Anatomy & Physiology: Biology of the Cell

Flashcards covering the 'Biology of the Cell' chapter, focusing on cell size, shape, components, cell cycle, membrane transport, and organelles.

Nerve cells

Irregular-shaped cells.

Red blood cells

Biconcave disc-shaped cells.

Kidney tubule cells

Cube-shaped cells.

Intestinal lining cells

Column-shaped cells.

Cartilage cells

Spherical cells.

Skeletal muscle cells

Cylindrical cells.

Cytoplasm

Includes cytosol and organelles.

Cytosol

Also known as intracellular fluid.

Interphase

The longest phase of the cell cycle (about 23 hours), including G1, S, and G2 phases.

G1 phase

A phase of interphase characterized by growth and preparation for DNA replication.

S phase

A phase of interphase characterized by DNA replication.

G2 phase

A brief phase of interphase characterized by growth and preparation for division of DNA, completion of centriole replication, and synthesis of enzymes for cell division.

Mitotic (M) phase

The phase of the cell cycle involving mitosis (division of nucleus) and cytokinesis (division of cytoplasm), lasting about 1 hour.

Mitosis

Cell division occurring in somatic cells (all cells other than sex cells), necessary for development, tissue growth, replacement of old cells, and tissue repair.

Meiosis

Cell division occurring in sex cells (cells that give rise to sperm or oocytes).

Prophase

The first stage of mitosis where chromatin supercoils into chromosomes (each with two sister chromatids), the nucleolus breaks down, spindle fibers grow from centrioles, and the nuclear envelope dissolves.

Metaphase

The second stage of mitosis where replicated chromosomes align on the equatorial plate of the cell, with spindle fibers attached to their centromeres.

Anaphase

The third stage of mitosis where sister chromatids separate and are pulled apart toward opposite poles, becoming single-stranded chromosomes. Cytokinesis begins during this stage.

Cytokinesis

The division of the cytoplasm between two newly formed cells, which may overlap with anaphase and telophase, forming a cleavage furrow that pinches the mother cell into two daughter cells.

Tumors

Arise when cell signaling is disrupted, interfering with normal cell function, and may metastasize to other body areas.

Cholesterol

A four-ring lipid molecule scattered within the phospholipid bilayer that strengthens and stabilizes the cell membrane against temperature extremes.

Glycolipids

Lipids with attached carbohydrate groups, located only on the outer phospholipid region of the plasma membrane.

Plasma membrane

Functions as a physical barrier, selectively permeable boundary, establishes electrochemical gradients, and facilitates cell communication through receptors.

Integral proteins

Proteins that penetrate or span the plasma membrane, performing most of the membrane's functions.

Peripheral proteins

Proteins located on one side of the plasma membrane.

Passive processes (Membrane Transport)

Do not require cellular energy expenditure; substances move down their concentration gradient (e.g., diffusion, osmosis).

Active processes (Membrane Transport)

Require cellular energy expenditure; involve movement of a substance up its concentration gradient or the formation/loss of a vesicle.

Diffusion

Movement of solutes down their concentration gradient until equilibrium is reached.

Concentration gradient

Measure of the difference in concentration between two areas; a steeper gradient causes a faster rate of diffusion.

Equilibrium (Diffusion)

A state where molecules are evenly distributed throughout a given area, and diffusion ceases if unopposed.

Simple diffusion

Molecules move unassisted between phospholipid molecules (e.g., small, nonpolar solutes like O2, CO2, fatty acids, ethanol, urea), dependent on the concentration gradient.

Facilitated diffusion

Transport process for small charged or polar solutes that requires assistance from plasma membrane proteins (channel-mediated or carrier-mediated).

Channel-mediated diffusion

Ions move down their concentration gradient through water-filled channels in the plasma membrane.

Carrier-mediated diffusion

Small polar molecules are assisted across the membrane by a specific carrier protein that changes shape upon binding and releases the substance on the other side, moving substances down their gradient.

Transport maximum

The maximum rate of substance transport, determined by the number of available channels and carriers in the membrane.

Osmosis

The passive movement of water, not solutes, through a semipermeable membrane from an area of higher water concentration to an area of lower water concentration.

Aquaporins

Protein channels that allow the bulk transport of water during osmosis.

Osmotic pressure

Pressure exerted by the movement of water across a semipermeable membrane due to differences in water concentration; a steeper gradient leads to greater osmotic pressure.

Hydrostatic pressure

Pressure exerted by a fluid on the inside wall of its container.

Tonicity

The ability of a solution to change the volume or pressure of a cell by osmosis.

Isotonic solution

A solution where both the cytosol and the solution have the same relative concentration of solutes, resulting in no net movement of water (e.g., 0.9% NaCl).

Hypotonic solution

A solution with a lower concentration of solutes than the cytosol, causing water to move into the cell, increasing its volume and pressure, potentially leading to lysis (bursting).

Lysis

The bursting of a cell due to excessive water intake in a hypotonic solution.

Hemolysis

The specific bursting of red blood cells in a hypotonic solution.

Hypertonic solution

A solution with a higher concentration of solutes than the cytosol, causing water to move out of the cell, decreasing its volume and pressure, leading to crenation (shrinking).

Crenation

The shrinking of a cell due to water loss in a hypertonic solution.

Active transport

Movement of a solute against its concentration gradient (from lower to higher solute concentration), maintaining the gradient between the cell and interstitial fluid.

Primary active transport

Uses energy directly from the breakdown of ATP; phosphorylation of the carrier protein changes its shape to move the substance across the membrane.

Na+/K+ pump

A primary active transport pump that moves 3 Na+ ions out of the cell and 2 K+ ions into the cell per ATP molecule, maintaining membrane potential.

Vesicular transport

Also called bulk transport; involves energy input to transport large substances across the plasma membrane by a membrane-bounded sac (vesicle).

Exocytosis

A process where large substances are secreted from the cell; material packed within intracellular transport vesicles fuses with the plasma membrane, releasing contents outside the cell (e.g., neurotransmitter release).

Endocytosis

A process where a vesicle is formed as material is brought into a cell; categorized into phagocytosis, pinocytosis, and receptor-mediated endocytosis.

Phagocytosis

Cellular eating; occurs when a cell engulfs a large particle external to the cell, enclosing it in a membrane sac that is internalized and digested after fusing with a lysosome (e.g., white blood cell engulfing a microbe).

Pinocytosis

Cellular drinking; the internalization of droplets of interstitial fluid containing dissolved solutes through the formation of multiple, small vesicles.

Receptor-mediated endocytosis

Uses receptors on the plasma membrane to bind specific molecules (ligands) within the interstitial fluid and bring them into the cell, often involving clathrin-coated pits (e.g., cholesterol transport).

Electrochemical gradient

Established and maintained by the plasma membrane, relating to the resting membrane potential (RMP), essential for muscle and nerve cell function.

Resting membrane potential (RMP)

The electrical charge difference across the plasma membrane, typically between -50 mV to -100 mV, maintained by ion channels and pumps.

Membrane-bound organelles

Organelles enclosed by a membrane, such as the nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, and mitochondria.

Non-membrane-bound organelles

Organelles not enclosed by a membrane, such as ribosomes, centrosomes, proteasomes, and the cytoskeleton.

Rough Endoplasmic Reticulum (Rough ER)

Synthesizes proteins for secretion, plasma membrane incorporation, and lysosomal enzymes; modifies and stores proteins; helps form peroxisomes and transport vesicles; has ribosomes attached.

Smooth Endoplasmic Reticulum (Smooth ER)

Site of lipid (e.g., steroid) synthesis and carbohydrate metabolism (e.g., glycogen synthesis); detoxifies drugs, alcohol, and poisons; forms transport vesicles.

Golgi apparatus

Composed of cisternae; functions in modification, packaging, and sorting of proteins; forms secretory vesicles that deliver membrane components, release contents by exocytosis, or provide digestive enzymes to lysosomes; also forms proteoglycans and synthesizes lysosomes.

Endomembrane system

A network of organelles including the ER, Golgi apparatus, lysosomes, and vesicles that work together for synthesis, modification, and shipping of proteins and other materials into, out of, and within a cell.

Lysosomes

Membrane-bound organelles containing digestive enzymes that break down waste materials and cellular debris.

Peroxisomes

Pinched off vesicles from the rough ER that carry out metabolic functions, including the chemical digestion of hydrogen peroxide, beta oxidation of fatty acids, and lipid synthesis.

Tay-Sachs disease

A lysosomal storage disease caused by a mutation in genes for lysosomal enzymes, leading to the accumulation of complex membrane lipids in nerve cells, resulting in paralysis, visual/hearing impairment, and early death.

Ribosomes

Organelles containing protein and ribonucleic acid, responsible for protein synthesis. Bound ribosomes (on ER) synthesize proteins for export, membrane, or lysosomes; free ribosomes (in cytosol) synthesize proteins for use within the cell.

Centrosome

A pair of perpendicularly oriented cylindrical centrioles surrounded by amorphous protein; primarily organizes microtubules within the cytoskeleton and functions in cellular division by forming spindle fibers.

Cytoskeleton

A network of protein filaments that provides structural support and organization to the cell, maintains cell shape, organizes organelles, crucial for cell division (separating chromosomes, splitting cells), and facilitates movement of organelles, vesicles, and muscle contraction.

Cilia

Hairlike projections from the cell surface containing supportive microtubules, which move substances along the cell surface.

Flagella

Longer and wider structures similar to cilia in base structure, but primarily function to propel the entire cell (e.g., sperm cells).

Microvilli

Extensions of the plasma membrane supported by actin microfilaments, which primarily increase the surface area of the cell for absorption.

Tight junction

A type of membrane junction where membrane proteins form a virtually impermeable barrier, preventing substances from passing between adjacent cells.

Desmosome

A type of membrane junction that provides strong adhesion between cells through protein plaques and intermediate filaments, resisting mechanical stress.

Gap junction

A type of membrane junction composed of connexons (protein channels) that allow direct communication and passage of small molecules between adjacent cells.

Hemidesmosome

A type of membrane junction that anchors the basal surface of epithelial cells to the basement membrane.

Nucleus

The largest structure in the cell, often called the 'control center'; typically found one per cell (exceptions: mature erythrocytes have none, skeletal muscle cells have multiple); houses DNA and produces ribosomal subunits.

Nuclear envelope

A double membrane that encloses the nucleus.

Nuclear pores

Openings in the nuclear envelope that regulate the passage of molecules between the nucleus and the cytoplasm.

Nucleoplasm

The internal fluid of the nucleus.

Nucleolus

A dense, spherical body within the nucleus responsible for producing ribosomal subunits.

Chromatin

The complex of DNA and proteins (histones) found within the nucleus, which condenses to form chromosomes during cell division.