The Cell Objectives

Are human somatic cells prokaryotic or eukaryotic?

Eukaryotic.

What is the normal chromosome count in human somatic cells vs. gametes?

Somatic cells: 46 (diploid, 2n). Gametes: 23 (haploid, 1n).

Which ion has a higher concentration inside the cytoplasm, $K^+$ or $Na^+$?

Potassium ($K^+$).

Which ion has a higher concentration in the extracellular fluid, $K^+$ or $Na^+$?

Sodium ($Na^+$).

What is the primary structural framework of the plasmalemma?

An amphipathic phospholipid bilayer containing embedded integral/peripheral proteins and cholesterol.

What structural feature differentiates membranous organelles from nonmembranous organelles?

Membranous organelles are enclosed by one or more lipid bilayers; nonmembranous organelles lack a membrane wrapper.

Name three nonmembranous organelles.

Ribosomes, centrioles/centrosomes, and cytoskeletal filaments.

Name three membranous organelles.

Mitochondria, endoplasmic reticulum, and Golgi apparatus (or lysosomes, peroxisomes, nucleus).

What protein subunit polymerizes to form microfilaments?

Actin (G-actin monomers assembling into F-actin helices).

What is the primary functional role of intermediate filaments?

Providing mechanical strength, structural stability, and resisting tensile stress.

What tubulin-based structure serves as the primary microtubule-organizing center (MTOC) during cell division?

Centrosome (containing a pair of centrioles).

What is the characteristic microtubule arrangement in a cilium or flagellum (axoneme)?

"9 + 2" arrangement (9 outer doublets surrounding 1 central pair).

Which organelle is the primary site of ATP generation via oxidative phosphorylation?

Mitochondrion.

What double-membrane structure encloses the nuclear chromatin?

Nuclear envelope.

What dense nuclear subregion is responsible for ribosomal RNA (rRNA) synthesis and ribosome assembly?

Nucleolus.

How do Rough ER and Smooth ER differ in structure and primary function?

Rough ER is studded with ribosomes (protein synthesis); Smooth ER lacks ribosomes (lipid/steroid synthesis and calcium storage).

What is the core function of the Golgi apparatus?

Modifying, packaging, and sorting proteins and lipids received from the rough ER.

Which organelle contains acid hydrolases responsible for intracellular digestion?

Lysosome.

Which organelle breaks down fatty acids and neutralizes toxic hydrogen peroxide ($H_2O_2$) via catalase?

Peroxisome.

What specialized smooth endoplasmic reticulum in skeletal muscle cells stores and releases calcium ($Ca^{2+}$)?

Sarcoplasmic reticulum.

Which neuronal process receives incoming synaptic signals and conducts them toward the cell body?

Dendrite.

What specialized vesicle at the tip of a sperm head contains enzymes necessary for penetrating the zona pellucida?

Acrosome.

Which organelle is highly concentrated in the sperm midpiece to supply energy for flagellar movement?

Mitochondria.

What apical membrane projections increase surface area for absorption in intestinal epithelial cells?

Microvilli (forming the brush border).

What cell junction creates an impermeable barrier to prevent paracellular movement between adjacent epithelial cells?

Tight junctions (zonula occludens).