Lecture 11 : Gastrointestinal System V : Nutrition and Metabolism II

Question 1

Glucose is a major fuel for our body:

Answer 1

When glucose is plentiful, cells use it as their main energy source

To get maximum ATP from glucose, it must be converted to products that go through the citric acid cycle and oxidative phosphorylation

Question 2

You can’t store ATP: excess glucose can be stored as _____

Answer 2

glycogen

Question 3

Liver and skeletal muscles are main cell types capable of holding large stores of glycogen =

Answer 3

~600 g total, 2400 kcal

less than one day’s worth of energy

Question 4

When glycogen stores are full, excess glucose gets converted to ____

Answer 4

fat

Question 5

Different processes control amount of glucose available for cellular respiration:
The 4 G’s of Glucose Regulation =

Answer 5

Glycolysis
Glycogenesis
Glycogenolysis
Gluconeogenesis

Question 6

Glycolysis =

Answer 6

(sugar splitting)

converts glucose to pyruvic acid (producing 2 ATP) – all cells

Question 7

Glycogenesis =

Answer 7

polymerize glucose to form glycogen

(storage of glucose – occurs in liver* and skeletal muscle)

Question 8

Glycogenolysis =

Answer 8

hydrolyzes glycogen into glucose monomers

(release glucose from storage – only liver can release to blood)

Question 9

Gluconeogenesis =

Answer 9

forms glucose from non-carbohydrate precursors

(make new glucose from noncarbohydrate sources) – mostly in liver*

Question 10

Helpful root words:
glyco, gluco =
lysis =
genesis =
neo =

Answer 10

glyco, gluco = sugar

lysis = splitting

genesis = the formation of; origin

neo = new

Question 11

To fully utilize protein or fat as an energy source, they must be converted to ____

Answer 11

substrates of citric acid cycle

Question 12

____ are the most concentrated source of energy in the body

Answer 12

Fats

Question 13

Fats contain very little ____; yield 9 kcal/gm fat

Answer 13

water

Question 14

Products of fat digestion transported as ______.

Answer 14

chylomicrons

Question 15

Lipases in capillaries hydrolyze ____ through ____

Answer 15

triglycerides
lipolysis

Question 16

Of fats, only ___ routinely oxidized for energy

Answer 16

triglycerides

Question 17

Liver, cardiac muscle, resting skeletal muscle prefer ____ as fuel

Answer 17

fatty acids

Question 18

___ and ____ can be taken up into most body cells and converted to acetyl CoA (through different pathways) to enter citric acid cycle

Answer 18

Glycerol
free fatty acids

Question 19

____ allows Glycerol and Fatty Acids to be converted to energy substrates

Answer 19

Lipolysis

Question 20

Glycerol =

Answer 20

Glycerol is a 3-carbon sugar

Converted to pyruvic acid through glycolysis pathways

Pyruvic acid converted to acetyl CoA which can enter Citric Acid cycle

Net energy ~15 ATP

Question 21

Fatty Acids carbon-hydrogen chains broken down in cycles of
_____

Answer 21

beta oxidation

Question 22

beta oxidation =

Answer 22

2 carbon fragments broken off

Form Reduced coenzymes along with acetyl CoA

acetyl CoA enters Citric Acid cycle

Question 23

____ are formed from Acetyl CoA if there aren’t sufficient carbohydrate substrates for citric acid cycle to run

Answer 23

Ketone bodies

Question 24

____ is triglyceride synthesis

Answer 24

Lipogenesis

Question 25

Lipogenesis =

Answer 25

Occurs mainly in liver and adipose tissue during states when cellular ATP and glucose levels are high Excess acetyl CoA (2 carbons) join together to make fatty acids Excess glyceraldehyde 3-phosphate (glycolysis intermediate) converted to glycerol Note these pathways are reversible

Question 26

Amino acids can also be oxidized for energy =

Answer 26

: Occurs in the liver we can make nonessential amino acids from keto acids Transamination and deamination : removes amine group from an amino acid >nitrogen converted to ammonia and then urea Keto acid formed in transamination reaction is modified for citric acid cycle or conversion to fats or glucose

Question 27

There is no storage form of ______

Answer 27

amino acids

Question 28

Amino acids are built into proteins when there is an excess =

Answer 28

Any given protein is only synthesized if all its amino acids are available Every protein has a “job” – we don’t make extras just to store amino acids If amino acids are needed for energy, we lose important protein

Question 29

Amino acids can also be converted to glucose : gluconeogenesis

Answer 29

converted first to pyruvic acid , then converted to glucose by reversing the steps of glycolysis

Question 30

Nutrient pools are interconvertible because their pathways are linked by ______

Answer 30

key intermediates

Question 31

The body draws on nutrient pools to meet its metabolic needs =

Answer 31

Carbohydrates are easily and frequently converted to fats Fats and carbs are oxidized directly to supply energy

Question 32

Amino acid pools must be converted to ____ that can enter citric acid cycle

Answer 32

metabolites

Question 33

Pyruvic acid can be converted to glucose (______)

Answer 33

gluconeogenesis

Question 34

Fats and carbs can be stored, but excess amino acids can’t be – they are ______

Answer 34

oxidized for energy, or converted to fat or glycogen for storage

Question 35

________ are key in managing nutrient load and ensuring all tissues have adequate energy

Answer 35

Liver, skeletal muscle, and adipose tissue

Question 36

Prefer ____ as major energy source = Allow glucose to remain in blood for brain if glucose is in short supply

Answer 36

triglycerides

Question 37

Skeletal muscle:

Answer 37

Protein synthesis and protein breakdown >Muscle proteins can liberate amino acids for gluconeogenesis Glycogen storage

Question 38

Adipose tissue:

Answer 38

Lipolysis and lipogenesis Major organ of triglyceride storage Also secretes novel hormones regulating metabolism – the kind of adipose tissue matters

Question 39

Carbohydrate metabolism:

Answer 39

Convert non-glucose monosaccharides to glucose Glycogenesis, glycogenolysis, gluconeogenesis Converts glucose to fat

Question 40

Fat metabolism:

Answer 40

Breakdown fatty acids (FA) to acetyl CoA (beta-oxidation) Convert excess acetyl CoA to ketone bodies (ketogenesis) Stores fats Synthesizes lipoproteins for transport of FA, fats and cholesterol in blood Synthesis of cholesterol from acetyl CoA Production of bile, converts cholesterol to bile salts

Question 41

Protein metabolism:

Answer 41

Synthesizes urea to remove ammonia from body Deaminates amino acids for conversion to glucose or use as fuel Synthesizes plasma proteins Interconversion of nonessential amino acids

Question 42

Vitamins/Minerals:

Answer 42

Storage of vitamin A, D, B12, iron

Question 43

Biotransformation functions:

Answer 43

Metabolizes alcohol, drugs, hormones other toxins by inactivating them for excretion in kidney Perform reactions to make products more active or less active Processes bilirubin excretes bile pigments in bile

Question 44

Absorptive (fed) state =

Answer 44

Lasts about 4 hours after eating begins Anabolism exceeds catabolism and nutrients are stored

Question 45

Post-absorptive (fasting) state =

Answer 45

Catabolism of fat, glycogen, and proteins begins Primary goal is maintaining blood glucose levels (70-110 mg/dl) Can be short (between meals) or long-lasting (fasting, starvation)

Question 46

Major events in the absorptive state =

Answer 46

Anabolism exceeds catabolism and nutrients are stored Glucose is the major energy fuel

Question 47

Major metabolic pathways in the absorptive state =

Answer 47

Carbohydrates and Amino acids absorbed into blood go to liver first (via portal vein) Most lipids travel via lymph in chylomicrons

Question 48

____ dominates hormonal control of the absorptive state

Answer 48

Insulin

Question 49

Insulin Stimulus: rising blood glucose levels > Beta cells of pancreas increase insulin secretion Result:

Answer 49

Insulin promotes increased uptake of glucose and amino acids to cells increased use of glucose by cells for energy or storage as glycogen and fats Insulin inhibits glucose release and gluconeogenesis in liver

Question 50

Insulin is a ______ – decreases blood glucose levels

Answer 50

hypoglycemic hormone

Question 51

Lack of insulin or insulin response: _____

Answer 51

diabetes mellitus

Question 52

Major events and metabolic pathways in the post-absorptive state =

Answer 52

Catabolism of fat, glycogen, and proteins Goal is to maintain homeostatic glucose levels (70-110 mg/100ml)

Question 53

_____ and other hormones dominate hormonal control of the post-absorptive state

Answer 53

Glucagon

Question 54

Glucagon Stimulus: falling blood glucose levels > Alpha cells increase glucagon secretion > Beta cells decrease insulin secretion Result:

Answer 54

glycogenolysis and gluconeogenesis by liver restore blood glucose levels lipolysis in adipose tissue releases fatty acids for use by tissue cells = “glucose sparing”

Question 55

Carbohydrates absorbed by:

Answer 55

Glucose primarily

Question 56

Carbohydrates absorptive state metabolism:

Answer 56

Used immediately for energy through aerobic pathways (glycolysis & citric acid cycle) Stored as glycogen in liver & muscle (glycogenesis) Excess converted to fat and stored in adipose tissue (lipogenesis)

Question 57

Carbohydrates post-absorptive state metabolsim:

Answer 57

Glycogen polymers broken down (glycogenolysis) to glucose

Question 58

Fats absorbed by:

Answer 58

Fatty acids, triglycerides, cholesterol

Question 59

Fats absorptive state metabolism:

Answer 59

Stored as triglycerides primarily in liver and adipose tissue (lipogenesis) Cholesterol used for steroid synthesis or in membranes

Question 60

Fats post-absorptive state metabolsim:

Answer 60

Triglycerides broken down into fatty acids and glycerol (lipolysis) Fatty acids used for ATP production through aerobic pathways (Beta-oxidation)

Question 61

Proteins absorbed by:

Answer 61

Amino acids

Question 62

Proteins absorptive state metabolism:

Answer 62

Most amino acids go to tissues for protein synthesis If needed for energy, amino acids covered in liver to intermediates for aerobic metabolism (deamination) Excess converted to fat in adipose tissue (lipogenesis)

Question 63

Proteins post-absorptive state metabolsim:

Answer 63

Proteins broken down into amino acids Amino acids deaminated in liver for ATP production or used to make glucose (gluconeogenesis)

Question 64

Insulin in regulation of metabolic processes =

Answer 64

Stimulates glucose uptake by cells Stimulates amino acid uptake by cells Stimulates glucose catabolism for energy Stimulates glycogenesis Stimulates lipogenesis & fat storage Inhibits gluconeogenesis Stimulates protein synthesis (anabolic)

Question 65

Glucagon in regulation of metabolic processes =

Answer 65

Stimulates glycogenolysis Stimulates lipolysis & fat mobilization Stimulates gluconeogenesis

Question 66

Insulin is necessary for cells to take glucose out of the blood =

Answer 66

No insulin = high blood glucose levels High concentration of glucose in filtrate is lost in urine along with water (high urine production)

Question 67

Type I Diabetes :

Answer 67

autoimmune disease where immune system attacks beta cells of pancreas little or no insulin produced (“insulin dependent diabetes”)

Question 68

Type II Diabetes:

Answer 68

Pancreas makes insulin Receptors lose sensitivity to insulin (“insulin resistant diabetes”)

Question 69

Metabolic Syndrome

Answer 69

2-8% of world population 1 in 3 US adults Group of conditions that increase risk of cardiovascular disease, diabetes, stroke, other diseases Altered metabolism

Question 70

Many hormones involved in metabolism =

Answer 70

“traditional” endocrine glands Gut hormones from enteroendocrine cells

Question 71

Recent drugs for diabetes treatment:

Answer 71

Hormone GLP-1 : Glucagon-like peptide 1 Metformin Semaglutide

Question 72

Hormone GLP-1 : Glucagon-like peptide 1

Answer 72

secreted from intestine doesn’t behave like glucagon slows digestion by delaying gastric emptying stimulates insulin secretion to lower blood glucose

Question 73

Metformin:

Answer 73

stimulates GLP-1 release

Question 74

Semaglutide:

Answer 74

(Ozempic) : GLP-1 agonist