Cell Structure and Function C H A P T E R 7

Cell Structure and Function C H A P T E R 7

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

Prokaryote vs. Eukaryote Prokaryotes Very small in size Single chromosome present Nucleolus absent Membrane bound cell organelles are absent Cell division by fission or budding (no mitosis) Eukaryotes Fairly large in size More than one chromosome present Nucleolus present Membrane bound cell organelles are present Cell division by mitosis or meiosis

Compare and Contrast these Cells

Plant vs. Animal 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

Leaf Cells Different types of Plant 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 Low power objective lens Scanning power objective lens

EQ: What is the cell membrane and why is it important for a cell to have?

7.2 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 Phospholipid bilayer, proteins, cholesterol, and carbohydrates

Cell Membrane Plasma Membrane -(Phospholipid Bilayer) 2 layers of phospholipids Phosphate heads faces out (hydrophilic) Lipid tails= inside (hydrophobic) 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 through cell membrane 3 Main parts of the cell membrane: Lipid Bilayer Membrane proteins Carbohydrates cell membranecarbohydrate chain cholesterol protein protein channel protein

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

The Fluid Mosaic Model Fluid Mosaic Model Mosaic

EQ: What is the difference between diffusion and osmosis?

7.4 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 It is by passive transport through the process of osmosis Facilitated Diffusion transport of larger molecules by use of transport proteins as a pathway Examples: Glucose, sodium ions, and chloride ions must efficiently get across the plasma membrane but to which the lipid bilayer of the membrane is virtually impermeable. Their transport must therefore be "facilitated" by proteins that span the membrane and provide an alternative route or bypass

Passive transport of water across a selectively permeable membrane Type of diffusion through a membrane Movement of water Osmosis

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 sodium and potassium use ion channels (that require ATP) to transport across membranes. This is very important in generating action potentials for nerve stimulation.

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.