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(HS) Biology 12 > 2.7 Proteins > Flashcards

2.7 Proteins Flashcards

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1
Q

What is a protein?

A

a polymer composed of amino acid monomers

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2
Q

What is an amino acid?

A

an organic molecule composed of a central carbon atom bonded to a hydrogen atom and 3 functional groups

  • amino group (–NH2)
  • acidic group (–COOH)
  • ‘R’ group
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3
Q

What does the ‘R’ group of an amino acid determine?

A

the uniqueness of each amino acid

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4
Q

What is the ‘R’ group of an amino acid?

A

varies from having a single carbon to being a complicated ring structure

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5
Q

What is keratin?

A

structural protein that makes up hair and nails

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6
Q

What is collagen?

A

structural protein that lends support to ligaments, tendons, and skins

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7
Q

What are enzymes?

A

proteins that speed up chemical reactions and are necessary contributors to the chemical workings of the cell, and the body

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8
Q

What are hormones?

A

proteins that are messengers that influence cellular metabolism

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9
Q

What are actin and myosin?

A

proteins that account for the movement of cells and the ability of our muscles to contract

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10
Q

What is hemoglobin?

A

a complex protein in our blood that transports oxygen

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11
Q

What are antibodies?

A

proteins in blood and other body fluids that combine with foreign substances, preventing them from destroying cells and upsetting homeostasis

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12
Q

What are the functions of proteins in the plasma membrane of cells?

A
  • some form channels that allow substances to enter and exit cells
  • some are carriers that transport molecules into and out of the cell
  • some are enzymes
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13
Q

What does the synthesis reaction between two amino acids result in?

A

a dipeptide and a molecule of water

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14
Q

What is a polypeptide?

A

a chain of amino acids that are joined to one another by a peptide bond

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15
Q

What is a peptide bond?

A

a type of bond that joins amino acids together in a polypeptide

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16
Q

Why do the atoms associated with a peptide bond unevenly?

A

because oxygen is more electronegative than nitrogen

  • the hydrogen attached to the nitrogen has a slightly positive charge
  • oxygen has a slightly negative charge
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17
Q

What does the polarity of the peptide bond mean?

A

hydrogen bonding is possible between the C=O of one amino acid and the N-H of another amino acid in a polypeptide

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18
Q

What does hydrogen bonding influence in proteins?

A

structure/shape of a protein

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19
Q

What are the 4 levels of protein organization?

A

primary
secondary
tertiary
quaternary

20
Q

What is the primary structure?

A

the linear sequence of the amino acids joined by peptide bonds

21
Q

How do polypeptides differ from one another?

A

a polypeptide chain is made from 20 different amino acids, each with its own sequence of amino acids and its own sequence of ‘R’ groups

22
Q

How does the secondary structure come about?

A

when the polypeptide takes on a certain orientation in space

23
Q

What are the 2 possible shapes of the secondary structure?

A

alpha helix

beta pleated sheet

24
Q

What causes the polypeptide to form a alpha helix or beta pleated sheet?

A

hydrogen bonding between amino acids

25
Q

What results in an alpha helix?

A

a coiling of the chain

26
Q

What results in a beta pleated sheet?

A

a folding of the chain

27
Q

What is the tertiary structure?

A

the final 3D shape of a protein

28
Q

What shape do myosin molecules in muscles have?

A

a rod shape ending in globular heads

29
Q

What shape do enzymes have in the tertiary structure?

A

the polypeptide bends and twists in different ways

30
Q

Where are hydrophobic and hydrophilic portions in the tertiary structure?

A

hydrophobic: packed mostly on the inside
hydrophilic: on the outside where they can make contact with water

31
Q

How is the tertiary shape of a polypeptide maintained?

A

by various types of bonding among the ‘R’ groups: covalent, ionic, and hydrogen bonding all occur

32
Q

What is a common form of covalent bonding between ‘R’ groups?

A

a disulfide (S-S) linkage between 2 cysteine amino acids

33
Q

How do proteins differ from one another?

A
  • the number of polypeptides (each with its own primary, secondary, and tertiary structure)
  • length
  • sequence
  • structure
34
Q

What gives the tertiary structure a characteristic globular shape?

A

the polypeptide folds and twists due in part to covalent bonding between ‘R’ groups

35
Q

What is the quaternary structure?

A

occurs when 2 or more polypeptides join to form a single protein

in proteins with multiple polypeptide chains, these separate polypeptides are arranged to give such proteins a fourth level of structure

ie. hemoglobin and most enzymes

36
Q

Why is the final shape of a protein very important to its function?

A
  • enzymes cannot function unless they have their normal shape
  • ONCE A PROTEIN LOSES ITS NORMAL SHAPE, IT IS NO LONGER ABLE TO FUNCTION NORMALLY
37
Q

What does ‘denatured’ mean?

A

describes a protein that has had an irreversible change in its shape due to exposure to extremes in heat and pH

38
Q

Give examples of denaturation?

A
  • adding acid to milk causes curdling

- heating causes egg white (contains a protein called albumin) to coagulate

39
Q

Why does denaturation occur?

A

becasue the normal bonding between the ‘R’ groups has been disturbed

40
Q

What are prions?

A

structures formed by the alteration in protein organization and is related to the development of Alzheimer’s diease and Creutzfeldt-Jakob disease (human ‘mad cow’ disease)

41
Q

What is the ‘R’ group of the amino acid Alanine?

A

a single carbon

CH3

42
Q

What is the ‘R’ group of the amino acid Valine?

A

a branches carbon chain

     CH
     /    \   H3C     CH3
43
Q

What is the ‘R’ group of the amino acid Cysteine?

A

contains sulfur

CH2
|
SH

44
Q

What is the ‘R’ group of the amino acid Phenylalanine?

A

a ring structure

CH2
|
[hexagon]

45
Q

What are waxes?

A

long chain fatty acid attached to an alcohol, solid at room temperature

46
Q

What do waxes do?

A

protect from water (plants, ears) and energy storage in plankton

47
Q

What test do you use to detect the presence of protein? What colours does it change to and from?

A

Biuret’s solution

blue to violet

(HS) Biology 12 (46 decks)

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