PCAT (Pharmacy College Admission Test) Biological Processes Syllabus

Distinguish bacterial transformation, transduction, and conjugation.

Transformation: uptake of free environmental DNA. Transduction: DNA transfer via a bacteriophage. Conjugation: direct DNA transfer between bacteria through a pilus (often plasmid-mediated).

What distinguishes a lytic cycle from a lysogenic cycle in bacteriophages?

Lytic: the virus replicates immediately, lysing and killing the host. Lysogenic: viral DNA integrates into the host genome as a prophage and replicates passively until induced into the lytic cycle.

How do enveloped and non-enveloped (naked) viruses differ?

Enveloped viruses have a lipid bilayer derived from the host membrane and are more sensitive to desiccation/detergents. Naked viruses have only a protein capsid and are generally more environmentally stable.

What is a retrovirus and which enzyme is characteristic of it?

A retrovirus (e.g., HIV) is an RNA virus that uses reverse transcriptase to convert its RNA genome into DNA, which is then integrated into the host genome by integrase.

Compare the basic cellular structures of fungi, protozoa, and helminths.

Fungi: eukaryotic, chitin cell walls, can be yeasts or molds. Protozoa: single-celled eukaryotes, no cell wall, often motile (flagella/cilia/pseudopods). Helminths: multicellular eukaryotic worms.

Name the causative organism of malaria and its vector.

Plasmodium species (protozoa), transmitted by the female Anopheles mosquito.

What is the difference between bacteriostatic and bactericidal antimicrobials?

Bacteriostatic agents inhibit bacterial growth/reproduction (relying on host immunity to clear them); bactericidal agents directly kill the bacteria.

Why are beta-lactam antibiotics (e.g., penicillins) selectively toxic to bacteria?

They inhibit transpeptidase (penicillin-binding proteins) involved in peptidoglycan cross-linking in the bacterial cell wall. Human cells lack peptidoglycan walls, so the drug is selectively toxic.

List four major mechanisms of antibiotic resistance.

(1) Enzymatic drug inactivation (e.g., beta-lactamase); (2) target modification; (3) decreased drug uptake/altered permeability; (4) efflux pumps that expel the drug.

Distinguish the resting membrane potential from the threshold and peak of an action potential.

Resting potential is about $-70\,\text{mV}$. The threshold (around $-55\,\text{mV}$) triggers an all-or-none action potential, which peaks near $+30\,\text{mV}$ as voltage-gated $\ce{Na+}$ channels open.

What ion movements cause depolarization and repolarization in a neuron?

Depolarization: voltage-gated $\ce{Na+}$ channels open and $\ce{Na+}$ rushes in. Repolarization: $\ce{Na+}$ channels close and voltage-gated $\ce{K+}$ channels open, letting $\ce{K+}$ flow out.

Contrast the sympathetic and parasympathetic nervous systems.

Sympathetic: 'fight or flight,' increases heart rate, dilates pupils/airways, mobilizes energy (mainly norepinephrine). Parasympathetic: 'rest and digest,' slows heart rate, stimulates digestion (acetylcholine).

Trace the path of blood through the heart starting from the right atrium.

Right atrium $\to$ tricuspid valve $\to$ right ventricle $\to$ pulmonary valve $\to$ lungs $\to$ left atrium $\to$ mitral (bicuspid) valve $\to$ left ventricle $\to$ aortic valve $\to$ aorta $\to$ body.

Write the formula for cardiac output and define its components.

$$CO = HR \times SV$$ where $CO$ is cardiac output, $HR$ is heart rate (beats/min), and $SV$ is stroke volume (mL/beat).

What is the role of hemoglobin and how does the Bohr effect influence it?

Hemoglobin carries $\ce{O2}$ in red blood cells. The Bohr effect: increased $\ce{CO2}$/$\ce{H+}$ (lower pH) decreases hemoglobin's $\ce{O2}$ affinity, promoting $\ce{O2}$ unloading in active tissues.

Which hormone lowers blood glucose and which raises it, and where are they produced?

Insulin lowers blood glucose (beta cells of pancreatic islets); glucagon raises blood glucose (alpha cells of pancreatic islets).

Distinguish the anterior and posterior pituitary in terms of hormone production.

The anterior pituitary synthesizes its own hormones (e.g., GH, ACTH, TSH, FSH, LH, prolactin). The posterior pituitary stores and releases hormones (ADH, oxytocin) made by the hypothalamus.

Compare the action mechanisms of peptide hormones and steroid hormones.

Peptide hormones bind cell-surface receptors and act via second messengers (e.g., cAMP) for fast, short-lived effects. Steroid hormones are lipid-soluble, cross the membrane, bind intracellular receptors, and alter gene transcription for slower, lasting effects.

List the four primary functions/segments of the nephron in order of filtrate flow.

Glomerulus/Bowman's capsule (filtration) $\to$ proximal convoluted tubule (bulk reabsorption) $\to$ loop of Henle (concentration gradient) $\to$ distal convoluted tubule (regulated reabsorption/secretion) $\to$ collecting duct (water reabsorption via ADH).

Where in the digestive tract does most chemical digestion and nutrient absorption occur, and via what structures?

The small intestine. Absorption is maximized by villi and microvilli (brush border), which vastly increase surface area; pancreatic enzymes and bile complete digestion there.

Distinguish innate from adaptive immunity.

Innate immunity is nonspecific, rapid, and present from birth (skin, phagocytes, inflammation, complement). Adaptive immunity is specific, slower, and develops immunological memory (B and T lymphocytes).

Contrast the roles of B cells and the two main T cell types.

B cells produce antibodies (humoral immunity). Helper T cells ($\ce{CD4+}$) coordinate the immune response via cytokines; cytotoxic T cells ($\ce{CD8+}$) directly kill infected/cancerous cells.

Compare the protein filaments responsible for skeletal muscle contraction.

Thin filaments are actin; thick filaments are myosin. Per the sliding filament theory, myosin heads bind actin and pull the thin filaments inward (using ATP), shortening the sarcomere.

In a monohybrid cross of two heterozygotes ($Aa \times Aa$), what are the genotypic and phenotypic ratios?

Genotypic ratio $1\,AA : 2\,Aa : 1\,aa$. Phenotypic ratio $3$ dominant $: 1$ recessive.

Define incomplete dominance versus codominance.

Incomplete dominance: heterozygote shows a blended/intermediate phenotype (e.g., red $\times$ white $\to$ pink). Codominance: both alleles are fully and simultaneously expressed (e.g., AB blood type).

State the two Hardy-Weinberg equations and what each term represents.

$$p + q = 1 \quad\text{and}\quad p^{2} + 2pq + q^{2} = 1$$ where $p$ and $q$ are allele frequencies; $p^{2}$, $2pq$, and $q^{2}$ are the frequencies of homozygous dominant, heterozygous, and homozygous recessive genotypes.

Why is DNA replication described as semiconservative, and which enzyme synthesizes the new strands?

Each daughter molecule retains one parental (template) strand and one newly synthesized strand. DNA polymerase synthesizes the new strands in the $5' \to 3'$ direction.

Distinguish the leading strand from the lagging strand in DNA replication.

The leading strand is synthesized continuously toward the replication fork ($5' \to 3'$). The lagging strand is synthesized discontinuously as Okazaki fragments, later joined by DNA ligase.

In transcription and translation, what are the roles of RNA polymerase and the ribosome?

RNA polymerase synthesizes mRNA from a DNA template ($5' \to 3'$) during transcription. The ribosome reads mRNA codons and links amino acids via tRNA during translation.

How many nucleotides form a codon, and what are the start and common stop codons?

Three nucleotides per codon. The start codon is $\text{AUG}$ (methionine); the stop codons are $\text{UAA}$, $\text{UAG}$, and $\text{UGA}$.

What is PCR and what are the three temperature steps of each cycle?

PCR (polymerase chain reaction) amplifies specific DNA sequences. Each cycle: denaturation (~$95\,^{\circ}\text{C}$, strands separate), annealing (~$50$–$65\,^{\circ}\text{C}$, primers bind), and extension (~$72\,^{\circ}\text{C}$, Taq polymerase synthesizes new strands).

How does gel electrophoresis separate DNA fragments?

DNA, being negatively charged (phosphate backbone), migrates toward the positive electrode through an agarose gel. Smaller fragments move faster/farther, separating fragments by size.