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Biology: Biological Molecules > Proteins > Flashcards

Proteins Flashcards

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1
Q

Size of proteins

A

Usually very large

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2
Q

Each organism…

A

Makes its own unique proteins. It’s proteins that give the organism their characteristics and allow key functions to occur

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3
Q

Proteins are key biological molecules - why?

A

The shape is highly specific and there fore different to other type of types

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4
Q

Monomers of proteins

A

Amino acids

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5
Q

Amino acids contain which elements?

A

Nitrogen (N), Carbon (C), Oxygen (O), Hydrogen (H) and sometimes sulphur (S)

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6
Q

Variety of proteins: Different roles

A

-Haemoglobin -> Transports oxygen by binding to it
-Antibodies -> Defends the body against infection
-Enzymes -> Biological catalysts
-Actin and myosin -> Involved in muscle contraction

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7
Q

Variety of proteins: Structural role

A

-Keratin -> Found in nails, hair and hooves
-Collagen -> Found in tendons

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8
Q

How many types of amino acids?

A

20 different types of amino acids, all with the same general structure

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9
Q

Essential and non-essential amino acids

A

You must ingest the essential amino acids in your diet, non-essential amino acids can be synthesised by your body

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10
Q

General amino acid structure

A

H H O
| | | |
H—-N—-C—-C—-OH
|
R

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11
Q

Each amino acid contains

A

A central carbon and 4 different chemical groups
-A nitrogen containing amine group (NH^2 or H^2N)
-A carboxyl group (COOH)
-A hydrogen atom (H)
-A ‘R’ variable side chain or group

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12
Q

What is different in amino acids in the general structure?

A

‘R’ variable side chain. Each R group has a different size and are grouped together by different properties e.g. charge and polarity

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13
Q

Formation of a peptide bond

A

Two amino acids joined together to form a dipeptide by a condensation reaction. The hydroxyl group (OH) from the carboxyl group of one amino acid reacts with a hydrogen (H) from the amine group of the second amino acid via a condensation reaction. The water is removed in the formation of a PEPTIDE BOND

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14
Q

Many (hundreds of) amino acids form what?

A

Form a polypeptide chains as a result of many condensation reactions

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15
Q

Important points of peptide bonds

A

-A peptide chain will always have an amine group at one end (N terminus) and a carboxyl at the other end (C terminus)
-Number of peptide bonds in the chain will be one less than the number of amino acids originally joined together

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16
Q

Proteins structure

A

Primary -> Secondary -> Tertiary -> Quaternary

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17
Q

What is the primary structure?

A

-The number and sequence of amino acids in a polypeptide chain. Because there is 20 amino acids, there is a limitless number of possible sequences
-Determines the positions of the bonds = Hydrogen, ionic and disulphide -> between R groups and final shape of protein
-Specific shape indicates it’s function
-PROTEINS ARE DIFFERENT FROM EACH OTHER BECAUSE OF THE PRIMARY STRUCTURES BEING DIFFERENT

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18
Q

what is the secondary structure?

A

-The linked amino acids all have -NH and -C=O groups on either side of the polypeptide chain. NH group has overall positive charge and C=O has an overall negative charge.
-A hydrogen bond forms between the slight positive charge on the H and the slight negative charge on oxygen
-These 2 groups form weak hydrogen bonds through put the polypeptide but because there is so many they are strong
-Due to hydrogen bonding the chain coils into alpha helices or folds it’s beta pleated-sheets

19
Q

What is the tertiary structure?

A

-This is the further folding of the secondary structure into a specific, complex 3D shape. Determined by the R groups
-Held together by bonds and interactions between R groups of different amino acids
-Hydrogen bonds = weak bonds
-Ionic bonds = Weak, Bonds form between oppositely charged R groups
-Disulphide bonds = covalent bonds which form between sulphur atoms
-Specific tertiary structure which gives them specific shape necessary for their function

20
Q

What is the quaternary structure?

A

-When proteins form complex molecules that contain more than one polypeptide chain that are also linked hydrogen, ionic and disulphide bridges
-Haemglobin -> made up of 4 polypeptide chain and also contain non-protein groups (contains Fe 3+), Called a haem group and is where oxygen binds to
-Keratin is made up of 3 polypeptide chains held together by many hydrogen bonds between each chains. Produces a strong structural proteins

21
Q

Why is denaturing of enzymes important?

A

It changes the shape of proteins which is essential to its function. When bonds break it changes the specific tertiary shape

22
Q

Why do enzymes denature at high temperatures?

A

Increases in temperature increases the kinetic energy of the molecules causing them to vibrate more. This means it can break the weak hydrogen bonds that hold the structure together. As these bonds break the tertiary shape is lost

23
Q

What is denaturation?

A

When the specific tertiary structure shape is lost

24
Q

What is denaturation caused by pH change?

A

It disrupts the ionic and hydrogen bonds in the tertiary structure

25
Q

Test for proteins

A

1) Place a small volume of sample into a test tube
2) Add equal volumes of Biuret solution
3) If present the colour change is purple/violet
4) The colour stays blue if there is not protein present

(Enzymes are proteins and so give a positive result)

26
Q

What is the primary structure?

A

This is the number and sequence of amino acids in the polypeptide chains

27
Q

What does the primary structure determine?

A

The position of the hydrogen, ionic and disulphide bridges between the R groups of two amino acids which determines the final shape

28
Q

Why is the specific shape important?

A

It dictates their function

29
Q

why are proteins different from each other?

A

Because their primary structures are different

30
Q

What bonds are in the primary structure?

A

Peptide bonds between the amino acids

31
Q

What is the secondary structure?

A

The folding of the polypeptide chain into alpha helices or beta pleated-sheets

32
Q

Linked amino acids all have…

A

A -NH of the amine group which has a positive charge and a -C=O of the carboxyl group which has a negative charge on opposite ends of the chain

33
Q

What bonds are in the secondary structure

A

Weak hydrogen bonds between the slight positive of the -H in the amine group and the -O in the carboxyl group

34
Q

Despite being weak hydrogen bonds they are…

A

Strong because there are so many of these bonds between the -H and -O

35
Q

What is the tertiary structure?

A

The further folding of the secondary structure into specific, complex 3D shapes determined by the R groups of the amino acids that are joined

36
Q

What is the tertiary structure held together by?

A

Interactions and bonds between the R groups of different amino acids

37
Q

What bonds are within the tertiary structure?

A

Hydrogen bonds, ionic bonds and disulphide bridges

38
Q

What are hydrogen bonds?

A

Weak bonds between the -H and -O

39
Q

What are ionic bonds?

A

Weak bonds but not as weak as hydrogen formed between the oppositely charged R groups

40
Q

Why is the tertiary structure important?

A

The specific tertiary structure gives them specific shapes necessary for their function to be carried out

41
Q

What is the quaternary structure?

A

When proteins form complex molecules that contain more than one polypeptide chains

42
Q

What are the bonds within the quaternary structure?

A

Hydrogen bonds, ionic bonds and disulphide bridges

43
Q

Quaternary structure of haemoglobin

A

Made up of 4 polypeptide chains that also contain non-protein groups (Fe 3+). This is called a haem group and is where oxygen binds to

44
Q

Quaternary structure of keratin

A

Made up of 3 polypeptide chains held together by many hydrogen bonds between chains which produces a strong structural protein

Biology: Biological Molecules (7 decks)

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