BIO TOPIC 5

Prokaryotic cell

A cell without a nucleus or membrane-bound organelles

Eukaryotic cell

A cell with a true nucleus and membrane-bound organelles

Prokaryote vs. eukaryote DNA

Prokaryotic DNA is circular and free in the cytoplasm; eukaryotic DNA is linear and stored in the nucleus

Prokaryote vs. eukaryote size

Prokaryotic cells are generally smaller than eukaryotic cells

Prokaryote vs. eukaryote ribosomes

Prokaryotes have smaller (70S) ribosomes; eukaryotes have larger (80S) ribosomes

Cell Theory

All living things are made of cells, cells are the basic unit of life, and all cells come from pre-existing cells

Universal cell features

All cells have a plasma membrane, cytoplasm, DNA, and ribosomes

Organelle

A specialized structure within a cell that performs a specific function

Subcellular structures

Non-membrane structures like ribosomes, cytoskeleton, and centrioles

Nucleus

Contains DNA in eukaryotic cells and controls gene expression

Nuclear envelope

Double membrane that encloses the nucleus and contains nuclear pores

Nucleolus

Dense region inside the nucleus where ribosomal RNA is produced

Ribosomes

Sites of protein synthesis; can be free in the cytoplasm or bound to rough ER

Rough endoplasmic reticulum

Produces proteins for membranes or secretion; covered in ribosomes

Smooth endoplasmic reticulum

Synthesizes lipids, metabolizes carbohydrates, detoxifies drugs

Golgi apparatus

Modifies, sorts, and packages proteins and lipids for delivery

Vesicles

Small membrane-bound sacs that transport substances within or outside the cell

Lysosomes

Contain digestive enzymes to break down waste and damaged organelles

Peroxisomes

Break down fatty acids and detoxify harmful substances

Plasma membrane

A selective barrier that controls what enters and exits the cell

Mitochondria

Produce ATP through cellular respiration; contain their own DNA

Chloroplasts

Sites of photosynthesis in plant cells; contain their own DNA

Cytoskeleton

A network of fibers that provides structure, movement, and transport inside the cell

Microtubules

Thick hollow tubes that help maintain cell shape and form the spindle during division

Microfilaments

Thin strands of actin involved in cell movement and muscle contraction

Intermediate filaments

Provide mechanical support and help anchor organelles in place

Centrosome

Microtubule-organizing center that includes centrioles in animal cells

Cilia and flagella

Extensions of the cell that aid in movement; built from microtubules

Endomembrane system

A group of membranes and organelles that work together to modify, package, and transport lipids and proteins

Organelles in the endomembrane system

Nuclear envelope, rough and smooth ER, Golgi apparatus, lysosomes, vesicles, and plasma membrane

Membrane flow

Movement of membrane and contents between endomembrane system components via vesicles

Organelles not in the endomembrane system

Mitochondria, chloroplasts, peroxisomes, and the cytoskeleton

Mitochondria and chloroplasts origin

Believed to have originated from free-living prokaryotes via endosymbiosis

Function of the nucleus

Stores genetic material and controls cell activities through gene expression

Function of ribosomes

Translate mRNA into proteins

Function of the ER

Smooth ER makes lipids and detoxifies; rough ER processes and folds proteins

Function of the Golgi apparatus

Receives proteins from ER, modifies them, and sends them to their destinations

Function of lysosomes

Digest macromolecules, recycle damaged organelles

Function of peroxisomes

Break down fatty acids and neutralize toxic compounds

Function of mitochondria

Produce ATP through aerobic respiration

Function of chloroplasts

Capture light energy to make glucose through photosynthesis

Function of cytoskeleton

Maintains cell shape, enables intracellular transport, and supports cell movement

Genetic information flow

DNA → RNA → Protein

Transcription

Occurs in the nucleus; DNA is used to make mRNA

Translation

Occurs at ribosomes; mRNA is used to assemble amino acids into a polypeptide