Proteins And Amino Acids Flashcards
(126 cards)
1
Q
What are proteins?
A
Organic compounds containing carbon, hydrogen, oxygen and nitrogen
2
Q
What distinguishes proteins from fats and carbohydrates?
A
Nitrogen
3
Q
What does it mean that proteins are macromolecular peptides?
A
Proteins are very large molecules composed of many peptide-bonded amino acids
4
Q
What are amino acids?
A
The building blocks of proteins
Made of
- Amino group (NH2)
- Carboxyl group (COOH)
- Unique side group (R-group)
5
Q
What is the structure of proteins?
A
Proteins are made of amino acids -> the amino acid chain (= primary structure) folds in a certain pattern to create a 3D structure which determines the function of the protein
6
Q
How many amino acids are used in our body for protein synthesis?
A
20
7
Q
Of the 20 amino acids that the body uses, how many are essential? I.e. cannot be synthesised by the body
A
9
8
Q
What are the non essential amino acids? (5)
A
- Alanine
- Aspartic acid
- Glutamic acid
- Serine
- Asparagine
9
Q
What are the 9 essential amino acids?
A
- Phenylalanine
- Valine
- Threonine
- Tryptophan
- Isoleucine
- Methionine
- Histidine
- Leucine
- Lysine
10
Q
What are conditionally essential amino acids and what are the 6 conditionally essential amino acids
A
Non-essential amino acids that become essential under specific circumstances
- Arginine
- Cysteine
- Glutamine
- Glycine
- Proline
- Tyrosine
11
Q
Can a vegetarian diet supply all essential amino acids?
A
Yes, with a variety of legumes, grains, nuts and seeds
12
Q
What is the debate around the number of essential amino acids?
A
Histidine is not produced in adults, so most experts nowadays call it essential. However, it can be produced by bacteria, although not clear how much of our need is met by bacteria production of histidine.
Histidine is the only amino acid that doesn’t impair protein synthesis when deficient in diet
13
Q
What is protein denaturation?
A
Loss of protein 3D shape by heat exposure / pH variations / heavy metals exposure -> structure unravels = loss of function
14
Q
What is the difference between protein denaturation and proteolysis
A
Denaturing does not change the amino acid sequence, proteolysis does that
Denaturation facilitates proteolysis by making proteins more accessible to be worked on by proteolytic enzymes (e.g. pepsin)
15
Q
What are the 10 functions of protein in the body?
A
- Structure of body tissues (e.g. collagen)
- Movement (e.g. actin and myosin fibres)
- Carrier molecules
- Storage molecules
- Fluid balance in the blood
- Enzymes
- Hormones
- Immune function
- Clotting mechanisms
- Alternative energy sources
16
Q
What hormones are derived from amino acids?
A
- Tyrosine + iodine = thyroid hormones
- Tyrosine -> dopamine, norepinephrine, epinephrine
- Tryptophan -> serotonin, melatonin
- 2 polypeptide chains = insulin
- 1 polypeptide chain = glucagon, PTH, calcitonin
+ hormones receptors on cell membranes = proteins
17
Q
What are immunoglobulins?
A
Proteins found in blood/bodily fluids -> used by the immune system to identify and neutralise foreign materials (i.e. microbes)
(most abundant is IgG)
18
Q
How can proteins work as buffers?
A
Some amino acids have side chains (R-groups) that can BIND or LET GO hydrogen ions, helping to regulate the acid-base balance in the fluids
Amino acid histidine is the best buffer at pH 7.35-7.45
19
Q
How do proteins maintain fluid balance?
A
Proteins attract water -> they exert ONCOTIC pressure
- If protein levels are too low -> water leaks out of blood vessels -> accumulate in interstitial space = oedema
Causes include : protein losses due to kidney disease, inadequate synthesis due to liver disease, malnutrition
20
Q
What are glycoproteins?
A
- Mucins : provide protective lubricating barrier (e.g. mucus, saliva)
- ABO blood antigens
- Hormones (LH, FSH, TSH)
- Major histocompatibilty complex (i.e. cell surface receptors involved in adaptive immunity, e.g. antigen presentation)
- Proteoglycans = subclass of glycoproteins
21
Q
What is protein deamination?
A
Removal of the nitrogen-containing amino group from amino acids (occurs primarily in liver)
Needed x individual amino acids to be used as energy sources or stored as fat
22
Q
What happens during protein delamination?
A
When nitrogen group is removed = ammonia formed —> need to go through the urea cycle in the liver to be converted to a water soluble compound (urea) to be finally excreted by the kidneys
The remaining fragments of amino acids can be used to produce glucose or ketones (as energy or energy storage)
23
Q
Other than getting rid of the ammonia formed by deaminatinon, why is the urea cycle important?
A
It is the sole endogenous source of amino acids arginine and citrulline
Also creates ornithine = important liver detox support agent
24
Q
What happens if the urea cycle is impaired?
A
Hyperammonaemia = serious metabolic state associated with liver cirrhosis
Symptoms : chronic fatigue, headache, irritability, nausea and diarrhoea, poor concentration, confusion, intolerance of high protein foods
25
What is transamination?
Important step in synthesis of some non-essential amino acids
- The amino group of an amino acid is transferred on to an enzyme -> the enzyme transfers the amino group on to a ketoacid -> new amino acid is formed
This is dependent on B6 as coenzyme
26
What is protein turnover?
A process whereby proteins in the body are continually being made and broken down
27
What is the amino acids pool?
When body proteins are broken down, amino acids are freed and join the general circulation -> together with dietary amino acids, they form the amino acids pool
Amino acids in the pool will be utilised or excreted, NOT stored (essential ones have longer half life, as body will break down own tissue to obtain them if not available in the pool)
28
When and how are proteins used for energy
When : starvation, prolonged fasting, metabolic disorders
How : in absence of glucose and fatty acids, body breaks down own tissue (no storage of amino acids!) and uses own amino acids to create energy -> over time = lean tissue wasting
29
What are protein sources
Abundant sources : legumes, nuts and seeds, greens, whole grains, eggs, fish, poultry and meat
But protein is found in all whole foods, only processed foods have 0
30
Is meat the best source of protein?
Meat provides the most protein, but requires more energy to digest it -> heavy animal protein can accumulate in the intestinal wall, impairing absorption
31
What determines the quality of a protein?
Its digestibility and amino acid composition
32
What affects protein digestibility?
- Gut function (i.e. HCL and digestive enzymes), presence of fibre, presence of phytates and lectins (for plant proteins)
- Gut microbiome : undigested protein in colon is fermented = toxic metabolites -> increase inflammatory response and encourages the proliferation of opportunistic pathogens
33
What are some fermentation products of protein in the colon?
Ammonia, amines, sulphides, N-nitroso compounds -> systemic toxicity, nephrotoxicity, carcinogensis
34
How to optimise protein digestion?
- Plant sources : soak it, sprout it, ferment it (reduce anti-nutrients)
- Chew properly
- No drinking with meals
- Support stomach acid (zinc and B6, apple cider vinegar, bitters,..)
35
What are limiting amino acids?
An essential amino acid supplied in less than the amount needed to support protein synthesis
- For a cell to make a protein, it needs all the essential amino acids available simultaneously
- If one is missing, a cell needs to either cease making the protein or dismantle an other one to obtain it
36
Which ones are the limiting amino acids?
Lysine, threonine, methionine and tryptophan -> found in the shortest supply in incomplete protein
This is why it is important to rotate protein sources
37
What is a complete protein?
A food containing all 9 essential amino acids
38
What are some vegan options for complete protein?
Quinoa, buckwheat, pumpkin seeds, chia, hemp seeds, tempeh
39
What are incomplete proteins?
Foods low in 1 or more of the essential amino acids (most plant foods)
40
How can you combine plant foods to ensure you are obtaining all the essential amino acids?
Legumes + nuts/seeds
Whole grains + legumes
Vegetables + grains
41
Do plant foods always need combining in one meal?
One meal is ideal, but it is only necessary to be combining in the same day as the amino acids pool is quite stable
42
What is the issue with animal protein and the amino acid methionine?
Methionine is highly abundant in animal protein -> it has a stimulating effect on T-cells -> if used in excess, associated with 1. Autoimmunity and 2. Chronic inflammation
Excess methionine also linked to increased homocysteine
43
What is a problem of non-organic animal protein?
Can contain chemical residues, by either oral or topical contamination of the animal
44
Are there adverse effects associated with long term high animal protein intake?
1. Osteoporosis
2. Kidney disease
3. Increased cancer risk
4. Disorder of liver function
5. Atherosclerosis
6. Increased muscle soreness after exercise
45
What is generally considered a high protein intake?
20% + of daily caloric intake
46
How can you buffer the protein derived acidic load?
Eating alkaline rich fruit and veggies
47
What are established carcinogenic present in animal proteins?
While red meat is classified by WHO as probable cause of cancer, PROCESSED MEATS (salted, cured, fermented, smoked) are deemed carcinogens
Polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs) produced during high temperature cooking of meat
48
What is the link between excess animal protein intake and skeletal disease?
Acidic burden of excess animal protein can DRAW CALCIUM from bones = increased risk of osteoporosis
49
What is the link between excess animal protein and kidney disease?
Extra acidity from high animal protein = need buffering by kidneys
Kidneys also filter increased urea generated
50
What is the impact of animal VS plant protein on CDV health?
Animal = associated with oxidation and inflammation of endothelium
Plant = protective due to health-supporting fibre, phytonutrients and prebiotics
51
What are protein requirements for adults?
0.5 = deficient
0.75 = normal
1.0 = minimal physical activity
1.3 = moderate physical activity
1.6 = intense physical activity
52
53
Do you need to supplement athletes with protein due to increased demand?
No : increased need will likely be met as a proportion of the increased calorie demand
54
How can you calculate appropriate protein intake for pregnancy and lactation?
- Pregnancy : RNI + additional 6g x day
- Lactation : RNI + 11g x day 0-6 moths; 8g x day 6+ months
55
Who suffers protein deficiency in the developed world?
- Children/teens with highly refined/processed food diets
- Teens dieting
- Older people (both preparation and digestive issues)
- Anorexia nervosa sufferers
- Patients recovering from trauma
- Homeless/disadvantaged people
- Chronic digestive conditions or chronic use of PPI
- Chronic or active infections
56
Other than protein synthesis, what are amino acids crucial for?
- Synthesis of hormones and neurotransmitters
- Act as neurotransmitters themselves (e.g. glycine)
- Act as methyl donors (e.g. methionine)
- Build bile acids (e.g. glycine and taurine)
- Precursors for nitric oxide production (e.g. arginine)
- Precursors for manufacture of endogenous antioxidants
- Contribute to phase 2 liver detox
57
How can amino acid status be assessed?
Insufficiency or deficiency can be investigated using plasma or urine samples
58
When can testing amino acids status be useful?
E.g. chronic fatigue syndrome due to mitochondrial inefficiency, following long term PPI use
59
How can I use information about essential amino acids status in clinics?
E.g. in risk of CDV disease : high levels of branched amino acids (leucine, isoleucine, valine) and homocysteine are linked to heart disease -> lower dietary intake
60
What is glutamine?
Most abundant amino acid in the body -> 60% of the total pool of free amino acids
CONDITIONALLY ESSENTIAL : body’s synthesis becomes insufficient during acute stress (e.g. injury and infections)
61
What are the functions of glutamine?
1. Preferred fuel for RAPIDLY DIVIDING CELLS : enterocytes (gut support), lymphocytes and macrophages (immunity)
2. Behaves as a buffer : receives excess ammonia and releases it when needed to dorm amino acids/nucleic acids
3. Hypoglycaemia support : substrate for gluconeogenesis
4. Muscle recovery : promotes faster recovery and reduces muscle breakdown
5. Neurotransmitter : converted to GLUTAMATE (excitatory) and then to GABA (inhibitory)
62
What does the conversion of glutamate into gaba need and how can it be assessed
It needs : B6, taurine and zinc
If it works, GLUTAMINE can be used to relieve anxiety and support sleep
An organic acids test can assist this understanding
63
What does glutamine do for the intestinal barrier?
Primary amino acid source for intestinal cells -> helps regulate tight junction integrity and enterocyte proliferation
Depletion = decreased tight junction proteins = increased intestinal permeability
64
What are some causes of intestinal permeability?
Coeliac disease, SIBO, IBD, candidiasis, alcohol, food allergies/intolerances, chronic stress, nutrient deficiencies, NSAIDs, chemotherapy
65
What is the outcome of intestinal permeability?
Leakage of substances into the body which can lead to chronic diseases, e.g. autoimmunity
66
How can you support intestinal permeability?
1. Remove the cause
2. Supply nutrients that support enterocyte junctions : glutamine (supplementation or food sources, e.g. cabbage juice), zinc (for rapid cell division), antioxidants, bone broth (collagen, glucosamine, chondroitin, glycine)
67
What are the “rules” of glutamine supplementation?
- Dosage : start low and gradually increase (1-30g x day, morning)
- Interactions : anti-seizure medications
- Toxicity : not on short term
- Caution : glutamine fuels cancer cells’ growth
68
What is cysteine?
A conditionally essential amino acid formed from methionine and serine in the liver
(Need : B6, B9, B12)
69
What are direct food sources of cysteine?
Legumes, sunflower seeds, eggs, chicken
70
What does cysteine do?
1. Component of glutathione* -> needed x formation of Coenzyme-A and taurine
2. Source of sulphate (-SO4) used in phase 2 liver detox
* it is a limiting amino acid for glutathione synthesis -> important x detox and antioxidant support
71
What is N-Acetyl cysteine? (NAC)
A derivate of L-cysteine, used in supplements because easier to absorb
72
What are the functions of N-Acetyl cysteine?
1. Liver detox : building block of glutathione + crucial for drug metabolism (drugs deplete glutathione while cysteine regenerates it)
2. Reproductive health : increase sperm concentration + positively impacts testosterone
3. Respiratory health : breaks down mucus and aids elimination from respiratory tract
4. Increase insulin sensitivity
73
What are further therapeutic uses of N-Acetyl cysteine?
HIV support = increase glutathione, reduce oxidative stress, enhance T-cell count and activity
Neurodegenerative diseases e.g. Parkinson’s, Alzheimer’s
74
What are the “rules” for NAC supplementation?
Dosage : 600-1.5 g x day
Drug interactions : nitro-glycerine (can cause hypotension, headaches) and careful with insulin
Caution : can cause GI adverse effects
75
What is methionine?
Sulphur-containing essential amino acid
76
Food sources of methionine?
Animal foods, Brazil nuts, sunflower seeds, beans, whole grains
77
Function of methionine?
Major methyl donor (homocysteine cycle) -> use B6, folate and B12 to support methylation AND restrict dietary methionine (animal produce) to lower homocysteine
78
When do you need to be cautious with methionine?
Excess methionine can increase acidity in the body and homocysteine levels
79
What is Carnitine?
An amino acid derivative that can be obtained by diet OR synthesised by body from METHIONINE and LYSINE (requires iron, vit. C, B3 and B6)
80
What are direct food sources of carnitine?
Nuts, seeds, avocado, asparagus, spinach, red meats, dairy
81
Is Carnitine an essential amino acid?
No, but can be made conditionally essential by genetic mutation (gene SLC22A5)
82
What is a therapeutic use of Carnitine?
In cases of hyperthyroidism : acts as a peripheral thyroid hormone antagonist
83
What is the function of Carnitine?
Assist ATP synthesis from fatty acids : facilitates transport of long-chain fatty acids across mitochondria membrane -> burnt to create ATP
+ removes toxic metabolites from mitochondria (= antioxidant)
84
What are the “rules” of Carnitine supplementation?
Dosage : 1-2g, twice x day
Drug interactions : anticoagulants (increase blood thinning effect), thyroid hormones (thyroid hormone antagonist)
Caution : L-carnitine use associated with various GIT symptoms at high doses
85
What is creatine?
A small peptide made of arginine, glycine and methionine -> formed in the liver, kidneys and pancreas
86
Where is 95% of creatine?
Mainly muscles and some in the brain -> functions as fast source of ATP in the form of creatine phosphate
87
What are direct food sources of creatine?
Meat, fish, eggs
88
What is creatine function?
Storage of ATP -> enables explosive power in muscles (8-12 s) also enhances muscular activity (skeletal and cardiac)
89
What are the “rules” for creatine supplementation?
1. Skeletal muscle has a saturation point
2. Drug interactions : combining caffeine + ephedra + creatine = ischaemic stroke; high doses might affect renal function + combining with NSAIDs worse x kidneys
Caution : causes muscles to draw water from body -> hydration is important!
May also cause GIT symptoms
90
What is glycine?
Conditionally essential amino acid in the case of metabolic stresses, e.g. collagen formation for growth/repair; glycine conjugation in detoxification
Made with serine and B6
91
Food sources of glycine?
Legumes, seaweed, spinach, kale, cauliflower, cabbage, banana, pumpkin, bone broth, meat, fish, eggs
92
What are the functions of glycine?
- 1/3rd of collagen is made of glycine
- Needed x glutathione synthesis (hence phase 2 liver detox)
- Is an inhibitory neurotransmitter (also reversibly converted to serine -> used to form acetylcholine)
- Needed x DNA and RNA synthesis
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94
What is taurine?
A conditionally essential amino acid (normally synthesised by the body using cysteine and B6) -> may become essential in cases of extreme stress/illness
95
Direct food sources of taurine?
Only in animal-sourced food (and breast milk! Supplementation needed x non-breastfed infants)
96
Functions of taurine (5) ?
1. Muscle health : contraction + heart health -> anti-inflammatory and blood-pressure lowering
2. Antioxidant
3. Neurological : inhibitory neurotransmitter, supports development of the cerebellum, neuro-protective functions
4. Bile acid conjugation
5. Improve insulin resistance
97
“Rules” of taurine supplementation?
Dosage : 500mg 3 x day
Drug interactions : lithium (decrease excretion), blood pressure meds
Contraindicated : bipolar disorders (caution : added to some energy drinks)
Toxicity : safe up to 6g x day
98
What is theanine?
Non-essential but has various beneficial effects
Found only in green tea!
99
What does theanine confer to green tea?
It reduces the negative effects of caffeine by having opposite effects (relaxing)
100
What is the function of theanine?
Neurological (calming) :
- Blocks glutamate receptors whilst increasing GABA activity
- Increases alpha brain waves = mood enhancing
- Increase serotonin and dopamine levels
101
What are the “rules” for theanine supplementation?
Therapeutic doses : 50-200 mg (drinking green tea not enough)
Drug interactions : can lower blood pressure -> careful with pressure-lowering drugs
102
What is tyrosine?
Conditionally essential amino acid derived from phenylalanine
103
Food sources of tyrosine?
Nuts, seeds, legumes, whole grains, fish, meat, poultry
104
What is the function of tyrosine?
Endocrine health : a precursor of thyroid hormones, dopamine, adrenaline and noradrenaline (and melanin -> skin pigment)
105
“Rules” of tyrosine supplementation
Dosage : 400-6000 mg
Drug interactions : MAOI antidepressants, levdopa, thyroxine
Contraindications : overactive thyroid and melanoma
Caution : high doses can upset GIT
106
What is tryptophan?
An essential amino acid
107
Food sources of tryptophan?
Brown rice, quinoa, pumpkin seeds, oats, banana, turkey, fish, eggs
108
Tryptophan’s functions
1. Endocrine health (serotonin and melatonin synthesis)
2. ATP synthesis (used to make B3 -> needed for ATP)
109
What is the link between tryptophan and insulin?
Tryptophan is assisted through the BBB by insulin -> carbs aid its absorption -> explains why low serotonin cause carbs cravings
110
“Rules” of tryptophan supplementation
Dosage : 100-600 mg x day (5HTP preferred)
Drug interactions : antidepressants, sedatives, …
Adverse effects : L-tryptophan can cause GIT side effects / headaches and drowsiness
111
What is Phenylalanine
An essential amino acid
112
Food sources of phenylalanine
Avocado, brown rice, lentils, eggs, fish, meat, soy
113
Functions of phenylalanine
1. Endocrine health : converted to tyrosine -> thyroid hormones, dopamine, …
2. Skin pigmentation : melanin production -> via tyrosine pathway
114
“Rules” for phenylalanine supplementation
Dosage : 150-7000 mg x day
Drug interactions : antipsychotics, neuroleptics
Caution : can worsen schizophrenia symptoms
Contraindications : PKU
115
What is lysine?
An essential amino acid
116
Food sources of lysine
Quinoa, legumes, tempeh, chicken, eggs, dairy, fish, red meats
117
Key therapeutic use of lysine
Herpes simplex virus : helps prevent and fight outbreaks (more effective if combined with vit. C)
Virus uses arginine to replicate, so increases in lysin can limit viral replication
Dosage : 300-3000 mg x day
118
Functions of lysine
1. Structure : part of collagen -> tissue repair + muscular tissue
2. Absorption : aids intestinal absorption of calcium, iron, zinc
3. Glucose lowering effect
119
What is arginine?
A conditional essential amino acid
120
Dietary sources of arginine
Nuts, seeds, seaweed, meat
121
Function of arginine
Precursor of nitric oxide = blood pressure lowering
122
“Rules” for arginine supplementation
Dosage : 6-12 g x day -> competes with lysine and histamine for absorption, take away from foods
Interactions : antipsychotic and antihypertensive
123
General guidelines on amino acid supplementation
- Safety has not been studied in pregnancy/breastfeeding -> avoid
- Amino acids compete with each other x absorption
- Using just 1 gives an advantage in terms of absorption : good for short term therapy but can cause imbalances on the long run
124
What functions can amino acids help restore?
1. Assist neurotransmitters and hormone synthesis
2. Restore physical and immunological gut barriers
3. Stabilisation of blood glucose (through gluconeogenesis)
4. Better mitochondrial performance x utilisation of fatty acids for energy (-> carnitine)
5. Hepatic and GIT detox (phase 2 conjugation)
6. Reduction of oxidative damage (maintain glutathione)
125
What is the main reason for impaired utilisation of amino acids?
Dietary lack of micronutrients needed for amino acids interconversions : zinc, B6 and B12
126
What are free-form amino acids formulas good for?
Because they’re not peptide-linked, they are very efficiently absorbed (even in absence of stomach acid/pancreatic secretions) —> useful when extra protein is needed and/or absorption is compromised
