Introductory Concepts Flashcards
What is a distinguishing factor of Protein in Comparison to the other macronutrients?
Contains Nitrogen
Protein is a major ______ and _______ component of all cells
functional and structural
Protein in the human body is used for
1) All enzymes
2) Membrane components and carriers
3) Blood transport molecules
4) Intracellular matrices
5) Muscle, bone, skin, hair, fingernails
6) Keratin, collagen
7) Some hormones
The largest energy store in the body is ________.
Fat
The components of the body listed from highest to lowest is:
Body and Water Minerals –> Fat –> Protein –> Glycogen
Does fat or protein provide more energy?
Fat
What is the bioavailability in days of protein?
13 days
Can you use up all of your protein stores?
No, you would die
Humans eat protein, but need ________
amino acids
How many amino acids are there?
hundreds
α-amino acids except for proline (α-imino)
1) 20 with cognate tRNA
2) tRNA for selenocysteine
What is post transcription?
Adding a hydroxy or methyl group after the AA becomes apart of the chain
Most of our amino acids are what kind of amino acids?
α-AA
Non-Protein α-AA’s (6)
Ornithine Citruline Homocysteine Hydroxylysine Hydroxyproline 3-methyl-histidine
Not an α-AA
Taurine
beta-alanine
Protein contains ______ % Nitrogen by weight
16%
Weigh ratio of protein/nitrogen (p/n)
6.25
100g protein = 16g nitrogen
100/16 = 6.25
So,
Nitrogen (g) x 6.25 = _________
Grams of Protein
Amino acids are linked together via ______ to form _____
Peptide Bonds(linkages), Peptide Chains
Protein Structure can be
Primary
Secondary
A Secondary Protein Structure forms a ______ ______
double helix
Why does a helical structure form?
The hydrogen bonds are not very strong, so it results in a winding structure
The Amino end is also called the __ - _____ ____ and is on the ______ side
N-terminal end, left
H3N+
The Carboxyl end is also called the __ - _____ ____ and is on the ______ side
C-terminal end, Right
COOH
C=0
=0-
The total effect of AA’s is ______
neutral
Peptide bonds form between….
Carboxyl group of one AA and the Amino group of another AA
__ - Amino acids are of nutritional significance
L
Indispensable (essential) AA’s
Need to attain from diet
Isoleucine (Ile) Leucine (Leu) Lysine (Lys) Methionine (Met) Phenylalanine (Phe) Threonine (Thr) Tryptophan (Trp) Valine (Val) Histidine*(His)
Dispensable (non-essential)
Can be synthesized in the body
Alanine (Ala), Arginine (Arg), Aspartic acid (Asp) Asparagine (Asn) Glutamic acid (Glu) Glytamine (Gln) Glycine (Gly) Proline (Pro) Serine (Ser)
Conditionally dispensable
Synthesis may be limited under special physiological conditions
Cysteine (Cys)
Tyrosine (Tyr)
Hadaad Notes
Structural formulas of the 21 common α-amino acids.
The α-amino acids all have a carboxyl group, an amino group, and a differentiating functional group attached to the α-carbon.
The generic structure of amino acids is shown in the upper left corner with the differentiating functional group marked by R.
The functional group for each amino acid is shown below. Amino acids have been grouped by functional class.
Proline is actually an imino acid because of its cyclic structure involving its nitrogen (N).
What is the structure of Amino Acids
1) α-amino group (NH2)
2) α-carboxyl (COOH)
3) Side Chain (R)
Neutral (non-polar AA)
4
Glycine (Gly) (3 sections) - Alanine (Ala)
Serine (Ser) - Threonine (Thr): Both have an OH group, but Thr has an extra branch
Glycine is the simplest
Threonine = secondary alcohol because the main CHCH has two branches coming off of it
Neutral non-polar Branched AA)
3
BCAA’s: serve as an energy source for muscle, all essential
Isoleucine (Ile): 5 carbon chain, not a “V” branch
Valine (Val): If turn your head on teh side it forms a “V” shape, but also has a NH2, 3 carbon chain
Leucine: Almost the same as Valine, but its downward branch has an NH3, 4 carbon chain
Sulfer Amino Acids
2
Contain a Sulfer!
Cysteine (Cys): Conditional, “HS” on the amino end
Methionine (Met): Secondary thiol, S is sandwiched between CH3 and CH2CH2CH
Aromatic Amino Acids (Phenols)
Contain a Benzene ring structure (C6H5OH) .The molecule consists of a phenyl group (−C6H5) bonded to a hydroxyl group (−OH)
Phenylalanine (Phe):
Tyrosine (Tyr): Same as Phe, but has a hydroxyl group
Phe and Tyr have what kind of ring?
Phenol Ring
Aromatic Amino Acids: Tryptophan (Trp)
Indole ring (double ring)
Aromatic Amino Acids: Histidine (His)
- Imidazole ring
- One ring present with two double bonds
Formula (CH)2N(NH)CH
What are all of the Aromatic AA’s?
4
Phe
Tyr
Trp
His
Basic Amino Acids
2
When put in water they become more Basic
Lysine (Lys):
- primary amine - straight chain with one NH2 downward branch
Arginine (Arg):
- Has a guanidino group
- H2N – C –NH
(downward form C is a = NH2+)
Body Protein Reserves
Skeletal muscle: 43% Skin: 15% Blood: 15% Viscera (liver, kidneys) organs:10% Rest in brain, lung, heart, etc
50 % of total protein in the body is in the following forms:
1) Collagen
2) Myosin and actin
3) Hemoglobin
Collagen
Structure of connective tissue of skin & bone
Myosin and Actin
Proteins in muscle
Hemoglobin
Blood
Acidic amino acids and their amides
- Glutamic acid (glutamate) is longer than Aspartic acid (aspartate)
- Glutamate –> Glutamine
- Aspartate –> Asparagine
This occurs when the acid form takes up an amino group
- Acidic amino acids have 2 carboxyl groups, one at each end
What is protein turnover?
- Body proteins are constantly being synthesized and then degraded
- In healthy adults, the total amount of protein in the body remains constant
- The rate of protein synthesis sufficient to replace the protein that is degraded is protein turnover
- Plasma proteins and most intracellular proteins are rapidly degraded (1/2 life = hours to days). Extracellular structural proteins such as collagen are metabolically stable and have half-lives of years.
EXTRA:
Albumin, Transferrin have a short half life and are broken down faster
- Proteins in muscle may have a longer half life
- Protein turnover mostly happens in visceral
Turnover = about 250g per day
Amino Acid Pool
1) The free amino acids distributed throughout the body
- Intracellular
- Extracellular: Blood, fluid between cell
2) The amino acid pool contains about 90 - 100 g of amino acids
How much protein is digested and absorbed per day?
- Protein intake (dietary) = 90 g (70-100g)
- Secreted protein or endogenous (from body to gut) = 70 g (35-200g)
- Absorbed = 150 g
- Fecal loss = 10 g (6-12g)
What two types of cells does the stomach contain?
Secrete Chief cells and Parietal (oxyntic) cells
What do chief cells secrete in the stomach?
pepsinogen, which is an inactive form: zymogen
What do parietal (oxyntic) cells secrete in the stomach?
HCl (pH 2-3)
- Denatures protein
- Kills microorganisms
- Activates pepsinogen --> pepsin (active form(
Intrinsic factorWhat percent of protein digestion occurs in the stomach
about 10-20%
- Results in oligopeptides, polypeptides and amino acids
Most protein digestion results from the action of
pancreatic proteolytic enzymes
Hadaad Notes:
The proteolytic enzymes are all secreted in an inactive form, to prevent auto-digestion, and are activated in the lumen of the gut: by HCl in the case of stomach pepsinogen and by enteropeptidase and trypsin in the case of the pancreatic enzymes.
What stimulates the pancreas to secrete its enzymes?
The intestinal endocrine cells secrete:
Cholecystokinin (CCK) and Secretin
-CCK and secretin stimulate the pancreas to secrete -
the protein digesting enzymes. However, the -
pancreatic enzymes are secreted as zymogens
(inactive forms) such as trypsinogen,
chmotrypsinogen, proelastase, procarboxypeptidase,
etc.
How are the pancreatic enzymes activated?
CCK stimulates the mucosal epithelial cells to secrete enteropeptidase which which activates trypsinogen to trypsin. The other pancreatic enzymes are activated by trypsin
Brush border enzymes (intestinal peptidases)
The intestinal brush border has: \_\_\_\_\_, \_\_\_\_\_, \_\_\_\_
Dipeptidases
Tripeptidases, and
Aminopeptidases
Brush border enzymes (intestinal peptidases)
Absorption of peptides and whole proteins
Rare
Brush border enzymes (intestinal peptidases)
\_\_\_\_\_\_ peptides may be absorbed intact and hydrolyzed within intestinal cell
Small
Action of Peptidases: Endopeptidases
Hydrolyze bond (cleave) in the middle of the chiain
Action of Peptidases: Exopeptidases
Hydrolyze bond (cleave) at the terminal end of the chain, either at the Aminopeptidase end of the caboxypeptidase end
Transport (absorption) of amino acids: Transport systems
What are amino acid transporters?
Membrane bound proteins that recognize different amino acids and move them into and out of cells
Transport (absorption) of amino acids: Transport systems
The ______ _______ and ______ _______have common transport systems
Small intestine and Kidney Tubules
What are the two types of Transport Systems?
1) Sodium independent
2) Sodium dependent
-Co-transport (secondary active transport) of amino acids
and peptides
Hadaads Notes on: Transport and absorption of amino acids and peptides
1) How are amino acids mostly absorbed?
2) How are Di-peptides and tri-peptides transported?
3) How are some large peptides or protein can be carried across the cell
1) By sodium dependent co-transporters.
2) By a H+ ion dependent co-transporter
3) Transcytosis
- This is particularly true in babies and is a mechanism
whereby the immunoglobulins in mothers milk can be
transfered to the child.
About how much protein is degraded (broken down) per day?
250-300g per day
The proteins that are broken down are typically the ones that are damaged or not needed anymore
Why is protein degradation (breakdown) important?
1) Cell growth
2) Adaptation to different physiological conditions
3) Elimination of abnormal or damaged protein
4) Normal functioning of the immune system
What are the two pathways of Protein degradation?
Lysosome and Ubiquitin-proteasome pathways
Lysosome pathways
1) Energy ________
2) Contains acidic ______
3) Breaks down ______
1) indepedent
2) enzymes
3) proteins
Lysosomes have digestive enzymes in them which take damaged/bad proteins and digests them. AA’s are produces and goes to cytoplasm of cell
Where does protein degradation happen?
Inside the cell (intracellular)
UBP Pathways
1) Energy ________
2) Notes
1) dependent
2) Damaged or unneeded proteins are marked for destruction by covalent attachment to a small protein called ubiquitin.
- Polyubiquinated proteins are degraded by intracellular proteosomes
- This system degrades abnormal proteins, normal proteins and proteins of the endoplasmic reticulum
What is UBP pathway activated (+) by? (2)
1) Fasting (not eating)
2) Hormones
What is UBP pathway activated (-) by? (2)
1) Feeding and increased protein intake
2 )Hormones (insulin, growth factors)
What hormones activate (+) UBP Pathways?
glucagon, glucocorticoids, thyroxin
What hormones activate (-) UBP Pathways?
insulin, growth factors
What are the Physiological roles of dietary proteins and amino acids? (4)
1) Protein synthesis
2) Synthesis of nitrogen containing molecules
- Dispensable amino acids
- Enzymes, nucleic acids, hormones, neurotransmitters,
etc.
3) Provide energy (ATP) from “carbon skeleton”
- Oxidation of “carbon skeletons” to: energy + CO2 +
H2O
- Amino group is excreted as urea and ammonia
4) Provide amino acids for conversion to:
- Acetyl CoA –> fats and sterols
- Carbohydrate intermediates –> glycogen
Amino Acids can also be broken down and used for _______.
Energy
Extra: Amino Acids are used not only for synthesis, but also for energy (ATP) from the carbon skeleton
What does the breakdown of Amino Acids begin with?
What types of reactions follow? (3)
The removal of the amine group mainly by the following types of reactions:
1) Transamination (all tissues)
2) Oxidative Deamination
3) Synthesis and hydrolysis of gluatamine
Transamination
Transamination (all tissues) the funneling of amino groups to glutamate
-Enzymes are called transaminases (also called aminotransferases) - Transaminases use pyridoxal phosphate (PLP) as cofactor - The keto acid α-ketoglutarate accepts amino groups from most amino acids to produce glutamate
Transamination Hadaad Notes
Transamination (or aminotransfer) is a chemical reaction between two molecules. One is an amino acid, which contains an amine (NH2) group. The other is a keto acid, which contains a keto (=O) group. In transamination, the NH2 group on one molecule is exchanged with the =O group on the other molecule. The amino acid becomes a keto acid, and the keto acid becomes an amino acid.
Transamination in biochemistry is accomplished by enzymes called transaminases or aminotransferases. This process is an important step in the synthesis of some non-essential amino acids (amino acids that can be synthesized de novo by the organism). Transamination reactions use the coenzyme PLP, and has been shown to be a kinetically perfect reaction. The product of transamination reactions depend on the availability of alpha-keto acids. The products usually are either alanine, aspartate or glutamate, since their corresponding alpha-keto acids are produced through metabolism of fuels.
What happens in oxidative deamination?
Enzyme glutamate dehydrogenase converts glutamate to α-ketoglutarate and ammonia
What happens in the Synthesis and hydrolysis of glutamine?
Enzyme glutaminase hydrolyzes glutamine to produce glutamic acid and ammonia
What are the 2 important transamination reactions?
1) Reaction catalyzed by ALANINE TRANSAMINASE (ALT)
2) Reaction catalyzed by ASPARTATE TRANSAMINASE (ASP)
Alanine Transaminase Reaction (ALT)
The enzyme ____________ catalyzes the transfer of the amino group of alanine to ________ resulting in the formation of ________ and ________ .
Is this reaction reversible?
1) alanine transaminase
2) α-ketoglutarate
3) pyruvate and glutamate
Yes, The reaction is reversible, but during amino acid catabolism, the enzyme functions in the direction of glutamate synthesis. Thus glutamate, acts as a collector of nitrogen from alanine.
Aspartate transaminase (AST)
Aspartate transaminase transfers amino groups from glutamate to _______ to form ________,
Asparate is used as a source of nitrogen in the ___ cycle
1) oxaloacetate
2) aspartate
3) urea
ALT
Alanine –> α-ketoglutarate = pyruvate and glutamate
In ALT, glutamate acts as a collector of _____ from alanine
nitrogen
AST
Glutamate –> OAA –> Aspartate = Nitrogen used in urea cycle
Amino form: Alanine
Keto form: Pyruvate
Amino form: Aspartic Acid
Keto form: OAA
Amino form: Glutamic Acid
Keto form: α-ketoglutarate
Amino form: Leucine (BCAA)
Keto form: α-ketoisocaproic acid (BCAA keto-acid)
What is removed in Oxidative Deamination?
Amino group
Where does Oxidative Deamination occur?
Liver and Kidney
What catalyzes Oxidative Deamination?
glutamate dehydrogenase
What is released as a result of Oxidative Deamination?
Ammonia (NH3)
- Amino group is removed entirely as ammonia
What must be present for Oxidative Deamination to happen?
NAD, thus it requires energy
What are the end products of Oxidative Deamination?
α-ketoglutarate and ammonia
Synthesis and hydrolysis of gluatmine is the removal of ______ ____ __
Amino acid Nitrogen (N)
What enzyme synthesizes glutamine (Gln)
glutamine synthetase
What does glutamine synthetase do?
Adds ammonia to glutamate = glutamine
Where does the synthesis of glutamine occur?
Most tissues
Where does the hydrolysis of Glutamine (Gln) occur?
Liver
What enzyme is used for the hydrolysis of Glutamine (Gln)
glutaminase
What does glutaminase do?
Coverts Glutamine –> glutamate + free ammonia
How is Glutamine degraded back to glutamate?
Liberation of the amide-N to release ammonia by a different enzymatic pathway (glutaminase). NH3, ammonia.
In the Urea cycle, What is the major disposal form of NH3
Urea
In the Urea cycle, Where is NH3 generated (via glutamate dehydrogenase)?
Mitochondria
In the Urea cycle, Where does the first reaction of the Urea cycle take place?
Mitochondria
In the Urea cycle, amino groups of many amino acids are transferred primarily to ____________
α-ketoglutarate (in skeletal muscle to pyruvate)
In the Urea cycle, what 2 amino acids are transported via the blood to the liver, where they are deaminated to form ammonia
glutamate and alanine
In the Urea cycle, Where do the 2 Urea N groups come from?
One comes from free NH3 (from oxidative deamination of glutamate)
One comes from aspartate (which got it from glutamate)
In the Urea cycle, Glutamate is the primary source for the
Aspartate N
In the Urea Cycle, glutamate is also an important source of the _________ into the cycle.
ammonia
Approximate distribution of nitrogen in urine in human consuming 100 g of protein per day is
16g N
If a person has 12.8g N (i.e. from Urea) per day, you multiply that by ________ to = g of _______
6.25, protein
What are the 4 sources of ammonia? aka where does ammonia come from
1) Amino acids
- glutamate dehydrogenase
2) Glutamine and other amides
- glutaminase
3) Nucleic acids
4) Bacterial UREASE in intestine
How is extra Nitrogen disposed? aka How do we get rid of ammonia from our bodies?
1) Formation of urea
2) Excretion by kidney as ammonia (acid-base balance)
Define Glucogenic
Yield pyruvate or one of the intermediates of the citric acid cycle
Define Ketogenic
Yield acetyl-CoA or intermediates of fatty acid oxidation
What AA is purely ketogenic?
Leucine
What AA’s are both ketogenic and glucogenic?
Ile, Lys, Phe, Tyr, Trp
What AA’s are purely glucogenic?
alanine, serine, glycine, cysteine, aspartic acid, asparagine, glutamic acid, glutamine, arginine, histidine, valine, threonine, methionine, proline
What is the intestinal tract lined with?
Continuous layer of epithelial cells
What is the Is the largest lymphoid organ in the body (gut associated lymphoid tissue)?
Intestinal Tract
What are the major fuels for the small intestinal mucosa?
Which 3?
Dietary AA’s
glutamine, glutamate, aspartate
Dietary Amino Acids
1) Are major fuels for the small intestinal mucosa (glutamine, glutamate, aspartate)
2) Are substrates for synthesis of intestinal
3) Show trophic and cytoprotective effects on gut integrity
4) Show potential therapeutic applications
In regards to proteins, the gut accounts for __- __% of whole-body protein synthesis
9-12%
In regards to dietary amino acids
what are Are substrates for synthesis of intestinal
1) Proteins (gut accounts for 9-12% of whole-body
_______ synthesis
2) Nitric oxide (\_\_\_\_\_\_\_) 3) Polyamines (putrescine, spermidine, etc. (\_\_\_\_\_\_) 4) Glycoproteins (\_\_\_\_\_\_\_) 5) Ornithine, citrulline, and arginine (from \_\_\_\_\_\_\_)
1) protein
2) arginine
3) from arginine
4) threonine, found in mucous
5) proline
Glycoproteins are made up of ______ and ______
protein and sugar
What is an example of a FAST protein that is digested and absorbed quickly
Whey
What type of protein increases satiety?
Whey
What kind of protein increases protein synthesis?
Whey
What is an example of a SLOW proteins that is digested and absorbed more slowly
Caesein
Which type of protein allows plasma concentrations of amino acids are maintained over a longer period of time
Caesein
After protein is ingested, it is absorption from the small intestines into the _______ _________
Portal circulation
Which organ is in charge of distribution and control of blood concentrations?
Liver
After protein is ingested, utilization by cells for protein synthesis depend on what 3 things?
1) Quality of protein
2) Size of meals
3) Slow and fast proteins
____ and _______ exert different effects on plasma amino acid profiles, gastrointestinal hormone secretion and appetite.
Casein and Whey
Individuals consume less calories when they are preloaded with which type of protein? Casein or Whey?
Whey
Circulating concentrations of the various amino acids reflect the composition of the proteins and amino acids consumed
in which state?
Postprandial state
Which state does the following describe?
- The amino acid profile of blood is stable and characteristic of species
- There is a net release of amino acids from muscle to
plasma
- There is uptake of amino acids by kidneys for
gluconeogenesis and ammonia formation - Conditions which results in changes in the concentrations of amino acids in blood
- The neonatal period
- Catabolic and disease conditions
Postabsorptive
True of False: Different animals/humans have difference postabsorptive states rates/Postabsorptive states depend on the species
True
AA in the Colon
Some proteins and amino acids escape digestion and absorption and end up in the ________.
Colon
- Are absorbed and metabolized by colonic cells
- Are metabolized by bacterial flora to produce ammonia, hydrogen sulfide, amines, short-chain fatty acids
AA in the Colon
Bacterial flora also produce ammonia from urea catalyzed by bacterial _________
urease
AA in the Colon
Are amino acids synthesized de novo by gut bacteria absorbed by humans?
Some evidence exists
The following are all roles of what organ?
1) Monitors absorbed amino acids and adjusts rate of metabolism according to body needs
2) Increased protein intake results in higher activity of liver enzymes which metabolize amino acids. Liver breaks down most amino acids except branched chain.
3) There is a difference in the metabolism of dispensable versus indispensable amino acids by the liver depending on the diet
- There is a direct correlation between the amount of
protein in the diet and catabolism of dispensable amino
acids
- Indispensable amino acids catabolism increases only
when the diet provides substantial amounts of those
amino acids
Liver
What explains the interaction between muscles and liver cells?
Skeletal muscle: The alanine cycle
Skeletal muscle: The alanine cycle
The Skeletal muscle: The alanine cycle likes to oxidize which AA’s
BCAA’s: Ile, Leu, and Val
Skeletal muscle: The alanine cycle
Does the release of amino acids from muscle reflect the amino acid profile of muscle?
No
Skeletal muscle: The alanine cycle
What fraction of amino acids released from muscle are alanine and glutamine?
2/3rds
Skeletal muscle: The alanine cycle
_______ 1st undergo transamination and then are oxidized in muscle tissue for energy
BCAA’s
Skeletal muscle: The alanine cycle
The amino groups are carried from:
alanine –> ____ and
glutamine –> ______
alanine –> liver
- it is then changed to glucose for energy
glutamine –> gut
Postabsorptive state means
after we have eaten
Fasting means
we have not eaten for a while
The brain uses what for energy?
Glucose
In a postabsortive state there is more ___ and less ___
more glucose
less ketones
In a fasting state the brain oxidizes more _____ and less ______
more ketones
less glucose
Ketones come from the oxidation of Ketogenic AA’s, Glycerol, and _____
FFA’s
Glycerol is the backbone of _____
Triglycerides
The Gut loves to use glutamate and _____
glutamine
Skeletal muscle
What are the two biomarkers for meat intake?
3-methyl histidine and 1-methyl histidine
- excreted in the urine
- bodybuilders produce more because of protein turnover
- these biomarkers result from muscle turnover and consumption of meat from the diet
