L18: Post-Absorptive Metabolism Flashcards Preview

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Flashcards in L18: Post-Absorptive Metabolism Deck (22)
1

*List the major metabolic fuels

  • Glucose
  • FFA
  • Glycogen
  • Ketone bodies
  • Triacylglycerols
  •  

2

Can nutrients be converted from one form to another?

Yes. eg fat can be obtained from food, or synthesised from protein or CHO

3

What molecule is the main energy currency?

ATP
(adenosine triphosphate)

4

*Understand what is meant by ATP being the energy currency

What is the structure of ATP?

contains 3 phosphate bonds, two of which are high energy

5

*Understand the various fates of glucose

What is glucose converted to when it enters a cell?

What is the four possible fates of this molecule?

  • Converted to glucose-6-phosphate by glucokinase or hexokinase
  • 4 possible fates:
    -Aerobic metabolism to generate energy
    -Anaerobic metabolism to generate energy
    -Glycogen synthesis for short-term energy store
    -Fat synthesis, for long-term energy store

6

*Understand what is meant by ATP being the energy currency

What are the four stages of aerobic glucose metabolism, and how many ATP in total does it produce?

  • stage 1: glycolysis (glucose => pyruvate)
  • stage 2: pyruvate converted to acetyl CoA
  • Stage 3: citric acid cycle
  • stage 4: oxidative phosphorylation
  • TOTAL ATP PRODUCED = 38

7

​*Understand what is meant by ATP being the energy currency

How many ATP is produced in stage 1 of aerobic metabolism?

2 ATP and 4 H

8

​*Understand what is meant by ATP being the energy currency

How many ATP is produced in stage 2 of aerobic metabolism?

No ATP and 4 H

9

​*Understand what is meant by ATP being the energy currency

How many ATP is produced in stage 3 of aerobic metabolism?

16H and 2 ATP

10

​*Understand what is meant by ATP being the energy currency

How many ATP is produced in stage 4 of aerobic metabolism?

produces water and 34 ATP

11

What are the four control points in aerobic metabolism of glucose?

  • amount of glucose taken up by cell is limigted by insulin
  • ATP exerts -ve feedback inhibition of enzymes
  • Citrate iions also exert -ve feedback
  • ADP and AMP which activate process become limiting as they are converted to ATP

12

*Understand the fates of glucose

Where is glycogen stored and what is its main advantage?

  • All cells store some, but  mainly in liver and muscle
  • Adv. is to provide a store of energy that can be accessed quickly

13

*Understand the fates of glucose

Where glucose is stored as fat, where is the energy supplied from for this process?
Describe this e source

  • pentose phosphate pathway
  • occurs in liver and fat cells
  • on each cycle 6 glucose molecules enter and 5 come out (5-sugar) w/ one CO2 and H
  • H atoms can be oxidised to give ATP, but normally used in fat synth.

14

*Understand the various fates of lipids

What are the 3 possible fates of FFA's taken up by liver?

  • partial breakdown for transport out of liver as smler FFA (catabolism)
  • Complete breakdown to provide energy (catabolism)
  • conversion to triglycerides for storage (anabolism)

15

*Understand the various fates of lipids

describe fate 1 partial break down for TRANSPORT to other tissues

  • Liver breaks down LCFA into SCFA using lipase
  • FA carried by protein albumin
  • Reffered to as non-esterified FA or NEFA's
  • Ketosis occurs when plasma [ ]  of FFA too high
    -liver ketone formation occurs in mitochondria
    -ketone bodies can't be used by liver, can be toxic!

16

*Understand the various fates of lipids

describe fate 2 complete break down to provide ENERGY

  • Transport of FFA into mito by carnitine
  • beta oxidation occurs -cleavage of two C at a time from FA to give acetyl CoA and 4 H atoms
  • A-CoA enters TCA cycle where H atom undergoes oxidative phosph.
  • Total ATP yield depends on FFA length
     

17

When does the synthesis of triglycerides from CHO occur?

Where does it occur?

List the steps

  • When? CHO are present in excess of animal's energy needs and glycogen storage capacity
  • Where? Mainly in liver, also in adipose
  • Steps?
    -conversion of CHO to a-CoA
    -a-CoA converted to FA (mostly 14 - 18C) and subsequently into TG's

18

When does synthesis of fat from protein occur?

is this an efficient process?

  • when dietary protein is in excess of energy reqs
  • highly inefficient

19

Describe lipoproteins

  • main form of lipids in blood
  • synthesised in liver
  • Classified by density, which refers to relative amont of protein they contain
    -high or low density
    -HDL's, LDL's

20

*Understand the various fates of proteins

How are protens absorbed?

What are the 3 possible fates of proteins?

  • absorbed from gut as aa and sml peptides transported to liver where they have 3 possible fates:
  • used to synthesise new protein in liver
  • deamination and further mtabolism to provide energy
  • pass through liver and enter hepatic vein -excretion

21

*Understand the various fates of proteins

Describe deamination

  • Amino group is removed to form a keto acid + ammonia
  • ammonia combined w/ CO2 to form urea and water
  • Urea enters blood from liver and is excreted by kidneys
    -in ruminants may enter urea cycle
  • remaining keto acid is converted to energy or stored

22

*Describe why ruminants are 'special' with respect to glucose homeostasis

  • very little absorption of glucose from rumen
  • ALL glucose for ruminants originates from gluconeogenesis
  • PROPRIONATE -only VFA to support glucose production
  • most proprio extracted from portal blood by liver
  • FA only synthesised in adipose of ruminants