Proteins Flashcards
1
Q
What are some functions of proteins?
A
- Movement
- Structural proteins
- transport
- protect against infections
- communication
- Participate in and regulate metabolism
2
Q
Why do we need to acquire proteins from the diet?
A
- Maintain protein balance (replacement of obligate protein loss and for growth)
- Essential amino acid supply
3
Q
What is the primary structure of a protein?
A
- Linear number and order (amino acids)
4
Q
True or False
Secondary structure codes for proteins
why or why not
A
primary does, the create order for the genes
5
Q
What determines secondary structure
A
Primary structure
6
Q
What is the secondary structure of a protein?
A
- Determines the conformation of a protein
- B pleated sheets and A heli
7
Q
What interactions maintains the structure of a secondary protein?
A
- postive and negative charges
- hydrogen bonds
8
Q
What is teritary structure?
A
Addition folding of proteins because of R-groups, spatial arrangements of poly-peptide chains
9
Q
What maintains the structure of a tertiary protein
A
- Hydrophobic interactions
- Van Der Waals
- Hydrogen bonds
- Ionic bonds
10
Q
What is quarternary structure?
A
- Interactions between poly-peptide chains
11
Q
What are prostetic groups
A
Non protein componets
12
Q
What are the 9 essential amino acids
A
- Histidine
- Isoleucine
- Leucine
- Threonine
- Lysine
- Methionine
- Phenylalanine
- Trytophan
- Valine
13
Q
What amino acids are semi essential and what are they made from
A
Met make Cysteine
Phe makes tyrosine
14
Q
Why would amino acids be conditionally essential
A
- under-developed/ insufficient synthesis
- Increased requirements (stress, surgery, injury)
- decreased synthesis
- defective synthesis (lacking enzyme)
15
Q
First stage of protein digestion
(where, what)
A
- occurs in the mouth and salivary glands
- Mechanical
- moistens protein rich food and mixes them with saliva
16
Q
2nd stage of protein digestion
A
- beginning of chemical digestion
- Gastric juices release HCL and Pepsin
17
Q
What is HCL effect on protein digestion
A
- denatures proteins
- Activates pepsiongen to pepsin
18
Q
What is pepsin effect on protein digestion
A
- breaksdown into smaller peptides and free AA
- inhibits pepsinogen (precursor) synthesis
19
Q
Third step of protein digestion
A
- Pancreas and small intestine
- CCK release and pancreatic juices
- enzymes of stomach denatures (pH: 6-7)
- inactive zymogens converted to active enzymes to breakdown proteins into di-, tri-, and oligo-peptides
20
Q
What do polypeptides and AA stimulate the release of and where does this occur
A
-cck and pancreatic juices
21
Q
List the steps in the zygmogen cascade
A
- Epthieal cells release CCK
- Pancreas acinar cells release inactive zygmogen enzymes
- Duodenal enterocyte releases enterodiase
- Enterodiase release activate tripsinigen to form trypsin
- Trypsin activates whole cascade to active enzymes
22
Q
What are incretins
A
The stimulates an insulin response
23
Q
What are the 2 important incretins?
A
Glucagon-like peptide 1 GLP-1
Glucose dependent insulintropic polypeptide GIP
24
Q
How do DPP-4’s work on incretins
A
DPP’s inactivate enzymes release of incretins which increase insulin response and decrease glucagon response —> decreases blood sugar
25
Not all proteins are broken down by pancreas enzymes, how is this solved?
BB peptidases (originate in the enterocyte)
26
How are proteins absorbed/transported?
-Diet brings in proteins, it’s gets broken down by duodenal and pancreatic enzymes. Which leaves amino acids, di and tri peptides along with large peptide
-Amino acids are taken into the enterocyte by BB aa transport system and di/tri peptides are taken up by BB peptide transport system which go into the enterocyte and di/tri peptides are turned into amino acids via cytoplasmic peptidases which can be exported out via basolateral amino acid transporter system and di/tri peptides are exported out via basolateral peptide system
27
Describe the sodium dependent amino acid transporter
- Na binds the the transporter, which increases the affinity for amino acid to bind
- amino acids binds which causes a conformational changes and amino acid and amino acid move to the inside of the cell
- Na/ k atpase then transports Na out of the cell
28
Where in the intestine is the majority of amino acids taken up?
In the jejunum
29
What impacts the rate of absorption in a protein
- structure of the protein
- charge of the protein
- food matrix
- essential vs nonessential
- amino acid vs oilgopeptides
30
How does the small intestine change to regulate amino acid absorption?
1. Change is absorbtion surface area
- hypertrophy associated with obesity/ diabetes/ lactation pregnanci
2. Gene expression on enterocyte
31
Why are intact proteins generally not absorbed
1. BBM proteases
2. Tight junctions
3. There aren’t any transporters for it
32
How does colostrum help babies with protein digestion?
- provides nutrients for growth
- immunoglobulin for protection
- growth factors for GI track to mature
33
What happens in celiac disease
Gliadin protein get thru tight junction which enters the blood stream and causes an immune response
34
What role does the enterocyte play in aa avaiblity and absorption
1. Enterocyte absorb amino acids
2. Can use them for energy
3. Used for protein synthesis
4. Intermediary metabolic conversion
35
Reason for protein malabsorption
- Severe pancreatic dysfunction
- intestinal resection
- serve chronic malnutrition
36
Name the different fates of aa breakdown in the body
1. Non protein nitrogenous compounds
2. Protein synthesis
3. Catabolism with excretion of nitrogenous chains
37
Describe the process of transamination
Keto acid turn into an amino acid and the amino acid turns into a keto acid
- keto acid is regenerated to be used again
- NH3 from amino acid is then combined with CO2 to be excreted
38
Glutamate + OAA produce what products , with which enzyme
Produces : alpha- ketoglutarate + aspartate
With AST
39
Glutamate + pyruvate produce what with what enzyme
ALT
Alpha ketoglutarate and alanine
40
Where is ALT **mainly** found?
In the liver
41
Where is AST **mainly** found
In the heart
42
What does a high ALT?
Liver disease
43
AST/ALT ratio increase, indicates what?
alcoholic hepatitis, cirrhosis
44
What is the purpose of delamination?
provide NH3 for urea synthesis and alpha keto acids for a variety of reactions including energy production when needed
45
What AA stimulates the synthesis of NAG
Arginine and Glutamate
46
What increase the urea cycle
High protein diet and starvation
47
What is ammonia toxicity
Free ammonia is produced during the catabolism of AAs as well as nucleic acids that causes a raise in pH and neurotoxicity
48
What are gluconeogenic AA
Come primary from CAC or pyruvate, removes OAA from CAC therefore AA’s used as intermediates. are gluconeogenic
49
What are ketogenic AA
Uses primarily ACoA acetoacetate
A. CoA can enter CAC if sufficient OAA therefore ketogenic
50
Explain single AA substitution?
Single nucleotide is switched which causes a change in AA which can cause major changes
51
Why is protein degradation important
Because it regulates protein abundance and gets rid of mutated proteins
52
Describe the UPS system
- Proteins to be degraded are ligated to ubiquitin (‘tagged’) in an ATP-requiring reaction
- increase during pathological conditions
53
Describe Autophagy-lysosomal pathway (ALP)
- large scale breakdown for energy
- cushion with a Lysome which causes a breakdown of stuff inside
54
What does the UPS system breakdown?
Degrades damaged, abnormal, relocated proteins
55
What are some diseases associated with a malfunctioning UPS system?
Alzheimer’s and CVD
56
When would the ALP system be activated?
- when in need of energy
- infection
57
What contributes to the flux rate of proteins?
Flux rate = Degradetion + excretion = synthesis + intake
58
What are the 2 compartments in the protein turnover model?
Free A.A - A.A in blood, tissue, and cellular compartments
Body Protein - all tissue and circulating proteins
59
What are the different components of N metabolism?
Protein turnover (protein synthesis and degradation) and nitrogen balance (N input and output)
60
What generally impacts nitrogen balance?
Protein turnover
61
Is protein turnover a futile cycle? Why or why not?
It it is, it’s energetically expensive (10-25% BMR, we are constantly breaking down and synthesizing)
62
What processes is protein turnover useful for?
1. Used for gluconeogenesis, mobilize aa for glucose source
2. Meet nutritional and physiological needs
3. Nitrogen excretion
4. Replace lost or damaged proteins
63
What is the main site of AA degradation and why
Liver, closely linked to urea cycle
64
What are the 2nd most important tissues when it comes to AA degradation?
Muscles - branched aa
Small intestine - uses AA as fuels, glu, gin, asp
65
What are AA used for?
To create other molecules that use C skeletons and out that towards the body’s needs
66
Why is skeletal muscles not the primary storage organ for AA?
- the have more than enough proteins for demands
- have storage for gluconeogenic precursors
67
When does uptake of AA’s occurs?
Once protein is ingested
68
What metabolic processes does protein turnover support?
Gluconeogenesis and protein synthesis
69
Why is there limited free amino acids floating around?
Because it’s toxic and could cause affect transporters into the brain
70
What are some protein catabolic signals?
-glucagon, catacholeamine, glucocorticoids, thyroid hormone and cytokines
71
Protein anabolic signals?
Insulin and AA
72
What processes are active during the fed and fasted state of proteins
Gluconeogensis
Ureagenesis
AA oxidation
73
What happens is you eat a ton of protein
- protein increase = body tries to get rid of it by making glucose
- produces both glucagon and insulin
74
Rank proteins that have to highest turnover rate to the slowest turnover rate
Fastest: Regulatory proteins
Non regulatory proteins
Slowest: structural proteins
75
What occurs during anaorxia and physical inactivity in regards to protein
Anorexia: lower protein intake
Physical inactivity: muscle protein dyshomeostasis
Leads to loss in lead body mass and physical performance —> Increase mortality morbidity and disability
76
What is the consequence of hyper metabolism or inflammatory state
Muscle wasting
77
How can you induce muscle hypertrophy/anabolism
Increased muscle stress= increase local protein synthesis
Increased Ingestion of AA = decreases protein degradation = some acute muscle synthesis
78
Ear for protein
0.66
79
RDA for protein
0.8
80
AMDR for protein
10-35%
81
What happen when there is insufficient energy and we consume protein
It is used for fuel rather that protein synthesis
82
What cells are impacted the most by short term protein deficiencies
Cells with quick turnover rates
83
What cells are impacted the most by long term protein deficiencies
All organs +immune system + GI + kidneys
84
What plasma proteins are assessed for deficiency
Albumins and transferrins
- other factors could impact
85
What rapidly growing tissues could help determine a protein deficiency
Skin - thin + pale
Hair - doesn’t grow + falls out + changes colour
86
Marasmus
- Energy and protein deficiency
- Muscle wasting, subcutaneous fat loss, growth retardation
- Diet lacking in calories & protein likely also lacking in micronutrients & essential fatty acids
87
Kwashiorkor
- just protein deficiency
- Growth retardation, edema, swollen abdomen, fatty liver, skin & hair changes, anemia, diarrhea
- Causes: decreased Synthesis of enzymes (lipid transport), hypoalbuminemia
88
Which leads to more mortality marasmus or kwashiorkor
- kwashiorkor
- Hypoalbuminemia leads to defects in body fluid homoeostasis and edema, and deficiencies in apoB-lipoprotein synthesis to a fatty liver
89
Short term effects of high protein diets?
weight loss, calcium loss, ketoacidosis
90
Why is dietary protein required
To provide nitrogen for despensibile AA
91
What are the different properties of protein quality
- AA pattern or score
- degestibility ( hydrolysis and availability of AA
92
What AA is degraded by Maillard reaction?
Lys
93
What aa is degraded by heat damage
Met, try
94
What is the difference between true digestibility and appearent digestibility?
Da, fraction of amino acids that is absorbed (accounted for ingestion and fecal excretion)
Dt is counted for endogenous losses
95
Why is protein digestibility in plant sources low?
- proteins may be encapsulated in cell wall and we cannot degest that
96
What impacts AA avaibility in food?
- food processing and storage
- heat can modify and degrade
- Treat with strong acids
97
Limiting AA definition
Most defieceint AA has **relative** to its requirment
98
How do you calculate the PDCAAS
= AA score x Digestibility
99
What are the possible inadequacies of a vegan diet?
- protein
- Fe, B12, Zn --> meat and eggs
- Ca. Vit D, Riboflavin --> dairy products
100
Benefits of a vegetarian diet
- maintaince of weight
- decreased blood pressure
- Decrease CHD and T2D risk
-
101
what amino acids dont participate in transamination
Lys, thr, pro
102
what is deamination
- liberation of free ammonia from the aa coupled with oxidation
103
Where does deamination occur
liver and kidneys
104
What the purpose of deamination
Provide NH3 for urea and A-ketoacids for a variety of reactions
105
What stimulates the synthesis of NAG
arginine and glutamate
106
What increases the urea cycle
- high protein diet
- Early starvation (proteins are degraded, C'c used for energy, increased N output and if N does not get excreted then increase free ammonia and increase toxicity
107
Describe the glucose alanine cycle
1. Ala is formed in the muscle from transamination with gluamate (Leucine is generated from transamination) from pyruvate
2. Ala travels thru the blood to the liver
3. In the liver, Ala travels into the blood to the liver
4. ALA is transaminated to A-KG from pyruvate
5. Pyruvate is converted back to glucose
6. Glucose is release from liver into the blood and uptake by tissue for energy
