Biology Chapter 2.4: Proteins Flashcards

Study Notes

Polypeptides Overview

Polypeptides consist of amino acids linked by condensation reactions during protein synthesis (translation) at ribosomes.
Peptide bonds form between the amine group of one amino acid and the carboxyl group of another, producing water.

Formation of Polypeptides

Combining two amino acids forms a dipeptide plus water.
Adding more amino acids to a dipeptide yields a polypeptide and also releases water.

Peptide Bonds

Peptide bonds are uniform, connecting the amine group (-NH2) of one amino acid to the carboxyl group (-COOH) of the next.
This bond formation occurs during condensation reactions in polypeptide synthesis.

Amino Acid Characteristics

There are 20 different amino acids used to build polypeptides in ribosomes during translation.
Each amino acid features a central carbon atom bonded to an amine group, carboxyl group, hydrogen atom, and a unique R group.

Differences Among Amino Acids

R groups vary among amino acids, contributing to distinct chemical properties.
Some amino acids are hydrophilic, others hydrophobic; they may be polar or contain rings, influencing their function.
Certain amino acids can be modified post-synthesis.

Amino Acid Sequences

The order of amino acids in a polypeptide is dictated by the DNA sequence, copied by mRNA during transcription.
There are 20^n possible sequences for a polypeptide of 'n' amino acids, highlighting the vast diversity of polypeptides.

Genetic Influence on Polypeptides

Genes are segments of DNA that encode the sequence for specific polypeptides, with each amino acid corresponding to a triplet of base pairs.
The DNA base sequence directly determines the amino acid sequence produced at ribosomes.

Polypeptide Structure

Proteins can consist of one or multiple polypeptides; short polypeptides (fewer than 50 amino acids) are not classified as proteins.
Examples include lysozyme (single polypeptide) and hemoglobin (four linked polypeptides).

Protein Folding and Function

The sequence of amino acids determines protein structure and function; folding creates three-dimensional shapes.
Interactions among R groups, including hydrogen bonds, ionic bonds, and disulfide bridges, shape proteins into functional forms like globular proteins.

Functions of Proteins

Enzymes act as catalysts to accelerate chemical reactions.
Actin and myosin proteins facilitate muscle contraction and movement.
Tubulin maintains animal cell shape and is involved in chromosome movement during mitosis.
Fibrous proteins strengthen structures such as ligaments, tendons, and blood vessel walls.
Plasma proteins, including clotting factors, play vital roles in blood coagulation.
Hemoglobin transports oxygen and other molecules in the bloodstream.

Description

Test your knowledge on proteins with these flashcards focusing on polypeptides. Learn about the processes involved in protein synthesis, including translation and the formation of peptide bonds. This quiz will help reinforce your understanding of the basic building blocks of proteins.