Download Chapter 4 A Tour of the Cell CONTENT I. The Microscopic world of

Bio100’15, Medina
Chapter 4
A Tour of the Cell
Objectives:
1. Define terms in bold. Name the two general types of cells and list their characteristics.
2. Sketch the basic structures found in the cell membrane and provide their functions. Explain how faulty membranes may
cause disease.
3. Compare and contrast several ways in which molecules move across membranes.
4. List the processes by which cells connect and communicate with each other.
5. Sketch an animal and a plant cell, label their organelles and provide their functions. Provide the differences between plant
and animals cells.
CONTENT
The Microscopic world of cells
Cell membrane structure
Nucleus & Ribosomes
Endomembrane System
Chloroplasts & Mitochondria
Cytoskeleton
The Microscopic world of cells
A. Types of Microscopes
Light Compound
Scanning Electron
Factors
Microscope (LM)
Microscope (SEM)
Function
I.
II.
III.
IV.
V.
VI.
I.
Transmission Electron
Microscope (TEM)
Maximum magnification
1,000X
100,000X
100,000X
Special specimen preparation
View using a beam of:
Magnification: size enlargement of object’s image as compared to actual size.
Resolving power (resolution): ability to show two objects as separate points (clarity of magnified image).
B. Cell theory: the cell is the smallest unit of life that can function independently and perform all the
necessary functions of life; all living organisms are made up of cells; and all cells arise from other
pre-existing cells.
Three Domains:
Bacteria
Archaea
Eukaryotes
Prokaryotes (before nucleus)
Prokaryotes (before nucleus)
True nucleus
Ubiquitous
“Extremophiles”
Protista, Fungi, Plants, & Animals
• DNA forming a “nucleoid” region, no nuclear membrane
• DNA enclosed by nuclear membrane
• Smallest cells
• Larger cells
• Unicelullar / colonial
• Mostly multicelullar
• No membrane-bound organelles
• Membrane-bound organelles
• Simple structure
• Complex structure (see below)
• Faster reproduction
• Slower reproduction
• May not need oxygen
• Usually need oxygen
C. Main components of eukaryotic cells:
1. Plasma membrane: enclosing walls or lining; flexible & chemically active
2. Nucleus: double layer of phospholipids encloses the genetic material
3. Cytoplasm: all the contents of the cell
a. Cytosol: medium where everything moves
b. Cytoskeleton: supporting structure
c. Organelles (“little organs”): internal, highly organized structures inside the cell that
serve a specialized function. Theories about the formation of organelles:
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i.
ii.
The Endosymbiosis Theory: Explains that an ancestral prokaryotic cell was
probably engulfed by a larger cell becoming an integral component. Both cells lived
in a mutualistic symbiotic relationship (the little one inside the larger one), this means
they benefited each other. This theory applies to the mitochondria and chloroplasts
because they both perform energy conversions, they both have their own DNA, and
their size is very similar to the size of prokaryotic cells.
Invagination: may explain the formation of the other membrane-bound organelles;
the cell membrane created an inner folding and then it detached itself forming an
organelle, such as the endomembrane system (RER, SER, Golgi).
Sketch & label the main components of a prokaryotic.
Sketch & label the main components of a eukaryotic cell.
Checking:
What type of microscope would you need to observe motion?
What type of microscope would you need to observe the pores on the surface of the nuclear membrane?
How are magnification and resolution different?
Prokaryotic cells are smaller than eukaryotic cells. Eukaryotic cells contain more complex cellular structures than prokaryotic cells. T / F
Eukaryotic cells contain a true nucleus with DNA, whereas prokaryotic cells contain free DNA forming a “nucleoid” T / F
What are the 3 main components of a cell?
What are the contents of the cytoplasm?
II. Cell membrane structure
A. Basic structure: phospholipid bilayer holds the contents of a cell and regulates what enters and exits the
cell. Phospholipids create a hydrophilic external layer combined with a hydrophobic internal layer that
allow for flexibility and regulation.
B. Molecules imbedded in the plasma membrane:
1. Proteins:
a. Transmembrane proteins: penetrate membrane
b.Receptor proteins: bind external chemicals to regulate internal processes
c. Recognition proteins: identify the cell from other cells: HIV and organ transplants,
d.Transport proteins: passageway for molecules
e. Enzymatic proteins: accelerate intra/extracellular reactions
2. Cholesterol: provides flexibility, antifreeze at low temperatures
Sketch & Label a cell membrane
C. Cell Surface:
1. Extracellular matrix: sticky coat that holds cell together in tissues, protection & support.
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2. Cell Junctions: structures that connect cells into tissues in different ways.
3. Cell channels: open channels found in plant cells to join the cytoplasm of neighboring cells.
4. Cell wall: found in plant cells and absent in animal cells; cellulose for protection, strength &
shape.
III.
Nucleus & Ribosomes: genetic control
A. Nucleus:
1. Nuclear membrane: phospholipid bilayer with transmembrane proteins that create pores.
2. DNA and its associated proteins form chromatin fibers that in turn constitute chromosomes:
humans have 46 chromosomes, dogs 78, & rice 24. Regulation of cell’s functions, growth,
characteristics, and even death is regulated by information found in the chromosomes.
3. Nucleolus: Formed by necleolar organizer regions of chromosomes, it also contains proteins and
RNA. Site for synthesis of ribosomal ribonucleic acid (rRNA) (1000/min), it plays a role in the
cell’s response to stress, and produces signal recognition proteins.
B. Ribosomes:
1. Involved in protein synthesis
2. Attached to Rough Endoplasmic Reticulum (RER) or suspended in cytosol; may switch location
C. Endomembrane System
1. Rough Endoplasmic Reticulum (RER)
a. Embedded with ribosomes
b.Synthesis of new membrane for the whole cell
c. Synthesis of proteins with the help of ribosomes
d.Use transport vesicles for protein delivery
2. Smooth ER (SER)
a. Lacks ribsomes
b.Synthesis of lipids
c. Detoxifying enzymes destroy sedatives (sleeping pills), stimulants (amphetamines), some
antibiotics.
d.More SER production increases tolerance to drugs addiction
3. Golgi Apparatus
a. Receives, refines, stores, distributes products
b.Stack of membranous plates receive proteins on one side, modify them (adding phosphate
groups, carbohydrates) in the middle plates, and ship them on the opposite end of the
plates within transport vesicles that may be carried to the plasma membrane for
exocytosis.
4. Lysosomes
a. Sac of digestive enzymes in animal cells, absent from most plant cells
b.Safe compartment for digestion of proteins, polysaccharides, fats, nucleic acids
c. May fuse with food vesicles
d.Destroy harmful bacteria (white blood cells)
e. Break down worn out organelles
f. Sculpting functions in embryonic development: destroy webbing between fingers
g.Tay-Sachs Disease (TSD): hereditary, lysosomes lack a lipid-digesting enzyme, this
accumulation of lipids destroys nerve cells leading to paralysis, dementia, blindness,
psychosis, and even death. Prevalent in Ashkenazi Jewish from Eastern Europe; 1/27
Jews in USA is a carrier of the TSD gene.
http://www.who.int/genomics/public/geneticdiseases/en/index2.html#ts
http://www.zo.utexas.edu/faculty/sjasper/bio301L/gendisorders.html neuron w/TS
5. Vacuoles
a. Large sacs of membrane
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b.Freshwater protists: contractile vacuoles pump water out the cell
c. Plant cells: central vacuole stores 90-98% water (turgor pressure), organic nutrients, may
contain pigments & poisons.
D. Chloroplasts & Mitochondria: Existence explained by endosymbiotic theory: a smaller simpler cell
became an important component of a larger cell. Basis for this theory: these organelles have their own
DNA, produce energy, and are similar in size to prokaryotic cells.
1. Chloroplasts
a. Found in all plants and eukaryotic algae
b.Site of photosynthesis: conversion of sunlight energy into chemical energy
(carbohydrates) with oxygen as a by-product.
c. Structures: chloroplast membrane, grana made of thylakoids, stroma (thick fluid).
Sketch & label the components of a chloroplast
IMPORTANT NOTE: 3 organelles found only in plants and absent in animal cells:
___________________________
___________________________
___________________________
2. Mitochondria
a. Transform organic energy molecules into ATP (energy form needed for cell work)
b.Plants & animals, almost all eukaryotic cells
c. Structures: outer and inner membranes, matrix, intermembrane space, cristae.
Sketch & label the components of a mitochondrion:
E. Cytoskeleton
1. Network of protein fibers
2. Mechanical support, shape
3. Anchorage & reinforcement for organelles
4. Dynamic: changes the cell shape (crawling as in Amoeba & some white cells)
5. Different types of proteins: microtubulesstraight, hollow; intermediate filaments &
microfilamentsthinner & solid
6. Types of locomotion by microtubules (cell movement)
a. Cilia: hair-like, short projections, often in large numbers, beat swiftly. They clear airways
to our lungs, tobacco smoke can inhibit or destroy them.
b.Flagella: tail-like extension, whiplike motion, one or more, found in many prokaryotes
and single-celled eukaryotes (in animals: the sperm cell).
Checking:
Connect the cellular structure or molecule to its function:
Nucleus
Involved in protein synthesis
DNA +histones
distribution center to final destination
mitochondria
regulates exit and entry of molecules to the cell
RER & ribosomes
condensed chromatin
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chloroplast
Information center containing DNA and nucleolus ( RNA)
Transport vesicle
Chromatin
Golgi complex
Lipid synthesis and detoxification
Cell membrane
Photosynthesis
chromosome
transforms organic energy molecules to ATP
SER
Transports proteins and other substances within the cell
Fats are synthesized in the ________________________________
What organelle has the ability to get rid of old and foreign cellular material in the animal cell? ____________________
Cilia are ____________(tail-like or hair–like), flagella are____________(tail-like or hair-like)
Name 3 organelles found in a plant cell and absent in an animal cell:___________________________________________________________
In the plant cell, what organelles possess the following functions?
Photosynthesis: ___________________________
Storage of water, nutrients, wastes, and pigments:_____________________________
Structural strength and protection:__________________________
Plant cells communication: permanently open channels called_______________________________
How do animal cells communicate?__________________________________________________________________________
Questions 1,3,4,6-12 in your textbook p. 7
--------------------------------------------------------------------------------END-----------------------------------------------------------------------------HOMEWORK: Chapter 5: Energy (1 pt)
Answer the following:
1. Define Energy
2. Define Potential energy
3. Define Kinetic energy
4. ATP stands for:
5. Provide the 3 main kinds of work ATP does in a cell.
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