Proteins

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  • Created by: kay
  • Created on: 28-05-19 18:42
Carbon rich side chains are a feature of what class of amino acids?
Hydrophobic
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Ferritin stores iron in what form?
Non toxic Fe3+ ferritin
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What type of protein is casein?
Phosphoprotein
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What is the role of casein?
Chaperone for Ca2+ transport
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What bonds does heating effect?
Hydrogen
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What bonds does acid effect?
Ionic/electrostatic/salt bridges
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How do we name amino acids?
N to C side
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How is a peptide bond formed?
Condensation: nucleophillic attack by N on amine on electrophillic C of carboxylase
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Where are the side chains in an alpha helix?
Outside
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What side are the amino and carboxyl groups facing in an alpha helix?
Amino = left, carboxyl = right
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In an amphiphatic helix, where do the hydrophobic and hydrophillic groups face?
Hydropphobic = outside, hydrophilic on inside
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Why is proline a main destabiliser?
It can form trans and cis bonds
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Why are parallel beta sheets weaker?
hydrogen bond is at an angle
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What are beta turns made up of?
2 antiparallel strands, 4 amino acids, hydrogen bond between amino acids 1 and 4 and high proline and glycine
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Why does alpha keratin interwine?
Hydrophobic interactions
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What is a disulphide bond?
1 cystine
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What are silk proteins made of?
Beta sheets, antiparallel, ala and gly side chain
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What is collagen made of?
Triple left handed helix, high gly, hydroxyproline and hydroxylysine
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What is the amino acid in globins?
Histidine
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What is the function of the cleft in haem?
Protects Fe2+ from oxidation
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What is Kd and how does it affect affinity?
Kd is the dissociation constant, ligand concentration at 50% max binding.. Lower the Kd, higher the affinity.
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Why is haem protein bound?
To protect iron, provide solubility and prevent free radicals
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What are porphyrin rings broken down into?
Billirubin
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Why is myoglobin not effective at transporting O2?
Same affinity at the PO2 of lungs and tissues
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What happens to the R and T states in the lungs?
Transition of T to R state for high affinity so oxygen binds
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What is positive cooperativity?
When one oxygen binds, increases affinity for other oxygens
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What happens to R and T states in the tissues?
Transition of R to T state for low affinity so oxygen released
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Why is there a lower pH in tissues
CO2 released from metabolism
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What enzyme converts CO2 into carbonic acid?
Carbonic anhydrase
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What happens to 1,3-BPG at low PO2/high altitude?
1,3-BPG is converted to 2,3-BPD which regulates oxygen binding
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Where do you get biocytin from in the diet?
Biotin, B vitamin
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Where do you get FADH2 in the diet?
Riboflavin
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Where do you get NADH in the diet?
Nicotinic acid/niacin
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Where do you get coenzyme A in the diet?
Pantothenic acid
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Where do you get tetrahydrofolate in the diet?
Folate
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Where do you get thiamine pyrophosphate in the diet?
Thiamine/B1
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What cofactor does hexokinase use?
Mg2+
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What does selenium do?
Reduces oxygen free radicals
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What does Zn2+
Orientates ethanol to enhance reaction with NAD+ in alcohol dehydrogenase
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What is an apoenzmye?
Protein with no cofactor
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What is an holoenzyme?
Protein with cofactor
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Where is aconitase found?
Citric acid cycle
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What parts of the enzyme equation are reversbile in an irreversible enzyme?
Only ES binding
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What do enzymes do?
Facilitate formation of transition state (lower Gibbs free energy of transition state (ES and EP)
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WHat is the equation for miachelis-menten?
V= Vmax[S] / Km + [S]
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What is Vmax dependent on?
Substrate, pH, temp, [enzyme]
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What is Km?
Substrate concentration at 1/2 vmax
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What is Km dependent on?
Substrate and pH
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What do aminopeptidase and carboxypeptidsase do?
Degrade peptides to single amino acids in the small intestine
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When does oxidation of amino acids occur?
Where there are excess/spare amino acids or when carbohydrates are scarce
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What happens in the transamination step of amino acid catabolism?
Amino group transferred to alpha ketoglutarate to form gluatmate
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The pyroxidal phosphate cofactor can be obtained from which vitamin?
Vitamin B6
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What happens to the carbon cycle in amino acid catabolism?
Goes to TCA or to make ketones
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What happens in skeletal muscle tissues in terms of amino acid catabolism?
GLucose-alanine cycle: transamination of pyruvate to form alanine
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What is an advantage of the glucose-alalaine cycle?
Reduces prodcution of lactic acid in anaerobic respiration
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What are the only 2 purely ketogenic amino acids?
Leucine and lysine
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What sort of diet does a high urea content of urine suggest?
High protein, low carb
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How do aquatic animals release nitrogen?
As ammonia
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How do terrestial vertebrates release nitrogen?
As urea
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How to birds and reptiles excrete nitrogen?
As uric acid
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How to humans excrete nitrogen?
As urea and uric acid
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Ferritin stores iron in what form?

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Card 3

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Card 4

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Card 5

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What bonds does heating effect?

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