Proteins, Enzymes, and DNA Structure and Function

These flashcards cover key concepts related to proteins, enzymes, and DNA structure, function, and regulation.

Protein Functions

Proteins serve many functions including structure, catalysis, movement, transport, regulation, protection, and storage.

Collagen

A structural protein that is a major component of skin, bones, hair, and nails.

Keratin

A structural protein found in hair and nails providing protection and support.

Enzymes

Proteins that catalyze reactions in living systems, significantly increasing reaction rates.

Myosin and Actin

Proteins involved in muscle movement.

Hemoglobin

A protein in blood that transports oxygen from the lungs to cells.

Antibodies

Proteins produced by the immune system to counteract foreign proteins.

Fibrinogen

A protein necessary for blood clotting.

Casein

A protein found in milk that stores nutrients for newborn mammals.

Amino Acid

A compound that contains both an amino group (NH2) and a carboxyl group (COOH).

Zwitterion

The internal salt form of α-amino acids, which carries both positive and negative charges.

Polar Amino Acids

Amino acids that have side chains containing OH or NH2 groups capable of forming hydrogen bonds.

Glycine

The simplest amino acid; its side chain makes it nonpolar, but the entire molecule can be polar.

Chirality

Property of amino acids where they have a stereocenter and can exist in L- and D- forms.

Stereocenter

An atom bonded to four different groups, resulting in stereoisomers.

Isoelectric Point (pI)

The pH at which the majority of molecules of an amino acid have no net charge.

Cysteine

An amino acid with a sulfhydryl group that can form disulfide bonds.

Peptide Bond

The bond formed between the α-carboxyl group of one amino acid and the α-amino group of another.

Dipeptide

A molecule containing two amino acids joined by a peptide bond.

Polypeptide

A macromolecule containing many amino acids joined by peptide bonds.

Primary Structure of Proteins

The linear sequence of amino acids in a polypeptide chain.

Secondary Structure of Proteins

The localized conformations of amino acids, such as alpha helices and beta-pleated sheets.

Tertiary Structure of Proteins

The complete 3-dimensional arrangement of atoms in a polypeptide chain.

Quaternary Structure of Proteins

The arrangement of multiple polypeptide chains in a multi-subunit protein.

Denaturation

The process of destroying the native conformation of a protein by chemical or physical means.

Enzyme

A biological catalyst that increases the rates of chemical reactions.

Active Site

The specific part of an enzyme where the substrate binds.

Cofactor

A nonprotein portion of an enzyme necessary for catalytic function.

Substrate

The substance on which an enzyme acts.

Lock and Key Model

A model of enzyme action where the substrate fits into a rigid active site.

Induced Fit Model

A model of enzyme action where the enzyme changes shape to fit the substrate.

Allosteric Regulation

Enzyme regulation that occurs when a substance binds to a site other than the active site.

Feedback Control

A mechanism where the product of a pathway inhibits an earlier step in that pathway.

Zymogen

An inactive form of an enzyme that must be activated by hydrolysis.

Chemical Communication

Process through which cells signal each other using neurotransmitters and hormones.

Neurotransmitter

A chemical messenger that transmits signals between nerve cells or targeted cells.

Hormone

A chemical messenger released by endocrine glands into the bloodstream.

Acetylcholine

The main cholinergic messenger involved in neurotransmission.

Calcium Ions (Ca2+)

Ions that trigger the release of neurotransmitters from nerve cells.

G-protein Coupled Receptors

Receptors that mediate the effects of many neurotransmitters and hormones.

Nucleic Acids

Polymers of nucleotides, primarily DNA and RNA.

DNA Structure

DNA is a double helix made of two antiparallel strands of nucleotides.

Complementary Base Pairing

A key feature of DNA where adenine pairs with thymine and cytosine pairs with guanine.

Gene Expression

The process by which information in a gene leads to the synthesis of a protein.

DNA Replication

The process through which DNA makes duplicate copies of itself.

Helicase

An enzyme that unwinds DNA during replication.

DNA Ligase

An enzyme that joins Okazaki fragments during DNA replication.

DNA Polymerase

The enzyme responsible for synthesizing new DNA strands by adding nucleotides.

Primase

An enzyme that synthesizes RNA primers during DNA replication.

Okazaki Fragments

Short sequences of DNA synthesized on the lagging strand during replication.

Telomeres

Repeated DNA sequences at the ends of chromosomes that protect against degradation.

Hayflick Limit

The number of times a normal somatic human cell can divide before cell division stops.

Semi-Conservative Replication

A type of DNA replication in which each new DNA molecule contains one old strand and one new strand.

Nucleotide

The building block of DNA and RNA, composed of a sugar, phosphate group, and nitrogenous base.

Phosphodiester Bond

The covalent bond that links nucleotides together in a DNA strand.

Hydrogen Bond

Weak interactions between the nitrogenous bases that stabilize the DNA double helix.

Deoxyribose

The sugar component of DNA nucleotides.

Ribose

The sugar component of RNA nucleotides.

Adenine

A purine base found in both DNA and RNA.

Guanine

A purine base found in both DNA and RNA.

Thymine

A pyrimidine base found only in DNA.

Cytosine

A pyrimidine base found in both DNA and RNA.

Uracil

A pyrimidine base found only in RNA.

Transcription

The process by which RNA is synthesized from a DNA template.

Translation

The process by which proteins are synthesized from mRNA.

base stacking

The interaction between nucleobases that provides stability to the DNA helix.

Human Genome Project

Research initiative aimed at mapping and understanding all the genes of the human species.

Condensation Reaction

A chemical reaction that joins two molecules while releasing water.

Glycosidic Bond

The bond formed between a nitrogenous base and a sugar in nucleotides.

Nucleoside

A nucleotide without a phosphate group.

Nucleotide Dephosphorylation

The removal of a phosphate group from a nucleotide, releasing energy.

Molecular Biology

The branch of science concerned with the molecular basis of biological activity.

Enzyme Kinetics

The study of the rates of enzyme-catalyzed reactions.

Saturation Curve

Graph showing the rate of reaction as a function of substrate concentration.

Temperature Optimum

The temperature at which an enzyme's activity is maximized.

pH Optimum

The pH at which an enzyme exhibits peak activity.

Competitive Inhibitor

A substance that competes with a substrate for binding to the active site.

Noncompetitive Inhibitor

A substance that inhibits enzyme activity without competing for the active site.

Zymogen Activation

The process of converting an inactive enzyme into an active form.

Endocrine System

The system of glands that produce hormones to regulate various bodily functions.

Signal Transduction

The process by which a cell responds to substances or signals from outside its membrane.

Transcription Factors

Proteins that bind to specific DNA sequences to regulate transcription.

Intron

A non-coding section of a gene that is removed during RNA processing.

Exon

A coding section of a gene that remains in the final mRNA product.

RNA Splicing

The process of removing introns from pre-mRNA and joining exons together.

Histone Acetylation

The addition of acetyl groups to histone proteins to regulate gene expression.

Protein Folding

The process by which a protein assumes its functional shape or conformation.

Hydrophobic Interaction

The tendency of nonpolar molecules to aggregate in aqueous solutions.

Sulfhydryl Group

A functional group consisting of a sulfur atom bonded to a hydrogen atom (-SH).

Amino Acid Side Chain

The variable group that gives each amino acid its unique properties.

Peptidyl Transferase

An enzymatic activity associated with ribosomes that forms peptide bonds between amino acids.

Gene Regulation

The control of the timing and rate of gene expression.

Chromosomal DNA

DNA that is organized into chromosomes within the nucleus of eukaryotic cells.

Replication Fork

The area where the DNA double helix is unwound and replicated.

Antiparallel Orientation

Referring to the opposite direction of the two strands of DNA.

Helix Stabilizing Forces

Forces such as hydrogen bonds and base stacking that stabilize the DNA helix.

Gene Therapy

A technique used to treat or prevent disease by modifying or manipulating genes.

DNA Sequencing

The process of determining the exact sequence of nucleotides in a DNA molecule.

Plasmid

A small, circular piece of DNA commonly found in bacteria.

CRISPR

A technology that allows for precise editing of DNA within organisms.