MDCAT Biology High-Yield Review: Acellular Life, Bioenergetics, and Biological Molecules

A collection of vocabulary flashcards covering the essential biological terms, classification of viruses, bioenergetic pathways, and the structure of biological molecules for MDCAT preparation.

Viruses

Non-cellular, obligate intracellular parasites that lack metabolic machinery and replicate exclusively inside host cells using host cellular machinery.

Bacteriophages

Complex viruses (such as $T2$ and $T4$) consisting of a head and tail that specifically infect bacteria and typically possess a $dsDNA$ genome.

Parvovirus

A type of virus characterized by having a single-stranded DNA ($ssDNA$) genome.

Enveloped Viruses

Viruses, such as $HIV$ and $Influenza$, whose outer layer is derived from the host cell membrane.

HIV (Human Immunodeficiency Virus)

An enveloped, positive-sense single-stranded RNA ($ssRNA$) retrovirus that targets Helper T-lymphocytes ($CD4+$ T-cells).

Reverse Transcriptase

An enzyme used by retroviruses to synthesize $cDNA$ from a viral $RNA$ template, reversing the central dogma of molecular biology.

gp120

A viral glycoprotein on $HIV$ that facilitates attachment by binding to $CD4$ receptors on host cells.

Glycolysis

The initial stage of cellular respiration where glucose is broken down to yield $Pyruvate$.

Energy Yield of Fats

Approximately $9\,kcal/g$, which is more than double the energy yield of carbohydrates due to a higher proportion of $C–H$ bonds.

$\beta$-Oxidation

A mitochondrial process where fatty acids are broken down to produce $Acetyl-CoA$ for entry into the Krebs Cycle.

Deamination

The removal of an $-NH_2$ group from amino acids, resulting in carbon skeletons that enter cellular respiration at various points and nitrogen excreted as urea.

High Specific Heat Capacity

The ability of water to absorb a high amount of energy to raise the temperature of $1\,g$ by $1\,^℃$, acting as a thermal buffer.

Cohesion

The phenomenon of water molecules sticking together via hydrogen bonds, facilitating processes like transpiration pull.

Adhesion

The attraction of water molecules to polar surfaces, such as xylem walls, aiding in capillary action.

Monosaccharides

Simple sugars like $Glucose$ and $Fructose$ that consist of a single polyhydroxy unit, are reducing sugars, and cannot be further hydrolyzed.

Sucrose

A non-reducing oligosaccharide (cane sugar) formed by a glucose and fructose unit joined by an $\alpha-1,2$ glycosidic linkage.

Amylopectin

A branched component of starch containing both $\alpha-1,4$ and $\alpha-1,6$ glycosidic linkages.

Cellulose

A structural polysaccharide in plant cell walls consisting of linear, unbranched chains of glucose with $\beta-1,4$ linkages.

Peptide Bond

The $-CO-NH-$ linkage formed via dehydration condensation between the carboxyl group of one amino acid and the amino group of another.

Primary Structure

The specific linear sequence of amino acids in a polypeptide chain joined by covalent peptide bonds, dictated by the genetic code.

Secondary Structure

Regular folding of a polypeptide into an $\alpha$-helix or $\beta$-pleated sheet, stabilized by hydrogen bonds along the backbone.

Tertiary Structure

The complex $3D$ globular conformation of a protein maintained by disulfide bonds ($S–S$), ionic bonds, hydrogen bonds, and hydrophobic interactions.

Phospholipids

Amphipathic molecules composed of $1$ glycerol, $2$ fatty acids, and $1$ phosphate group attached to an alcohol, forming the structural basis of cell membranes.

Waxes

Esters of long-chain fatty acids with high molecular weight long-chain monohydric alcohols that provide protective hydrophobic coatings.

Ester Linkage

The chemical linkage ($C–O–C=O$) found in lipids, specifically between glycerol and fatty acids in triglycerides.