Cell Biology: Cell Structures, Membranes, and Transport

A comprehensive vocabulary review of cell structures, organelle functions, membrane composition, selective permeability, passive and active transport mechanisms, and endosymbiotic theory.

CFTR Protein

A transmembrane channel protein that controls the flow of $H_2O$ and chloride ions ($Cl^-$) in and out of cells inside the lungs.

$\Delta F508$ Mutation

A deletion mutation of three nucleotides resulting in the loss of the amino acid phenylalanine ($F$) at the $508\text{th}$ position on the CFTR protein, accounting for $90\%$ of cystic fibrosis cases in the United States.

Phospholipid

An amphipathic lipid molecule consisting of a polar hydrophilic head group (choline, phosphate, glycerol backbone) and two nonpolar hydrophobic fatty acid tails.

Diffusion

The passive intermingling of substances by the natural movement of their particles, resulting in net movement of solute from an area of higher concentration to an area of lower concentration.

Osmosis

The passive process by which solvent molecules pass through a semipermeable membrane from a solution of lower solute concentration to one of higher solute concentration.

Osmolyte

Compounds that affect osmosis, such as sodium, potassium, and chloride ions, as well as sugars and proteins.

Integral Membrane Proteins

Membrane proteins permanently attached to the lipid bilayer, including transmembrane proteins that span the entire membrane.

Peripheral Membrane Proteins

Proteins temporarily associated with either the internal or external side of the cell membrane.

Facilitated Diffusion

The passive movement of molecules across a membrane down their concentration gradient aided by transport proteins such as channels or carriers.

Primary Active Transport

A transport mechanism that moves solutes across a membrane against their concentration gradient directly using energy derived from $ATP$.

Cell Theory principal 1

All living organisms are composed of one or more cells.

cell theory principal 2

The cell is the basic unit of structure and organization in organisms.

cell theory principal 3

All cells arise from pre-existing cells.

Which scientist first observed cells in cork in 1665?

Robert Hooke

3 domains of life

Archaea, Bacteria, and Eukarya

What does Archea consist off

prokaryotes

What does Bacteria consist of

prokaryotes

what does Eurkaya consist of

Eukaroytes

Why does a cell's efficiency decrease as its volume increases?

As a cell grows, its surface area-to-volume ratio decreases. Volume increases faster than surface area, making simple diffusion inefficient across the plasma membrane for transport of nutrients and waste

3 main regions of prokaryotic cell

Cell envelope, Cytoplasmic region, Appendages

Prokaryotic Cell

A cell that lacks an internal membrane-bound nucleus and organelles, generally single-celled, and measures $0.1\,m$ to $5.0\,\mu m$ in diameter.

Eukaryotic Cell

A cell containing a membrane-bound nucleus and membrane-bound organelles, typically measuring $10\,\mu m$ to $100\,\mu m$ in diameter.

Nucleoid Region

The central area within a prokaryotic cell that contains the chromosomal $DNA$. Where the genetic material is stored

Plasmid

A small, extrachromosomal $DNA$ molecule found in prokaryotes that can replicate independently.

Gram-Positive Bacteria

Bacteria with thick cell walls composed of peptidoglycan that retain crystal violet dye and stain purple.

Gram-Negative Bacteria

Bacteria with a thin peptidoglycan layer and an outer membrane, which stain red or pink during Gram staining.

Endomembrane System

A group of membrane-bound eukaryotic structures—including the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and plasma membrane—that function together to synthesize, modify, package, and transport proteins and lipids.

Nucleolus

A condensed region within the eukaryotic nucleus where ribosome assembly takes place.

Chromatin

The unwound complex of $DNA$ and associated histone proteins that constitutes chromosomes in the nucleus.

Rough Endoplasmic Reticulum (RER)

A membrane-bound organelle studded with ribosomes involved in synthesizing, folding, and modifying proteins.

Smooth Endoplasmic Reticulum (SER)

A membranous organelle involved in lipid synthesis, carbohydrate metabolism, detoxification, and the production of steroid hormones.

Golgi Apparatus

An organelle made up of flattened stacked pouches called cisternae that modifies, sorts, and packages proteins and lipids.

Lysosome

An acidic eukaryotic organelle containing hydrolytic digestive enzymes that break down biomolecules, cellular waste, and worn-out organelles.

Peroxisome

A single-membrane organelle that carries out oxidation reactions to break down fatty acids and amino acids, and detoxifies substances such as peroxide and alcohol.

Mitochondria

Double-membrane eukaryotic organelles responsible for generating energy ($ATP$) through aerobic respiration.

Cristae

Infoldings of the inner mitochondrial membrane where the chemical reactions of aerobic respiration take place.

Chloroplast

A plant and algal organelle bounded by double membranes and containing thylakoids that carries out photosynthesis.

Cytoskeleton

A network of microfilaments, intermediate filaments, and microtubules that organizes cell structure, maintains shape, anchors organelles, and enables cellular movement.

Microfilaments

Cytoskeletal fibers with a diameter of $7\,nm$ composed of actin monomers ($G\text{-actin}$) involved in cell shape and movement.

Microtubules

Hollow cylindrical cytoskeletal structures with a diameter of $25\,nm$ composed of tubulin dimers that form mitotic spindles, cilia, and flagella.

Intermediate Filaments

Cytoskeletal elements with a diameter of $8\,nm$ to $12\,nm$ made of supercoiled tetramer sheets that provide mechanical resistance and hold organelles in place.

Endosymbiotic Theory

The theory proposed by Lynn Margulis stating that eukaryotic organelles such as mitochondria and chloroplasts evolved from free-living prokaryotes that were engulfed by an ancestral host cell.

Ribosomes

Protein synthesis (translating mRNA into polypeptide chains