Chapter 4: Metabolism, Enzymes, Cellular Respiration, DNA & Protein Synthesis

Vocabulary flashcards covering the key terms and concepts from Chapter 4 lecture notes.

Metabolism

Sum of all chemical reactions in the body; includes both anabolic and catabolic pathways.

Anabolism

Building larger molecules from smaller ones; requires energy (ATP); examples include dehydration synthesis forming polysaccharides, proteins, and triglycerides.

Catabolism

Breaking down larger molecules into smaller ones; releases energy and yields ATP.

Enzyme

Protein catalysts that speed up chemical reactions by lowering activation energy; highly specific for their substrate and are not consumed in the reaction.

Substrate

The molecule that binds to an enzyme at the active site and is transformed during the reaction.

Active site

Region of the enzyme where the substrate binds; determines enzyme specificity.

Cofactor

Non-protein substance that activates an enzyme; can be an ion, element, or small molecule.

Coenzyme

Organic molecule that acts as a cofactor; many are vitamins.

Denaturation

Irreversible loss of enzyme structure and function due to conformational change.

Energy

Capacity to do work; forms include chemical energy stored in ATP.

ATP

Adenosine triphosphate; main energy-carrying molecule; energy released when the terminal phosphate bond is broken.

ADP

Adenosine diphosphate; formed when ATP loses a phosphate; can be rephosphorylated to ATP.

Phosphorylation

Addition of a phosphate group to ADP to form ATP; requires energy input.

Glycolysis

First stage of glucose breakdown in the cytosol; anaerobic; yields 2 ATP per glucose and produces pyruvate and NADH.

Pyruvate

End product of glycolysis; can enter aerobic pathways as acetyl-CoA or be reduced to lactate under anaerobic conditions.

Lactic acid

Byproduct of anaerobic glycolysis; accumulation can inhibit glycolysis.

Aerobic respiration

Requires O2; includes formation of acetyl-CoA, the citric acid cycle, and the electron transport chain; yields most ATP.

Anaerobic respiration

Occurs without O2; limited ATP production; glycolysis dominates and can yield lactic acid in humans.

Citric acid cycle

Krebs cycle in mitochondria; per glucose turn yields 1 ATP (per acetyl-CoA turn), CO2, and reduces NAD+ and FAD to NADH and FADH2.

NADH

Electron carrier produced during glycolysis and the citric acid cycle; donates electrons to the electron transport chain.

FADH2

Electron carrier that donates electrons to the electron transport chain.

Acetyl-CoA

Two-carbon acetyl group carrier formed from pyruvate; enters the citric acid cycle.

Oxaloacetic acid

Four-carbon molecule that combines with acetyl-CoA to form citrate in the citric acid cycle.

Oxygen

Final electron acceptor in the electron transport chain; forms water.

DNA

Deoxyribonucleic acid; genetic material that stores information in its nucleotide sequence; bases are A, T, C, G.

RNA

Ribonucleic acid; usually single-stranded; contains ribose and bases A, U, C, G; types include mRNA, tRNA, rRNA.

Purine

A and G; larger two-ring nitrogenous bases.

Pyrimidine

C and T (DNA) or U (RNA); single-ring bases.

Complementary base pairing

A pairs with T (or U in RNA); C pairs with G; base-pairing governs nucleic acid structure.

DNA replication

Process to produce identical copies of DNA; strands separate and new nucleotides are added by DNA polymerase.

Transcription

Copying a DNA sequence into an RNA sequence; performed by RNA polymerase; produces mRNA.

Translation

Process of converting the genetic code in mRNA into a polypeptide chain; occurs at the ribosome.

mRNA

Messenger RNA; carries genetic code from DNA to the ribosome for protein synthesis.

tRNA

Transfer RNA; brings amino acids to the ribosome and contains an anticodon that pairs with mRNA codons.

rRNA

Ribosomal RNA; structural and catalytic component of ribosomes.

Codon

Triplet of nucleotides on mRNA that codes for an amino acid (or start/stop signals).

Anticodon

Three-nucleotide sequence on tRNA that pairs with a complementary mRNA codon.

Start codon AUG

Signals the start of translation and codes for methionine.

Stop codons

UAA, UAG, UGA; signal termination; do not code for amino acids.

Ribosome

Ribonucleoprotein complex that translates mRNA into protein; consists of two subunits.

Gene

A DNA sequence that encodes the information to produce one protein.

Genome

Complete set of genetic material in a cell.

Gene expression

Process by which information from a gene is used to synthesize a functional product (protein or RNA).

Chromosome

DNA-protein complex that carries genes; organized packaging of DNA.

Chromatin

Uncondensed form of DNA-protein complex in the nucleus; condenses during cell division.

Histone

Protein around which DNA is wrapped in chromatin.

Nucleotide

Building block of DNA and RNA; consists of a sugar, phosphate, and nitrogenous base.

Glycogen

Storage form of glucose in liver and muscle tissue.

Triglyceride

Major storage form of fat; glycerol backbone with three fatty acids.

Protein synthesis

Process of making proteins from amino acids via transcription and translation.

Amino acid

Building blocks of proteins; 20 standard types available for polypeptide chains.

Peptide bond

Bond linking adjacent amino acids in a protein chain.

Codon table

Reference mapping of mRNA codons to amino acids and start/stop signals.