Test 3: Utilization of Organic Nutrients Flashcards
How is most energy transferred to the animal body? In what form?
- glucose
- fatty acids
- amino acids
What happens to molecules which are not utilized for synthesis of new organic molecules? What is produced?
- oxidation
- CO2 and H2O is produced
What happens during oxidation?
- most energy is released as heat (converted to heat)
- energy released during oxidation of nutrients is transferred to ATP (used to transfer energy inside the cells)
How is energy supplied to the body?
digestion of food
What must the body be able to do due to digestion not being continuous?
Store energy during digestion, and mobilize it during periods when there is no supply of exogenous energy.
What hapens when the body doesnt fully utilize the nutrients absorbed from the intestines? What form is it stored in?
Excess is stored as glycogen and triglycerides (lipids).
What molecule is the most suitable form of energy for storage? Why?
fat
- contains much energy per unit weight
- contains very little water
- storage requires less space
What form of energy is easily mobilized?
glycogen
What is metabolism?
A collective term for all the chemical reactions that occur in the body.
What processes does metabolism consist of?
- catabolism (release energy by breaking down complex molecules into simpler ones)
- anabolism (require energy to synthesise large organic molecules)
What is catabolism?
- produce energy
- break down molecules
What is anabolism?
- requires energy
- synthesise large molecules
What are the two phases of metabolism?
- absorptive state (body obtains energy by oxidizing nutrients that enter the blood from the intestine)
- postabsorptive state (nutrients are mobilized from the body’s stores)
What is the absorptive state?
Body obtains energy by oxidizing nutrients that enter the blood from the intestine.
What is the postabsorptive state?
Nutrients are mobilized from the body’s stores.
Is the absorptive state anabolic or catabolic? What happens?
anabolic!
- excess amino acids are converted into triglycerides in the liver
What happens in the postabsorptive state?
energy is released from the source
- glycogenolysis (glycogen is broken down into glucose)
Where does the absorptive state take place?
in the gastrointestinal tract
Where does the postabsorptive state take place?
- muscles
- adipose tissues
- liver
glucose
What organ plays a big role in metabolism and the conversion of nutrients? Why?
Liver
- maintains a stable glucose concentration in blood
What does the liver do in the absorptive state?
removes glucose from the portal blood
- prevents any large rise in glucose concentration in systemic blood
What does the liver do in the postabsorptive state?
exports glucose to the blood
- mobilized glycogen stores (glycogenesis)
- produces glucose from other sources (gluconeogenesis)
List the small and large carbohydrate molecules in the diet.
small:
- glucose
- lactose
- sucrose
large:
- starch
- glycogen
- cellulose
Explain what is absorbed in a non-herbivore diet.
GLUCOSE: main monosaccharide absorbed
Galactose + Fructose: also absorbed
liver: galactose and fructose converted to glucose
Explain what is absorbed in a herbivore diet.
CELLULOSE constitutes most of dietary carbohydrates.
Explain what is absorbed in a ruminants diet. What are they converted into? How?
most carbohydrates (including cellulose) are converted into VFA’s (volatile fatty acids)
(by microbial enzymes in the forestomach)
Explain what is absorbed in simple-stomached herbivores. Where is it metabolised?
metabolism of cellulose occurs in the large intestine.
What happens to glucose in after it is absorbed?
LIVER:
- stored in hepatocytes as glycogen
- converted to lipids
MUSCLES:
- transported to muscle cells, stored as glycogen
- (easily mobilizable energy source during muscle work)
ADIPOSE TISSUE:
- removed from the body by adipocytes, glucose is used for triglyceride synthesis.
What are the three postabsorptive state mechanisms? What do they do?
keep glucose concentration in plasma fairly stable:
- glycogenesis (make glucose)
- gluconeogenesis (make glucose)
- glucose sparing (utilization of lipids)
What is glycogenolysis? What are the main organs involved in the process?
the process which converts glycogen back into glucose.
- liver mobilizes glycogen reserves and releases glucose into the blood.
What is gluconeogenesis? Where does it happen? What are the substates?
- the production of glucose from non-carbohydrate sources
- major organs: liver and kidneys
- substrates: lactate, glycerol, and glucogenic amino acids
What is glucose sparing? What is its function?
- tissues gradually convert to utilizing lipids as the major energy source
- supports gluconeogenesis by preventing a rapid decline in blood glucose during starvation.
Explain protein metabolism. What is special in ruminants?
amino acid is converted to glucose or fatty acids by hepatocytes.
ruminants:
- most amino acids supply is derived from microbial proteins synthesised in the forestomach.
What is the difference between non-essential amino acids and essential amino acids?
non-essential amino acids: amino acids which hepatocytes can form.
essential amino acids: must be obtained by food
What do hepatocytes produce in protein metabolism?
- albumin
- fibrinogen
- enzymes
- coagulation factors
- complement
- hormone-transporting globulins
What is the major part of amino acids converted into? Where? How?
amino acid (major part) –> keto acid
- hepatocytes
- by deamination of the amino group (-NH2)
What happens to keto acids?
- enter pathways for carbohydrate metabolism (completely degraded providing energy for hepatocytes)
- used to synthesise fatty acids (triglycerides transported out of the liver)
What are some amino groups from deamination of amino acids used in?
the formation of non-essential amino acids (transamination).
What is transamination?
The formation of non-essential amino acids by using amino groups from the deamination of amino acids.
What is released when keto acids are formed?
keto acids formed from amino acids.
released (toxic substances):
- ammonia (NH3)
- ammonium (NH4)
What do hepatocytes do to NH3 and NH4? State differences in simple-stomached animals, ruminants and birds.
Hepatocytes convert NH3 and NH4 into urea.
Simple-stomached animals:
- kidneys excrete all urea produced.
Ruminants:
- urea is transferred to forestomachs
- by diffusion from plasma & secretion of saliva
- urea is converted to NH3 and NH4
- used for microbial protein synthesis
Birds:
- amino acids are sequestered in uric acid
- excreted to urine
- uric acid enables the developing avian embryo to avoid deleterious osmotic and toxin effects
What happens if the body recieves more amino acids than are needed? What happens with the products?
The surplus of amino acids is not stored in cells! It is deaminated into keto acids.
keto acids:
- used as cellular fuel
- converted to glucose and glycogen
- used in fat synthesis
Explain the main features of lipid metabolism. Types of lipids. Transport. Use.
Types fo lipids:
- triglycerides: major component of dietary lipids and lipid stores
- cholesterol and phospholipids: cell membranes
Transport:
- transported from intestinal epithelial cells in the form of chylomicrons
- stored as triglycerides in adipose tissue
Use:
1) Chylomicrons
- used directly as energy source
- degraded to fatty acids
- by lipoprotein lipase
2) Free fatty acids
- diffuse across endothelial cells
- used for resythesis of triglycerides (in adipose, mammary and other cells)
3) Chylomicron remenants (remaining particles)
What happens after a meal is ingested (lipids)?
- lipid content of blood increases
- lipids stem from chylomicrons and lipids produced in the liver (VLDL’s very low density lipoproteins)
- chylomicrons are rapidly released from blood
- 4-5h before all absorbed lipids are removed from the plasma (after a fatty meal)
- plasma has a milky appearance (high concentration of lipid particles)
What is the exogenous and endogenous lipid metabolism pathway?
exogenous: chylomicrons
endogenous: LDL and VLDL
What are the hormones used for the regulation of the metabolism of organic nutrients?
- insulin
- glucagon
- cortisol
- epinephrine
- growth hormone
What does insulin do?
Regulates the metabolism of glucose, amino acids, and lipids.
What does insulin and glucagon do?
insulin and glucagon collaborate (in opposite directions) to stabilize the level of glucose and fatty acids in plasma.
What does glucagon do?
stimulate glycogenolysis and gluconeogenesis
What does epinephrine do?
potent inducer of glycogenolysis
What does the growth hormone do?
stimulate the mobilization of fatty acids and glycerol (during starvation and long term stress)
What is adipose tissue innervated by? What happens in a decrease in plasma glucose concentration?
- sympathetic nervous system
- decrease in plasma glucose concentration = increase in activity of sympathetic neurons = triggered rise in catecholamine secretion from adrenal medulla
What does norepinephrine do?
- released by sympathetic nerve fibers
- pancrease
- epinephrine- adrenal medulla
- inhibits insulin secretion
What is hypoglycemia? How can it be seen in piglets?
low glocose concentration in plasma.
- piglets lay on belly, dehydrated, shivers, hair standing on ends.
