BIOL 190 - Cellular & Organismal BIO Week 5: Cells

Vocabulary flashcards covering cell theory, prokaryotic vs eukaryotic cells, plasma membrane structure, cell transport, organelles, and cell communication/death.

Cell Theory

The scientific principle stating that cells are the fundamental unit of life, all organisms are made of one or more cells, all cells arise from other cells, and they contain an organism's life functions and genetic information (DNA).

Prokaryotic

The oldest form of cell on Earth; they do not have a nucleus (DNA is not enclosed in a membrane) or membrane-bound organelles, though they contain ribosomes, and are always single-celled organisms like Bacteria and Archaea.

Eukaryotic

Cells that developed roughly $2.1\text{ billion}$ years ago containing a nucleus and membraned organelles; these cells can be single-celled or multicellular organisms such as animals, plants, fungi, and protists.

Plasma membrane

The major barrier of the cell, primarily composed of lipids, that separates internal contents and fluids from the outside environment.

Cytosol

The viscous fluid inside the cell, also known as intracellular fluid.

Organelles

Membrane-bound structures inside the cell that perform specialized functions.

Cellular polarity

The concept that many cells have asymmetric designs based on their functional needs, such as being long and tubular or round and flat.

Microvilli or cilia

External accessory structures that help the cell capture nutrients.

Flagella

External structures that allow the cell to swim, usually in fluids.

Phospholipid bilayer

A two-layered membrane structure where hydrophobic (water-fearing) fatty tails face inward and hydrophilic (water-loving) phosphate heads face the aqueous environment.

Cholesterol

A component making up approximately $20\%$ of the plasma membrane that stabilizes it by providing ideal rigidity.

Glycolipids and Glycoproteins

Membrane components used for cell recognition, composed of polysaccharides combined with fatty acids or proteins respectively.

Integral proteins

Transmembrane proteins wedged within the lipid bilayer that allow molecules and water to pass through.

Peripheral proteins

Proteins attached on the extracellular or intracellular sides of the membrane, important for signaling and enzymatic processes.

Tight junctions

Cell junctions where integral proteins fuse cells together tightly like sewing to create a watertight seal and prevent leaking.

Desmosomes

Cell junctions that hook and anchor adjacent cells together like Velcro, linked with intermediate filaments of the cytoskeleton for strength.

Gap junctions

Protein channels that align between two cells to allow for very rapid transportation of goods.

Passive transport

A method of moving substances across the membrane that does not require energy, moving molecules from High to Low concentration "down the concentration gradient."

Osmosis

The diffusion of water across a semi-permeable membrane toward the region of higher solute concentration to establish equilibrium.

Active transport

A method of moving substances across the membrane that requires energy ($ATP$) to move molecules from Low to High concentration "up the concentration gradient."

Bulk Transport

Moving very large items across the membrane using cytosis, which involves breaking off a piece of the membrane to create a vesicle; this always requires energy.

Phagocytosis

A form of endocytosis known as "cell eating" where the cell engulfs large particles at once.

Pinocytosis

A form of endocytosis known as "cell drinking" where the cell engulfs many small particles with fluids at one time.

Tonicity

The ability for a solution to change a cell's shape through osmosis.

Isotonic

A solution where solute concentrations inside and outside of the cell are equal, resulting in a normal/balanced cell shape.

Hypertonic

A solution with a higher concentration of solutes outside the cell than inside, causing water to flow out and the cell to shrink.

Hypotonic

A solution with a lower concentration of solutes outside the cell than inside, causing water to flow into the cell and expand its size.

Microfilaments

The narrowest part of the cytoskeleton with functional roles in cell movement and shape changes.

Intermediate filaments

Cytoskeleton parts with structural roles that withstand tension and hold organelles in place.

Microtubules

Small hollow tubes that resist compressive forces and provide tracks for vesicles to move around the cell.

Mitochondrion

The "powerhouse of the cell" that transforms glucose and oxygen into the universal fuel called $ATP$.

Ribosomes

Structures made of mixed RNA and proteins that synthesize new proteins from RNA; they can be free-floating or bound to the rough ER.

Rough Endoplasmic Reticulum (ER)

A part of the ER containing bound ribosomes used to manufacture and synthesize proteins.

Smooth Endoplasmic Reticulum (ER)

A part of the ER that synthesizes lipids, processes drugs, and detoxifies harmful chemicals in liver cells.

Golgi Apparatus

An organelle that collects, processes, and packages proteins from the rough ER into vesicles for transport.

Peroxisomes

Organelles that break down fatty acids and neutralize the hydrogen peroxide ($H_{2}O_{2}$) produced during the process.

Lysosomes

Organelles that digest biomolecules for recycling and also digest foreign invaders.

Nuclear envelope

A double membrane barrier surrounding the nucleus that contains nuclear pores to allow for transport.

Nucleolus

A spherical body in the middle of the nucleus responsible for assembling the parts needed to make ribosomes.

Chromatin

Composed of DNA and histone proteins; the histones protect the DNA when it is not in use.

Ligands

Chemical signals that land on receptor proteins in target cells to induce a signaling pathway.

Signal transduction

A series of protein activations within a target cell leading to a final goal after a ligand binds to a receptor.

Paracrine signaling

Chemical signals that act between near or adjacent cells by crossing extracellular fluids.

Endocrine signals

Chemical signals that originate from distant cells.

G-protein-coupled receptors (GPCR)

Integral protein receptors linked to a peripheral G-protein; approximately $1/3$ of all drugs on the market target these receptors.

Autophagy

The "self-eating" recycling process where cells dispose of dysfunctional proteins or organelles by engulfing them in autophagosomes and fusing them with lysosomes.

Cell Senescence

A state of "cell sleep" that is a factor in how cells age.

Apoptosis

Programmed cell death activated by digestive enzymes to destroy a cell from the inside out; triggered by DNA mutation, mitochondrial destruction, or pathogens.

Aging reversal

The scientific concept that aging may be reversible by altering faulty mechanisms in $3-4$ genes in the DNA.