Digestive Enzymes, Lipids, Membranes, Protein Synthesis, Cell Cycle, and Genetics – Lecture Review

Vocabulary flashcards covering digestive enzymes, lipid chemistry, membrane dynamics, protein synthesis, the cell cycle, mitosis, meiosis, and related genetic concepts.

Maltase

Enzyme in the small intestine that breaks maltose into two glucose molecules.

Lactase

Small-intestinal enzyme that hydrolyzes lactose into glucose and galactose.

Sucrase

Digestive enzyme that splits sucrose into glucose and fructose.

Alpha bonds are

Digestible (ex. Starch, Maltose)

Beta bonds

Aren’t digestible (ex. Cellulose)

What beta bond enzyme is an exception and able to be digested?

Lactose, needs lactase to be digested

Reducing disaccharides

Possess a free anomeric carbon allowing them to act as reducing agents; examples are maltose and lactose

Non-reducing disaccharides

Both anomeric carbons are involved in a glycosidic bond and unable to act as reducing agents; Example is sucrose (table sugar)

Saturated fatty acid

Lipid with only single C–C bonds, fully hydrogenated, straight-chained, solid at room temperature; makes membranes more rigid.

Unsaturated fatty acid

Lipid containing one or more C=C double bonds, kinked, less tightly packed, liquid at room temperature; increases membrane fluidity.

Cis unsaturated fat

Naturally occurring unsaturated fat with hydrogens on the same side of the double bond; generally considered heart-healthy.

Trans fat

Artificially hydrogenated unsaturated fat with hydrogens on opposite sides of a double bond; raises cardiovascular disease risk.

Membrane potential

Electrical potential difference between the inside and outside of a cell.

Resting membrane potential

Typical negative membrane voltage (≈ –70 mV) present when a neuron is unstimulated.

Depolarization

Change in membrane potential toward more positive values.

Hyperpolarization

Membrane becomes more negative, often due to K⁺ efflux.

Ligand-gated channel

Membrane channel that opens when a specific chemical messenger binds.

Voltage-gated channel

Ion channel that opens or closes in response to changes in membrane voltage.

Mechanically-gated channel

Channel that opens in response to physical deformation of the membrane.

Scramblase

Bidirectional enzyme that swaps phospholipids between membrane leaflets without ATP.

Flippase

ATP-dependent enzyme that moves phospholipids from the outer to inner leaflet.

Floppase

ATP-dependent enzyme that transports phospholipids from inner to outer leaflet.

ATPase

Enzyme that hydrolyzes ATP, releasing energy by removing the terminal phosphate.

Lateral diffusion

Side-to-side movement of lipids or proteins within one membrane leaflet; energetically favorable.

Vertical (transverse) diffusion

Flip-flop movement of molecules between membrane leaflets; energetically less favorable.

Amphipathic molecule

Compound possessing both hydrophilic and hydrophobic regions (e.g., phospholipid).

Sphingomyelin

Myelin-rich sphingolipid that electrically insulates neuronal axons.

Ribosome

Ribonucleoprotein complex that synthesizes proteins; small subunit reads mRNA, large subunit forms peptide bonds.

A site (aminoacyl site)

Ribosomal site where incoming aminoacyl-tRNA first binds during translation.

P site (peptidyl site)

Ribosomal site that holds the tRNA carrying the growing polypeptide chain.

E site (exit site)

Ribosomal site where deacylated tRNA leaves the ribosome.

Translation initiation

Stage where small ribosomal subunit binds mRNA, finds AUG, and first tRNA enters the P site.

Translation elongation

Cycle of aminoacyl-tRNA entry, peptide bond formation, and ribosomal translocation along mRNA.

Translation termination

Process triggered when a stop codon enters the A site; release factor disassembles the complex.

60S subunit

Large ribosomal subunit in eukaryotes.

40S subunit

Small ribosomal subunit in eukaryotes.

80S ribosome

Complete eukaryotic ribosome (40S + 60S).

50S subunit

Large ribosomal subunit in prokaryotes.

30S subunit

Small ribosomal subunit in prokaryotes.

70S ribosome

Complete prokaryotic ribosome (30S + 50S).

Interphase

Stage encompassing G1, S, and G2 phases; cell grows, replicates DNA, prepares for division.

G1 phase

First gap phase in which the cell grows and accumulates energy and materials.

S phase

Phase of interphase during which DNA is replicated.

G2 phase

Second gap phase; cell replenishes energy, synthesizes proteins, and prepares for mitosis.

G0 phase

Resting state entered from G1 where cells are metabolically active but non-dividing.

Mitosis

Process that segregates duplicated chromosomes into two identical nuclei.

Cytokinesis

Division of cytoplasm, forming two daughter cells after mitosis.

Sister chromatid

One of two identical DNA copies of a duplicated chromosome, joined at the centromere.

Prophase

Mitotic stage with chromatin condensation, nuclear envelope breakdown, and spindle formation.

Metaphase

Mitotic stage where chromosomes align along the metaphase plate.

Anaphase

Stage in which sister chromatids separate and move toward opposite poles.

Telophase

Final mitotic stage; chromosomes decondense, nuclear envelopes reform, cytokinesis completes.

Meiosis

Two-round cell division that produces haploid gametes from diploid cells.

Diploid (2n)

Cell containing two sets of homologous chromosomes (46 in humans).

Haploid (n)

Cell with one set of chromosomes (23 in human gametes).

Crossing over (recombination)

Exchange of genetic material between homologous chromosomes during Prophase I of meiosis.

Genetic linkage

Tendency of genes close together on the same chromosome to be inherited together.

Recombination frequency

Percentage of offspring with recombinant genotypes; ≤50 % indicates linkage, >50 % indicates independent assortment.

Nondisjunction

Failure of homologous chromosomes or sister chromatids to separate properly during meiosis.

Aneuploidy

Abnormal number of chromosomes in a cell, often due to nondisjunction.

Trisomy 21 (Down syndrome)

Aneuploid condition with three copies of chromosome 21, commonly caused by meiotic nondisjunction.