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Food Protiens > lecture 3-protien classification > Flashcards

lecture 3-protien classification Flashcards

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1
Q

List the paramaters used to classify protiens?

A
  1. composition→ simple or conjugated
  2. native or derived
  3. Solubility
  4. Ultracentrifugation properties→mass and density
  5. Electrophoretic properties→charge, MW, IEP
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2
Q

what does ultracentrifugation of protiens seperate them by?

A

seperates them on the basis of MW and shape

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3
Q

Describe what a simple protien is vs a conjugated protien

A

simple protien→ are protiens which contain only amino acids in their molecules and these are divided into 2 groups: globular and fibrous protiens

conjugated protien→ are protiens that contain amino acids and are conjugated with another molecule like carbohydrates, lipids or a mineral

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4
Q

List which simple protiens are globular and which are fiborous

A

Globular= albumins,globulins,glutelins,prolamins, histones, protamines

Fiborous=collagen,elastin

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5
Q

what are the general differences between fiborous and globular protiens?

A

shape: fiborous are long and narrow while globular are round/spherical

purpose: fiborous have a purpose in structure and globular have functional purposes

AA sequence: fiborous have a repatative amino acid sequence and globular have an irregular acid sequence

Durability: fibourous is less sensative to changes in pH and temperature compared to globular who is really sensative

solubulity: generally fiborous class of protiens is insoluble in water and globulins are soluble

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6
Q

What are albumins soluble in?

A

soluble in neutral, salt free water and dilute salt soluations and dilute acids and bases

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7
Q

what perticipates albumins?

A

percipitated with a saturated solution of salt such as ammonium sulphate

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8
Q

what coagulates albumins\

A

heat

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9
Q

give three examples of albumins

A
  1. serumbumin (blood)
  2. lactalbumin (milk)
  3. egg white (ovolbumin)
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10
Q

What are globulins soluble/ insoluble in?

A

they are soluble in neutral salt solutions and then almost insoluble in water

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11
Q

what are globulins percipated in?

A

percipated with half saturated solution of ammonium sulphate

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12
Q

describe some characteristcs of globulins

A

they are coagluated by heat. They are a diverse group of protiens with many functions (actually almost every protien)

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13
Q

give examples of globulins

A

Myosin (muscle)

actin (muscle

beta-lactoglobulin (milk)

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14
Q

what are glutelins soluble/insoluble in?

A

soluble in dilute acid or base and insoluble in neutral solvents (distilled water, dilute salt solution, alcohol)

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15
Q

describe some important characteristcs of glutelins

A

They are rich in hydrophobic amino acids → making them not soluble in certain solutions. They can form disulfide bonds between molecules especially during baking

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16
Q

give an example of a glutelin

A

glutenin which is in wheat and is one of the protiens of gluten

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17
Q

what are prolamins soluble and insoluble in?

A

they are insoluble in water and absolute alcohol and are soluble in 70 to 80% alcohol

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18
Q

what are the 2 protiens of gluten

A

glutenin and gliadin

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19
Q

give some characteristics of prolamins

A

they are coagulated by heat, they are rich in proline and glutamine and are found in plants

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20
Q

give an example of a prolamin

A

gliadin in wheat which is actually the protien responsible for sensitivity, allergy and celiac diease

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21
Q

What are histones soluble in?

A

water

22
Q

what are histones percipitated by?

A

ammonia

23
Q

describe characertics of histones and what they are

A

They are weakly basic protiens that are NOT coagulated by heat and have a high content of arginine and lysine

DNA is compated into chromatin which is wrapped around histones complexes, it is bound by hydrogen bonds with phosphoric acid

24
Q

what is the signficane of lysine in histones

A

Lysine residues are often sites for methylation/acetylation. In histones this is significant because it is important in the regulation of chromatin and gene expression. Lysine acetylation and methalyation leads to the relaxtion of chromatin which means greater transcription

25
Q

how does lysine hydroxylation impact gene expression and chromatin sructure

A

because it can prevent or modify acetylation/methylation of lysine which normally would lead to the relaxation of chromatin allowing for greater trasncription

26
Q

What are protamines soluble in?

A

water and ammonium hydroxide solution

27
Q

what are some characteristcs of protamines?

A

they are strongly basic protiens that are not coagulated by heat but rich in arginine and lysine.

27
Q

what perciptiates protamines

A

aqueous solution of alcohol

28
Q

describe protamines and DNAs relationship

A

Protamines binds with DNA in the embryonic stage and is later replaced by histones

29
Q

describe the general structure of fiborous protiens

A

made up of polypeptide chains that are elongated. they have a sheet like structure. They are mechincally quite strong.

30
Q

describe the structure of collagen

A

It is a triple helix structure. The amino acid sequence is repeating Gly-X-Y. X is often proline which is hydrophobic and Y is either hydroxyproline or hydroxlysine

31
Q

describe how the structure of collagen is related to its function

A

the triple helix provides external protection, shape, support and form

32
Q

Describe what hydroxyproline do for collagen or how it affects it

A

Have OH which increase polarity and hydrophilicity. Hydroxyproline maintains collagen rigidty and elasticity as hydrogen bonds with water molecules and other amino acids stabilize collagen structure.

33
Q

Explain what happens to lysine in collagen

A

it undergos hydroxylation to form hydroxylysine which will increase polarity and hydrophilicty which allows for hydroxyl groups to form hydrogen bonds and interact with other polar groups increasing stability. Not only that but hydroxylysine serves as an attachment site for carbohydrate groups further increasing the structural integrity of collagen

34
Q

describe elastin and its structure

A

Stretchy protien rich in glycine, valine, alanine and proline which are all hydrophobic.

35
Q

what are prosthetic groups?

A

the non protien part of conjugated protiens

36
Q

List the types of conjugated protiens and briefly describe them

A
  1. metalloprotiens (aa+ metal ions)
  2. chromoprotiens (aa + colored pigments)
  3. nucleoprotiens ( aa+ nucleic acids→DNA/RNA)
  4. phosphoprotiens ( protiens+ phosphoric acid)
  5. glycoprotiens( carbs and protien)
  6. lipoprotien( lipid + protien)
37
Q

briefly describe lipoprotiens

A

lipid + protien. They have excellent emulsifying capacity they are found in milk, egg yolk, plasma membrane and as LDL and HDL

38
Q

what are the linking type of glycoprotiens

A

N or O linked

39
Q

Give an example of phosphorotiens and explain the process of their phosphorlyation

A

example= milk caesin

Phosphorylation typically happens on specific amino acids like serine, threonine and tyrosine which have hydroxide groups.

40
Q

protamines or histone are nucleoprotiens?

A

yes they are the phosphate group on nucleic acid binds with amide group on protien

41
Q

give some examples of chromoprotiens

A

haemoglobin, myoglobin, chlorophyll, flavoprotiens

42
Q

give example of metalloprotiens and describe them a little

A

They have metal ions connected to them like iron, copper, zinc, maganese, and cobalt. An example would be hemoglobin. But they function in a wide variety of biological processes.

43
Q

describe derived protiens

A

They are protiens that have been modified by physical or chemical means. This normally results in a physical change like in solubility or hydrophobicity. They are classified by the extent of change into primary and secondary derivived protiens

44
Q

describe primary derived protiens

A

These protien derivatives are fromed by processes causing only slight changes in the protien molecule and its properties so there is no or very little hydrolytic cleaving

45
Q

give examples of primary derived protiens

A

metaprotien: it is produced by the action of an acid or base @ 30-60 degrees. It is water insoluble but soluble in dil acid/alkali. An example of this is curd

coagulated protien: this is produced by the action of heat or alcohol on protien. It is insoluble in wateer. an example is a coagulated egg

46
Q

Define secondary derivatives

A

more extensivly changed protiens, they are formed by progressive hydrolytic cleavage of peptide bonds or by the action of strong acid or digestive enzymes

47
Q

how are secondary derivatives grouped and what happens as you get smaller?

A

They are grouped based on average molecular weight. As they are hydrolyzed they will become smaller decreasing in molecular weight. The more you break down a protien the more soluble the protien because lower molecular weight meaning they will not be coagulated by heat. The ranking is as follows proteoses (10-100 kDa), peptones (1 kDa to 10) and peptides (less then 1 kDa)

48
Q

What can dervived secondary protiens be used for

A

Yeast extract and vegtable protien is often hydrolyzed to enhance flavor because upon hydrolysis free glutamic acid is released which gives that unami taste. Hydrolysis of protiens can also be used to modify allergenic properties of protiens, like in baby infant fromula

49
Q

Classify protiens based on biological function and provide a brief description

A
  1. Catalytic protien: catalyze biochemical reactions (enzymes, coenzymes)
  2. structural protien: structural componenets ( collagen, elastin)
  3. nutrient protien: have nutrional value (milk)
  4. regulatory protien: regulates metabolic and cellular activities (hormones)
  5. defense protien: provides defensive mechanisms against pathogens in immune systme ( antibodies, complement protiens)
  6. transport protiens: transport nurtrients/molecules from one ogran to another ( haemoglobin)
  7. storage protien: store molecules and ions in cells (ferrtin store iron)
  8. contractile or mobile protien: help in movement of various body parts (actin, myosin)
  9. toxic protien: toxic and can damage (snake venom, bacterial exotoxins)

Food Protiens (9 decks)

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