1. Cell Theory

Early studies led to the development of the cell theory .

• The invention of the compound microscopes progressed the studies of cells.

  • Most cells cannot be seen without microscope.

• A compound microscope has two or more lenses to increase magnifying power.

Discovery of Cells

• Robert Hooke and Anton van Leeuwenhoek were two of the earliest scientists to identify and study cells in the late 1600s.

Cell Theory

• Matthias Schleiden observed that plants were made of cells in 1838.

• Theodor Schwann proposed that all living things were made of cells in 1839, known as the cell theory.

• Rudolf Virchow added to the cell theory by proposing all cells are made of other cells.

• Cell Theory: A theory that states that all organisms are made of cells, cells reproduce, and cells are the basic unit of life.

Prokaryotic cells lack a nucleus and most internal structures of eukaryotic cells.

• Cells are enclosed by membrane that lets materials in and out.

• Cytoplasm: A jellylike substance that holds building blocks like proteins and nucleic acids.

  • Also contains organelles.

• Organelles: Structures in a cell that have a specific function

  • A nucleus is one type of organelle.

• Prokaryotic cells: Single-celled organisms that do not have a nucleus or any other organelles.

  • DNA is in the cytoplasm.

• Eukaryotic cells: Multi-cellular OR single-celled organisms that have a nucleus and other organelles.

  • DNA is in nucleus.

2. Cell Organelles

Cells have an internal structure.

• Organelles in a Eukaryotic cell have specific locations they are held in.

  • Cytoplasm and cytoskeleton contribute to cell structure.

• Cytoskeleton: Network of proteins that is always changing to meet the needs of a cell.

• Different fibers make up cytoskeleton

  • Microtubules give the cell its shape and help move organelles.

  • Intermediate filaments give strength to a cell.

  • Microfilaments help cells to move and divide.

Several organelles are involved in making and processing proteins.

• Cells mainly focus on making proteins, which are critical to organisms.

Nucleus

• Nucleus: Where all the genetic information (DNA) is stores in eukaryotic cells.

  • Protects DNA and makes DNA available for use.

• Nucleus contains nucleolus.

  • Region where ribosomes are made.

Endoplasmic Reticulum and Ribosomes

• Endoplasmic reticulum: organelle where proteins and lipids are produced.

  • Also called the ER.

• “Rough ER” is studded with ribosomes.

• “Smooth ER” has no ribosomes on it.

• Ribosomes: small organelles that link amino acids to form proteins.

  • Ribosomes are made of proteins and RNA.

Golgi Apparatus

• Golgi apparatus: organelle that packages, sorts, and delivers proteins in the cell.

  • Enzymes in golgi apparatus make alters to proteins as well.

  • Proteins are delivered within the cell and out of the cell.

Vesicles

• Vesicles: organelles that transport materials from place to place within the cell.

  • This is how proteins are carried to and from the Golgi apparatus.

Other organelles have various functions

Mitochondria

• Mitochondria: Organelle that supplies energy to the cell.

  • Mitochondria have their own ribosomes and DNA from the rest of the cell.

Vacuole

• Vacuole: organelle used for storing materials needed by a cell.

  • In animal cells there are many small vacuoles.

  • In plant cells there is a central vacuole that contains mostly water.

Lysosomes

• Lysosomes: Organelles bound to the membrane than contain enzymes.

  • Defend the cell from outside bacteria and viruses.

  • Break down old cell parts.

Centrosome and Centrioles

• A centrosome is a region of cytoplasm in the cell that makes microtubules.

  • Contains centrioles.

• Centrioles: organelles made of microtubules arranged in a circle.

  • Centrioles divide DNA during cell division.

Plant cells have cell walls and chloropasts.

Cell Walls

• Cell wall: structure outside the membrane of a plant cell.

  • gives support, shape, and protection to the cell.

Chloropasts

• Chloropasts: organelles that carry out photosynthesis to create energy for plant cells.

  • Photosynthesis converts solar energy into molecules that the cells uses for energy.

  • Chloropasts have their own ribosomes and DNA like mitochondria.

3. Cell Membrane

Cell membranes are composed of two phospholipid layers.

• Cell membrane: The boundary between a cell and the outside environment.

  • Controls what materials come in and out of a cell.

  • Has a double layer of phospholipids.

  • Has additional molecules like cholesterol, proteins, and carbohydrates that help protect the cell.

• Phospholipid: A molecule that has a charged phosphate group, glycerol, and two fatty acid chains.

  • Glycerol and phosphate groups form the head of the Phospholipid (polar)

  • The fatty acid chains form the tail. (nonpolar)

Fluid Mosaic Model

• Fluid Mosaic Model: Model that shows the arrangement of the molecules that make up a cell membrane.

Selective Permeability

• Selective Permeability: Property that only allows some materials to cross through.

• Selective Permeability allows a cell to maintain homeostasis.

  • There is less interference from the outside environment that impacts the cell.

Chemical signals are transmitted across the cell membrane.

• Molecules within the cell can act like signals to communicate with other cells.

• Receptor: A protein that detects a signal molecule and responds with action.

• A ligand is a molecule a receptor binds to.

Intracellular Receptor

• An intracellular receptor is located inside the cell.

  • Molecules that can cross the cell membrane can bind with an intracellular receptor.

Membrane Receptor

• Membrane receptors are in the cell membrane.

  • Molecules that can’t cross the cell membrane can bind with a membrane receptor.