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BMS107 > Metabolism and Energy Balance > Flashcards

Metabolism and Energy Balance Flashcards

1
Q

Definitions;

-Nutrient (and it’s 2 types)

A

-Nutrient: A substance used in an organism’s metabolism or physiology

  • Essential nutrient: those that MUST be supplied in diet
  • Non-essential nutrient: Those that can be synthesized de novo
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2
Q

Major Nutrients; Carbohydrates

  • % constitute of our diet
  • formula - most common one too
  • 3 groups
A

-approx 55-60% of total energy intake
-general formula CnH2nOn
-most common is glucose (C6H12O6)
3 groups;
i. Monosaccharides
ii. Disaccharides
iii.Polysaccharides

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3
Q

3 types of carbohydrates - features

A

i. Monosaccharides; e.g. glucose
- single C ring
- Used as an energy source and can pass epithelial lining
ii. Disaccharides; e.g. lactose, maltose, sucrose
- two sugar rings - to break is a dehydration reaction
iii. Polysaccharides; e.g. starch glycogen, fibre
- are long chains of C rings

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4
Q

Major Nutrients; Proteins

  • % of energy intake
  • what is is
  • no in animals and essential a.a.
A
  • approx 10-20% of total energy intake
  • Are large, complex organic molecules - are building blocks of all cells
    - animals have 20 a.a. linked by peptide bonds
    - 8 essential a.a. (deficient diets in these = developmental defects and slower growth)
  • Higher quality a.a. in animal tissue than plant tissue
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5
Q

4 types of protein folding

A
  1. Primary structure: a.a./DNA code
  2. Secondary structure: alpha helix or beta sheet - when sequence of a.a. linked by H bonds
  3. Tertiary structure: Occurs by folding of proteins
  4. Quaternary structure: protein consisting of more than one a.a. chain (e.g. Haemoglobin)
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6
Q

Major Nutrients; Lipids

-% of energy intake

  • What they are
  • What they do
  • What stored as
A
  • approx 25-30% of total energy intake
  • large, organic, hydrophobic molecules - important form of energy storage
  • provides barrier function
  • Comprised of fatty acids; can have short, medium and long chain
  • Stored as triacylglyceral in liver, muscle and adipose tissue
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7
Q

Essential Fatty acids (2)

A
  • Omega - 3 and Omega - 6 (as animals cannot produce sufficient amounts
  • Ingested as alpha linolenic acid (from plant seeds) or linoleic acid found in fish (respectively)
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8
Q

Major Nutrients; Vitamins

  • what they are
  • categories and e.g. from each
A

-Unrelated molecules with diverse functions
-Categorized based on solubility (water soluable or fat soluble)
Fat soluble;
-A (retinol - eyesight), D (Calcium and Phosphorous), E (antioxidant) and K (blood clotting)
Water soluble;
-B vitamins (are all coenzymes

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9
Q

Major Nutrients; Minerals

e. g.
- E.g. of functions

A
  • e.g. Calcium, Phosphorus, iron, copper, zinc
  • variety of functions;
    • Co-factors in enzyme-catalysed reactions
    • Regulation of acid-base balance
    • Nerve conduction
    • Muscle contraction
    • structure
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10
Q

Major Nutrients; Water

  • energy value?
  • % of what we consume
A
  • approx 60% of what we consume

- no energy value - acts as solvent for other nutrients

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11
Q

Digestion - what is it?

-Hydrolysis defin.

A
  • Digestion is the breakdown of large molecules into absorbable units, achieved by mechanical and chemical digestion
  • Hydrolysis: chemical breakdown of feed via addition of water molecule to broken bond
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12
Q

Absorption - what is it and where does it occur mainly

A
  • Absorption = uptake into the body
    • most nutrient absorption occurs in the small intestine (additional absorption of water, ions and some acids in large intestine)
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13
Q

Digestive enzymes

  • what they do
  • 4 types
A

-Convert complex macromolecules into forms that can be absorbed and processed

  • Amylases: break down polysaccharides into oligosaccharides
  • Proteases: break down proteins to shorter polypeptides
  • Lipases: Release fatty acids from triglycerides and phospholipids
  • Nucleases: break down DNA into nucleotides
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14
Q

Carbohydrate breakdown

A
  • Glycogen -> glycogen and oligosaccharides (via salivary amylases in mouth)
  • Glycogen and oligosaccharides -> disaccharides (via pancreatic amylase in small intestine)
  • Disaccharides -> monosaccharides (via disaccharidases in small intestine)

*no breakdown in stomach

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15
Q

Protein breakdown

A
  • Proteins -> large polypeptides (via pepsin in stomach)
  • Large polypeptides -> Dipeptides (via trypsin, chymotrypsin and carboxypeptidases in small intestine)
  • Dipeptides -> amino acids (via dipeptidases in small intestine)
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16
Q

Lipid Breakdown

  • problem - how overcome
  • Transportation of different types of lipids
A
  • Complicated by hydrophobicity - Gi tract secretes bile that emulsify lipids into small droplets (micelles)
    • transport of lipids depends on physical properties
      • in blood w/out assistance = short chain fatty acids and glycerol
        - In lymph as complexes called chylomicrons (larger chain) = triglycerides, cholestrol
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17
Q

Definitions;

  • Assimilation
  • GI tract
  • Elimination (Egestion)
A
  • Assimilation: the sequential processes of nutrient breakdown and absorption
  • GI tract: continguous w/ external enviro (molecules that cross epithelia are apart of our body)
  • Elimination: expulsion of undigested food
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18
Q

Gastrointestinal Tracts involved in the breakdown of food

-where reclamation of water and release of indigestible materials occur

A
  • Mechanical breakdown: mouth, pharynx, esophagus
  • Acidic: stomach
  • Most digestion and absorption: upper or small intestines
  • Reclamation of water: lower or large intestines
  • Release of indigestible material: anus
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19
Q

Food quality on digestion

-high vs low quality diet

Digestive Limitation - definition

A
  • High quality food:
    - requires minimal energy to capture and eat
    - higher rate of digestion
    - releases lot of energy
  • Low quality food:
    - More energy to capture and eat
    - lower rate of digestion
    - yields less energy

-Digestive Limitation: the rate in which the stomach is working

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20
Q

Features of the GI Tract that assist in its function (2)

A
  • Specialised compartments: increase efficiency of digestion (differ in vary in pH, enzyme comp, etc)
  • Muscular valves (sphincters): control passage of food from one compartment to next

*complexity of gut morphology varies across taxa

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21
Q

4 layers of the stomach

A
  1. Mucosa (innermost)
  2. Submucosa
  3. Circular (muscle)
  4. Longitudinal (muscle)
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22
Q

Cells of the Mucosa surface of the stomach (5)

-what they secrete

A

-Composed of columnar epithelial cells

  • Mucous Neck cells: Secrete mucus
  • Parietal Cells: Secrete HCL acid
  • Chief cells: Secrete pepsin
  • Enteroendrocrine cells: Secrete hormones into blood (w/in microvilli)
  • Paneth cells: secrete antimicrobial molecules

*mucus is important as it stops autodigestion

23
Q

The Liver - things produced that assist with digestion (3)

A
  • Bile: solution of digestive chemicals and liver waste products
    • produced in liver and stored in gallbladder
  • Phopholipids - aid in uptake of lipids
  • Bile salts - emulsify fats
24
Q

The Pancreas

A
  • Pancreatic exocrine secretions: contain digestive enzymes
    • protease, amylase, lipase, nuclease
  • Pancreatic endocrine secretions: control blood glucose
    - alpha cells secrete glucagon
    - beta cells secrete insulin
25
Q

Patterns of GI tract in different animals (4)

A
  • Carnivores have a small small intestine, as they mainly rely on their stomach to break down proteins
  • Ruminants have a large fore-stomach
  • Horses have a large large intestine
  • Birds have a crop (where they keep stones to break down food)
26
Q

GI tract of Ruminants/Foregut fermenters

-features

A
  • Have fore-stomach w/ 4 chambers
  • cellulose converted to Volatile Fatty acids (VFA) by bacteria, protozoa and fungi
    • same with carbohydrate
    • glucose requirements met by conversion to glucose in the liver
27
Q

GI tract of Hindgut fermenters (e.g. horses)

-kangaroos, foregut or hindgut fermenters?

A
  • Cellulose passes through large intestine
  • Fermentation in large intestine - produces VFAs

*Kangaroos are foregut fermentors (have a v. large stomach)

28
Q

Metabolism Definiton

-2 types of metabolism

A

-Collective term for huge no. of biochemical and physiological reactions that are necessary for life

  • Anabolic: large molecules synthesised from smaller ones
  • Catabolic: processes that break down complex structures to smaller, simpler ones

*release of energy not 100% efficient due to heat increment

29
Q

Heat lost in Metabolism

A
  • 75% of energy from nutrients -> ATP -> cellular systems is lost as heat during transfer
    • only 25% of nutrients available for work
30
Q

Metabolism: Absorptive and Postabsorptive states (definition)

-type of fuel most important in both conditions

A
  • Absorptive (Fed) state: the period of time following a meal where products of digestion are being absorbed, used and stored
    - primarily anabolic - glucose is most important fuel (except in ruminants - use VFAs)
    • v. llittle fat/a.a used immediately - get stored
    • most cells used glucose first (except gut enterocytes - use a.a. as helps maintain conc. w/ glucose
  • Post- absorptive (fasted) state: the period of time when nutrients from a meal are no longer available
    - primarily catabolic - body reserves are fuel used
31
Q

Post-Absorptive State

A
  • Primary goal = spare glucose
  • Endogenous energy stores (fat and glycogen) mobilised
    • if starving, proteins are the next to be broken down
32
Q

Starvation Response

A
  • Reorganisation of metabolism to ensure long-term survival
  • Preserve glucose to protect glucose-dependent tissues
  • muscles shift to lipid metabolism
  • Once lipid and glucose stores depleted, a.a. converted to FAs and carbs
    • degradation occurs
33
Q

Key tissues/organs in different states and their roles

-Liver, adipose tissue, muscle and brain

A
  • Liver: maintain blood glucose levels; also stores glycogen
  • Adipose tissue: main energy storage site
  • Muscle: primary site of a.a. storage and major energy user
  • Brain: relies primarily on glucose for fuel (uses ketone bodies after fatty acid oxidation in starvation)
34
Q

Meal Frequency in humans

  • Herbivores
  • Carnivores
A
  • Average meal absorbed within 4 hours
    • 3 meals a day = intermittent fasting
  • Herbivores: v. little fasting as continuously graze and have a full rumen
  • Carnivores: Long fasting periods; gorge on only few prey per month
35
Q

Change of state following metabolism - pythons

A
  • Reduce energetic costs in between meals, seen in pythons that eat v. infrequently
  • B/ween large meals, mucosa and submucosa degrade, gut becomes thinner and brush border decreases
    - smooth muscles and nerves are maintained
  • Following a meal, snake rebuilds GI tract just ahead of bolus of food
    • Very high Specific dynamic activity (neg. energy associated with meal)
36
Q

Role of Hormones in metabolism

  • main 2
  • Which one is involved in fed state and fasted state
A

-Insulin and Glucagon regulate metabolism

  • Fed state: insulin is dominant hormone - net anabolism
    - triggers GLUT 4 translocation to increase uptake of glucose
  • Fasted state: glucagon dominant hormone - net catabolism
    - involved in breaking down glycogen
37
Q

Relationship between Insulin and Glucagon

A
  • Insulin rises with glucose, which leads to a decrease in circulatory glucose concentration (as being taken up by cells)
  • Glucagon antagonistic to insulin; less glucose in system stimulates glucagon release to start breaking down stores

*Ratio of insulin:glucagon important for direction of metabolism

38
Q

Out of control Hormones - what it can lead to (2 types)

A
  • Diabetes;
    i. Type 1 (juvenile onset): lack of insulin production
    - often requires insulin injections
    ii. Type 2 (adult onset): insulin insensitivity/hypersensitivity
    - usually managed w/ diet and exercise
39
Q

3 hormones involved in the control of appetite (how they all work)

A
  1. Leptin: white adipose tissue
  2. Ghrelin: Stomach
  3. Peptide YY: Colon

*all work by binding to receptors in hypothalamus

40
Q

Positive and negative energy balance

A
  • Positive Energy Balance: when the rate of energy assimilation is greater than energy output (gain weight as fat)
  • Negative energy balance: when the rate of energy assimilation is less than energy output (lose weight)
41
Q

What energy that is not lost as heat is used for (3)

A
  1. Transport: movement of molecules across membranes
  2. Mechanical: use of intracellular fibres and filaments to create movement
  3. Chemical: for growth, maintenance and storage of info and energy
    i. Synthesis (tissues) or ii. Storage (fat and glycogen)
42
Q

Barrel model of energy balance

A
  • Stores contain amount of energy - amount we can store depends on the rate we absorb food, which is dependent on the rate of digestion, which is dependent on the rate of foraging.
  • barrel of energy has 3 taps - heat, work and tissue (heat tap is constantly dripping)
43
Q

Energy Expenditure

-4 stages

A
  • 4 stages
    1. Gross Energy: total energy content of a food
    2. Digestible energy: energy contained in nutrients absorbed from digestive tract
    3. Metabolisable energy: Chemical energy available
    4. Net energy: represents true amount of energy available for maintenance, work, growth and reporduction
44
Q

Relationship of mass and metabolic rate

A
  • Is non-proportional
    • smaller animals usu. have higher metabolic rates per unit body mass than larger animals
      - small animals have a large SA = more heat loss
  • Mass specific metabolic rate declines w/ increasing body mass
45
Q

Basal Metabolic Rate

A

BMR= amount of energy expended while at rest in a neutrally temperate environment in a post-absorptive state
-v. specific set of conditions required to measure, therefore resting MR used (is the energy our body needs to maintain barrel reserve)

46
Q

Metabolisable energy requirement at maintenance (MEM) equation

A

aW^0.75
a = constant (average of 525 - higher for carnivores, varies with climate)
W = Body mass (Kleiber’s Law)

e.g. for 30 kg dog
525 x 30^0.75 = 6410kJ/d

47
Q

Direct Calorimetry

  • what it is
  • Process
  • Calorie definition
  • Kilocalorie definition
A
  • Is a direct measurement of a Food’s energy content
  • volume of water w/ crucible of food w/in
    - food is burnt, and the heat produced heats up the water which can then be measured
  • Amount of heat released can be used to measure the chemical energy of the food

Calorie: energy required to increase temperature of 1 gram of water by 1 deg.
Kilocalorie: energy required to increase temp of 1 kg water by 1 degree

48
Q

Atwater factors for Carbs, protein, fat and alcohol (kJ/gram)

-How to work out energy

A
  • Carbs: 17kJ/gram
  • Protein: 23kJ/gram
  • Fat: 39 kJ/gram
  • Alcohol: 29kJ/gram

-Multiply total grams of each category by its Atwater factor

49
Q

Indirect Calorimetry

  • what it is
  • figures for carbs, fat and protein and mixed diet

-Respiratory Quotient -> what is it?

A

-Indirect Calorimetry: consumption of O2 and/or production of CO2 being measured

  • Consuming 1 L of O2 associated with releasing 21.1kJ carbs, 19.8 kJ fat and 18.6 kJ protein
    • average for mixed diet = 20.2kJ

Respiratory quotient (RQ) = ration of CO2 produced and O2 consumed

50
Q

What Respiratory Quotient is used for

A

-Used to determine the metabolic substrate used by an animal

RQ 1 = carbs
RQ 0.7 = fats
RQ 08-0.9 = proteins

51
Q

Which body organs are using energy at rest

A
  • Liver = 27%
  • Brain = 19%
  • Skeletal muscle = 18%
  • Kidneys = 16%
  • Heart = 7%
52
Q

Factors affecting BMR/RMR (7)

-Usual value

A
  • usually is 20-25kcal per kg body mass
    1. Age and gender (higher in males - have more muscle/less fat); declines w/ age
    2. Body composition (fat-free mass uses more energy)
    3. Diet (diet induced thermogenesis associated w/ digestion and absorption - fat causes little)
    • Specific dynamic action
      1. Temperature
      2. Growth and reproduction (pregnancy - higher)
      3. Hormones and drugs (thyroid hormones increase metabolic rate; smoking, drugs, caffeine can increase BMR trhough increased thermogenesis
      4. Physical activity
53
Q

Maintenance Metabolic rate

Maintenance energy requirement

A

MMR: energy use of animal that is permitted to eat and digest food in amounts needed to maintain constant body mass and composition
-always higher than BMR because it includes SDA

MER: amount of energy animal needs from food during ‘maintenance’ conditions

BMS107 (15 decks)

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