ANSC 303 - Exams 4 - Proteins
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What are proteins made of?
Amino acids.
What does EAA stand for?
Essential amino acids.
What does NEAA stand for?
Non-essential amino acids.
What mnemonic is used in the notes for essential amino acids?
MATT HILL UP.
Which essential amino acid contains sulfur?
Methionine.
What are the essential amino acids listed in the notes?
Methionine, arginine, threonine, tryptophan, histidine, isoleucine, leucine, lysine, valine, and phenylalanine.
Why are essential amino acids required in the diet?
They are not synthesized by the body at a fast enough rate to meet requirements.
How must essential amino acids be supplied to optimize animal performance?
They must be absorbed from the small intestine in proper quantities.
Why can essential amino acids be expensive?
They must be supplied in the diet because the body cannot make enough of them.
What happens to excess amino acids when they are overfed?
They can be made into glucose or used for energy.
What are non-essential amino acids?
Amino acids synthesized by the body in sufficient amounts to meet the animal's requirements.
Are non-essential amino acids required for normal metabolism?
Yes.
Why do ruminants generally not need essential amino acids supplied directly in the diet?
Ruminal microbes have the capacity to synthesize all amino acids.
Do ruminants still require essential amino acids to be absorbed from the small intestine?
Yes.
What do ruminal microbes require to make amino acids?
A carbon skeleton, volatile fatty acids (VFA), ammonia (NH3), ATP, and building equivalents (BE).
What is the general sequence for microbial amino acid and protein synthesis in the notes?
Carbon skeleton + VFA + ammonia + ATP + BE → amino acids + ATP + BE → microbial crude protein (MCP).
Which type of cattle may require essential amino acids in excess of what microbes can synthesize?
High-producing dairy cows.
Which essential amino acid is specifically important for high-producing dairy cows?
Methionine.
Why is methionine important in high-producing dairy cows?
It supports greater milk production.
How can methionine be protected in the rumen?
Protect it from microbial degradation.
What other type of cattle may require essential amino acids in excess of microbial synthesis?
Implanted growing steers grazing on wheat.
What protein source is supplied to implanted growing steers grazing on wheat?
Ruminal undegradable protein (RUP).
What are maintenance amino acid requirements?
The amino acid requirements needed to maintain the animal.
How do maintenance requirements change as animal size increases?
They increase.
How do maintenance requirements change as lean muscle size increases?
They increase.
How do maintenance requirements change with age?
They decrease as age increases.
How do amino acid requirements relate to production potential?
They increase as production potential increases; for example, a high-producing dairy cow has greater requirements than a beef cow.
What is a peptide bond?
A bond between two amino acids.
What is released when a peptide bond forms?
Water (H2O).
What enzyme forms peptide bonds according to the notes?
A proteolytic enzyme (peptidase).
What is a polypeptide?
A chain containing more than 10 amino acids.
How many amino acids and peptide bonds are in a tripeptide?
Three amino acids and two peptide bonds.
How many amino acids and peptide bonds are in a dipeptide?
Two amino acids and one peptide bond.
How many amino acids and peptide bonds are in a single amino acid?
One amino acid and zero peptide bonds.
What are amino acids, dipeptides, and tripeptides in relation to small-intestinal digestion?
They are products of digestion and are absorbed by the small intestine.
What is the primary structure of a protein?
The sequence of amino acids.
What is the secondary structure of a protein?
Hydrogen bonding between amino acids.
What is the tertiary structure of a protein?
Clustering of hydrophobic regions.
What is the quaternary structure of a protein?
Interaction between polypeptides.
What does HCl in the stomach do to proteins?
Denatures proteins.
Which protein structures are affected by denaturation?
Secondary, tertiary, and quaternary structures (2°, 3°, and 4°).
What breaks peptide bonds during protein digestion?
Enzymatic hydrolysis.
What are the three main stages of non-ruminant protein digestion?
Denaturation, enzymatic hydrolysis of peptide bonds, and absorption.
What happens during protein denaturation in a non-ruminant?
Stomach acid exposes peptide bonds for enzymatic digestion.
Where does enzymatic hydrolysis of peptide bonds occur?
In the stomach and small intestine.
Which protein structure is affected by enzymatic hydrolysis of peptide bonds?
Primary structure (1°).
What protein digestion products are absorbed?
Dipeptides, tripeptides, and amino acids.
What happens to food in the mouth during protein digestion?
Particle size is decreased.
What does HCl do in the stomach during protein digestion?
It decreases pH and denatures proteins, affecting structures 2°, 3°, and 4°.
What is a zymogen?
An inactive enzyme precursor.
Why is pepsinogen kept in an inactive state?
If active, it could digest the organs where it is produced.
What activates pepsinogen?
HCl or pepsin.
What enzyme is formed when pepsinogen is activated?
Pepsin.
How is pepsinogen activation described in the notes?
HCl activation is reversible; pepsin activation is irreversible.
What does pepsin do?
Hydrolyzes peptide bonds.
Where is pepsinogen made?
In the stomach.
Where does pepsin act?
In the stomach.
What type of enzyme is pepsin?
An endopeptidase.
Where is trypsinogen made?
In the pancreas.
What activates trypsinogen?
Enteropeptidase or trypsin.
What enzyme is formed from trypsinogen?
Trypsin.
Where does trypsin act?
In the small intestine.
What type of enzyme is trypsin?
An endopeptidase.
Where is chymotrypsinogen made?
In the pancreas.
What activates chymotrypsinogen?
Trypsin.
What enzyme is formed from chymotrypsinogen?
Chymotrypsin.
Where does chymotrypsin act?
In the small intestine.
What type of enzyme is chymotrypsin?
An endopeptidase.
Where is procarboxypeptidase made?
In the pancreas.
What activates procarboxypeptidase?
Trypsin.
What enzymes are formed from procarboxypeptidase?
Carboxypeptidases A and B.
Where do carboxypeptidases A and B act?
In the small intestine.
What type of enzyme are carboxypeptidases A and B?
Exopeptidases.
What does an endopeptidase do?
Hydrolyzes peptide bonds within the interior of a protein.
What does an exopeptidase do?
Hydrolyzes peptide bonds at the exterior of a protein.
Where is enteropeptidase produced?
By the enterocyte.
What does enteropeptidase activate?
Trypsinogen.
Which hormones are noted as signals associated with release of digestive secretions?
CCK and secretin.
What are brush border enzymes (BBE)?
Peptidases.
What does aminopeptidase do?
Cleaves one amino acid from oligopeptides.
What does dipeptidylaminopeptidase do?
Cleaves dipeptides from oligopeptides.
What does tripeptidase do?
Cleaves one amino acid from a tripeptide.
What does RUP stand for?
Ruminal undegradable protein; also called undegradable intake protein (UIP).
What is RUP?
The fraction of protein that ruminal microbes cannot degrade.
What happens to the amino acid profile of RUP as it leaves the rumen?
It leaves with the same amino acid profile as the feed.
What digestibility value is given for RUP in the notes?
80% digestible (the notes indicate a range of 0%–100%).
What does RDP stand for?
Ruminal degradable protein; also called degradable intake protein (DIP).
What happens to RDP in the rumen?
The notes state that 100% of RDP is degraded.
How do ruminal microbes use RDP?
They use it to synthesize microbial crude protein (MCP).
What happens to the amino acid profile of RDP?
Ruminal microbes alter the amino acid profile.
What can RDP supply or generate in relation to non-protein nitrogen (NPN)?
Urea, ammonia, and amino acids.
What determines the ratio of RUP to RDP in a feedstuff?
The feedstuff and its passage rate (Kp).
What happens to RDP and RUP when Kp increases?
RDP decreases and RUP increases because retention time is shorter.
What happens to RDP and RUP when Kp decreases?
RDP increases and RUP decreases because retention time is longer.
What does RDP supply for microbial crude protein synthesis?
Ammonia (NH3).
What can excess ammonia indicate in relation to RDP?
RDP may be supplied in excess of microbial needs.
Why is RDP fed to ruminants?
To meet microbial requirements so microbes can synthesize cells and enzymes.
What happens when RDP is limited?
Carbohydrate fermentation is prevented or reduced, decreasing the energy available to the cow.