Molec Cell: Ch. 2 pt. 2

The Molecules of Cells pt. 2

The information in DNA and RNA is conveyed…

by the order of the bases.

DNA is made up of __. The bases are on the __, joined by __ btween _____ base pairs

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

Complementary base pairing

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

Nucleic Acids

self-replication

The information carried by and ___ directs _____ of specific ______, which control __________.

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

Other important nucleotides include:

* ATP
* some act as signaling molecules within cells

_______ are the most diverse of all macromolecules.

Proteins

Each cell contains ______ different proteins.

Each cell contains several thousand different proteins.

Proteins direct _______.

Proteins direct virtually all activities of the cell.

Functions of proteins include:

* structural components
* transport and storage of small molecules (O2)
* Transmit information between cells (protein hormones)
* Defense against infection (antibodies)
* Enzymes

Proteins are polymers of _____.

Proteins are polymers of 20 different amino acids.

What does each amino acid consist of?

* *a* carbon bonded to a carboxyl group (COO-)
* amino group (NH3+)
* hydrogen
* distinctive side chain

Amino acids are grouped based on what? What are some examples?

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

What are some basic amino acids?

* Lysine (Lys) K
* Arginine (Arg) R
* Histidine (His) H

What are some acidic amino acids?

* Aspartic Acid (Asp) D
* Glutamic Acid (Glu) E

How to join the amino acids?

Peptide bonds

Polypeptides

chains of amino acids, hundreds or thousands of amino acids

What are the on the ends of a polypeptide?

* One end of a polypeptide terminates in an *a* amino group (N terminus)
* Other ends in an *a* carboxyl group (C terminus)

What do amino acid sequences define?

characteristics of proteins

What did Frederick Sanger do in 1953?

Worked out the amino acid sequence for insulin

How are protein sequences now deduced from?

Sequences of mRNAs

Complete amino acid sequences of over _____ proteins have been established.

100,000

Insulin consists of____. The side chains of three pairs of ___ are joined by _______.

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

How are the sequences are amino acids in a protein determined by?

the order of nucleotide bases in a gene

Proteins also have distinct ________ that are critical to their ____.

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

The shape and functions of proteins are determined by….

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

What did Chirstian Anfinsen do?

* 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 conformation of a protein is contained in its ___ _____ ___ ____.

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

Primary Protein Structure

the sequence of amino acids in the polypeptide chain

Secondary Protein Structure

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

Tertiary Protein Structure

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

Domains

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

What are the 3 critical determinants of tertiary structure?

* 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

Where are the critical determinants of tertiary 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.

Quaternary Protein Structure

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

Hemoglobin is composed of…

4 polypeptide chains

A fundamental role of proteins is to act as…

enzymes

Enzymes

Catalysts that increase the rate of all chemical reactions in cells

What would happen to most biological reactions without enzymes?

They would be so slow that they would not occur.

What are the two fundamental props of enzymes?

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.

When a substrate (s) is converted to a product (P), the chemical equilibrium between S and P is determined by…

the laws of thermodynamics

If an enzyme is present, the conversion is ___ , but the equilibrium is ___.

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

Equilibrium is determined by…

the final energy states of S and P

The substrate must first be converted to a higher energy state, the…

transition state

activation energy

energy requires to reach the transition state

Enzymes…

reduce the activation energy

What are enzyme-substrate complexes (ES)?

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

Active site

Where the substrate binds to a specific region of the enzyme

The substrate is converted to ___ while bound to the ____ ____, then _____.

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