smaller, inferior lobes
    Dual blood supply
    1. hepatic artery
    -> supplies oxygenated blood from the abdominal aorta (20% of input)
    2. Hepatic portal vein
    -> supplies nutrient rich blood from the small intestine (80% of input)
40
Q

What are the livers lobules?

A
  • Hexagonal “plates” of hepatocytes = lobule, the structural and functional unit of the liver that radiate from a central vein
  • > Portal triad at each corner
  • arteriole branch of the hepatic artery (supplies oxygen rich blood from systemic circulation
  • Venule branch of the hepatic portal vein (supplies nutrient- rich blood from the small intestine
  • Bile duct
  • > Between the plates are leaky capillaries
  • Allows hepatocytes to filter and process nutrient-rich blood
  • > Capillaries lined by macrophages
  • remove debris (e.g. old RBC, bacteria)
  • > Bile canaliculi (little canals) run between hepatocytes —> collect and drain bile into the duct of the portal triad
41
Q

What are the functions of the liver?

A
  1. Digestive function –> production of 900mL bile per day
  2. Hematologic functions –> synthesis of plasma proteins, e.g. albumin, clotting factors
  3. Metabolic functions
    - Processing of blood-borne nutrients
    • Removing and storing excess nutrients e.g. glucose –> glycogen
    • Use of amino acids to make protein or to yield energy
    • Break down fatty acids to yield energy
    • Vitamin and mineral storage
      • Correction nutrient deficiencies
    • Regulating circulating levels of glucose, triglycerides, fatty acids and cholesterol
    • Drug and hormone metabolism
    • Detoxification e.g. deamination of amino acid
  4. Heat production (chemical reactions) –> maintaining body temperature
42
Q

What is the bile in the liver?

A
  • Yellow- green alkaline solution
  • Produced by hepatocytes (1 L/day), stored in the gall bladder
  • Main pigment = bilirubin, a breakdown product of haemoglobin from recycled RBC
  • Contains bile salts and phospholipids which
    - Emulsifies fats (break them into small droplets) —> increases the surface area for digestive enzymes
    - Facilitates fate and cholesterol absorption
  • Release triggered by intestinal hormones secreted when chyme enters the duodenum
  • Reabsorbed in the ileum and recycled
43
Q

What is the gall bladder?

A
  • Thin-walled, muscular sac - 10cm long
  • Stores and concentrates unused bile
  • Bile is secreted into the duodenum directly from the liver or from that stored in the gall bladder
  • Gall stones (biliary calculi) are crystallised cholesterol which obstructs the flow of bile
44
Q

What is the pancreas?

A

Exocrine tissue –> produces and secretes pancreatic juice into ducts that deliver it to the duodenum
- pH 8.0, 1.2 - 1.5L produced per day, contains
- water
- Electrolytes e.g. bicarbonate ions which neutralise stomach acids and facilitate enzyme function
- Enzymes
- Proteases - secreted in inactive form, activated within the duodenum —> digest products
- amylases —> digest carbohydrates
- Lipases —> digest lipids
- Nucleases —> digest nucleic acids
- Release stimulated by presence of chyme in the duodenum
Endocrine tissue —> scattered “islets” of a and b cells which secrete hormones (insulin and glucagon) into the blood to regulate blood glucose levels

45
Q

What are the functions of the large intestine?

A
  1. Chemical digestion
  2. Absorption
  3. Temporary storage and compaction of waste materials
  4. Propulsion
  5. Defecation
46
Q

What is the gross anatomy of the large intestine?

A
  • 1.5m long, 7cm diameter tube
    Subdivisions
  • Caecum - pouch lying below the ileocaecal sphincter
  • Vermiform appendix - lymphoid tissue
  • Colon - puckered by longitudinal muscle to form haustra
    • Ascending, transverse, descending, sigmoid - “S” shaped
  • Rectum
    - Final 15cm portion
    - Expandable for temporary storage
    - Presence of faeces triggers the defecation reflex
  • Anus
  • 3cm long, within the perineum
  • Internal and external anal sphincters
47
Q

More about the large intestine?

A
  • Transit time in the large bowel: 12-24 hours
  • Mucosa = simple columnar epithelium
    • Abundant crypts with large numbers of goblet cells that produce mucus
      - ease the passage of faeces
      - protect the intestinal wall from bacterial acids and gases
  • Digestive processes
    • Chemically digestion - performed by enteric bacteria only
    • Absorption
      - Water and electrolytes (Na+ and CI-)
      - Vitamins produced by enteric bacteria
      - 0.5-1.5L material enters/day —> 150-200 ml faeces
      - Temporary storage and compaction of waste materials
      - Propulsion - movement of waste towards the rectum
      - Defecation - Parasympathetic reflex, involves well-developed Muscularis externa in the rectum
48
Q

What is the large intestines enteric flora?

A

¬ 500 species

  • Origin: some survive the stomach and small intestine, others enter via the anus
  • Mutualistic relationship:
    - Metabolise host-derived mucus
    - ferment cellulose, releasing acids and gases e.g. dimethyl sulphide ¬ 500mL/day
    - synthesize vitamins B and K
  • Host immune system prevents breach of the mucosal barrier, otherwise opportunistic infections occur
49
Q

What is chemical digestion of the large intestine?

A

Chemical digestion is the catabolic process
- Complex food molecules (polymers) are broken down into chemical bonding blocks (monomers) which are small enough to be absorbed from the gastrointestinal tract into the blood or lymph

  • Catalysed by specific enzymes
50
Q

What do carbohydrates have to do with chemical digestion of the large intestine?

A

Common dietary carbohydrates

  • Polysaccharides e.g. glycogen, starch, cellulose
  • Oligosaccharides e.g. sucrose, lactose, maltose
  • Monosaccharide’s e.g. glucose, fructose, galatose

Carbohydrate digestion occurs in the mouth and small intestine
All carbohydrates must be converted to their component monosaccharide’s

51
Q

What do proteins have to do with chemical digestion of the large intestine?

A

Digested proteins include:
- Dietary proteins
- Digestive enzymes
- Proteins from sloughed mucosal cells
All proteins must be degraded to amino acids
Proteases involved in protein digestion:
Stomach - pepsin
- Active at low pH (inactivated by high pH in duodenum)
- Hydrolyses 10-15% of protein
Duodenum
- pancreatic proteases
- brush border enzymes

52
Q

What do lipids have to do with chemical digestion of the large intestine?

A
  • Fats form globules in aqueous solution —> inaccessible to water-soluble enzymes —> must be emulsified by bile salts
  • Triglycerides (most abundant dietary fats) —> digested by pancreatic lipases to free fatty acids and monoglyceries
  1. Large fat globules are emulsified (physically broken up into smaller fat droplets) by bile salts in the duodenum
  2. Digestion of fat by the pancreatic enzyme lipase yields free fatty acids and monoglyceries. these then associate with bile salts to form micelles which “ferry” them to the intestinal mucosa
53
Q

What do nucleic acids have to do with chemical digestion in the large intestine?

A
  • Nuclei acid include DNA and RNA
  • Present in the cells that form our ingested food e.g. fruit, meat
  • Digested in the small intestine by the:
    • Pancreatic nucleases - break nucleic acids down to nucleotides
    • Brush border enzymes - break nucleotides down to their component bases (e.g. adenine, guanine, cytosine, thymine) pentose sugars and phosphate ions
54
Q

What is nutrient absorption?

A

¬ 9-10L of food, drink and secretions enter the gastrointestinal tract daily, only ¬ 150-300ml exits

  • 90% of absorption occurs in the small intestine - almost all food, most electrolytes and water
  • 10% of absorption occurs in the:
    - stomach (lipid soluble substances, e.g. alcohol)
    - large intestine (water, electrolytes and some vitamins

Absorption occurs through mucosal epithelial cells
- mucosal epithelial cells joined by tight junctions –> nutrients cannot pass between them

55
Q

Absorption of water-soluble nutrients?

A
  1. Small proteins (peptides) or carbohydrates are digested to monomeric form (amino acids or monosaccharide’s) by specific pancreatic and brush border enzyme
  2. The monomers are then absorbed by active transport into the epithelial cells, and move to their opposite side
  3. The monomers leave the villus epithelia cells by facilitated diffusion and enter the capillary via intercellular clefts –> liver
56
Q

What happens in nutrient absorption of lipids?

A
  1. Large fat globules are emulsified bile salts in the duodenum
  2. Digestion of fat by the pancreatic enzyme lipase yields free fatty acids and monoglyceries. these then associate with bile salts to form micelles which “ferry” them to the intestinal mucosa
  3. Fatty acids and monoglyceries leave micelles and diffuse into epithelial cells. they are recombined and packaged with other lipid substances and proteins to form chylomicrons
  4. Chylomicrons exit the epithelial cells by exocytosis. the chylomicrons enter lymphatic capillaries (lacteals) and are carried away from the intestine by lymph.
57
Q

Movement of nucleic acids in nutrient absorption?

A

Active transport with specific protein carriers (as for proteins)

58
Q

Movement of fat-soluble vitamins?

A
  • Simple diffusion through protein channels

- Vitamin b12 - binds intrinsic factor in stomach –> actively absorbed in the ileum

59
Q

Absorption of Na+ ions?

A

Are actively absorbed along with glucose and amino acids

60
Q

Absorption of K+ ions?

A

Are absorbed by passive, facilitated diffusion in response to osmotic gradients

61
Q

Absorption of iron and calcium?

A

Absorbed by active transport

62
Q

Absorption of water?

A

Is absorbed by osmosis, following the absorption of organic nutrients and electrolytes that create and osmotic gradient e.g. glucose and sodium

63
Q

What happens when nutrients are absorbed?f

A
  • Once absorbed, nutrients are used by cells in a huge variety of biochemical reactions:
    • Substances are being built up and broken down
    • Energy is extracted and used to drive cellular activities
64
Q

What is metabolism?

A

The sum total of the chemical reactions occurring in body cells

65
Q

What is anabolism?

A

Reactions that build larger molecules from smaller ones

66
Q

What is catabolism?

A

Reactions that break down complex structures into simpler ones

67
Q

What is the metabolic rate?

A

The energy the body used to drive metabolism

68
Q

What is basal metabolic rate?

A 
The energy the body uses to perform essential activities 
- fluctuates throughout the day 
- Influenced by several factors: 
    - Body surface area
    - Age and gender 
    - Body temperature 
     - Stress 
     - Hormones e.g. thyroxin
Total metabolic rate = The energy the body uses to drive all its activities (both voluntary and involuntary) 
    - 20 y/o female - 8000kj/day
    - 20 y/o male - 11000kj/day
69
Q

Why do cells need energy?

A

Energy drives all the work of the cell
Energy is temporarily stored in the cell as ATP
The breakdown of ATP releases energy that the cell uses for work

70
Q

Where does the energy come from?

A

Cellular respiration - biochemical processes that lead tot he production of ATP
- Breaking the chemical bonds in glucose molecules (a catabolic reaction) release energy that is used to make ATP:

Glucose + O2 —-> CO2 + H2O + energy
I
I
ATP + H2O <—- ADP + Pi + energy

71
Q

What are the three biochemical processes in glucose catabolism?

A

Glucose catabolism involves three biochemical processes:

  • glycolysis
  • TCA cycle
  • Electron transport chain (ETC)
72
Q

What is glycolysis?

A
  1. Glycolysis
    - Occurs in the cytoplasm of all cells
    - Does not require oxygen - at this stage
    - One molecule of glucose is broken in half into 2 molecules of pyruvate (pyruvic acid) in a multi-step processes called glycolysis
    - A small amount of energy is released to make ATP
73
Q

What is tricarboxylic acid cycle?

A
  1. Tricarboxylic acid cycle
    - Occurs in the mitochondria
    - Pyruvate is converted to acetyl CoA
    - Acetyl CoA cycles through a series of reactions (TCA cycle) that release CO2, H+ IONS and a small amount of energy to make some ATP
74
Q

What is the electron transport chain?

A
  1. Electron transport chain
    - Occurs in the mitochondria
    - Requires oxygen
    - H+ ions, produced by the TCA cycle, proceed through a series of chemical reactions (ETC) that produce water and release lots of energy to make lots of ATP
75
Q

What are other sources of energy?

A

Fuels other than glucose can be used to produce energy:

  • Proteins —> amino acids —> removal of the amino group (deamination, occurs in the liver) —> carbon skeleton —> glycolysis pathway or acetyl CoA
  • Fats (triglycerides) –> fatty acids and glycerol
    • fatty acids —> acetyl CoA
    • glycerol —> glycolysis pathway
  • Alcohol —> acetyl CoA
  • Ketones (generated in the liver from fatty acids which are released by the breakdown of stored fats) —> acetyl CoA
76
Q

What are metabolic states?

A

Our body exists in a dynamic catabolic-anabolic state
- Cells are continually breaking down and rebuilding organic molecules and extracting energy

Cells draw on nutrient pools to meet their metabolic needs

- Nutrients (glucose, amino acids, and glycerol and fatty acids) - derived from the digestion of food - are 
          - available in the blood 
          - stored within the body e.g. glycogen and adipose tissue 
 - The levels of these blood-borne nutrients are carefully regulated by 
           - hormones e.g. insulin and glycogen 
           - the co-ordinated activities of the liver, skeletal muscles and adipose tissue
77
Q

What are the two nutritional states?

A

The availability of nutrients determines the overall metabolic state of cells:

  1. The anabolic or absorptive state – when nutrients are in abundance (during and for 4 hours after a meal) –> anabolism exceeds catabolism and nutrients are stored
  2. The catabolic or post-absorptive state – when no food is being digested ad body reserves must be broken down to provide nutrients –> catabolism exceeds anabolism
78
Q

What happens in the anabolic or absorptive state?

A
  • During and within 4 hours after eating
  • Nutrients are being absorbed from the small intestine —> abundant supply in the blood
  • Within cells:
    • glucose is used as an energy source (all cells)
    • anabolic reactions are occurring, e.g. amino acids used in protein synthesis in any tissue as required
    • excess nutrients are stored:
      - Glucose –> converted to glycogen (a polymer of glucose found in the liver and skeletal muscles) by a process called glycogenesis, or converted to triglycerides (fat)
      - Amino acids –> deaminated –> carbon skeleton –> energy production and conversion to triglycerides (fat)
      - glycerol and fatty acids —> conversion to triglycerides (fats)
79
Q

What happens in the catabolic or post-absorptive state?

A
  • Fasting state, more than 4 hours after eating
  • Nutrients are no longer being absorbed from the small intestine —> blood nutrient levels decrease
  • Stored nutrients broken down to maintain blood glucose levels and to provide energy

Sources of blood glucose:

      - Glycogenolysis = breakdown of glycogen in the liver and skeletal muscles 
     - Gluconeogenesis = Production of new glucose in the liver 
                  - Fats are broken down to glycerol -> glucose 
                   - Proteins are broken down -> amino acids -> deamination -> carbon skeletons -> glucose

Glucose sparing:

       - Glucose is used by neural tissues for energy (absolute requirement)
       - All other tissues use fatty acids and ketones (from fat breakdown)
80
Q

What is the energy fuels of the catabolic state?

A

Glucose (provided by Glycogenolysis & gluconeogenesis), fatty acids, ketones

81
Q

What are the major metabolic thrust in catabolic state?

A

Catabolism and replacements of fuels in the body

82
Q

What is the hormone that controls this phase?

A
  • Glycogen

adrenaline, noradrenaline, thyroxin, growth hormone

83
Q

What is the liver metabolism?

A
  • Amino acids & glycerol converted to glucose, fatty acids to ketone
84
Q

What hormone controls the anabolic state?

A

Insulin

85
Q

What is glucose used for?

A

Glucose is used as fuel by all cells.

86
Q

What are excess nutrients stored as?

A

Excess nutrients are stored as glycogen (liver and skeletal muscle) and fat (adipose tissue) - anabolic reactions

87
Q

Where are nutrients absorbed in the anabolic or absorptive state?

A

Nutrients absorbed from the small intestine and abundant in blood

Semester 2 BMA 1912 (5 decks)

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