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C H A P T E R 7
Cell Structure and Function
EQ: What Scientists and inventions helped aid in creating Cell Theory?
7.1 Cell Theory (Cells and Living Things)
Cells are the basic building block of all life
Cells are small & cannot be seen with the unaided eye
Advances in cell biology were not made until the microscope was invented
Robert Hooke (1665) discovered cells in cork and named them
Anton van Leeuwenhoek (1700) observed living creatures and pond water
Named them animalcules
Cell Theory
Developed by many scientists over a period two centuries
Schleiden, Schwann, Virchow
Cell Theory (statements)
All living things are composed of cells
Cells are the basic unit of structure and function of living things
Cells are produced from pre-existing cells
Overview of Cell Parts
4 major types of cell Structures
Cell or Plasma Membrane (all cells)
Regulates what enters and leaves the cell
Cytosol (all cells)
Fluid region inside cell membrane
Nucleus (some cells)
Controls cell activities, contains DNA
Organelles (varies by type of cell)
Carry out various functions in cells
Provide energy, breakdown wastes, expel wastes, etc.
Prokaryotic vs. Eukaryotic
Two types of cells:
Prokaryotic Cell – cells that lack a nucleus and most other organelles
Usually smaller than eukaryotic cells
Eukaryotic Cell – cells that have a nucleus and other membrane bound organelles
Prokaryotes Eukaryotes
Very small in size
Single chromosome present
Nucleolus absent
Membrane bound cell organelles are absent
Cell division by fission or budding (no mitosis)
Fairly large in size
More than one chromosome present
Nucleolus present
Membrane bound cell organelles are present
Cell division by mitosis or meiosis
Prokaryote vs. Eukaryote
Compare and Contrast these Cells
Plant Cells: Animal Cells:
Have nucleus, cell membrane & cytoplasm
Have chloroplasts
Do photosynthesis
Have a cell wall
Protects cell & keeps its shape
One large vacuole
Have nucleus, cell membrane, & cytoplasm
Many of the same organelles as plants
Have lysosomes, many small vacuoles, & centrioles
Plant vs. Animal Cells
Different types of Plant cells
Leaf Cells
Different types of Plant cells cont.
Flower Cells
Different types of Plant cells cont.
Root Cells
Different types of Animal Cells
Epithelial Cells
Different types of Animal Cells cont.
Cardiac Cells
Different types of Animal Cells cont.
Nerve Cells
Light Microscope
Scanning power objective lens
Low power objective lens
EQ: What is the cell membrane and why is it important for a cell to
have?
8.1 Cell (Plasma) Membrane
Separates cell interior from the surroundings outside of the cell
Very Thin Stack 8,000 together to = paper thickness!
Regulates movement of chemicals and substances in and out of the cell.
Composed of a Phospholipid & some proteins
Cell Membrane
-(Phospholipid Bilayer)
2 layers of phospholipids Phosphate end faces out Lipid ends in middle Water will be on either side,
but not in middle Allows for non-polar
molecules to pass easy Polar molecules have a harder
time moving 3 Main parts of the cell
membrane: • Lipid Bilayer• Membrane proteins• Carbohydrates
cell membrane
protein
cholesterol
proteincarbohydrate
chain
protein channel
Plasma Membrane
Plasma Protein Functions
Many types of proteins are embedded with in the plasma membrane bilayer
4 major functions of the proteins
Enzyme Activity
Cell-to-Cell recognition
Cell signaling
Transport of Materials
EQ: What is the difference between diffusion and osmosis?
8.2 Cellular Traffic
Materials such as water, nutrients, dissolved gases, ions, and wastes must be able to move in and/or out of cells through the cell membrane
Diffusion – movement of particles from an area of high concentration to an area of low concentration
Diffusion occurs until equilibrium
Equilibrium = when particles are balanced through out
Passive Transport
Selectively permeable membrane – allows some substances to pass through while keeping other things from passing Cell membrane is selectively permeable
Passive transport – movement across a membrane with no energy used by the cell
Facilitated Diffusion – transport of larger molecules by use of transport proteins
as a pathway
Osmosis
Passive transport of water across a selectively permeable membrane Type of diffusion
through a membrane
Movement of water
Osmosis cont.
Isotonic – solution in which concentrations of a solute are equal
Hypertonic – solution with a higher concentration of a solute
Hypotonic – solution with a lower concentration of solute
Active Transport
Movement of molecules of ions across a membrane involving the use of the cells energy
Usually done against the concentration gradient – moving from low to high concentration
Transport of Large Molecules
Large molecules need to be packaged in vesicles
Small membrane sacs that move products into and out of cells
Fuse with the cell membrane and empty
Exocytosis – movement of molecules out of the cell through a vesicle
Endocytosis – movement of molecules into a cell through a vesicle
Exocytosis (above left) expels molecules from the cell
that are too large to pass through the plasma membrane.
Endocytosis (below left) brings large molecules into the
cell and packages them in vesicles.