Download “The Cell”

“The Cell”
I)
Section 7.1 Life is Cellular
History:
 Hooke (1665) – observed cork – named the cell
 Leeuwenhoek (1675) – observed living cells in pond water
 Schleiden (1838) – plants are made of cells
 Schwann (1839) – animals are made of cells
 Virchow (1858) – cells come only from other cells
A) The Cell Theory
1) All living things are composed of 1 or more cells
2) Cells are the basic units of structure and function in living things
3) New cells are produced only from existing cells
B)
Basic Cell Structures
1) Cell Membrane – thin, flexible barrier around the cell
2) Cell Wall – strong layer around cell membrane
3) Nucleus – contains cell’s genetic material and controls the cell’s activities
4) Cytoplasm – the fluid material inside of the cell membrane (does not include the nucleus)
C) Prokaryotes and Eukaryotes
1) Prokaryotes – no nucleus or membrane bound organelles

small and simple

unicellular

single, circular molecule of DNA

oldest known cells

Ex: bacteria
2) Eukaryotes – have a nucleus and membrane bound organelles

contains organelles (structures specialized to perform specific functions within the cell)

unicellular/multicellular
II) Section 7.2 Cell Structures
A) Cell Wall – provides support and protection for the cell; allow water, oxygen, carbon dioxide and other
substances to pass through

found in plants, algae, fungi, most prokaryotes

animal cells DO NOT have a cell wall

mostly made of cellulose (tough carbohydrate fiber) and protein

lies outside cell membrane
*Cellulose is the main component of wood and paper*
B) Nucleus – controls cell processes and contains genetic information
1) Chromatin – protein with DNA bound to it
2) Chromosomes – chromatin condensed; distinct, threadlike structure containing genetic information
3) Nucleolus – small, dense region within nucleus; ribosomes made here
4) Nuclear Envelope – double membrane layer that surrounds nucleus; contains thousands of “nuclear
pores” for material to move in and out of the nucleus
C) Cytoskeleton – a network of protein filaments that help cell to maintain its shape; also involved in cell
movement
1) Cytoskeleton is made up of:
(a) Microtubules – hollow tubes of protein; they maintain cell shape and serve as “tracks” for organelles to
move

Important in cell division – makes centrioles (not found in plant cells)

Form hairlike projections (cilia, short hairlike and flagella, long whip like tail) at cell surface; allows
cell to swim rapidly through liquids
(b) Microfilaments – long, thin fibers that function in movement and support of cell

more narrow than microtubules

produce tough, flexible framework to support cell
D) Organelles (little organs)
1) Ribosomes – site of protein synthesis; found free or attached to ER
2) Endoplasmic Reticulum – transport system

Rough ER – ribosomes are attached; parts of cell membrane are made here; proteins are modified

Smooth ER – does not have ribosomes attached; contains enzymes to perform specialized tasks;
makes lipids
3) Golgi Apparatus (Golgi Body) – packaging and distribution of proteins
4) Lysosomes – contains digestive enzymes to break down food and old organelles
5) Vacuoles – stores water, food and waste

Plants have single large central vacuole

Smaller vacuoles involved in transport are called vesicles
6) Chloroplasts – site of photosynthesis

contains green pigment, chlorophyll

has double membrane

not found in animal cells
7) Mitochondria – produces energy through respiration

“powerhouse” of the cell

has double membrane
III) Diversity of Cellular Life
A) Unicellular Organisms
B) Multicellular Organisms
C) Levels of organization
1) Cells
2) Tissues
3) Organs
4) Organ systems