Proteins

Proteins are _______ made up of _______ _____ joined by ________ _____

polymers, amino acids, peptide bonds

Main functions of proteins (6)

1. Enzymes 🌀

2. Structural proteins 🔨

3. Contractile proteins 💪

4. Hormones 🌸

5. Transport proteins 🚚

6. Defence proteins 🛡️

enzyme example

amylase

structural proteins example

keratin, found in skin, hair, nails

contractile proteins example

actin and myosin in muscles

hormones example

insulin and growth hormones

transport proteins example

hemoglobin, which transports oxygen

defence proteins example

antibodies that protect the body against disease

all proteins are made of the ______ set of ___ amino acids, connected in different ___________

SAME, 20, combinations

Components of a a general amino acid

• Amino group

• Carboxyl group

• Side chain (R)

Amino acids’ ____________ and thus ___________ are determined by:

properties, classification, those of their side chain (R)

Identify this type of amino acid

non-polar amino acids

Identify this type of amino acid

polar amino acids (uncharged)

Identify this type of amino acid

LEFT: negatively charged (acidic) amino acids

RIGHT: positively charged (basic) amino acids

4 structure levels of proteins

1. Primary

2. Secondary

3. Tertiary

4. Quaternary

Primary structure

• linear sequence of amino acids joined with peptide linkages

• forms a polypeptide chain

Circle the peptide linkage(s)

Includes the C=O and N-H

Peptide linkages are a kind of ___________ rxn

Condensation

Secondary structure

• Result of H-bonding btn atoms in the amino acid backbone

• Two forms: alpha helix and beta pleated sheets

The amino acid backbone

Electronegative Oxygen or Nitrogen with an electropositive Hydrogen further down the polypeptide

⇨ when hydrogen bonding occurs between these atoms, the polypeptide chain coils or folds (secondary structure)

Tertiary structure

• complex, 3D structure due to bonding interactions between the R groups

Interactions between R groups that contribute to tertiary structure include: (5)

1. Disulfide bridges 🌉 (between distant cysteines)

2. Hydrophilic associations 💧💓

3. Hydrophobic associations💧❌

4. Ionic bonds 🧲

5. Hydrogen bonds

Cystein

a non-polar amino acid with sulfhydryl group (-SH) as its side chain, allowing them to form disulfide bridges/linkages

⇨the two groups react to form a strong S-S covalent bond

Tertiary Structure is critical to the _________ of proteins, especially __________!!

FUNCTION, enzymes

Quaternary structure

• Occurs when multiple tertiary structures combine to make a functional protein

• Many forces hold these subunits together

Hemoglobin is composed of ___ _____________, making it at the _____________ level of structure

4 polypeptides, quaternary

Forces that hold subunits together in a quaternary structure include: (4)

1. Disulfide linkages

2. Negatively-charged groups fitting against positively-chatged groups

3. Hydrogen bonds

4. Hydrophobic regions of two subunits associating, thus excluding water

Extreme conditions, like _____________ or ___, can unfold a protein, causing ________________

temperature, pH, denaturation

Denaturation

the loss of both the structure and function of a protein, often causing the formation a precipitate (protein is no longer soluble)

The same bonds and forces that fold single polypeptide chains into tertiary structures are also responsible for:

Holding multiple peptide chains together in quaternary structure