Chapter 7 Cells
7.1 Discovery of Cells Cell Theory 1.All organisms are composed of one or more cells 2.The cell is the basic unit of structure and organization of living things 3.All cells come from preexisting cells
Types of Cells 1. Prokaryotes- cells that lack membrane- bound organelles, no nucleus Example- bacteria 2. Eukaryotes- cells that have organelles and nucleus Example- plants, animals, fungi, protists
Types of Microscopes 1. Light Bends light coming through object Limited to x magnification Living cells and tissues Inexpensive, mobile, easy to use
Light Microscope Image
2. Scanning electron microscope (SEM) Bounces electrons off surface of object 10,000-20,000x magnification Specimen must be sacrificed Expensive, large, extensive training required
SEM Image
Transmission electron microscope (TEM) Electrons travel through thin sections of specimen 100, ,000x magnification Specimen must be sacrificed Expensive, large, extensive training required
TEM Image
7.2: Plasma Membrane Plasma membrane- flexible boundary between a cell and its environment AKA cell membrane and phospholipid bilayer Demonstrate the function of the cell membrane and explain its role in maintaining homeostasis
Functions: Allow steady supply of nutrients into the cell Examples- oxygen, water, glucose Allow wastes and products of cell metabolism to leave the cell Examples- carbon dioxide, water, wastes Demonstrate the function of the cell membrane and explain its role in maintaining homeostasis
Selective Permeability Membrane allows some molecules to pass through while keeping others out The plasma membrane is picky! Demonstrate the function of the cell membrane and explain its role in maintaining homeostasis
Structure of the Membrane Phospholipid- lipid molecule composed of: Glycerol Phosphate group 2 fatty acids Demonstrate the function of the cell membrane and explain its role in maintaining homeostasis
Structure of the Phospholipid Molecule Head- polar, hydrophilic- “water-loving” Tail- nonpolar, hydrophobic- “water- fearing” Phospholipid molecules are arranged in two layers- tails facing each other to form the…. Demonstrate the function of the cell membrane and explain its role in maintaining homeostasis
Phospholipid bilayer- 2 layers of phospholipid molecules Because of nonpolar inner layers, cells can maintain their structure in a water environment and not dissolve! Demonstrate the function of the cell membrane and explain its role in maintaining homeostasis
Other components of the membrane: Cholesterol- helps stabilize proteins, keeps tails from tangling Proteins- move needed substances or waste materials through the membrane, attach cell membrane to inner cellular structures, help to identify cells & chemical signals (along with surface carbohydrates) Demonstrate the function of the cell membrane and explain its role in maintaining homeostasis
Plasma Membrane Demonstrate the function of the cell membrane and explain its role in maintaining homeostasis
Domains of Living Things All living things are divided into two Domains: Prokarya Eukarya
Prokaryotes Examples- bacteria and Archaea Small- 2-8 um Structurally simple
Prokaryotic Cell Structure Cell wall- composed of lipids, carbohydrates, & protein- no cellulose Plasma membrane- encloses cell Mesosome- in-folding of the plasma membrane involved in secretion & copying of chromosome Singular chromosome- circular, double- stranded DNA
Nucleoid region- general area where chromosome is located Plasmids- smaller, circular DNA molecules
Generalized Prokaryote
Great Diversity in Metabolic Processes Nutrient cyclers Decomposers Photosynthetic Source of antibiotics Mostly beneficial, some detrimental to human health
Eukaryotes Examples- everything but bacteria um Internally complex- organelles
Organelles Any part of a eukaryotic cell that has its own structure and function
Why have organelles? Many reactions that occur in cells are not compatible and need to be separated from each other Division of labor- Specific processes are isolated in organelles
Cell wall Found in plants, fungi, and prokaryotes Provides support and protection Outside of plasma membrane
Generalized Plant Cell
Cytosol Protein-rich semifluid Surrounds and bathes organelles Mostly water
Cytoplasm Cytosol plus all the other organelles
Nucleus Genetic control center Enclosed by two membranes- nuclear envelope Contains chromosomes (DNA)
Nucleolus Small body inside nucleus Involved in cell division and RNA production
Endoplasmic reticulum (ER) System of membranes and tubes that connects other organelles Snuggled up next to nucleus 2 types: Rough ER- covered in ribosomes Smooth ER- no ribosomes
Ribosomes Small, spherical bodies found throughout cell Location of protein synthesis
Golgi apparatus or body System of vesicles and tubes Next to ER Final assembly of proteins Transport of materials throughout cell
Vesicles Spherical membranes that pinch off of Golgi body Carry materials to other organelles and to plasma membrane for export
Lysosome Contains enzymes that break down old molecules for recycling
Vacuole Contain water, enzymes, & pigments Plant cells have one large vacuole that dominates cell; animal cells have several small vacuoles
Chloroplasts Double membrane Location of photosynthesis Found in plant cells and other autotrophic one-celled organisms
Mitochondria Double membrane Where ATP synthesis occurs Found in animal and plant cells
Centrioles Barrel-shaped organelle Involved in cellular reproduction Found in animal cells
Cytoskeleton and Related Structures Internal skeleton helps organize structure and activities of the cell
Cytoskeleton Functions in support, cell movement, cell signaling Three-dimensional network of:
1. Microfilaments- cell movement 2. Intermediate filaments- anchor organelles 3. Microtubules- guide movement of organelles through the cell, allow for movement of cilia and flagella All are composed of protein
Cilia Short extensions of plasma membrane Composed of microtubules Move materials across cell surface, cover surface
Flagella Long extensions of cell surface Composed of microtubules Move cell through the environment