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NUTRITION AND METABOLISM GUYTON > All Guyton Chaps Nutrition/metabolism > Flashcards

All Guyton Chaps Nutrition/metabolism Flashcards

1
Q

Where is phosphorylation of glucose in the cell reversible and why?

A

Liver, kidney, and intestinal cells — glucose phosphatase is present

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2
Q

How is glycogen formed?

A

G6P —> G1P —> uridine diphosphate glucose—> glycogen

Lactic acid, glycerol, pyruvic acid, and some deaminated amino acids can be converted to glucose then glycogen

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3
Q

What occurs during the process of glycolysis?

A

Splitting glucose to form 2 pyruvic acid molecules

Glucose —> g6P —> fructose 6P —> fructose 1,6, diphosphate —> 2 glyceraldehyde 3 phosphate —> 2 pyruvic acid molecules

Breakdown of fructose 1,6 diphosphate to pyruvate results in 4 ATP, but 2 ATP are needed to phosphorylation the original glucose before glycolysis can begin

Overall net products of glycolysis = 2 pyruvate, 2 ATP, and 4 hydrogen

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4
Q

Step one of the TCA cycle

A

2 pyruvate are converted to acetyl CoA

2 pyruvate + 2 CoA —> 2 acetyl CoA

Products per glucose molecule = 2 CO2, 4 H, no ATP

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5
Q

What is the process of oxidative phosphorylation?

A

Sequence of oxidative reactions that results in a large amount of ATP

Occurs in mitochondria by chemiosmotic mechanism (series of enzymatically catalyzed reactions)

Hydrogen ions produced by the earlier stages of cellular respiration are processed by dehydrogenase and produce reduced NADH and one hydrogen ion

The electrons are removed from the NADH and H as they enter the electron transport chain — a series of proteins (flavoprotein, iron sulfide proteins, ubiquinone, and cytochromes B, C1, C,A, and A3) found between the inner and outer chamber of the mitochondrion

Electrons are shuttled down the chain until they reach cytochrome oxidase (A3) which combines oxygen and hydrogen to form water

A large amount of potential energy is produced in the form of a hydrogen gradient between the inner and outer chamber of the mitochondrion

Hydrogen ions flow through ATPase converting ADP and ionic phosphate into ATP

ATP is transported out of the cell by facilitated diffusion and then simple diffusion
ADP is transported into the cell by simple diffusion and then facilitated diffusion

This results in 30 ATP by chemiosmotic mechanism and 4 H+ outside the chemiosmotic mechanism (these 4 H are produced during the succinct and fumaric acid stages of the TCA cycle)

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6
Q

Summarize total ATP formation during breakdown of glucose

A

Glycolysis: 2 ATP
TCA cycle 2 ATP
ETC: 30 ATP (by chemiosmotic mechanism) + 4 ATP (outside the chemiosmotic mechanism — H+ are produced during the succinct and fumaric acid stages of the TCA cycle)

Total = 38 ATP
Heat - unable to be used by cells

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7
Q

Which enzymes, regulated by concentrations of ADP and ATP help to regulate glycolysis and glucose oxidation?

A

Phosphofructokinase - early enzyme in glycolysis that is inhibited by ATP and promoted by ADP

Citrate ion (in the TCA cycle) — inhibits the function of phosphofructokinase, allows the TCA cycle to catch up

Finite amount of ADP - prevents unnecessary ATP formation

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8
Q

What occurs during anaerobic glycolysis?

A

Small amount of energy can be released from pyruvate without oxygen

Pyruvate + NADH+ H is converted to lactic acid, which can be shuttled into the extra cellular space or less vital cells

Anaerobic respiration can occur for minutes

When oxygen is available again, then lactic acid can be returned to pyruvic acid or glucose

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9
Q

What is the pentose phosphate pathway?

A

Another mechanism to degrade glucose to be used for energy

Can provide energy independent of all the enzymes of the TCA cycle

Glucose + 12 NADP + 6 H2O —> 6CO2+12H and 12NADPH

Unlike in glycolysis, H+ that is released does not combine with NAD+ but rather NADP+ to produce NADPH

NADPH is used to synthesize fats (this is a means of producing fat from carbohydrates )

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10
Q

What are the building blocks for triglycerides and phospholipids?

A

Fatty acids

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11
Q

What is the difference between triglycerides and cholesterol?

A

Cholesterol does not contain fatty acid, but rather a sterol from portions of fatty acid molecules

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12
Q

What is the basic chemical structure of triglyceride?

A

Made up of three long chain fatty acids with a glycerol backbone

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13
Q

How are triglycerides and other lipids absorbed from the GI tract?

A

Absorbed into intestinal lymph

  1. Triglycerides are split into monoglycerides and fatty acids during digestion
  2. Triglycerides are resynthesized from components in the intestinal epithelial cells and lymph into droplets call chylomicrons
  3. Cholesterol and phospholipids join triglycerides in chylomicrons
  4. Chylomicrons are then transported to the thoracic duct and emptied into venous blood (at junction of subclavian and jugular vein)

Chylomicrons have outer surface proteins to help prevent adherence to lymphatic vessel walls

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14
Q

How are chylomicrons removed from blood?

A

In capillaries, lipoprotein lipase, which is transported to the surface of capillary endothelium, hydrolysis triglycerides of chylomicrons as they contact the blood vessel wall. This releases fatty acid and glycerol

Fatty acids liberated by lipoprotein lipase diffuse into fat and muscle cells to make new triglyceride or be used as fuel

After removal of triglycerides, chylomicrons remnants are cholesterol rick and are rapidly cleared form plasma in liver sinusoids

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15
Q

How is stored fat broken down and transported to areas of the body that require energy?

A

Hydrolysis of triglyceride back into FFA and glycerol
FFA combine with albumin - aka FFA or nonesterified FA
Conditions such as starvation/ DKA may increase fat utilization and increased FFA concentration in blood

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16
Q

What are lipoproteins?

A

Predominant plasma lipid in fasting state that contain varying conmbinations of triglycerides, cholesterol, phospholipid and protein

Almost all are formed in liver

Primary function is to transport their lipid components in blood

Examples: VLDL, IDL,LDL, HDL

17
Q

Name the different lipoproteins and what their main components are

A

VLDL: high concentration of triglycerides and moderate concentrations of cholesterol and phospholipid
IDL - similar to VLDL with some triglyceride removed, increased concentrations of cholesterol and phospholipid
LDL - almost all triglyceride removed, increased concentration of cholesterol and phospholipid
HDL - high concentration of protein (50%) and smaller concentration of cholesterol and phospholipid

18
Q

What are important aspects about adipose tissue?

A

Store triglycerides as source for energy later
Provide heat and insulation
Secrete hormones lepton and adiponectin
Triglycerides inside fat cells are stored in liquid form
Tissue lipases permit exchange of fat between adipose tissue and blood

19
Q

What role does the liver play in fat metabolism?

A 
Degrades fatty acids into small compounds that can be used for energy
Makes triglycerides (mainly from carbs, but also proteins)
Makes other lipids from fatty acids (esp cholesterol and phospholipids)
20
Q

How are triglycerides used for energy/ formed into ATP?

A
  1. Hydrolysis of triglycerides into FFA and glycerol —> glycerol enters cytosol and is converted to Glycerol 3 phosphate —> G3P can enter glycolysis and form pyruvate, fatty acids are processed in mitochondria
  2. Fatty acids bind with carnitine to enter mitochondria, then they split from carrier
  3. Beta oxidation of FFA occurs, meaning that there is progressive release of Acetyl CoA and hydrogen from FA —> acetyl CoA can directly enter the TCA cycle
21
Q

What occurs in regards to fatty acid breakdown during starvation?

A

Fat is almost exclusively used for energy — starvation state: increased release of glucocorticoids, glucagon, and low insulin levels

Large amounts of ketone bodies are produces via fatty acid breakdown and release of acetyl CoA (acetoacetic acid —> beta hydroxybutyrate —> acetone)

This results in ketoacidosis (cells can’t use all Ketone bodies in the TCA cycle, as oxaloacetate is derived from carbohydrates

22
Q

How are triglycerides synthesized from carbohydrates?

A

Triglyceride synthesis occurs in the liver, and then once made they are transported to tissues via VLDL
Carbohydrates are first converted to acetyl CoA and then into FFA via Malonyl-CoA and NADPH

1 acetyl CoA + malonyl CoA + 16 NADPH + 16H —> 1 stearic acid + 8 CO2 + 9 CoA +.16 NADPH + 7 H2O

Once FFA have grown to contain 14 to 18 carbon atoms, they are bound to glycerol and glycerol 3 phosphate to form triglycerides

23
Q

How is fat utilization regulated?

A

Downregulation: high amounts of G3P —> act to form triglycerides, faster FFA synthesis than degradation, presence of acetyl CoA carboxylase (enzyme in lipogenesis) is upregulated due to high levels of intermediates of the TCA cycle

Hormonal regulation: absence of insulin, epinephrine and norepinephrine, glucocorticoids, thyroid hormone

24
Q

What are phospholipids and why are they important?

A

Major types: lecithins, cephalons, sphingomyelin
Lipid soluble, contain one or more fatty acid, one phosphoric acid radical, and nitrogenous base
Made ion all cells of the body but liver produces the majority
Functions:
Components of blood lipoproteins, component of thromboplastin, component of nerve sheath, donors of phosphate radicals during different chemical processes, component of structural elements of cells (membranes)

25
Q

What form of cholesterol accounts for the majority of cholesterol?

A

Endogenous (formed in liver)

26
Q

Why is cholesterol important/ what are its main functions?

A

Cholic acid/ bile salt formation = 80% of cholesterol use
Steroid hormone production
Skin deposition

27
Q

What are the building blocks of amino acids?

A

Acidic group (COOH) and nitrogen atom as an amino group

28
Q

What is the difference between essential and nonessential amino acids?

A

Essential - cannot be made in sufficient quantities in the body
Non-essential - not essential in the diet b/c they can be made in the body from the appropriate alpha keto acids or amino acid precursors. Produced by trans animation (transfer of amino acid radical onto alpha keto acid group) by aminotransferases (vit B6 derivative)

29
Q

How are amino acids transported and stored?

A

Exist in blood in ionized state
Most proteins are absorbed as amino acids, which enter the cell by facilitate diffusion or active transport

Excess amino acids are excreted in urine
Once cells reach their upper limit for protein storage, excess amino acid in circulation can be degraded and used for energy or converted to fat or glycogen for storage

30
Q

How can protein be used for energy?

A
  1. Deamination - removal of amino groups from amino acids by trans Amin action (Transfer of amino group to acceptor substance). —> ammonia is released during deamination of amino acids and removed from blood via conversion into urea. All urea in the body is made in the liver
  2. Oxidation of deaminated amino acids — this results from conversation of alpha keto acid to substance that can enter TCA cycle, participate in carb/lipid metabolism (e.g. acetyl CoA) or serve as an alternative energy source (e.g. ketone body)
31
Q

Which hormones regulate protein metabolism?

A

Growth hormone - increased synthesis of cell proteins
Insulin - synthesis
Glucocorticoids - increased protein breakdown
Testosterone- increased protein deposition in tissue
Estrogen. - increased protein deposition in tissues (less so than testosterone)
Thyroxine - increased metabolism of cells and thus protein metabolism if inadequate fats/ cats available

32
Q

What are important parts of the brain that regulate food intake?

A

Hypothalamus - feeding and satiety
Brain stem - controls mechanical process of eating
Amygdala
Prefrontal cortex

33
Q

What are important neurons/ neurotransmitters that regulate food intake?

A

Pro-opiomelanocortin (POMC) and Cocaine and amphetamine related transcript (CART) neurons — decrease food intake and increase energy expenditure, produce alpha melanocyte stimulating hormone, are stimulated by insulin, leptin and CCK

Neuropeptide Y (NPY) and agouti related protein (AGRP) neurons — increase food intake and decrease energy expenditure , produce NPY and AGRP, stimulated by ghrelin

34
Q

What are factors outside the CNS that regulate food intake?

A

Anorexigenic - sensory neural signals from the GI tract about stomach filling via vagus nerve

Chemical signals from nutrients in the blood (amino acids, fat, glucose) signify satiety

GI hormone signals:

Ghrelin - orexigenic, signals release of NPY or AGRP

CCK, peptide YY (PYY) - anorexigenic

Hormones released from adipose tissue (e.g. leptin) - anorexigenic

Other: influences of sign, smell, taste processed by cerebral cortex - can be orexigenic/anorexigenic

35
Q

What are factors that influence/ regulate short term quantity of food intake?

A
  1. GI filling/ stretch inhibitory signals (stomach, duodenum) are transmitted via vagus nerve to suppress feeding centers
  2. Anorexigenic hormones:
    PYY - secreted by entire GIT, but especially ileum and colon
    CCK - made in response to fats/ proteins in duodenum and activates receptors on local sensory nn. In the duodenum sending messages to brain via vagus nerve
    glucagon like peptide/ GLP - secreted from intestines in presence f good and enhances glucose dependent insulin production/ secretion (both of which suppress appetite)
  3. Orexigenic hormones - ghrelin is released from oxyntic cells of stomach and to a less extent the intestine
  4. Oral food intake meter (I.e. act of chewing, salivation, swallowing
36
Q

Factors that influence long term food intake?

A

Blood concentrations of glucose, amino acids, lipids

Temperature - cold? - more food, hot? - less food

Anorexigenic hormones -
Leptin - peptide hormone released from fat helps hypothalamus sense energy storage — acts to deactivate NPY and AGRP, activates POMC, increases production of CRH and increases sympathetic NS activity

37
Q

What does retinol deficiency/ vitamin A deficiency cause?

A

Night blindness

38
Q

What does Thiamine/ Vit B1 deficiency cause?

A

Lesions of the CNS/PNS - neuronal swelling and myelin sheath degeneration
Stargazing behavior

39
Q

What is the importance of vitamin K?

A

Essential cofactor to vitamin K epoxide re-educates that adds a carbonyl group to clotting factors II, VII, IX, X

NUTRITION AND METABOLISM GUYTON (1 decks)

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