Sem 2 Module 5 - Digestion and Metabolism

Question 1

What are the digestion major processes?

Answer 1

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

Question 2

What happens in ingestion?

Answer 2

• Taking food into the digestive tract

- Involves the oral cavity - lips and tongue

Question 3

What happens in propulsion?

Answer 3

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

Question 4

What happens in mechanical digestion?

Answer 4

• 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

Question 5

What happens in chemical digestion?

Answer 5

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

Question 6

What happens in absorption?

Answer 6

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

Question 7

What happens in defecation?

Answer 7

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

Question 8

What are the fours layers of the alimentary canal?

Answer 8

1. Mucosa
2. Sub mucosa
3. Muscularis externa
4. Serosa

Question 9

What is the mucosa?

Answer 9

• 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

Question 10

What are the major functions of the mucosa?

Answer 10

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

Question 11

What is the sub mucosa?

Answer 11

• 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

Question 12

What is the Muscularis externa?

Answer 12

• 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

Question 13

What is the serosa?

Answer 13

• 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

Question 14

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

Answer 14

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)

Question 15

What is the digestive function of the pharynx and oesophagus?

Answer 15

1. Propulsion of food to the stomach

Question 16

What does the oral cavity include?

Answer 16

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

Question 17

What are the salivary glands

Answer 17

• 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)

Question 18

What are the functions of saliva?

Answer 18

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

Question 19

What are the functions of the stomach?

Answer 19

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

Question 20

What is the gross anatomy of the stomach?

Answer 20

• 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)

Question 21

What is the stomachs microscopic anatomy?

Answer 21

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

Question 22

Microscopic anatomy continued…

Answer 22

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

Question 23

What is the mucosal barrier?

Answer 23

Gastric juice create creates a harsh environment

• HCI is corrosive
• Proteases can digest the stomach wall

The mucous barrier has three parts

Question 24

What are the three parts of the mucous barrier?

Answer 24

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

Question 25

What are ulcers in the stomach?

Answer 25

- A breach of the mucous layer --> gastritis | - Persistent damage --> erosion of the stomach wall - gastric ulcer (--> perforation --> peritonitis)

Question 26

What are the symptoms of a stomach ulcer?

Answer 26

Epigastria pain 1-3 hours after eating

Question 27

What are the causes of stomach ulcers?

Answer 27

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

Question 28

What are the four digestive functions of the small intestine?

Answer 28

1. Propulsion 2. Mechanical digestion 3. Chemical digestion 4. Nutrient absorption

Question 29

What is the small intestines gross anatomy?

Answer 29

- 2.4m long with muscle tone (6-7m without muscle tone)

Question 30

What are the three divisions of the small intestine?

Answer 30

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

Question 31

What is the microscopic anatomy of the small intestine?

Answer 31

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

Question 32

What are the circular folds?

Answer 32

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

Question 33

What are the villi?

Answer 33

- 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

Question 34

What are the microvilli?

Answer 34

- 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")

Question 35

What are intestinal crypts in the small intestine?

Answer 35

- 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

Question 36

What are the small intestine digestive processes?

Answer 36

1. Chemical digestion - Chyme - Segmentation 2. Absorption

Question 37

What is chemical digestion?

Answer 37

- 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

Question 38

What happens in absorption?

Answer 38

- 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

Question 39

What is the livers gross anatomy?

Answer 39

- 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)

Question 40

What are the livers lobules?

Answer 40

- 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

Question 41

What are the functions of the liver?

Answer 41

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

Question 42

What is the bile in the liver?

Answer 42

- 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

Question 43

What is the gall bladder?

Answer 43

- 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

Question 44

What is the pancreas?

Answer 44

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

Question 45

What are the functions of the large intestine?

Answer 45

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

Question 46

What is the gross anatomy of the large intestine?

Answer 46

- 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

Question 47

More about the large intestine?

Answer 47

- 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

Question 48

What is the large intestines enteric flora?

Answer 48

¬ 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

Question 49

What is chemical digestion of the large intestine?

Answer 49

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

Question 50

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

Answer 50

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

Question 51

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

Answer 51

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

Question 52

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

Answer 52

- 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

Question 53

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

Answer 53

- 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

Question 54

What is nutrient absorption?

Answer 54

¬ 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

Question 55

Absorption of water-soluble nutrients?

Answer 55

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

Question 56

What happens in nutrient absorption of lipids?

Answer 56

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.

Question 57

Movement of nucleic acids in nutrient absorption?

Answer 57

Active transport with specific protein carriers (as for proteins)

Question 58

Movement of fat-soluble vitamins?

Answer 58

- Simple diffusion through protein channels | - Vitamin b12 - binds intrinsic factor in stomach --> actively absorbed in the ileum

Question 59

Absorption of Na+ ions?

Answer 59

Are actively absorbed along with glucose and amino acids

Question 60

Absorption of K+ ions?

Answer 60

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

Question 61

Absorption of iron and calcium?

Answer 61

Absorbed by active transport

Question 62

Absorption of water?

Answer 62

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

Question 63

What happens when nutrients are absorbed?f

Answer 63

- 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

Question 64

What is metabolism?

Answer 64

The sum total of the chemical reactions occurring in body cells

Question 65

What is anabolism?

Answer 65

Reactions that build larger molecules from smaller ones

Question 66

What is catabolism?

Answer 66

Reactions that break down complex structures into simpler ones

Question 67

What is the metabolic rate?

Answer 67

The energy the body used to drive metabolism

Question 68

What is basal metabolic rate?

Answer 68

``` 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 ```

Question 69

Why do cells need energy?

Answer 69

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

Question 70

Where does the energy come from?

Answer 70

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

Question 71

What are the three biochemical processes in glucose catabolism?

Answer 71

Glucose catabolism involves three biochemical processes: - glycolysis - TCA cycle - Electron transport chain (ETC)

Question 72

What is glycolysis?

Answer 72

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

Question 73

What is tricarboxylic acid cycle?

Answer 73

2. 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

Question 74

What is the electron transport chain?

Answer 74

3. 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

Question 75

What are other sources of energy?

Answer 75

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

Question 76

What are metabolic states?

Answer 76

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

Question 77

What are the two nutritional states?

Answer 77

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

Question 78

What happens in the anabolic or absorptive state?

Answer 78

- 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)

Question 79

What happens in the catabolic or post-absorptive state?

Answer 79

- 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)

Question 80

What is the energy fuels of the catabolic state?

Answer 80

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

Question 81

What are the major metabolic thrust in catabolic state?

Answer 81

Catabolism and replacements of fuels in the body

Question 82

What is the hormone that controls this phase?

Answer 82

- Glycogen | adrenaline, noradrenaline, thyroxin, growth hormone

Question 83

What is the liver metabolism?

Answer 83

- Amino acids & glycerol converted to glucose, fatty acids to ketone

Question 84

What hormone controls the anabolic state?

Answer 84

Insulin

Question 85

What is glucose used for?

Answer 85

Glucose is used as fuel by all cells.

Question 86

What are excess nutrients stored as?

Answer 86

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

Question 87

Where are nutrients absorbed in the anabolic or absorptive state?

Answer 87

Nutrients absorbed from the small intestine and abundant in blood