Notes Chapter 7
Cell Structure and Function
7.1 Cell discovery and Theory
1665 Hooke looked at cork under a simple microscope and found tiny chambers he named cells .
Cells are the basic structural and functional unit of all living organisms.
1683 Anton van Leeuwenhoek looked at pond water, mold and other things under a microscope and found small free living organisms .
1838- Matthias Schleiden, a botanist looked at plant tissue and found they were made of cells.
1839- Theodor Schwann reported that all animal tissue was made of cells.
1855- Rudolph Virchow proposed that all cells come from pre-existing cells in a process called cell division.
The sum of these findings produced the cell theory .
Cell Theory
1. All organisms are composed of one or more cells . (S and S)
2. The cell is the basic unit of structure and function of organisms. (Hooke)
3. All cells come from other cells. (Virchow)
Compound Light Microscopes
Utilizes a series of glass lenses and visible light to enlarge an image.
Magnifies up to 1000 times the actual size.
Electron Microscopes
Utilizes magnets to aim a beam of electrons at a cell to produce an image.
Magnifies images up to 500,000 times the actual size.
Kinds of electron microscopes:
Transmission Electron Microscope (TEM)- Passes electrons through a dead, thinly sliced specimen in a vacuum, which produces black and white image of a specimen.

Scanning electron microscope (SEM)- uses electrons to scan the surface of a dead specimen to get a 3-D picture
Scanning Tunneling Microscope- (STM)- can be used with live specimens, a probe is brought close to the specimen and electrons tunnel between the two. Can see atoms on the surface of objects.
Basic Cell Types
Prokaryotic cell
Simple structure
Contains a plasma membrane .
Does not contain membrane bound organelles .
Eukaryotic Cell
More advanced structure than prokaryotic cell.
Contains a plasma membrane .
Contains membrane bound organelles.
7.2 The Plasma Membrane
Thin, flexible boundary between the cell and its environment.
Allows nutrients into the cell
Allows waste to leave the cell.
Selective Permeability- allows some substances through while keeping others out.
The plasma membrane controls the movement of substances into and out of the cell.
Plasma Membrane
The plasma membrane is composed of the lipid bilayer.
A phospholipid molecule is composed of a glycerol backbone, two fatty acid chains, and a phosphate group.
Fluid Mosaic Model

The phospholipid bilayer contains phospholipid heads which are polar and hydrophilic (water loving). It also contains fatty acid tails which are non polar and hydrophobic or water fearing.
This arrangement doesn't allow water soluble molecules in, only fat soluble. Because of this other components are necessary.
Other Components
• Cholesterol
• Proteins
• Carbohydrates
Proteins
Receptors signal inside the cell.
Act as an anchor structure.
Provide tunnels for substances to enter and leave the cell.
Cholesterol
Prevents fatty acid tails from sticking together.
Carbohydrates
Identify chemical signals.
7.3 Structures and Organelles
Cytoplasm- semifluid material that contains all substances needed for chemical reactions in the cell.
Cytoskeleton- supporting network of long, thin protein fibers that make a framework for the cell and provide anchor for the organelles. Also aids in movement .
Microtubules- long, hollow proteins that form a rigid skeleton and help move substances in the cell.
Microfilaments- thin protein threads that help give the cell shape and help it move .

Nucleus- directs all cell processes , contains DNA which stores information to make proteins, cell reproduction, cell growth and function.
Nuclear envelope (membrane)- surrounds the nucleus, allows large molecules to enter and leave the nucleus.
Chromatin- complex structure of DNA and protein found in the nucleus, makes up chromosomes .
Ribosomes- made in the nucleolus of the cell, made of RNA and protein, makes proteins .
Endoplasmic reticulum- folded membrane made of sacs and interconnected tunnels where proteins and lipids are made. The folds give more surface area for cellular functions to take place. Ribosomes attach to some ER (called rough ER), and make proteins to export into other cells.
Smooth ER- detoxes in liver and is a place of lipid and carbohydrate synthesis.
Golgi apparatus- flattened stacks of membranes that modifies, sorts and packages proteins into sacs called vesicles which can be transported in the body.
Vacuoles- large area to store wastes and cell products . Usually in plants, rarely found in animals.
Lysosomes- contains enzymes that digest worn out cell parts, bacteria and viruses and food particles. Can also fuse with vacuoles to digest wastes.
Centrioles- made of microtubules that organize the spindle in mitosis.
Mitochondria- convert glucose into usable energy ( ATP ).
Chloroplasts- organelles in plants that capture light energy and convert it to chemical energy .
Cell wall- in plants and bacteria, thick , rigid mesh of fibers that surround the plasma membrane, protects and gives support .
Cilia- Short, numerous projections that look like hair that row like oars.
Flagella- Longer and less numerous than cilia, usually aid in movement .
7.4 Cellular Transport
Passive Transport
Movement of particles across the cell membrane without using energy .

Three Modes of Passive Transport
• diffusion
• facilitated diffusion
• osmosis
Diffusion- Movement of particles from an area of high concentration to an area of low concentration. (A cube of sugar in hot water)
Diffusion is controlled by
• concentration
• temperature
• pressure
Dynamic Equilibrium- Reached when diffusion of material into the cell equals diffusion of material out of the cell.
Molecules continue to move , but the overall concentration remains the same .
Facilitated Diffusion- Movement o f materials across the plasma membrane using protein .
Osmosis- diffusion of water across a selectively permeable membrane .
Three Types of Solutions
• isotonic
• hypotonic
• hypertonic
Isotonic Solution- Water and dissolved substances diffuse into and out of the cell at the same rate . (No change to shape and size of cell)
Hypotonic Solution- Solute concentration is higher inside the cell. Water diffuses into the cell.
(Cell grows and can burst or lyse)
Hypertonic Solution- Solute concentration is higher outside the cell. Water diffuses out of the cell. (cell shrinks)

Active transport- Movement of particles across the cell membrane using energy .
Types of Active Transport
• Na+/ K+ ATPase pump
it moves three Na+ ions out of the cell and two K+ ions into the cell. (This changes the concentration gradient and provides energy to make ATP)
Endocytosis- Process by which the cell surrounds and takes particles into the cell.
Exocytosis- Secretion of material out of the plasma membrane. (Usually occurs with molecules too big to leave or come in through diffusion)