Cell Structure and Organelles

Plasma Membrane: semi-permeable membrane that separates the cell from its environment
Cytoplasm: jelly-like substance inside the cell where metabolic processes occur
Cytoskeleton: network of filaments that provides structural support and shape to the cell
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): organelle involved in protein synthesis and transport
Lysosomes: organelles responsible for cellular digestion and recycling
Golgi Apparatus: organelle involved in protein modification and transport

Cell signaling: allows cells to communicate with each other
Transport: regulates the movement of molecules in and out of the cell
Cell adhesion: allows cells to stick together
Cell recognition: allows cells to recognize and respond to specific molecules

Cell division: process by which a cell divides into two daughter cells
- Mitosis: process of nuclear division
- Cytokinesis: process of cytoplasmic division
Cell growth and development: process by which cells increase in size and complexity
Cell signaling and response: process by which cells respond to external stimuli
Cell death: process by which cells die and are removed

Passive transport: movement of molecules from high to low concentration
- Diffusion: random movement of molecules
- Osmosis: movement of water molecules
Active transport: movement of molecules from low to high concentration
- Carrier proteins: proteins that transport molecules across the cell membrane

Cell adhesion molecules: molecules that allow cells to stick together
Cell junctions: structures that connect cells and allow for communication
- Tight junctions: impermeable junctions that prevent leakage
- Desmosomes: junctions that hold cells together
- Gap junctions: junctions that allow for direct communication between cells

Plasma membrane is a semi-permeable membrane that separates the cell from its environment.
Cytoplasm is a jelly-like substance inside the cell where metabolic processes occur.
Cytoskeleton is a network of filaments that provides structural support and shape to the cell.
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 an organelle involved in protein synthesis and transport.
Lysosomes are organelles responsible for cellular digestion and recycling.
Golgi Apparatus is an organelle involved in protein modification and transport.

Cell division is the process by which a cell divides into two daughter cells.
Mitosis is the process of nuclear division.
Cytokinesis is the process of cytoplasmic division.
Cell growth and development is the process by which cells increase in size and complexity.
Cell signaling and response is the process by which cells respond to external stimuli.
Cell death is the process by which cells die and are removed.

Passive transport is the movement of molecules from high to low concentration.
Diffusion is the random movement of molecules.
Osmosis is the movement of water molecules.
Active transport is the movement of molecules from low to high concentration.
Carrier proteins are proteins that transport molecules across the cell membrane.

Composed of two layers of phospholipid molecules with hydrophilic heads and hydrophobic tails, allowing for regulation of material flow in and out of the cell
Hydrophilic heads face outwards and hydrophobic tails face inwards, making the cell membrane semi-permeable
This arrangement enables the cell membrane to control what enters and leaves the cell

Passive Transport
- Diffusion: molecules move from high to low concentration
- Osmosis: water molecules move from high to low concentration
- Facilitated Diffusion: molecules move with assistance from transport proteins
Active Transport
- Requires energy from the cell to move molecules against concentration gradients
- Involves transport proteins and ATP energy

Signal Transduction Pathways
- Series of molecular interactions transmitting signals from the cell surface to the nucleus
- Involves protein and enzyme activation to transmit signals
Types of Cell Signaling
- Autocrine signaling: signaling within the same cell
- Paracrine signaling: signaling between nearby cells
- Endocrine signaling: signaling between cells over long distances

Matthias Jakob Schleiden and Theodor Schwann (1839)
- Proposed the cell theory, stating that all living organisms are composed of cells
- Cells are the basic units of life and all living things are made up of one or more cells
Rudolf Virchow (1858)
- Added the concept that cells arise from pre-existing cells through cell division

Nucleus
- Controls cell growth and division
- Contains genetic material (DNA)
Mitochondria
- Generates energy for the cell through cellular respiration
- Converts glucose into ATP
Endoplasmic Reticulum (ER)
- Involved in protein synthesis and transport
- Has two types: rough ER (with ribosomes) and smooth ER (without ribosomes)
Lysosomes
- Contains digestive enzymes that break down and recycle cellular waste and foreign substances
- Maintains cellular homeostasis