Cell Structures Bio 9H

What is a cell?

• Cells are the basic units that make up every living thing.

Scientist Robert Hooke

• first named “cells” because when he looked at a cork under one of
  the first compound microscopes, the little boxes reminded him of
  monastery cells/rooms.
• This discovery led to the development of the classical cell theory.
• Worked with Anton Van Leeuwenhoek, who first discovered
  bacteria (he called them Animalcules)

Cytology

The study of cells

What is the cell theory?

• The cell is the basic unit of all living things.
• Cells perform all the functions of living things.
• Cells come from the reproduction of existing cells.

How are cells grouped together

• organized in multicellular (many-celled) organisms based on
  function (so they all work together and efficiently)

How do cells build an organism?

1. Cells
2. Tissues
3. Organs
4. Organ Systems
5. Organism

2 major types of cells

• prokaryotic
• eukaryotic

Eukaryotic cells

• Multi-celled organisms
• Plant and animal cells
• Eukaryotic cells have organelles bound by membranes.
• Each organelle performs a specific function in the cell.
• All eukaryotic cells consist of a nucleus, plasma membrane,
  cytoplasm, peroxisomes, mitochondria, and ribosomes.

Prokaryotic cells

• Single-celled organisms
• bacteria
• Prokaryotic cells do not have membrane-bound organelles

Where is DNA stored in cells

• prokaryotic cells have circular, loosely packed DNA.
• Eukaryotic cells have DNA tightly packed into a nucleolus to
  protect it

Animal cell vs Plant cells

• Animal cells each have a centrosome and lysosomes, whereas -
  plant cells do not.
• Animal cells have multiple large central vacuoles, and plants have only one large central vacuole,
• Plant cells have a cell wall, chloroplasts, and other specialized
  plastids, whereas animal cells do not.

Plasma Membrane

• Both prokaryotes & eukaryotes have plasma membranes.
• The cell membrane is a semipermeable layer surrounding the cell.
• It helps to give the cell shape and move materials in and out.

Semipermeable

• allows some things through but not others

Cell Wall

• Plant cells also have cell walls surrounding the plasma membrane
• The cell wall is rigid and comprised of cellulose and water.
• It provides protection and shape for the cell but contains pores to
  allow materials to pass through.

Mitochondria

• “Powerhouse” of the cell
• Responsible for metabolic reactions that turn sugar into energy for
  the cell
• Comprised of 2 layers:
  • Outer membrane
  • Folded inner cristae to increase surface area for chemical
    reactions

Ribosomes & Endoplasmic Reticulum

• Ribosomes- small organelles responsible for protein synthesis.
  Can be free-floating or attached to the endoplasmic reticulum (ER)
• ER is made of folded membranes that transport materials around
  the cell
• Can be smooth (no ribosomes on the surface) or rough (has
  ribosomes attached to the surface)

Golgi Apparatus (Golgi Bodies)

• Curved, flattened stack of sacs that sorts proteins & lipids
• Small sacs called vesicles can break off and carry materials to
  other parts of the cell.

Lysosomes

• Small, round organelles filled with digestive enzymes
• Responsible for breaking down waste, invading bacteria or viruses

Plastids

• Surrounded by 2 membranes, like mitochondria
• Not found in humans or animals
• Contain either starches or pigments
• Chloroplasts are the most common type- responsible for
  photosynthesis and contain the pigment chlorophyll

Vacuoles

• Can be various sizes
• Used for storage or water or wastes
• Plant cells usually have one large vacuole for water storage
• Animal cells often have many smaller vacuoles
• They can also secrete substances and/or water

Nucleus

• Control center of the cell
• Easiest structure to see through a microscope
• Contains the genetic material (DNA) for the cell, which provide all
  of the instructions for cellular processes
• Surrounded by a nuclear envelope to protect the DNA
• Materials can pass in and out through nuclear pores

Nucleolus

• Within the nucleus is the nucleolus, which creates ribosomes.
• Ribosomes are the protein-making factories within the cell.

Centrioles

• Centrioles are cylinder-shaped organelles that aid in the process of
  cell division (mitosis).

Label the plant cell

Label the animal cell