Chapter 04: Integrative Anatomy & Physiology – Cells and Membranes (Notes from McKinley et al.)

Flashcards covering cell study basics, cell size/shape, membrane structure and transport, cell signaling, organelles, nucleus, transcription/translation, cell cycle, and aging/death.

What is cytology the study of?

Cells.

What is the typical size of an erythrocyte?

About 7–8 micrometers (μm) in diameter.

What is the diameter of a human oocyte?

Approximately 120 μm.

Name three common shapes of cells.

Spherical, cubelike, columnlike (also cylindrical, disc-shaped, irregular).

What is the plasma membrane?

A forms outer boundary that separates the cell’s interior from the external environment.

What is the nucleus?

The largest cell structure, enclosed by a nuclear envelope, containing DNA and a nucleolus.

What is nucleoplasm?

The inner fluid of the nucleus.

What is cytoplasm?

The cellular contents between the plasma membrane and the nucleus, including cytosol, organelles, and inclusions.

What are the two categories of organelles?

Membrane-bound organelles and non-membrane-bound organelles.

What are inclusions?

Non-organelles stored in cytosol, such as pigments, glycogen, triglycerides.

Name the lipid components of the plasma membrane.

Phospholipids, cholesterol, and glycolipids.

Describe phospholipids.

Amphipathic molecules with a polar head and two nonpolar tails; form a bilayer.

What is the role of cholesterol in the membrane?

Strengthens and stabilizes the membrane; helps maintain integrity across temperature changes.

What is glycocalyx?

A layer formed by glycolipids and glycoproteins on the outer membrane.

What are the two structural types of membrane proteins?

Integral proteins (span the bilayer) and peripheral proteins (attached to surfaces).

Name functional categories of membrane proteins.

Transport proteins; cell surface receptors; identity markers; enzymes; anchoring sites; cell-adhesion proteins.

What are transport proteins?

Channels, carrier proteins, pumps, symporters, and antiporters that move substances across the membrane.

What is the function of cell surface receptors?

Bind ligands (e.g., neurotransmitters) to initiate cellular responses.

What is the glycocalyx?

Carbohydrate-rich layer on the cell surface formed by glycoproteins and glycolipids.

What does membrane transport refer to?

The process of moving substances across the plasma membrane; includes passive and active processes.

Define diffusion.

Net movement of ions or molecules from an area of higher concentration to an area of lower concentration.

What is simple diffusion?

Unassisted diffusion of small nonpolar solutes (e.g., O2, CO2) across the membrane.

What is facilitated diffusion?

Diffusion that requires membrane proteins (channels or carriers) for small polar/charged solutes.

What is channel-mediated diffusion?

Movement of ions through water-filled, ion-specific channels; can be leak or gated.

What is carrier-mediated diffusion?

Diffusion of small polar molecules via carrier proteins that change shape.

What is osmosis?

Passive movement of water through a semipermeable membrane.

What are aquaporins?

Integral membrane channels that facilitate water movement (osmosis).

Differentiate permeable and nonpermeable solutes.

Permeable solutes can cross the bilayer; nonpermeable solutes cannot.

What is osmotic pressure?

Pressure exerted by water movement across a semipermeable membrane due to solute differences.

Define tonicity.

The ability of a solution to change cell volume by osmosis; isotonic, hypotonic, hypertonic.

What is isotonic solution?

Same solute concentration as the cell cytosol; no net water movement.

What is hypotonic solution?

Lower solute concentration than cytosol; water enters cell; may cause swelling or lysis.

What is a hypertonic solution?

Higher solute concentration outside the cell; water leaves the cell; cell shrinks (crenation).

What are active processes?

Require energy and include primary and vesicular (bulk) transport.

What is primary active transport?

Moves substances against their concentration gradient using energy from ATP (e.g., Na+/K+ pump).

What is the Na+/K+ pump?

An exchange pump that exports Na+ and imports K+ to preserve gradients.

What are ion pumps?

Pumps that move ions to maintain intracellular concentrations (e.g., Ca2+ pumps).

What is secondary active transport?

Uses energy from the movement of a second substance down its gradient; includes symport and antiport.

What is vesicular transport?

Bulk transport via membrane-bound vesicles; includes exocytosis and endocytosis.

Describe exocytosis.

Secretion of large substances; vesicle fuses with the plasma membrane and releases contents.

Describe endocytosis.

Uptake of large substances by invagination of the plasma membrane and vesicle formation.

What are phagocytosis, pinocytosis, and receptor-mediated endocytosis?

Phagocytosis: cellular eating; pinocytosis: cellular drinking; receptor-mediated endocytosis: uptake via receptors.

What is resting membrane potential (RMP)?

The voltage difference across the plasma membrane when a cell is at rest.

Which ions are most important in setting the RMP?

Sodium (Na+) and potassium (K+); K+ is the major determinant.

What maintains the Na+/K+ gradient?

Na+/K+ pumps that export Na+ and import K+ to maintain gradients.

What roles does the cytoskeleton play?

Supports cell shape, organizes organelles, enables movement and division; made of microfilaments, intermediate filaments, and microtubules.

What external cell structures extend from the surface?

Cilia, flagella, and microvilli.

What are membrane junctions?

Tight junctions, desmosomes, and gap junctions that connect cells and regulate passage.

What is the nucleus’ nuclear envelope?

A double membrane surrounding the nucleus with nuclear pores.

What is the nucleolus?

A non-membrane-bound region that produces ribosomal subunits.

What are nucleotides composed of?

A five-carbon sugar (deoxyribose), a phosphate, and a nitrogenous base (A, C, G, T).

How many double-stranded DNA molecules are in a human cell?

46.

What is a gene?

A stretch of nucleotides that provides instructions to synthesize a specific protein.

What are promoters and terminators?

Promoter: start signal for transcription; terminator: stop signal.

What happens during transcription?

RNA polymerase synthesizes RNA using DNA as template; produces mRNA, tRNA, and rRNA.

What RNA types are produced in transcription?

mRNA, tRNA, and rRNA.

What is splicing?

Removal of introns; exons are joined to form mature mRNA.

What is translation?

Synthesis of protein at ribosomes using mRNA, tRNA, and amino acids.