chapter 7 cell structures
DESCRIPTION
Chapter 7 Cell Structures. Viruses - Considered nonliving in biology a. protein coat- capsid b. DNA/ RNA core. Prokaryotes vs Eukaryotes. *** Common features : - Cell membrane, cytoplasm, chromosomes, ribosomes. Contributions to Cytology :. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 7Cell Structures
Viruses- Considered nonliving in biologya. protein coat- capsidb. DNA/ RNA core
Prokaryotes vs EukaryotesProkaryotes EukaryotesNo nucleus- DNA in nucleiod area(DNA- circular/ no histone proteins)
Nucleus- DNA stored here(DNA- linear/ along w/ histone proteins)
Lacks membrane bound organelles Contains specialized organellesUnicellular MulticellularSmaller/ simpler Larger/ complex1-10 microns in diameter 10-100 microns in diameterDomain Bacteria & Archaea Domain Eukarya Kingdoms:
Protista, Fungi, Plantae, Animalia
*** Common features:- Cell membrane, cytoplasm, chromosomes, ribosomes
Contributions to Cytology:a. Robert Hooke (1665)- 1st to observe cells viewing
a slice of cork/ coined to the term “cells”b. Anton van Leeuwenhoek- 1st to view living cells
(protists- “animalcules”)c. M.J. Schleiden (1838)- plants composed of cellsd. Theodor Schwann (1839)- animals composed of
cellse. Robert Virchow (1858)- cells come from pre-
existing cells
Cell Theory
• Schleiden, Schwann, and Virchow contributed to the cell theory
1. All living things are composed of cells2. Cells are the basic unit of structure and
function3. Cells produced from pre-existing cells
Eukaryotic Cell Structures
• Domain Protista, Fungi, Plantae, and Animalia• Organelle “Little organ”
– Specialized subunits within a cell that has a specific function
– Usually enclosed within its own membrane
*** NOTE: [*] =These structures contain DNA and are capable of replication
a. Cell Membrane (Plasma membrane)
• Double layer of protein and lipid around ALL cells
• Separates the interior of a cell from the outside environment
• Semi-permeable (selective) allows only certain substances to pass through
Cell Membrane- Lipid Bilayer
b. Cell Wall
• Rigid, nonliving structure outside the cell membrane
• Not present in Animals, but present in: 1. Plants & some protists (algae) cellulose- provides support to cells2. Fungi chitin
c. Nucleus
• Double membrane bound organelle• Contains genetic material DNA• Known as the “control center of the cell”
d. [*] Chromosome
• Found within nucleus• Single DNA molecule• Segments represent
different genes • Within eukaryotic cells:
composed of DNA and proteins chromatin
• Principal nuclear structure visible during cell division
e. Nucleolus (i)• Small dense organelle within nucleus• Contains DNA, RNA, & protein• Within eukaryotic cells:assemble ribosomes
• Lily parenchyma cell (TEM x7,210) Note the large nucleus and nucleolus in the center of the cell
f. Nuclear Membrane (Envelope)
• Double membrane that surrounds the nucleus• Semi-permeable (selective)• Consists of protein-lipid molecules
g. Cytoplasm (Cytosol)
• All living material between the nuclear and plasma membrane
• Semi-liquid substance that contains organellesEx: ribosomes, chloroplasts, mitochondria
h. Ribosomes• Small organelles composed of
ribosomal RNA (rRNA) and proteins• 2 types:
1) Attached - Found on rough endoplasmic reticulum (RER) - Synthesizes extracellular proteins
2) Free - Found in cytoplasm - Synthesizes intracellular proteins
***[NOTE: Protein functions= a. enzymes/ b. structural parts]
i. [*] Mitochondrion (ia)• Double membrane bound
organelle• Produces ATP energy for ALL
cells• Contains own DNA and
ribosomes• Site of cellular respiration (Krebs
Cycle, respiratory chain, and oxidative phosphorylation)
j. Endoplasmic Reticulum (ER)
• Extensive system of membrane present in most eukaryotic cells
• Material transported through these channels and canals
• May connect to nuclear or cell membranes
Cont. Endoplasmic Reticulum• 2 types:
1)Rough ER (RER) - Ribosomes attached to RER/gives “rough” appearance - Synthesizes proteins and other materials for export
2) Smooth ER (SER) - No ribosomes attached
- Synthesizes lipids and steroids - Metobolizes CHOs - Detoxify drugs and poisons
k. Golgi Apparatus
• Layer of flattened, disc-shaped sacs, tubules, and vesicles near nucleus of gland cells
• Synthesizes cell secretions
• Source of lysosomes
l. Vacuoles
• Membrane-bound sac• Transport raw materials
to cell interior• Also transport wastes• Used for storage of
water/ food• In plant cells: typically
large and central
Vacuole in Plant Cell
m. Lysosomes• Double membrane bound sac
containing hydrolytic enzymes- Hydrolytic (“water-splitting”) breakdown substances by adding H2O
• Fuse with food vacuoles to digest contents
• “Suicide bag” digest cytoplasm if membrane ruptures
• - Present in white blood cells (WBC): leukocytes
n. [*] Plastids• Cytoplasmic, often pigmented
organelle in plant cells
• Includes:1. Amyloplast - Stores starch - Root and internal stem tissue- not exposed to light
2. Chromoplast - Contain variety of carotenoids yellow, red, orange pigments/ - Ex: carrots, tomatoes
Parenchyma cell containing chromoplasts: each red dot is a chromoplast that contains carotenoids
Amyloplasts in a potato cell
Cont. Plastids3. Chloroplast
- Contain carotenoids and chlorophylls a, b, c, d, e
- Contains DNA and ribosomes- Site for photosynthesis
o. Cytoskeleton
• Network of protein scaffolding or “skeleton” of the cytoplasm
• Provides shape, organization, and movement
• Consists of: 1. Microfilaments
- Thinnest, solid protein
tubules - Hold organelles in place - Enable cells to change
shape 2. Intermediate Filaments
Cont. Cytoskeleton3. Microtubules - Thickest, hollow protein rods
- Provides shape and support to cells- Serve as “tracks” for organelles to move on- Makes up the following:
a. [*] Centrioles • Forms spindle pole during mitotic and meiotic
cell division• Found in pairs at right angles near nucleus of
animal cells• Have own DNA• Microtubules in triplets• Present ONLY in animal cells
Cont. Microtubulesb. Cilium (ia)
• Short, numerous structures embedded in the surface of some eukaryotic cells
• Arranged in rows (9 + 2 arrangement of microtubules)
• Involved in locomotion and movement of substances across surface
c. Flagellum (a)• Long, single threadlike organelle • Used in locomotion• 9 +2 arrangement of microtubules
p. Kinetosome• Motion-controlling granules at
base of flagella and cilia q. Fibrils• Protein molecules that form
spindles during plant and cell division
• Functions in specialized cells: a. muscle contractionb. nerve cells carry impulses
r. Pinocytic Vesicle• Indentation in cell membrane
which results in vacuole formation
• 2 types:1) Pinocytosis -“Cell drinking” - Intake of fluid by cell2) Phagocytosis - “Cell eating” - Intake of solids - Function of WBC
(leukocytes)
s. Contractile Vacuole• Expels excess water in freshwater organisms
placed in hypotonic environment/ ex: distilled water
• Maintains appropriate concentrations of salts and other molecules
EUKARYOTIC CELLS PROKARYOTIC CELLS
Nucleus present? Yes, organized No, lack nuclear membrane
Membrane-enclosed organelles present?
Yes No
Chromosomes present? Yes, in pairs Yes, single
Cytoplasmic streaming present? Yes No
Cell division by mitosis? Yes No
Type of flagella present? Complex Simple
Type of ribosomes present? Large Small
Type of cytoskeleton present? Complex Simple
Cellulose present in cell wall? Yes No
DNA bound to histone proteins? Yes No
Prokaryotic Cell Structures
- Domain Archeabacteria and Eubacteria
a. Plasmid small circular DNA separated from main chromosomeb. Mesosome infolding of plasma membrane significant in copying DNA prior to divisionc. Nucleiod area of cell containing the main chromosome
Prokaryotic Replication