Ch. 19 Regulation of Metabolism

metabolism

all the chemical reactions in the body's cells that change food into energy

anabolism

energy that must be continuously given to tissues and organs via energy storage (building up molecules)

catabolism

energy liberation (taking large molecules & breaking them down)

What does plasma contain?

\- circulating glucose

\- fatty acids

\- amino acids used by the body's cells for production of energy via cell respiration

True/false: glucose concentration in blood must be maintained in normal, healthy range for production of energy?

true

How long does it take for complete absorption of an average meal?

4 hrs

True/false: There are energy reserves that are synthesized after a meal

true

What are the 2 functional states for providing energy for
- cellular activities
- maintaining blood glucose concentration

\- absorptive state

\- postabsorptive state

^^absorptive state^^

\- "feasting"

\- when nutrients enter blood from the GI tract during the 4 hr. period following a meal

==postabsorptive state==

\- "fasting"

\- after absorptive state

\- when GI tract is empty of nutrients and body's reserves supply energy

2 hormones that regulate the transition between *fasting* and *feasting* and maintain homeostasis of glucose

\- ==glucagon==

\- ^^insulin^^

What secretes glucagon

==*alpha cells*== of pancreatic islets (islets of Langerhans)

Inuslin is produced and secreted by…?

^^*beta cells*^^ of pancreatic islets

Which organ is ^^insulin^^ and ==glucagon== secreted from?

pancreas

When blood glucose increases what occurs?

\- insulin increases to bring blood glucose down (negative feedback)

How does insulin regulate blood glucose levels?

\- metabolic effects in muscle, adipose (fat) tissue, & liver for synthesis of energy reserves

\- entry of glucose into cells

Which state (absorptive or postabsorptive) is insulin secretion increased in?

\- ^^absorptive^^

\- increases when blood glucose is high (140-150 mg/dl)

When does insulin increase?

when blood glucose is high (140-150 mg/dl)

Which state (absorptive/postabsorptive) is glucose secretion increased?

==postabsorptive== state

When does glucagon increase?

when blood glucose is low

How does glucagon regulate blood glucose levels?

\- stimulates \*==__*breakdown*__==\* of glycogen by liver and skeletal muscles (==*glycogeno*__*lysis*__==)

\- ==__*synthesis*__== of glucose by liver and kidneys (__gluco__==__neo__==__genesis__)

\- ketone ==synthesis== by liver (keto==__genesis__==)

Which macromolecule is absorbed into blood from the GI tract as monosaccharides?

carbohyrdrates

What does carbohydrates do to the *blood glucose concentration*?

increases

___ is body’s major energy source during ___ state

\- glucose

\- absorptive

In absorptive state, insulin promotes (2 bullet points for \*glucose\*)

\- promotes cellular uptake of glucose

\- promotes storage of glucose as glycogen in liver and muscles (aka glycogenesis)

is glycogenesis anabolism or catabolism

\- anabolism bcuz formation of glycogen (building molecules)

In cells, glucose is catabolized (broken down to)…

\- CO2

\- H20

\- energy in the form of ATP = cell respiration

Adipose-tissue cells (adipocytes) transform glucose to fat. What is the term called?

triglycerides

Where are triglycerides stored?

in lipogenesis aka formation of fat (anabolism)

What macromolecule is absorbed into blood from the GI tract as AAs?

proteins

In absorptive state, insulin promotes (2 bullet points for \*proteins\*)

\- promotes cellular uptake of AAs

\- promotes their incorporation into proteins = protein synthesis (anabolism)

Where does protein synthesis occur?

\- in liver

\- other tissues

What happens to amino acids in liver in absorptive state?

deaminated (amino group removed)

What is amino group used for?

\- used to synthesize urea

* excreted by kidneys
* remainder is catabolized (broken down) to provide energy for liver cells

What macromolecule is absorbed into lymph as chylomicrons (a __droplet__ of fat present in the blood or __lymph__ after absorption from the small __intestine)__?

lipids

In absorptive state, insulin promotes (1 bullet points for \*lipids\*)

\- promotes conversion of lipids + glucose into triglycerides to be stored in adipose tissue

* aka lipogenesis (formation of fat)
* which is an anabolism

What type of fat is a component of plasma membranes?

cholesterol

___ is a precursor for bile salts and steroid hormones (BUT excess contributes to atherosclerosis - condition that occurs when plaque builds up in arteries)

cholesterol

What are the 3 macromolecules in absorptive state?

1. carbohydrates
2. proteins
3. lipids

What synthesis ends in postabsorptive state?

* synthesis of

\- glycogen

\- triglycerides

\- proteins

When does postabsorptive state occur?

when food has been digested, absorbed, & stored

Due to secretion of glucagon, what occurs?

catabolism of reserves begin

Term for breakdown of proteins (into AAs in all tissues)

protein catabolism

Term for breakdown of stored fats

lipolysis

Homeostasis of blood glucose maintained via: (3 things starts with G) (in postabsorptive state)

1. glycogenolysis
2. gluconeogenesis
3. glucose sparing

Homeostasis maintained via… Glycogenolysis (in depth)

hydrolysis (chemical breakdown of a compound due to reaction with water) of glycogen in liver to increase blood glucose (glucose from glycogenolysis in skeletal in skeletal muscle is USED locally)

Homeostasis maintained via… gluconeogenesis (in depth)

* synthesis of glucose using…
* AAs
* glycerol
* pyrubate
* lactate
* in liver & kidneys

Homeostasis maintained via… glucose sparing (in depth)

most tissue (EXCEPT nervous) can use free fatty acids (from lipolysis) for energy instead of glucose

Ketogenesis (in depth)

\- occurs in liver

\- __synthesis of ketone bodies__ from ==fatty acids==

\- used as __alternative energy source__ during ==prolonged fasting== (esp. nervous tissue)

During fasting, (__insulin/glucagon__) secretion decreases and (__insulin/glucagon__) secretion increases

1. insulin
2. glucagon

What 4 components are released into blood during postabsorbtive state?

1. glucose
2. fatty acids
3. ketone bodies
4. AA

Absorption of meal (what occurs)

* glucose increase
* insulin increases (negative feedback)
* glucagon decreases (only responds when glucose is low)
* ^^__**formation**__^^ of glycogen, fat, & protein
* Blood: *DECREASES*
* glucose __decreases__
* AA __decreases__
* fatty acids __decreases__
* ketone bodies __decreases__

Fasting - postabsorptive (what occurs)

* glucose decreases
* glucagon increases (negative feedback)
* insulin decreases (only responds when glucose is high)
* ==__**hydrolysis**__== of glycogen, fat, & protein
* gluconeogenesis + ketogenesis
* Blood: *INCREASES*
* glucose __increases__
* AA __increases__
* fatty acids __increases__
* ketone bodies __increases__

synthesis of energy reserves

anabolism

utilization of energy reserves

catabolism

Neuronal regulation:

parasympathetic and sympathetic NS innervate the ___ ___

pancreatic islets (groups of cells in pancreas)

(__Sympathetic/Parasympathetic__) NS is activated during meals

parasympathetic NS

What does parasympathetic NS stimulate?

* GI function
* insulin secretion from beta cells (due to ACh)
* bcuz insulin increases during meal time for negative feedback

What 2 hormones are from sympathetic NS?

* Epinephrine
* norepinephrine

What does E & NE from sympathetic NS inhibit?

* GI function
* insulin secretion

What does E & NE from sympathetic NS stimulate?

glucagon secretion from alpha cells

Individual with diabetes typically has abnormally high blood sugar concentration

hyperglycemia

glucose in the urine

glycosuria or glucosuria

ketone in urine

ketonuria

3 Ps symptoms of diabetes

1. polyuria
2. polyphagia
3. polydipsia

polyuria

frequent urination

polydipsia

frequent drinking

polyphagia

frequent eating

Is type 1 diabetes mellitus insulin dependent?

yes

Is type 2 diabetes mellitus insulin dependent?

no (non-insulin-dependent)

True/false: Type 1 diabetes is insulin deficient

true

* due to autoimmune destruction of beta cells
* insulin must be administered

What are the 3 ways insulin is administered for type 1 diabetes?

* injected
* pumped
* inhaled in powder form

What are the causes of the autoimmune attack (for type 1 diabetes)?

* genetics
* environmental causes

Why does hyperglycemia occur?

bcuz glucose doesn’t enter tissue cells

Why does glucosuria occur?

bcuz amount of glucose filtered into urine exceeds maximum for reabsorption in kidneys

True/false: diabetes increase ketone bodies

true

Ketosis: why is ketone body concentration elevated?

bcuz increased __lipolysis__ releases fatty acids

\- which are converted to ketone bodies (__acidic__)

Ketosis: increased glucagon → leads to….

\- __glycogenolysis__ in liver

\- conversion of fatty acids into ketone bodies

When does ketoacidiosis (and ketone breath) occur?

if there isn’t enough __bicarbonate__ to neutralize acid from ketone bodies

Why is there excessive excretion of water in urine (in type 1 diabetes)?

excessive glucose and ketone bodies in urine cause __osmotic diuresis__ (increased urination due to the presence of certain substances in the fluid filtered by the kidneys)

Non-insulin dependent (type 2) diabetes

\- insulin present, but target cells __resistant to insulin__

\- blood glucose concentration remains high

Which type of diabetes is common?

Type 2 diabetes

When does type 2 non-insulin dependent diabetes usually begin in (what age group)?

adulthood

Why is type 2 diabetes common in obese individuals?

insulin sensitivity is reduced by the presence of excess adipocytes (fat cells)

Best way to treat type 2 diabetes?

* weight reduction
* exercise to increase insulin sensitivity in target cells
* drug treatments improve insulin sensitivity

Effects of diabetes

* tissue damage
* eyes, kidneys, and peripheral nerves
* peripheral neuropathies
* damage to capillaries
* circulatory deficiencies

Peripheral neuropathies lead to…

decreased sensation in the extremities

circulatory deficiencies may result in…

* damage to feet
* infection
* gangrene (tissue death → amputation)

What happens when impaired response to OR failure to secrete insulin?

shifts metabolic dependence to acid-generating ketones

Hyperglycemia-induced diuresis reduces blood volume to the point of …

* hypotension (abnormally low blood pressure)
* inadequate blood delivery to the brain

Dietary cholesterol enters ___ ___

GI tract

In the SI, cholesterol is absorbed into __ in __

absorbed into __plasma__ in __chylomicrons__

Which organ synthesizes cholesterol?

liver that

* enters the plasma
* __secreted__ into bile
* or __converted__ into bile salts

Where is cholesterol found in (besides liver)?

plasma membrane

True/false: cholesterol is basis for steroids and bile salts

true

VLDLs

very low density lipoprotein

VLDL found in where?

liver

In liver, cholesterol combines with ___ and ___ to form VLDLs

1. triglycerides
2. proteins

Purpose of VLDLs

__secreted__ into __blood__ to deliver triglycerides to organs

LDLs

low density lipoproteins