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PHYL1007 > Metabolism > Flashcards

Metabolism Flashcards

1
Q

What are the two control centres in the hypothalamus in terms of feeding?

A
  • feeding centre

- satiety centre

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2
Q

What is the Glucostatic theory?

A

Regulation of food intake

- Glucose metabolism by hypothalamic centers regulates food intake

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3
Q

What is the lipostatic theory?

A
  • signals from fat stores to the brain modulate eating behaviour to maintain a particular weight
  • Leptin, neuropeptide Y, ghrelin, CCK, GLP-1, orexins
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4
Q

What is sensory input from the nervous system in regards to food intake?

A

Psychological factors, stress

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5
Q

What is direct calorimetry?

A
  • measures energy content of food in kilocalories

- metabolic energy slightly less because foods not fully digested

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6
Q

What is indirect calorimetry?

A
  • estimates metabolic rate as a measure of energy expenditure: oxygen consumption, CO2 production, ratio of CO2 to O2 (Respiratory quotient RQ, respiratory exchange ration (RER)
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7
Q

What six factors affect metabolic rate?

A
  1. Age and sex
  2. Amount of lean muscle mass
  3. Activity level
  4. Diet and diet-induced thermongenesis
  5. Hormones
  6. Genetics
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8
Q

What are the three places digestion and metabolism take place?

A
  1. GI tract
  2. Tissue cells
  3. Mitochondria
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9
Q

What are the three possible uses for ingested biomolecules

A
  1. Energy to do mechanical work
  2. Synthesis for growth and maintenance
  3. Storage as glycogen or fat
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10
Q

What are nutrient pools?

A
  • available for immediate use in plasma
  • Free fatty acids pool
  • Glucose pool
  • amino acid pool
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11
Q

How is the glucose pool regulated?

A
  • tightly regulated

- Glycogenesis and lipogenesis

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12
Q

What is glycogenesis?

A
  • synthesis of glycogen from glucose

- occurs when glucose supplies exceed demand for ATP

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13
Q

what is gluconegenesis?

A

synthesis of glucose from a precursor other than carbohydrate

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14
Q

How do enzymes control the direction of metabolism?

A

Through push-pull control

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15
Q

What is the livers role in metabolism?

A
  • intestinal blood supply flows directly to liver: gets all nutrients/metabolites
  • Linked closely to pancreatic blood supply: insulin/glucagon hormones exert their effects in the liver first
  • stores glucose as glycogen
  • can synthesise “new glucose”
  • can synthesise ketones
  • can synthesise lipids
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16
Q

What is glycongenolysis

A
  • breaks down glycogen to release glucose

- stimulated by low blood glucose

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17
Q

How does muscle tissue affect metabolism?

A
  • utilises glucose as energy source during fed state and activity, utilises lipids as energy source during fasting
  • stores glucose as glycogen - only be used by muscle cells
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18
Q

What is adipose tissues effect of metabolism

A

Key metabolic regulator of lipid storage and release

  • stores fatty acids as triglyceride
  • releases fatty acids
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19
Q

What is the brains effect on metabolism?

A

HIGH METABOLIC RATE

  • high blood supply
  • depends almost entirely of glucose
  • oxidises about 120g of glucose per day
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20
Q

Describe the kidneys role in metabolism

A
  • produce urine, maintaining osmolarity and pH of the body fluids
  • consume 10% of oxygen used in cellular respiration = needed for reabsorption
  • filters urea out
  • recovers metabolites such as glucose
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21
Q

Explain the three factors of push-pull control

A

a) without regulation of enzymatic activity, the pathway will simply cycle back and forth. There is no ney synthesis of substrate A or B
b) in fed-state metabolism under the influence of insulin, enzyme activity for the forward reaction increases. Enzymes for glycogen breakdown are inhibited. Net glycogen synthesis results
c) in fasted-state metabolism under the influence of glucagon, ensymes that break down lgycogen are more active, and enzymes for glycogen synthesis are inhibited. Net glucose synthesis results.

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22
Q

What are anabolic pathways?

A

ENDERGONIC REACTION
Anabolic pathways synthesise larger molecules from smaller constituent parts, using ATP as the energy source
- fed state, or absorptive state

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23
Q

What are catabolic pathways?

A

EXERGONIC REACTION
Catabolic pathways are break larger molecules such as carbohydrates, lipids and proteins from ingested food into smaller parts
- fasted state, or postabsorptive state

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24
Q

What are exergernic reactions?

A

reactions that release energy because the products have less energy than the reactants

25
Q

What is metabolism?

A

the sum of all reactions in the body:

metabolism = catabolic reactions + anabolic reactions

26
Q

What are enzymes

A
  • Enzymes speed up the rate of chemical reactions
  • catalysts
  • reactants are called substrates
  • mostly proteins
  • Isozymes
  • catalyze same reaction, but under different conditions
  • diagnostic enzymes
  • may be activated or inactivated or modulated
  • coenzymes (e.g. vitamins)
  • chemical modulators > temperature and oH
  • enzymes lower the activation energy of reactions
27
Q

How do cells regulate their metabolic pathways?

A
  1. Controlling enzyme concentrations
  2. Producing modulators that change reaction rates: feedback inhibition
  3. Using different enzymes to catalyze reversible reactions
  4. Compartmentalizing enzymes within organelles
  5. Maintaining optimum ratio of ATP to ADP
28
Q

What controls reversibility of metabolic reactions?

A

Enzymes

29
Q

Explain some factors of reversible reactions

A
  • some reversible reactions use one enzyme for both directions
  • reversible reactions requiring two enzymes allow more control over the reaction
30
Q

Explain a factor of irreversible reactions

A
  • irreversible reactions lack the enzyme for the reverse direction
31
Q

Explain how ATP transfers energy between reactions

A
  • high-energy phosphate bond
  • aerobic metabolism
  • anaerobic metabolism
  • catabolic pathways produce ATP: glycolysis, citric acid cycle, electron transport chain
32
Q

What does ATP supply energy for?

A
  1. Synthesis to make macromolecules
  2. Transport
  3. Muscle contractions and cellular motility
33
Q

How does cellular respiration to ATP

A

Oxidises glucose molecules to produce ATP through:

  • glycolysis
  • krebs cycle
  • oxidative phosphorylation
34
Q

How much ATP approx. comes from glucose?

A

30-32

35
Q

What type of cellular respiration occurs outside the mitochondria?

A

Glycolysis

* glucose -> pyruvic acid

36
Q

What types of cellular respiration occur inside the mitochondria

A
  • citric acid cycle

- electron transport chain

37
Q

Why does glucose produce more ATP than fat despite fat having higher calories?

A

It enters the metabolic reaction at a later state then glucose so produces less ATP

38
Q

How many steps are there in a normal metabolic reaction?

A

3

39
Q

Explain fed state metabolism in regards to carbohydrates and proteins

A
  • glucose makes ATP
  • excess is converted to: glycogen for short term storage, fat for long term storage
  • amino acids assembled into proteins, amine hormones, neurotransmitters
  • excess amino acids are converted to fat
40
Q

Explain fed-state metabolism in regards to fats

A
  • Chylomicrons leave intestine by the lymphatic vessels
  • contains: cholesterol, triglycerides, phospholipids, apoproteins
  • lipoprotein lipase convert triglycerides into glycerol and fatty acids
  • excess cholesterol secreted in bile and blood as a lipoprotein complex
  • complex with more protein is denser
  • complexes enter cells by receptor mediated endocytosis
  • cholesterol and other lipids can be synthesised from non-lipid precursors in fed-state metabolism
41
Q

Explain the steps of the transport and fate of dietary fats

A

Fat comes into the lymph, when its in the blood, it can follow different pathways:

  1. Glycerol react as storage for adipose cells
  2. Free fatty acids can be diffused into cells where they are oxidised for energy - produce ATP
  3. Cholesterol can metabolise into bile cells for reuse or become lipo-protein
42
Q

What does LDL-C do?

A

brings cholesterol from liver to most cells - lethal cholesterol

43
Q

What is HDL-C

A

transports cholesterol out of plasma - healthy cholesterol

44
Q

What do abnormal plasma levels of lipids do?

A

Increase risk of atherosclerosis and coronary heart disease: high LDL-C or low LDL-C

45
Q

Explain the major things that occur in fasted-state metabolism

A
  • Glycogen converts glucose in glycogenolysis
  • proteins used to make ATP:
  • Deamination of amino acids to organic acids, pyruvate, acetyl coA and intermediates of the citric acid cycle
  • Broken down with production of ATP
46
Q

Explain fasted-state metabolism in regards to lipids

A

Lipids broken down through lipolysis

  • glycerol feeds into glycolysis
  • fatty acids undergo beta-oxidation to produce acetyl coA
  • excess acetyl coA become ketone bodies: strong metabolic acids lead to ketoacidosis; ketogenic diets rich in proteins and fats low in carbohydrates
47
Q

What is deamination?

A

removal of the amino group from an amino acid creates ammonia and an organic acid

48
Q

What must happen to ammonia and why?

A

Its toxic so must be converted to urea

49
Q

How is insulin and glucagon released?

A

Endocrine pancreas secretes hormones insulin by beta cells and glucagon by alpha cells in the islets of langerhans

50
Q

What endocrine hormone dominates the fed state?

A

Insulin

51
Q

What endocrine hormone dominates in the fasting state?

A

glucagon

52
Q

What does insulin do to the metabolism?

A

inc. glucose oxidation
inc. glycogen synthesis
inc. fat synthesis
inc. protein synthesis

53
Q

What does glucagon do to the metabolism?

A

inc. glycogenolysis
inc. gluconeogenesis
inc. ketogenesis

54
Q

How does insulin promote anabolism?

A
  • increases glucose transport into most insulin-sensitive cells
  • enhances cellular utilization and storage of glucose
  • enhances utilization of amino acids
  • promotes fat synthesis
  • glucagon prevents hypoglycemia
  • antagonist to insulin
55
Q

Explain why insulin is so important

A

Insulin determines the whole of metabolic pathways happening in each cell

56
Q

what is type 1 diabetes

A

Characterised by insulin deficiency from beta cells destruction

  • without insulin, cells go into fasted-state metabolism: protein, fat breakdowns, hyperglycemia, excessive eating, glucose in urine, excessive urination and thirst
  • metabolic acidosis
57
Q

What is type 2 diabetes?

A

known as insulin-resistant diabetes

58
Q

how is body temperature homeostatically regulated?

A
  • normal metabolism generates enough heat to maintain body temperature in the thermoneutral zome
  • alterations in cutaneous blood flow conserve or release heat
  • sweat contributes to heat loss

PHYL1007 (5 decks)

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