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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: Page 1 of 5

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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. Page 2 of 5

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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 Page 3 of 5

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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 Page 4 of 5

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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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