Cells

Long, Long Ago….
 Before microscope, people thought that diseases were caused by curses and supernatural spirits
 Microscopes enabled scientists to view and study cells
 Anton VanLeeuwenhoek – developed the 1 st light microscope

Today’s microscopes
 Today we have much more advanced microscopes
 Compound light microscope – series of lenses to magnify objects
 SEM (Scanning Electron Microscope) – scans the surface of cells
 TEM (Transmission Electron Microscope) – see structures inside the cell

Cell Theory
 All organisms are composed of cells
 All cells come from other living cells
 Cells are the basic unit of structure and function

Homeostasis
 All organisms must maintain a balance regardless of internal and external conditions
 This task is controlled by the plasma membrane

Plasma Membrane
 The plasma membrane serves as the boundary between the cell and its environment
 Allows specific amount of nutrients to enter and allow waste to exit

Characteristics of cell membrane
 Selectively permeable – allows some molecules to enter and keeps others out
 Like a screen door

Plasma Membrane
 Made up of two layers of phospholipids
 Controls what moves into and out of the cell
 Selectively permeable
 AKA: Lipid Bilayer,
Fluid Mosaic, Cell
Membrane

Cell Wall
 Rigid structure
 Located outside of plasma membrane
 Found in plant cells, fungi, some bacteria and protists
 Provides support and protection
 Composed of cellulose
(carbohydrate)

Two Basic Cell Types
 Prokaryote  Eukaryote

Nucleus
 Control center of the eukaryotic cell
 Contains directions to make proteins
 Chromatin – strands of genetic material (DNA)

Nucleolus
 Structure within the nucleus
 Produces ribosomes

Ribosomes
 The site of protein synthesis
 Found in the cytoplasm or on the Endoplasmic
Reticulum

Cytoplasm
 Clear, gelatinous fluid inside the cell
 Helps suspend organelles

Endoplasmic Reticulum
 Site of cellular chemical reactions
 Series of highly folded membranes
 Rough Endoplasmic
Reticulum – have ribosomes attached
 Smooth Endoplasmic
Reticulum – does not have ribosomes attached

Golgi Apparatus
 AKA: Golgi Body
 Flattened system of tubular membranes
 Modifies and packages proteins
 Sort proteins to be sent to appropriate destination

Vacuoles
 Temporary storage of materials
 Store food, enzymes, other materials needed by the cell, and waste
 Plant cells usually have one large vacuole, animal cells usually contain many smaller vacuoles

Lysosomes
 Contain digestive enzymes that digest excess or worn out organelles, food particles, viruses and bacteria

Chloroplasts
 Found in the cells of green plants
 Organelle that captures light energy and produces food to store for later use
 Contains chlorophyll
– gives plants their green color

Mitochondria
 Organelles that transform energy for the cell
 Double membrane structure with highly folded inner membrane

Cytoskeleton
 Support structure for the cell
 Composed of microtubules and microfilaments
 Helps cell to maintain shape

Cilia and Flagella
 Aid in locomotion or feeding
 May move the entire cell, or aid in movement of substances across the cell surface

Identify the Following Cellular
Structures

Plant and Animal Cells
 Animal Cells
Don’t have a cell wall
- Contain centrioles
- Contain many small vacuoles
 Plant Cells
- Generally larger than animal cells
- Have a cell wall
- Contain chloroplasts
- Have one large central vacuole
Critical Thinking : Why are plant and animal cells similar?

Advantages of highly folded Membranes
 Folded membranes are an advantage to a cell because
 Cell processes can be more efficient
 Membranes provide a larger surface area for cell process to take place
 Remember all cell membranes are made up of phospholipids and by controlling what goes in and out of the membrane they help the cell maintain homeostasis