Molec Cell: Ch. 2 pt. 2

by the order of the bases.

DNA is made up of two polynucleotide chains. The bases are on the inside, joined by hydrogen bonds between complementary base pairs.

one strand of DNA (or RNA) to act as a template for synthesis of a complementary strand.

self-replication

The information carried by DNA and RNA directs synthesis of specific proteins, which control most cellular activities.

• ATP

• some act as signaling molecules within cells

Proteins

Each cell contains several thousand different proteins.

Proteins direct virtually all activities of the cell.

• structural components

• transport and storage of small molecules (O2)

• Transmit information between cells (protein hormones)

• Defense against infection (antibodies)

  • Enzymes

Proteins are polymers of 20 different amino acids.

• a carbon bonded to a carboxyl group (COO-)

• amino group (NH3+)

• hydrogen

  • distinctive side chain

Amino acids are grouped based on characteristics of the side chains:

• Nonpolar side chains

• polar side chains

• side chains with charged basic groups

  • acidic side chains terminating in carboxyl groups

• Lysine (Lys) K

• Arginine (Arg) R

  • Histidine (His) H

• Aspartic Acid (Asp) D

  • Glutamic Acid (Glu) E

Peptide bonds

chains of amino acids, hundreds or thousands of amino acids

• One end of a polypeptide terminates in an a amino group (N terminus)

• Other ends in an a carboxyl group (C terminus)

characteristics of proteins

Worked out the amino acid sequence for insulin

Sequences of mRNAs

100,000

Insulin consists of two polypeptide chains. The side chains of three pairs of cysteine residue are joined by disulfide bonds.

the order of nucleotide bases in a gene

Proteins also have distinct 3D conformations that are critical to their function.

The shape and functions of proteins are determined by their amino acid sequences.t

• demonstrated the importance of the 3D structure.

• disrupted proteins by treatments such as heating, which breaks non-covalent bonds (denaturation)

All the information required to specify the correct 3D conformations of a protein is contained in its primary amino acid sequence.

the sequence of amino acids in the polypeptide chain

Regular arrangement of amino acids within localized regions

• Two common types:

  • a helix

  • B sheet

  • both are held together by H bonds between CO and NH groups of peptide bonds

The folding of the polypeptide chain due to interactions between side chains of amino acids in different regions of the chain

The basic units of tertiary structure; are folded 3D structures usually containing between 50-200 amino acids

• Hydrophobic amino acids: in the interior of the protein

• Hydrophilic amino acids: on the surface - interact with water

  • Loop regions - connect the elements of secondary structure

They are on the surface of folded proteins, where the polar components of the peptide bonds form H bonds with water or with the polar side chains of hydrophilic amino acids.

Interactions between different polypeptide chains in proteins composed of more than one polypeptide.

4 polypeptide chains

enzymes

Catalysts that increase the rate of all chemical reactions in cells

They would be so slow that they would not occur.

1. Increase rate of chemical reactions without themselves being consumed or permanently altered.

2. Increase reaction rates without altering the chemical equilibrium between reactants and products.

the laws of thermodynamics

If an enzyme is present, the conversion is accelerated, but the equilibrium is unaltered.

the final energy states of S and P

transition state

energy requires to reach the transition state

reduce the activation energy

It is when enzymes bind their substrates to form an enzyme-substrate complex.

Where the substrate binds to a specific region of the enzyme

The substrate is converted to product while bound to the active site, then released.