Biological Structures and Functions

These flashcards cover essential concepts from biological structures, functions, protein interactions, and genetic mechanisms, aiding in exam preparation.

Life

A characteristic defined by a high degree of chemical and structural complexity, the ability to extract and use energy, defined functions for components, environmental responsiveness, self-replication, and evolution.

Hydrophobic Amino Acids

Amino acids that do not interact well with water; examples include Valine, Alanine, Methionine, and Leucine.

Hydrophilic Amino Acids

Amino acids that interact well with water; examples include Histidine, Aspartate, and Arginine.

Motifs vs Domains

Motifs are combinations of secondary structures associated with specific functions, while domains are distinct structural regions with specific functions in proteins.

Chaperones

Molecules that assist in the correct folding of proteins, utilizing ATP-binding cycles.

Proteasome

A protein complex that degrades polyubiquitinated proteins, recycling ubiquitins and breaking down proteins into short peptide fragments.

Km (Michaelis constant)

The substrate concentration at which the reaction velocity of an enzyme is half of its maximum velocity; lower Km indicates better affinity.

Kd (dissociation constant)

A thermodynamic constant quantifying the strength of the bond between a protein and its ligand; lower Kd indicates better affinity.

Primary Structure

The linear chain of amino acids linked by covalent peptide bonds.

Secondary Structure

The local 3D conformation of a polypeptide backbone, stabilized primarily by hydrogen bonds.

Tertiary Structure

The overall 3D arrangement of a polypeptide, determined by interactions among side chains.

Quaternary Structure

The 3D conformation of multiple polypeptide chains or subunits in a protein.

Telomeres

Protective structures at chromosome ends that prevent degradation and end-to-end fusion.

Telomerase

An enzyme that extends telomeres, allowing for restoration of chromosome length.

Non-homologous End Joining (NHEJ)

A DNA repair mechanism that is error-prone and may introduce mutations.

Affinity Chromatography

A technique where antibodies are used to purify proteins from a complex mixture based on their specific binding.

SINEs

Short interspersed elements that do not code for proteins and rely on LINEs for mobility.

G Proteins

Proteins that can bind GTP or GDP, existing in 'on' and 'off' states to regulate signaling pathways.

Calmodulin

A calcium-binding messenger protein that regulates various cellular activities by changing conformation upon Ca2+ binding.

Transcription Unit

A DNA segment that is transcribed into a primary transcript, bounded by start and termination sites.

Gene Families

Groups of related genes that arise from recombination and duplication events, leading to evolutionary changes in function.

Peptide Bond

A covalent bond linking the carboxyl group of one amino acid to the amino group of another.

Disulfide Bond

A covalent bond formed between the sulfur atoms of two cysteine residues, stabilizing protein structure.

Protein Denaturation

The process by which a protein loses its specific 3D structure, leading to loss of function, often due to physical or chemical stress.

Enzyme Active Site

A specific region on an enzyme where substrate molecules bind and undergo a chemical reaction.

Competitive Inhibition

A type of enzyme inhibition where an inhibitor molecule binds to the active site, preventing the substrate from binding.

Non-competitive Inhibition

A type of enzyme inhibition where an inhibitor binds to a site other than the active site, altering the enzyme's shape and reducing its activity.

Allosteric Regulation

Regulation of an enzyme's activity by the binding of an effector molecule at a site other than the active site, causing a conformational change.

DNA Replication

The biological process of producing two identical replicas of DNA from one original DNA molecule.

Transcription

The process by which genetic information from DNA is copied into an RNA molecule.

Translation

The process by which messenger RNA (mRNA) is decoded to produce a specific protein.

mRNA

Messenger RNA; an RNA molecule that carries genetic information from DNA in the nucleus to ribosomes in the cytoplasm for protein synthesis.

tRNA

Transfer RNA; an RNA molecule that helps decode mRNA sequences into proteins by carrying specific amino acids to the ribosome.

rRNA

Ribosomal RNA; a primary component of ribosomes, essential for protein synthesis.

Histones

Highly basic proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes.

Nucleosome

The basic repeating structural unit of eukaryotic chromatin, consisting of a segment of DNA wound around a histone protein core.

Chromatin

A complex of DNA and proteins that forms chromosomes within the nucleus of eukaryotic cells.

Promoter

A specific DNA sequence region located upstream of a gene that acts as a binding site for RNA polymerase, initiating transcription.

Enhancer

A short region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur.

Genetic Code

The set of rules by which information encoded in DNA or mRNA is translated into proteins by living cells.

Post-translational Modification

The chemical modification of a protein after its synthesis, which can alter its activity, localization, stability, or interactions with other molecules.