Biological Macromolecules; Proteins and Nucleic Acids

Biological Macromolecules

Large molecules built from smaller organic molecules, necessary for life.

Proteins

One of the most abundant molecules in living systems, with a diverse range of functions.

Amino acid polymers

Proteins are all polymers of these certain monomers arranged in a linear sequence.

Enzymes

Produced by cells and act as catalysts in biochemical reactions.

Catabolic enzymes

Enzymes that break down substrates.

Anabolic enzymes

Enzymes that build more complex molecules from substrates.

Catalytic enzyme

Enzymes that affect the rate of a reaction.

Hormones

Chemical-signaling molecules, usually small proteins or steroids, secreted by endocrine cells that act to control or regulate specific physiological processes.

Insulin

A protein hormone that helps regulate blood glucose level.

Digestive Enzymes

Help in food by catabolizing nutrients into monomeric units.

Transport Proteins

Carry substances in the blood or lymph throughout the body.

Structural Proteins

Construct different structures, which provide support and shape (collagen), like the cytoskeleton.

Defense Proteins

Protect the body from foreign pathogens.

Contractile Proteins

Effect muscle contraction.

Storage Proteins

Provide nourishment in early embryo development and the seedling.

hemoglobin=globular, and collagen=fibrous

Proteins have different shapes and their shape is critical to their function.

Denaturation

Changes in temperature, pH, and exposure to chemicals can change protein shape and cause loss of function.

Amino Acids

The monomers that make up proteins, each have the same basic structure.

Peptide Bond

Covalent bond that attaches to each amino acid, formed by dehydration synthesis.

Polypeptides

Multiple peptides together form polypeptides; they are not the same as proteins.

Carboxyl Terminal

End of polypeptide with free carboxyl group.

Amino Terminal

Other end of polypeptide, free amino group.

Primary Structure

The first level of protein structure.

Secondary Structure

The second level of protein structure.

Tertiary Structure

The third level of protein structure.

R Group

Another atom or group of atoms bonded to the central carbon in an amino acid.

Common Amino Acids

There are only 20 amino acids common in proteins, 9 of which we get from our diets.

Primary structure

Amino acids' unique sequence in a polypeptide chain.

Gene encoding

The gene encoding the protein ultimately determines the unique sequence; a change in nucleotide sequence in the gene's coding region can change the amino acid added to the polypeptide chain, changing structure and function.

Sickle cell

Change of one amino acid in the chain causes hemoglobin molecules to form long fibers that distort disc-shaped red blood cells to sickle shape.

Protein structure levels

Four levels of protein structure: Primary, Secondary, Tertiary, Quaternary.

Secondary structure

Local folding of primary structure results in secondary structure, typically: α-helix and β-pleated sheet.

Alpha helix

Every helical turn has 3.6 amino acid residues; R groups protrude from the chain (secondary structure)

Beta pleated sheets

R groups attached to carbons extend above and below pleat's folds; pleated segments align parallel or antiparallel.

Hydrogen bonds in secondary structure

H bonds between (partially +) H in amino group and (-) O atom in peptide backbone's carbonyl group.

Tertiary structure

Polypeptide's unique 3D structure, primarily determined by chemical interactions on polypeptide chains.

Chemical interactions in tertiary structure

R groups with like charges repel each other; ionic bonds form with unlike charges; only covalent bond is disulfide linkage (in presence of oxygen).

Hydrophobic interactions in Protein’s tertiary structure

Hydrophobic groups lie on protein's inside, hydrophilic on outside.

Quaternary structure

Some proteins form from several polypeptides which interact to form quaternary structure; weak interactions stabilize structure.

Denaturation

change in shape, NOT losing/changing primary structure; often reversible, can be irreversible leading to loss of function.

Irreversible denaturation

Denaturation that cannot be reversed, resulting in loss of protein function.

Biological Macromolecules

Large molecules built from smaller organic molecules, necessary for life: Carbohydrates, Lipids, Proteins, Nucleic acids.

Nucleic acids

Two main types: DNA -deoxyribonucleic acid and RNA -ribonucleic acid

RNA

ribonucleic acid

mRNA

intermediary used in protein synthesis to communicate to rest of cell; carries genetic code/protein info from DNA to ribosomes, where proteins are synthesized

tRNA

involved in protein synthesis and regulation, specifically transports amino acids to the ribosome(s) during translation

rRNA

involved in protein synthesis and regulation; forms the core of ribosome structure and catalyzes protein synthesis

microRNA

involved in protein synthesis and regulation, specifically regulates gene expression by interfering with mRNA

Nucleic acids

DNA and RNA

Monomers

nucleotides (3 parts)

Nitrogenous base

organic molecules containing C and N, have amino group that can bind H

Purines

adenine, guanine - 2 C, N rings

Pyrimidines

cytosine, thymine, uracil - 1 C, N ring

DNA nitrogenous bases

A, T, G, C

RNA nitrogenous bases

A, U, G, C

Pentose sugar

In DNA, pentose sugar is deoxyribose, RNA is ribose

Ribose

-OH group on 2nd C

Deoxyribose

-OH on 2nd Carbon

Phosphodiester linkage

Phosphate residue attaches to 5' C of one sugar and -OH of 3' C of sugar of next nucleotide

ATP

a nucleotide that acts as energy currency in cells

DNA double-helix

Sugar and phosphate lie on outside, forming backbone; nitrogenous bases facing inwards, connected by H bonds

Antiparallel strands

Two strands run in opposite direction; 5' C end of one strand faces 3' end of other

Base pairing

A pairs with T, G with C

RNA structure

Usually single-stranded, made of ribonucleotides linked by phosphodiester bonds

Types of RNA

1. mRNA (messenger), 2. rRNA (ribosomal), 3. tRNA (transfer), 4. miRNA (micro)

RNA in protein synthesis

mRNA synthesizes in nucleus complementary to the gene; tRNA brings correct amino acid to protein synthesis site

DNA features

Carries genetic information, remains in the nucleus, double helix, deoxyribose, pyrimidines: cytosine, thymine, purines: adenine, guanine

RNA features

Involved in protein synthesis, leaves the nucleus, usually single-stranded, ribose, pyrimidines: cytosine, uracil, purines: adenine, guanine