Proteins

Protein

• Also called polypeptides

• A protein consists of 1 or more polypeptides in specific conformations.

• Monomer: amino acids

• There 20 amino acids: all have the same basic structure but differ in the side chain (R group).

Multiple Choice

Every amino acid is built around a central

• carbon

• carboxyl

• nitrogen

• hydrogen

How many amino acids are grouped

• All have the same basic structure but differ in their side chain (R group).

• 4 groups amino acids are:

  • Non polar

  • Polar

  • Acidic

  • Basic

Multiple Choice

What is the monomer of a protein?

• amino acid
• monosaccharide
• fatty acid
• nucleic acid

Function of proteins

• Growth and maintenance

• biochemical reactions: enzymes, blood clotting, muscle contraction

• Messengers: hormones

• Structure: e.g. collagen

• Maintain pH

• Balance water

• Immunity

Multiple Choice

Which of the following is NOT a function of proteins?

• stored energy

• create muscle

• speed up reactions as enzymes

• fights infection in the form of antibodies

Multiple Choice

This is one job proteins do NOT have in the body

• insulation

• structure for tissues and organs

• speeds up chemical reactions

• transport things through cell membrane

Multiple Choice

Which of the following are examples of protein?

• cutin, waxes, fats, oils

• Collagen, enzymes, hemoglobin, insulin, and antibodies

• DNA& RNA

• Glucose, sucrose, glycogen, and cellulose

Multiple Choice

The diagram shows a bond forming between two amino acids. What is the name of this reaction?

• Dehydration Synthesis

• Hydrolysis

• Pepysis

• Oxidation

Multiple Choice

What is a peptide bond?

• Bond that holds two amino acids together.
• A bond that holds hydrogen and oxygen molecules together.
• A bond that holds the phosphate group of one nucleotide and a sugar of a neighboring nucleotide.
• A bond that is formed by the sharing of electrons.

Levels of protein structure

• Each protein has a specific 3-D conformation.

• 4 levels of protein structure are:

• Primary (1^o)

• Secondary (2^o)

• Tertiary (3^o)

• Quaternary (4^o)

Primary structure

• Unique sequence of amino acids joined by peptide bonds in a linear polypeptide chain

• The 20 common amino acids can be arranged in different ways (determined by genetic information)

• Eg: Glucagon consist of a sequence of 29 amino acids

Multiple Choice

A bond between amino acids is called a(n) _____ bond.

• acid

• hydrogen

• ionic

• peptide

Multiple Choice

The name of the initial chain of monomers in a protein is called.....

• polypeptide
• polysaccharide
• polyester
• polynucleotide

Secondary structure

• Once a linear chain of amino acids is formed, it spontaneously coils to form the alpha helix or folds to form the beta pleated sheet.

• Because of hydrogen bonds between the repeating constituents of the polypeptide backbone (not the amino acid side chains).

Multiple Choice

Figure 1 Represents a common process that occurs in organisms.

Which of the following is an accurate description of this process shown in figure 1?

• The linking of amino acids with an ionic bond as an initial step in the protein synthesis process

• The formation of a more complex carbohydrate with the covalent bonding of 2 simple sugars

• the hydrolysis of amino acids with the breaking of covalent bonds with the release of water

• The formation of a covalent peptide bond in a dehydration synthesis reaction

Multiple Choice

which of the following best describes how amino acids affect the tertiary structure of a protein?

• the number of amino acids determines the tertiary structure of the protein

• the interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein

• the R-group of the last amino acid that is added to a growing polypeptide chain determines the next amino acid that is added to the chain

• the sequence of the amino acids in the polypeptide chain determines the protein's primary structure but has no effect on it's tertiary structure

Secondary structure

• Two forms:

  - alpha helix (coiled)

  - beta pleated sheet (folded)

• alpha helix - Keratin found in hair, nails, horn

• beta pleated sheet - Silk protein produced by many insects & spiders  

Multiple Choice

Which of the following best describes the formation of the amino acids shown in figure 1?

• An ionic bond is formed between a carbon atom of one amino acid and the nitrogen atom of the other amino acid

• an ionic bond is formed when the negative charge of an OH group is balanced by the positive charge of a hydrogen ion

• a covalent bond is formed between a carbon atom and a nitrogen atom along with the formation of water

• a covalent bond is formed that replaces the hydrogen bond between the oH group and H atom

Tertiary structure

• A polypeptide may be further coiled into a globular shape which is maintained by bonds & interactions among side chains.

• The bonds and interactions that maintained the structure are:

  i. Disulfide bridges

  ii. Ionic bonds

  iii. Hydrogen bonds

  iv. Hydrophobic interactions

  v. Van der Waals interactions

Multiple Choice

The tertiary structure folding in proteins is primary due to the interactions of....

• the 'R' groups
• the 'P' groups
• the 'A' groups
• the 'S'

Quaternary structure

• Consists of 2 or more polypeptide chains joined to form a single functional molecule.

• The bonds that formed between the polypeptide chains are :

  i) Disulfide bonds

  ii) Ionic bonds

  iii) Hydrogen bonds

  iv)  Hydrophobic

  v)  Van der Waals interactions

Quaternary structure

• Eg : haemoglobin and collagen

  a) Haemoglobin

   • Consists of 4 polypeptide chains

   • 2 α-chains

   • 2 β-chains

• b) Collagen

   • Consists of 3 polypeptide chains that  forms triple- stranded helical coils.

   • Fibrous protein

Multiple Choice

which of the following terms refers to the order in which amino acids are linked together in a protein.

• Primary

• Secondary

• Tertiary

• Quaternary

Multiple Choice

The chain of amino acids folds and coils on itself

• Primary

• Secondary

• Tertiary

• Quaternary

Multiple Choice

The entire polypeptide forms a three-dimensional structure

• Primary

• Secondary

• Tertiary

• Quaternary

Multiple Choice

The main bonding in the secondary structure of a protein is due to.....

• covalent bonding
• ionic bonding
• hydrogen bonding
• polar bonding

Denaturing a
Protein

Proteins have their shape changed under harsh conditions

Conditions that can
denature enzymes:

▪ High temperature
▪ concentration
▪ extreme pH

Multiple Choice

If a protein is "denatured", what does that mean?

• The protein has broken down

• The protein has been created

• The protein has folded

• The protein has been domesticated