Download Biology – II Honors Welcome to Cells! Chapter 4

Biology – II Honors
Welcome to Cells!
Chapter 4, Pages 54 – 69
I.
Surface Area to Volume ratio
A. Why do cells remain small?
II.
Prokaryotic Cells
A. Does not have a nucleus
B. Flagellum – for locomotion
C. Contain plasma membrane
D. All have ribosomes
E. Have genetic material/information
F. Has cytoplasm
G. DNA is coiled into a region called the nucleoid
H. Examples: Bacteria, Archaea
III.
Eukaryotic Cells
A. Domain Eukarya: Kingdoms of Fungi, Protists, Animalia, Plantae
B. Membrane-bound structures called organelles (tiny organs)
C. Four basic functional groups of organelles:
1. Manufacturing
a. Nucleus: hereditary material
b. Ribosomes: proteins
c. Endoplasmic reticulum:
a. Smooth ER: (w/o ribosomes)
i. Produces lipids, including oils, phospholipids, and steroids
ii. Stores calcium ions
b. Rough ER: (w/ribosomes)
i. Makes more membrane
ii. Involved with production of proteins with the ribosomes.
Example: insulin, a secretory protein.
d. Golgi apparatus (bodies) – Green Bay Packers
a. Receives and modifies products manufactured by the ER
b. Packages substances in vesicles for movement to other parts of the cell
and out of the cell
c. Gives rise, or makes, the lysosomes
2. Hydrolysis of macromolecules
a. Lysosomes
a. Contain digestive enzymes
b. Used in protists to digest ingested food particles
c. White blood cells, lysosomes break down the bacterial cell walls
d. Recycling centers for animal cells, break down used cell parts.
b. Vacuole
a. Storage
b. Central vacuole used by plant for storage and to maintain turgor in
plants; may also contain poisons which protect plant from animals
c. Paramecium contain contractile vacuoles used to maintain water
balance within the cell.
c. Peroxisome
a. Involved in metabolic functions
b. Breakdown fatty acids to be used for fuel
c. Detoxifies alcohol
3. Energy processing
a. Mitochondria – powerhouse of the cell
a. Carry out cellular respiration
b. Aerobic (w/O2) or anaerobic (w/o O2) respiration
c. Break down glucose (sugar) to ATP for energy use in the cell.
b. Chloroplast
a. Converts solar energy to chemical energy
b. Process of photosynthesis
c. Stores energy in the sugar molecule (glucose)
IV.
4. Support, movement, communication
a. Cytoskeleton – non-membranous, protein tubules, microfilaments
b. Plasma membrane – bilayer of phospholipids
c. Cell wall – found in plants, fungi, and some protists
Plant cell walls are different in that they contain cellulose, a
polysaccharide.
D. Reasons for Compartmentalization
1. Chemical activities – collectively known as cellular metabolism
2. Many enzymatic proteins built into membranes of organelles
3. Organelles essentially fluid-filled sacs where specific chemical conditions maintained
for the metabolic processes to occur that are specific to that organelle
EXAMPLE: ER makes steroid hormones. Not far from the ER within the cell is
the Peroxisome which makes harmful H2O2 while detoxifying harmful
compounds. The H2O2 is confined within the Peroxisome where it is quickly
converted to H2O, thereby protecting the rest of the cell from destruction.
Structure of Membranes
A. Main component of biological membranes are phospholipids (See Fig. 4.5A)
B. Forms bilayer of phospholipids. Hydrophilic, polar heads face external and internal
environment; hydrophobic, non-polar fatty acid tails face inwardly
C. Structure of the plasma membrane includes:
D.
D. Diverse proteins are embedded in bilayers
E. Permeability of the membrane relates to the properties of the lipid bilayer
F. Some proteins form channels that allow specific ions and hydrophilic molecules to cross the
membrane
V. Nucleus: Cell’s Genetic Control Center
A. Directs protein synthesis
B. Contains most of cell’s DNA
1. Chromosomes made of chromatin
2. Chromatin is complex of proteins and DNA
3. During synthesis, DNA copied and thin chromatin fibers coil up, forming chromosomes
C. Enclosed by the nuclear envelope
1. Double-membrane with protein-lined pores
2. Controls flow of material into and out of the nucleus
3. Connects with endoplasmic reticulum (ER)
D. Nucleolus
1. Site of ribosomal RNA (rRNA) synthesis
2. Proteins brought in through nuclear pores from cytoplasm assembled with rRNA to
form subunits of ribosomes
3. Subunits exit through pores to cytoplasm – join together to form functional
ribosomes.
E. Directs protein synthesis by also making messenger RNA (mRNA), which then moves to
ribosomes in the cytoplasm where it is translated into amino acid sequences of proteins.
VI. Ribosomes make proteins
A. Carry out protein synthesis
B. Found in 2 locations in the cell
1. Free – suspended in fluid of cytoplasm
2. Bound – attached to ER or Nuclear envelope
3. Structurally identical
4. Can alternate between the 2 locations
5. Composed of a large and a small subunit (Fig. 4.7, pg. 59)
C. Free ribosomes function within cytoplasm
1. EXAMPLE: enzymes that catalyze 1st steps of sugar breakdown
D. Bound ribosomes
1. Make proteins that will be inserted into membranes, packaged in certain organelles,
or exported from the cell
VII. Endomembrane System
A. Include the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles,
and the plasma membrane
B. Many of these organelles work together in synthesis, storage, and export
C. Some are physically connected and some are related by transfer of membrane segments by
tiny vesicles
1. EXAMPLE: Some of the ER membranes are continuous with the nuclear envelope;
tubules and sacs of the ER enclose interior space separate from cytoplasmic fluid.
Dividing cell into separate compartments is major function of endomembrane system.
VIII. Endoplasmic reticulum
A. Review Fig. 4.9A, pg. 60
B. Smooth ER:
1. Does NOT have ribosomes attached
2. Enzymes in smooth ER important in synthesis of lipids, including oils, phospholipids,
and steroids
3. Smooth ER of the ovaries and testes synthesize steroid sex hormones
4. Human liver also contains large amounts of smooth ER
a. Help process drugs and other potentially harmful substances
b. Side effect, the cell will produce additional smooth ER in response to exposure
to certain drugs. This increases the detoxifying enzymes required to process
the drugs. The increased amount of smooth ER and detoxifying enzymes,
however, increases the body’s tolerance to the drugs. Thus, higher and higher
doses of a drug are needed to achieve an effect, such as sedation.
c. Growth of smooth ER in response to one drug can increase tolerance to other
similar drugs. This stems from the fact the detoxifying enzymes cannot
distinguish between related chemicals.
5. Function as calcium ion storage as well, particularly in muscle cells.
C. Rough ER: (Review Fig. 4.9B, pg 60)
1. Bound ribosomes attached
2. Functions:
a. Make more membrane; phospholipids made by enzymes in rough ER inserted
into membrane.
b. Produce proteins that will be inserted into ER membrane, transported to other
organelles, or secreted by the cell
c. EXAMPLE of secretory protein: Insulin, which is a hormone secreted by certain
cells in the pancreas.
IX. Golgi Apparatus
A. Membranous organelle discovered by Camillo Golgi
B. Consists of flattened sacs stacked on top of each other, but not interconnected
C. # of Golgi stacks depends on the type of cell and how active the cell is in secreting proteins
D. Works with ER by receiving and modifying products manufactured by the ER
1. Receiving
a. One side of Golgi acts as receiving dock for transport vesicles from ER. Vesicles
join and form new Golgi sac
b. Other side of Golgi acts as the shipping center by creating vesicles which bud
off and travel to other sites
2. Modifying
a. Modify products from ER as it moves from receiving to shipping side
b. EXAMPLE: Golgi enzymes modify carbohydrate portions of glycoproteins OR
molecular ID tags added, such as phosphate groups, to mark and sort
molecules into different batches for different destinations in and out of the
cell
3. Shipping
a. Secretory products packaged in transport vesicles (TV)
b. TV move to plasma membrane, join with the plasma membrane, release
product outside of the cell OR
c. TV join to plasma membrane where finished product becomes part of the
plasma membrane or part of another organelle, such as a lysosome
E. Not a static structure.
1. Believed each sac matures as it moves from receiving to shipping side, carrying and
modifying cargo (molecular products) as they go
X.
Lysosomes
A. Digestive enzymes contained in a membranous sac
B. Enzymes and membrane made by rough ER, then transferred to Golgi for further processing
C. Great example of compartmentalization. Acidic environment provided for enzymes, but
membrane keeps these safely isolated from the rest of the cell
D. Function:
1. Food digestion: protists engulf food particles into food vacuoles; lysosomes fuse with
food vacuole and release digestive enzymes which break down the food, thereby
releasing the nutrients to the cell
2. Immunology: white blood cells ingest invading bacteria into vacuoles; lysosomes fuse
with these vacuoles and release digestive enzymes which break down bacterial cell
walls, thereby destroying the bacteria
3. Recycling: break down damaged or dead cell parts
4. Pathology: in Tay-Sachs disease, lipid-digesting enzymes are missing; brain cells
become impaired by the buildup of undigested material and accumulation of lipids;
child with Tay-Sachs will die within a few years
XI. Vacuoles
A. Membranous sacs
B. Function:
1. Plant Cell: Central Vacuole
a. Helps cell grow in size by absorbing water and enlarging
b. Stores vital chemicals
c. Stores waste products
d. In Flowers: stores pigments that attract pollinating insects
e. Contain poisons that protect the plant against predators
X.
Peroxisome
A. Not part of the endomembrane system
B. Involved in various metabolic functions
1. Break down of fatty acids to be used as fuel
2. Detoxification of alcohol and other harmful substances
XII. Mitochondria
A. Carry out cellular respiration in nearly all eukaryotic cells
B. Converts chemical energy of food (glucose/sugars) into chemical energy of ATP (adenosine
triphosphate)
C. ATP main energy source for cellular work
D. Structure:
1. Two membranes, each a phospholipid bilayer
2. Unique collection of embedded proteins in the membranes
3. Two internal compartments
a. Intermembrane space – narrow region between inner and outer membranes
b. Mitochondrial matrix – enclosed by the inner membrane; contains
mitochondrial DNA and ribosomes, as well as many enzymes that catalyze
cellular respiration reaction
c. Inner membrane highly folded; folds called cristae
a. Embedded with protein molecules that make ATP
b. Cristae increase surface area, which enhances ability to produce ATP
XIII. Chloroplast
A. Photosynthesizing organelle of all photosynthetic eukaryotes
B. Converts light energy from sun to chemical energy of sugar molecules
C. Structure:
1. Inner and outer membrane separated by thin intermembrane space
2. Stroma: thick fluid within the intermembrane space that holds the chloroplast DNA
and ribosomes, as well as many enzymes necessary for Photosynthesis
3. Network of interconnected sacs called thylakoids
a. Within each thylakoid is the thylakoid space
b. Multiple thylakoids are stacked like coins
c. The stacks are called granum; grana are multiple stacks of thylakoids
d. The grana are the chloroplast’s solar power packs; site where the green
chlorophyll embedded in the membrane traps solar energy
XIV. Endosymbiosis
A. Similarities of mitochondria, chloroplasts, and prokaryotic cells
1. M/C contain singular DNA molecule, similar to chromosome of prokaryotes
2. M/C ribosomes more similar to prokaryotic ribosomes
3. M/C reproduce by splitting process similar to certain prokaryotes
4. M/C surrounded by double membrane; inner membranes have similarities to plasma
membranes of living prokaryotes
B. Endosymobiosis
1. Proposes M/C were formerly small prokaryotes that began living within larger cells
2. Endosymbiont – refers to a cell living within a host cell
3. Proposes small prokaryotes may have gained entry to larger cell as undigested prey or
internal parasites. (See Fig 4.16, pg 64)
4. Host and endosymbiont became interdependent through photosynthesis and cellular
respiration, thus evolving into the first eukaryotes
C. All eukaryotes have mitochondria, but not all eukaryotes have chloroplasts
D. Serial endosymbiosis proposes that mitochondria evolved before chloroplasts (?) What do
you think?
XV. Cell’s Internal Skeleton
A. Cytoskeleton – network of protein fibers within the cell
1. Provide structural support
2. Cellular motility/locomotion
B. Three types
1. Microfilaments
a. Thinnest
b. Called actin filaments
c. Solid rods composed of globular proteins called actin
d. Twisted double chain
e. Supports cell’s shape
f. Interact with myosin to cause muscle contractions
EX: Crawl-like motion of white blood cells
2. Intermediate filaments
a. Made of various fibrous proteins
b. Ropelike structure
c. Reinforce cell shape
d. Anchor certain organelles
EX: Nucleus held in place by cage of
intermediate filaments
e. Can be disassembled and reassembled where needed
3. Microtubules
a. Straight, hollow tubes composed of globular proteins called tubulins
b. Thickest
c. Elongate by adding subunits of tubulin
d. Can be reused elsewhere
e. Grow from “microtubule-organizing center” – the centriole
f. Shape and support
g. Act as tracks along which motor proteins move organelles and other structures
h. Main component of Cilia and Flagella
XVI. Cilia and Flagella
A. Eukaryotic Cells
1. Paramecium use cilia to move
2. Sperm use flagellum to “swim”
B. Multicellular organisms
1. Cilia sweep mucus and debris from lungs
C. Movement
1. Cilia movement is similar to the movement of coordinated oars
2. Flagellum have an undulating whiplike motion
D. Structure
1. Both are composed of microtubules wrapped in extension of plasma membrane
2. Ring of 9 microtubule doublets surrounds a central pair of microtubules
a. Called the 9 + 2 pattern
b. Basal body is the anchoring structure; similar in structure to centrioles
c. Dynein arms, motor proteins, grab adjacent doublets and exert a sliding force
as they “walk” along the doublet, which causes the bending motion necessary
for movement.
(Interesting application for the study of cilia, see section 4.19 in your book and read about the research
being undertaken to study sperm motility which, in one study, is related to respiratory issues as well.
Explain the connection between the sperm immotility and recurrent respiratory infections.)
XVII. Extracellular matrix (ECM)
A. External to the cell, holds cells together in tissue
B. Protects and supports the plasma membrane
C. Main components
a. Glycoproteins (proteins bonded with carbohydrates)
i. Collagen, which forms strong fibers outside of the cell, is an example of a
glycoprotein. Most abundant glycoprotein. These fibers are embedded in a
network woven from other types of glycoproteins
b. Large complexes form when hundreds of glycoproteins attach to a central long
polysaccharide molecule
c. Attaches to cell through other glycoproteins that bind to membrane proteins.
i. EXAMPLE: Integrins, which span the membrane and attach to proteins on the
other side of the membrane. These proteins are attached to microfilaments of the
cytoskeleton
D. Integrins transmit information between the ECM and cytoskeleton
E. Integrate changes occurring outside and inside the cell
F. Can regulate cell’s behavior, directing the path along which embryonic cells move and influencing
the activity of genes.
G. ECM of particular tissue may help coordinate behavior of all cells in that tissue
XVIII. Cell Junctions and Communication
A. Three types found in all animal tissues
1. Tight junctions: cells knit together by proteins, form continuous seals around cells,
prevent leakage of extracellular fluid across layer of epithelial cells
a. EXAMPLE: sheet of tissue lines the digestive tract, preventing the contents
from leaking into surrounding tissues.
2. Anchoring junctions: function like rivets, fasten cells to form strong sheets, keratin
proteins anchor junctions in cytoplasm
a. EXAMPLE: common in tissue subject to stretching and mechanical stress such
as skin and heart muscle
3. Gap junctions: AKA communicating junctions, channels through which small
molecules flow through protein-lined pores between neighboring cells.
a. EXAMPLE: flow of ions through gap junctions in cells of heart muscle
coordinating their contractions
XIX. Cell Wall
A. Rigid extracellular structure
B. Protects
C. Provides skeletal support
D. Consist of fibers of cellulose embedded in a matrix of other polysaccharides and proteins.
(resembles fiberglass)
E. Plasmodesmata: channels between adjacent plant cells form a circulatory and
communication system
F. The cells of plant tissue share water, nourishment, and chemical messengers.