Metabolic Pathways - PowerPoint PPT Presentation

Loading...

PPT – Metabolic Pathways PowerPoint presentation | free to view - id: 3d6faf-MTI5Z



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Metabolic Pathways

Description:

Glycogenesis: Making of glycogen Glycogenolysis: Breakdown of glycogen Glycolysis: Oxidation of glucose Hexosemonophosphate shut; Production of 5-C monosacch & NADPH – PowerPoint PPT presentation

Number of Views:104
Avg rating:3.0/5.0
Slides: 47
Provided by: chua2FiuE7
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Metabolic Pathways


1
Metabolic Pathways
  • Glycogenesis
  • Making of glycogen
  • Glycogenolysis
  • Breakdown of glycogen
  • Glycolysis
  • Oxidation of glucose
  • Hexosemonophosphate shut
  • Production of 5-C monosacch NADPH
  • Krebs Cycle
  • Oxidation of pyruvate acetyl CoA
  • Gluconeogenesis
  • Making of glucose from noncarbohydrate precursors

2
Fig. 4-10, p. 84
3
Glycogenesis
  • Glucose converted glycogen
  • Liver is major site of glycogen synthesis and
    storage
  • Other major sites of storage
  • Skeletal muscle (more)
  • Adipose tissue (less)

4
Fig. 4-11a, p. 85
5
Fig. 4-11b, p. 85
6
Glycogenolysis
  • Breakdown of glycogen into individual glucose
    units
  • Glucose 1-phosphate
  • Regulated
  • Glucagon (pancreatic hormone)
  • Epinephrine (adrenal medulla)
  • Fxn antagonistically to insulin

7
Fig. 4-12, p. 86
8
Fig. 4-13, p. 87
9
Glycolysis
  • Metabolic pathway where glucose is degraded into
    2 pyruvate molecules and a triose.
  • Next step is cell dependent (aerobic or
    anaerobic).
  • Anaerobic lactate conversion.
  • Aerobic Krebs cycle (prepared by glycolysis)

10
Krebs Cycle
  • Also known as the TCA cycle or the
    Embden-Meyerhaff cycle.
  • Catabolic
  • gt90 of food energy is metabolized via Krebs
  • Located in the mitochondria, ETC important.
  • 1mol of glu produces 262.8 kcal (38 ATP).

11
(No Transcript)
12
Lets Review
  • Pages 281 - 311.
  • Lets discuss the Krebs cycle steps (10).
  • Acetyl CoA - produced from beta oxidation, amino
    acid catabolism and GLYCOLYSIS.
  • Integral to developing the full potential of
    energy production via the TCA cycle.

13
Aerobic Anaerobic Glycolysis
  • Anaerobic conditions - NADH to NAD in redxn
    pyruvate to lactate via LDH.
  • With new NAD lactate can continue to be produced
    in the absence of O2
  • NADH cannot enter the mitochondrion., must be
    reduced. Gets shuttled into the mitochondria.
    Assists in energy production via the ETC (3ATPs
    per mole of NADH).
  • Malate and glycerol-3-phosphate are the shuttle
    systems.

14
(No Transcript)
15
Pentose Phosphate Pathway
  • Purpose is to metabolic shunt - generate
    important intermediates not produced in other
    pathways.
  • Pentose phosphates necessary for nucleic acids
    (DNA, RNA).
  • Reduced NADPH used for biosynthesis of fatty
    acids, assists in cell integrity, drug metabolism
    and reducing substrates in RBC.

16
Hexosemonophosphate Shunt
  • Involves at least three reactions.
  • Mammary glands, adipose, adrenal cortex and the
    liver have great need for NADPH.
  • Also active in the thyroid gland an testis but
    not skeletal muscle.
  • Pathway involves oxidative and non-oxidative
    reactions.
  • Pentoses, fructose-6-phosphate
    glucose-6-phosphate dehydrogenase are the major
    CHO involved in the PPP/HMP.

17
Gluconeogenesis
  • D-glucose is an essential nutrient for the fxn of
    many cells.
  • Glucose can be produced from amino acids,
    lactate, pyruvate and glycerol.
  • The process of producing glucose from non-glucose
    sources is gluconeogenesis.
  • Question - are carbohydrates essential?

18
Gluconeogensis
19
Gluconeogenesis
  • Essentially this is the reverse of glycolysis.
    Occurs in the liver kidneys.
  • This process involves circumventing irreversable
    rxns within glycolysis.
  • Turn to the middle of page 96.
  • Lets discuss, PEP, malate/aspartate conversion
    to oxaloacetate, use of glucogenic AA.

20
Lactate Metabolism
  • Effective gluconeogenesis enables the liver and
    body to regulate lactate production during
    physical exertion.
  • In muscle and adipose - since no
    glucose-6-phosphate, lactate cannot be
    metabolized into glucose. Thus it accumulates.
  • Lactate into glycogen is a taxing and slow
    process.

21
Lactate Utilization
  • During oxygen debt, lactate accumulates.
  • Slowly lactate is shuttled out of the muscle into
    the blood to be delivered to the liver.
  • In the liver lactate is converted into glucose.
  • What is the name of this cycle? (page 98)
  • Question - is lactate accumulation responsible
    for the burn felt during anaerobic exercise?

22
CHO Utilization in Exercise
23
Glycogenesis Summary
  • Glucose use is enhanced when fructose, glycerol,
    lactate are also available.
  • Ingested glucose does not automatically become
    glycogen.
  • Ingested glucose - RBC uptake - lactate produced
    via glycolysis - hepatic uptake - converted via
    Glu-6-PO4 by gluconeogenesis and than it is
    stored as glycogen.

24
Metabolic Regulation
  • The body has an ultimate goal of homeostasis - it
    wants catabolism not to out gun anabolism (vice
    versa).
  • Example is the classic Rockefeller University
    set-point study.
  • Suggest reading the Hirsch paper, early 1990s
    (do a PubMed search).

25
Metabolic Regulation
  • Modulated by allosteric enzymes or effector
    compounds.
  • Hormonal activation via covalent modification or
    enzyme induction.
  • Directional shifts in reversible reactions
  • Enzyme translocation within a cell.
  • Read pages 17 - 19, start at Enzymes.

26
Alcohol
  • Is ethyl alcohol (ETOH) a carbohydrate?
  • Structure CH3-CH2-OH
  • Who can tell us how many calories are in a gm of
    ETOH?
  • ETOH is metabolized into acetate?acetyl CoA and
    oxidized in the Krebs cycle.
  • Most ETOH is metabolized in the liver (cirrhosis)
    and by the enzymes ADH, microsomal ethanol
    oxidizing system (P450) and catalase.

27
Alcohol Metabolism
  • Discuss energy cost of alcohol metabolism.
  • ETOH increases lipid biosynthesis while reducing
    fat oxidation locally (fatty liver, beer gut).

28
Carbohydrates in the Diet
  • Controversies - high vs. low CHO, glycemic
    index/load, percent actually needed in the diet,
    etc.
  • CHOs used in health promotion pre and
    probiotics (ex, types of oligosaccharides - FOS,
    inulin), nutrient timing, resistant starch, and
    fiber (next topic!).

29
Fiber
  • Origin of human use 1850 (Germany, from animal
    feed).
  • The last 25 years have produced much research in
    the areas of dietary and functional fiber.
  • Fiber comes from fruit, vegetables, grains, can
    be man made.

30
(No Transcript)
31
Fiber
  • Dietary fiber is non-digestible (CHO, lignans
    intrinsic to plants.
  • Functional fiber - isolated non-digestible fiber
    that has been shown to have beneficial
    physiological effects in humans.

32
Fiber Plants
  • Plant cell wall gt95 of dietary fibers -
    cellulose, hemicellulose, lignan, pectins
    nonstarch polysaccharides.
  • Starch also found within plant cells.
  • Fruits vegetables provide equal amounts of
    cellulose pectin in the diet.

33
Fiber Foods
  • Cellulose - bran, legumes, nuts, peas, root
    vegetables, cabbage and the cabbage family.
  • Hemicellulose, dietary fiber that is also part of
    plant cell walls.
  • Can be water soluble or insoluble.
  • Fermented by intestinal microflora.

34
Fibers
  • Pectin - is also functional. Complex
    polysaccharide. From the primary cell wall of a
    plant. Not a bulking agent. From apples,
    strawberries and citrus fruits, legumes, nuts
    some vegetables.
  • Lignin - polymer, insoluble in H20. Also a fxnal
    fiber. From vegetables, wheat and fruits that
    have seeds.

35
Fibers cont.
  • Gums - hydrocolloid, secretory product from
    injured plants. Exudate. H20 soluble. Many
    sources, also fxnal.
  • B-glucan - homopolymer of glucopyranose. From
    cereals (bran/barley can be synthesized from
    yeast. FDA approved for heart health claim.

36
Fibers cont.
  • Fructans - inulin, oligosaccharides, FOS.
    Prebiotic. ? bifidobacteria.
  • Resistant starch - non-digestible. ? butyrate
    formation (SCFA).
  • Chitin/chitosan - amino-polysaccharide.
    Insoluble, extract from crustaceans, may also
    lower Tchol.

37
Fibers cont.
  • Polydextrose/polols - glucose-sorbitolunits that
    are polymerized. Used as a bulking agent. Can
    cause gastric distress.
  • Psyllium - husk extract from plantago. High H20
    binding property - bulking agent, think
    Metamucil.
  • Resistant dextrins - resistant maltodextrin from
    heating cornstarch tx with amylase.Functional,
    similar to B-glucan.

38
GI response to soluble/insoluble fiber.
39
Solubility
  • Fibers that dissolves in hot water is soluble.
  • Fiber that does not dissolveis not soluble.
  • Insoluble fiber enhance GI transit time fecal
    bulk.
  • Soluble fibers delay gastric emptying.
  • Vegetables, wheats some grains insoluble gt
    soluble fiber.

40
(No Transcript)
41
Soluble Effects
  • GI delayed emptying, interference with nutrient
    absorption, reduced enzyme fxn, attenuation of
    blood glucose response, altered transit time.
  • Diminished absorption of lipids - ? Tchol, ? bile
    excretion, may enhance mineral absorption (ex
    calcium).

42
Fermented Fibers
  • Enhance the microflora of the GI tract.
  • Produces lactate, butyrate and other SCFAs. Also
    produces CO2 methane gases.
  • Effects - ? H2O and NA absorption, stimulates
    mucosal cells, provides some energy, acidifies
    the lumen (may protect against colon Ca).

43
Nonfermentable Fibers
  • Cellulose, lignan, hemicellulose. Acts as a
    detoxifying bulking agent.
  • May ? conversion of procarcinogins to carcinogens
    via colonic bacteria enhancement.
  • Rice bran gt wheat bran. Cellulose, psyllium,
    inulin and oligosaccharides also increase fecal
    bulk.

44
Fiber Recommendations
  • 2002 National Academy of Sciences recommended for
    men 19 to 50 38gm/total/day for females 19 to
    50 25 gm/total/day.
  • In general from age 1 onward, we should be
    getting 19 gm/day and this ?s as we age to 25 to
    38 gm/d.

45
Fiber Guidance
  • To meet the needs, eat fiber-rich legumes (also a
    source of protein), at least 5 svgs of fruit
    vegetables and at least 2-3 servings/d of whole
    grains as part of the 6 to 11 servings
    recommended by the Food Guide Pyramid
    (www.mypyramid.gov)

46
Fiber Take Home
  • We do not eat enough.
  • Why?
  • How can we as healthcare professionals affect
    change?
  • Will this ? disease incidence?
  • Food first, functional foods second, supplements
    third. Teach lifestyle.
About PowerShow.com