Biology 2E Chapter 4: Cell Structure Flashcards

These flashcards cover the vocabulary and key concepts of cell structure, including microscopy techniques, organelles, and intercellular junctions as presented in Biology 2E Chapter 4.

Tissues

Groups of interconnected cells that share a common function within a multicellular organism.

Magnification

The process of enlarging an object in its appearance through microscopy.

Resolving power

The ability of a microscope to distinguish two closely spaced points or adjacent structures as separate entities.

Compound light microscopes

Instruments that bend visible light through various lenses to provide magnification of specimens, often requiring chemical stains to distinguish transparent cell parts.

Transmission electron microscopes (TEM)

Electron microscopes that use electromagnets as lenses and operate in a vacuum to provide 2D imaging of internal structures with a resolution of $0.2\,nm$; specimens must be between $20-60\,nm$ thin.

Scanning electron microscopes (SEM)

Electron microscopes used to observe external features by coating objects with gold or other heavy metals to produce a 3D image.

Cell Theory

An underlying principle of biology stating that cells are the basic units of life, all living organisms are made of cells, and all cells come from preexisting cells.

Plasma membrane

A phospholipid bilayer with embedded proteins that serves as a permeability barrier, a protein anchor, and a site for energy conservation.

Cytoplasm

The region of a cell between the plasma membrane and the nuclear envelope, consisting of organelles suspended in gel-like cytosol and the cytoskeleton.

Ribosomes

Cellular structures made of rRNA and proteins that synthesize proteins by assembling amino acids.

Peptidoglycan

A nitrogenous polysaccharide found in the cell walls of most prokaryotic organisms.

Nucleoid

The localized area within a prokaryotic cell where chromosomal DNA is found.

Nucleus

The largest eukaryotic organelle, containing the cell's DNA and separated from the cytoplasm by the nuclear envelope.

Nuclear Envelope

A double membrane that separates DNA from the cytoplasm and regulates the flow of molecules through nuclear pores.

Nucleolus

A specific region inside the nucleus where ribosomes are assembled from RNA and proteins.

Mitochondrion

The site for converting stored macromolecule energy into ATP, featuring an inner membrane folded into cristae and an internal area called the mitochondrial matrix.

Peroxisomes

Small, single-membrane-enclosed organelles that break down fatty acids and amino acids, producing $H_2O_2$ in the process.

Centrosome

A structure in animal cells consisting of two centrioles lying at right angles, appearing as cylinders made of nine triplets of microtubules.

Plant Cell Wall

A rigid protective structure external to the plasma membrane made primarily of cellulose.

Chloroplasts

Double-membrane organelles in plants containing thylakoids (stacked into grana) and stroma, serving as the site for photosynthesis.

Central Vacuole

A large plant cell organelle that regulates water concentration and contributes to cell expansion by maintaining pressure against the cell wall.

Endosymbiosis

A hypothesis, championed by Dr. Lynn Margulis, suggesting that mitochondria and chloroplasts originated as independent prokaryotic organisms that became endosymbionts of eukaryotic ancestors.

Endomembrane System

A group of internal membranes and organelles in eukaryotes, including the nuclear envelope, lysosomes, vesicles, ER, and Golgi apparatus, that work to modify, package, and transport lipids and proteins.

Rough Endoplasmic Reticulum (RER)

A system of membranous sacs with attached ribosomes that manufacture and modify proteins by folding or adding side chains.

Smooth Endoplasmic Reticulum (SER)

A system of membranous tubules that synthesizes carbohydrates, lipids, and steroid hormones, detoxifies poisons, and stores $Ca^{2+}$.

Golgi Apparatus

A series of flattened membranes that sorts, packages, and tags lipids and proteins transported from the ER; features a receiving (cis) face and a shipping (trans) face.

Lysosomes

Organelles in animal cells containing digestive enzymes used to break down large biomolecules and worn-out organelles.

Cytoskeleton

A network of protein fibers including microfilaments, intermediate filaments, and microtubules that maintains cell shape and enables movement.

Microfilaments

Cytoskeletal components made of actin monomers involved in movement and stabilizing cell shape.

Microtubules

Rigid internal skeleton components made of tubulin dimers that provide a framework for motor proteins and form the 9+2 array in cilia and flagella.

Plasmodesmata

Channels passing between plant cell walls that connect the cytoplasm of adjacent cells.

Tight Junctions

Watertight seals found between animal epithelial cells that prevent materials from leaking between them.

Desmosomes

Protein structures (cadherins) that act as 'spot welds' to join adjacent animal cells in tissues that stretch, such as heart and muscle.

Gap Junctions

Protein-lined pores composed of six proteins called connexins that form a connexon, allowing water and small molecules to pass between adjacent animal cells.