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Chapter 6: A Tour of the Cell
Pages 94-123
Concept 6.2
I) Every organism’s basic structure/function unit is either prokaryotic or eukaryotic
A) All cells have the same basic features
1) Plasma membrane: bind the cell together
2) Cytosol: found in the plasma membrane, semifluid substance, all organelles are found
in the cytosol
3) Chromosomes: carry genes in the form of DNA
4) Ribosomes: create proteins based on instructions from genes
Comparison: Eukaryotic & Prokaryotic
Eukaryotic

Chromosomes located in the nucleus, which is
bound by a nuclear envelope

Region between the plasma membrane and
nucleus is known as the cytoplasm (various
membrane bound organelles reside in cytoplasm


Prokaryotic

DNA concentrated in an area known as nucleoid,
no nucleus

Cytoplasm is the interior of the cell, does not
include membrane bound organelles
Tend to be bigger than prokaryotic
 Smaller than eukaryotic
Extensive/elaborate internal membranes which

compartmentalize the cells organelles
B) Plasma membrane
1) The boundary of every cell, a selective barrier that allows oxygen, nutrients, and
wastes to move in and out of the cell.
C) Plant and Animal Cells have mostly the same organelles:
Animal Cell
Plant Cell
In animal cells but not plant cells:



Lysosomes
Centrioles
Flagella
In plant cells but not animal cells:




Chloroplasts
Central Vacuole and Tonoplast
Cell Wall
Plasmodesmata
Concept 6.3
I) Organelle Interaction: Nucleus & Ribosomes
A) Nucleus contains most of the genes of a eukaryotic cell
1) Enclosed by a nuclear envelope which separates its contents from the cytoplasm
(a) Envelope is a double membrane, the two membranes are each a lipid bilayer
(b) The nuclear side of the envelope is lined by the nuclear lamina
(1) A net like array of protein filaments, maintains the shape of the nucleus by
supporting the nuclear envelope
2) Inside the nucleus DNA is organized into chromosomes which carry genetic
information
(a) Each chromosome is made of chromatin
3) Nucleolus, located in the nucleus, synthesizes a special type of RNA( ribosomal
RNA) using DNA instructions
(a) Proteins from the cytoplasm are assembled with rRNA into ribosomal subunits in
the nucleolus
(1) They exit the nucleus through nuclear pores where they are assembled into
ribosomes
(2) Once an mRNA is transported to the cytoplasm, ribosomes translate the
genetic message into a primary structure of a specific polypeptide
B) Ribosomes are protein factories (they carry out protein synthesis) in the cell made up of
ribosomal RNA and protein
1) Ribosomes build proteins in two different locations of the cell
(a) Free ribosomes are suspended in the cytosol
(b) Bound ribosomes are attached to the outside of the ER or nuclear envelope
Concept 6.4
I) The Endoplasmic Reticulum
A) An extensive network of membranes located in the cytoplasm
1) A network of membranous tubules and sacs called cisternae
2) The ER membrane separates the inner compartment (ER lumen) from the cytosol
B) Smooth ER: the outer surface lacks ribosomes
1) Synthesis of lipids
2) Metabolism of carbohydrates
3) Detoxification of drugs and poisons
4) Stores calcium ions
C) Rough ER: ribosomes located on the outer surface of the membrane
1) Manufactures membranes and secretory proteins
2) In some leukocytes, produces antibodies
3) The ER membrane expands and is transferred in the form of transport vesicles to
other components of the endomembrane system
II) The Golgi Apparatus
A) After leaving the ER, many transport vesicles travel to the Golgi Apparatus
1) Products of the ER are modifies and stored before being sent to other spots
B) Consists of flattened membranous sacs (cisternae)
1) Vesicles concentrated in the vicinity of the Golgi apparatus are engaged in the
transfer of material between the parts of the Golgi and other structures
C) Manufactures certain macromolecules by itself
III) Lysosomes
A) Membranous sac of hydrolytic enzymes used to digest macromolecules
1) Hydrolytic enzymes and lysosome membrane are made by the rough ER then
transferred to the Golgi apparatus for processing
B) Carry out intracellular digestion in various ways
1) Phagocytosis: eating by engulfing smaller organisms or other food particles
(a) A food vacuole is formed which combines with a lysosome which digests the
food
IV) Vacuole
A) Carry out hydrolysis
B) Food vacuoles are formed through phagocytosis
C) Contractile vacuoles pump excess water out of the cell to maintain appropriate
concentrations of salt and molecules
D) A central vacuole is found in plant cells surrounded by a membrane called a tonoplast
1) Develops by combination of smaller vacuoles
2) Stores reserves of important organic compounds, repository of inorganic ions
3) Used as a disposal site for metabolic by-products
4) Attributes to cell growth
Concept 6.5
I) Mitochondria and Chloroplasts. Each moves around the cell and can change shape.
A) Mitochondria: the site of cellular respiration
1) Enclosed by two membranes, each a phospholipid bilayer.
(a) The inner membrane divides the mitochondrion into two compartments: an intermembrane space and a mitochondrial matrix
(1) The matrix enzymes and mitochondrial DNA and ribosomes
B) Chloroplasts: the site of photosynthesis
1) Inside the chloroplast are thylakoids organized in stacks called grana
(a) The fluid outside the thylakoids is the stroma which contains chloroplast DNA
and ribosomes as well as enzymes
2) The chloroplast membrane divides it into three sections:
(a) Inter membrane space
(b) Stroma
(c) Thylakoid space
Concept 6.6
I) Cytoskeleton
A) Gives the cell support and maintains its shape as well helps with movement
1) Cell motility (movement) requires the interaction of the cytoskeleton and motor
proteins
B) Regulates the biochemical activities in the cell
C) Components:
1) Microtubules
(a) Shape the cell, guide movement of organelles, help separate the chromosome
copies in dividing cells
(b) Cilia and flagella are appendages that contain the microtubules
(c) In many cells microtubules grow out of centrosomes. Inside the centrosome is a
pair of centrioles which are composed of 9 sets of triplet microtubules arranged in
a ring
2) Microfilaments
(a) Thin rods made up of actin that function in muscle contraction, amoeboid
movement, cytoplasmic streaming, and support for microvilli
3) Intermediate Filaments
(a) Support cell shape and fix organelles in place
Concept 6.7
I) Cell Wall in Plant Cells
A) An extracellular structure which distinguishes plant cells from animal cells
1) Protects the plant, maintains its shape, prevents excessive water intake
II) Extracellular Matrix in Animal Cells (ECM)
A) Animal cells secrete glycoproteins which form the ECM
1) Helps support, adhesion, movement, and regulation