Cell Biology: Cell Structure

Plasma membrane: semi-permeable membrane that separates the cell from its environment
Cytoplasm: jelly-like substance inside the cell membrane where metabolic processes occur
Nucleus: control center of the cell where DNA is stored
Mitochondria: organelles responsible for generating energy for the cell through cellular respiration
Endoplasmic reticulum (ER): network of membranous tubules and cisternae involved in protein synthesis and transport
Ribosomes: site of protein synthesis
Lysosomes: membrane-bound sacs that contain digestive enzymes and help break down waste and foreign substances
Cytoskeleton: network of filaments that provides structural support and shape to the cell

Passive transport: movement of molecules from high to low concentration without energy input
- Diffusion: random movement of molecules from high to low concentration
- Osmosis: movement of water molecules from high to low concentration through a selectively permeable membrane
Active transport: movement of molecules from low to high concentration with energy input
- Carrier proteins: transport molecules across the membrane using energy from ATP
- Pumps: transport molecules across the membrane using energy from ATP

Signal transduction pathways: series of molecular interactions that allow cells to respond to stimuli
Receptors: proteins that bind to signaling molecules (e.g. hormones, neurotransmitters)
Second messengers: molecules that transmit signals from receptors to downstream targets

Mitosis: process of cell division that results in two daughter cells with identical DNA
Meiosis: process of cell division that results in four daughter cells with unique DNA combinations (gametes)
Cytokinesis: physical separation of daughter cells during cell division

Apoptosis: programmed cell death, a natural process of eliminating damaged or unwanted cells
Necrosis: unprogrammed cell death, often resulting from injury or disease

Plasma membrane is a semi-permeable membrane that separates the cell from its environment
Cytoplasm is a jelly-like substance inside the cell membrane where metabolic processes occur
Nucleus is the control center of the cell where DNA is stored
Mitochondria are organelles responsible for generating energy for the cell through cellular respiration
Endoplasmic reticulum (ER) is a network of membranous tubules and cisternae involved in protein synthesis and transport
Ribosomes are the site of protein synthesis
Lysosomes are membrane-bound sacs that contain digestive enzymes and help break down waste and foreign substances
Cytoskeleton is a network of filaments that provides structural support and shape to the cell

Diffusion is the random movement of molecules from high to low concentration
Osmosis is the movement of water molecules from high to low concentration through a selectively permeable membrane

Signal transduction pathways are a series of molecular interactions that allow cells to respond to stimuli
Receptors are proteins that bind to signaling molecules (e.g. hormones, neurotransmitters)
Second messengers transmit signals from receptors to downstream targets

Mitosis is the process of cell division that results in two daughter cells with identical DNA
Meiosis is the process of cell division that results in four daughter cells with unique DNA combinations (gametes)
Cytokinesis is the physical separation of daughter cells during cell division

Apoptosis is programmed cell death, a natural process of eliminating damaged or unwanted cells
Necrosis is unprogrammed cell death, often resulting from injury or disease