Chapter 3 Cell Structure and Function pt. 1

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.