Topic 1: Cells Cell Theory Discuss the theory

Topic 1: Cells Cell Theory Discuss the theory

Topic 1: Cells Cell Theory Discuss the theory that living organisms are composed of cells. The Cell Theory states that: All organisms are composed of one or more cells. All cells arise from pre-existing cells. All vital functions of an organism occur within cells. Cells are the most basic unit of life. Cells contain hereditary information. Why? Evidence for Cell Theory What is Evidence? What is a theory?

Evidence for Cell theory: Living tissues= composed of cells Cells of an organism can sometimes survive on their own but smaller cell components can NOT. Classic experiments showed that spontaneous generation of life= impossible. Exceptions to aspects of the theory? Skeletal muscle multinucleate cytoplasm Some fungal hyphaemultinucleate cytoplasm. Extracellular material (material outside the cell membrane), such as teeth

and bone, forms a significant part of the body. Some biologists consider unicellular organisms to be acellular. Do you think these constitute exceptions to cell theory? Justify your answer. State that unicellular organisms carry out all the functions of life. Discussion: What are the necessary functions of life? Metabolism Response to stimuli

Homeostasis Growth/development Reproduction Nutrition Excretion of wastes HW:Research each function of life in a Paramecium and Euglena. Create a Data Table for comparison.

Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using appropriate SI units. Molecules (1 nm) (Smallest) Cell membrane thickness (10 nm) Viruses (100 nm) Bacteria (1 m) Organelles (<10 m) Most cells (<100 m) (Largest) Interactive Calculate linear magnification of drawings. Drawings should show cells and cell ultrastructure. Include: A scale bar: |------| = 1 m Magnification: 250 To calculate magnification: Magnification = Measured Size of

Diagram Actual Size of Object Explain the importance of the surface area to volume ratio as a factor limiting cell size. The rate of exchange of materials (nutrients/ waste) and energy (heat) is a function of its surface area. (Why?) As cell size

increases, the surface area to volume ratio decreases This can make the exchange rate inadequate for large cells Cell size, therefore, remains small Explain that cells in multicellular organisms differentiate to carry out

specialized functions by expressing some of their genes but not others. Differentiation: becoming specialized in structure and function. Supporting examples? Multicellular organisms show emergent properties (What??) See ex. Next slide Video:

Define tissue, organ and organ system. Tissue: An integrated group of cells that share stucture and are adapted to perform a similar function. Organ: A combination of two or more tissues which function as an integrated unit, performing one or more

specific functions. Organ system: A group of organs that specialize in a certain function together. STEM CELLS Stem cells Retain the capacity to divide

Have the ability to differentiate along different pathways. Therapeutic Use: Many possibilities Repair of damaged tissue Actual uses Restore neural insulation tissue in rats. Use of umbilical cord blood stem cells for leukemia patients. Sources and ethical issues: Embryonic placenta/umbilical cord Many other tissues have stem cells Pluripotent vs. totipotent/omnipotent

Video: Stem Cell Uses Stargardts Disease Macular (eye) degeneration, causes central vision loss while periphial vision is still retained Photreceptors in the retina deteriorate.'s+disease&source=lnms&tbm=isch&sa=X&ei=hTLxU8O2DI2JogTA9oLIDA&sqi =2&ved=0CAYQ_AUoAQ&biw=1366&bih=565 Stem cell treatment using embryonic stem cells to grow new

retina cells containing new photoreceptors. These stem cells are transplanted into the patients retina to restore vision. HW: Research another Stem Cell Treatment and record into your notebook Prokaryotic Cells Draw a generalized prokaryotic cell as seen in electron micrographs

The diagram should include: the cell wall, plasma membrane, cytoplasm, Pili Flagella Ribosomes nucleoid ( region containing naked DNA).

State one function for each of the following: cell wall, plasma membrane, mesosome, cytoplasm, ribosomes and naked DNA. Cell Wall: Maintains the cell's shape and give protection. Plasma Membrane: Regulates the flow of materials (nutrients, waste, oxygen, etc.) into and out of the cell. Mesosome: A tightly folded region of cell membrane. (has attached proteins for respiration/

photosynthesis) Cytoplasm: Holds and suspends the cell's ribosomes and enzymes. Ribosome: Protein synthesis. Nucleoid region: Contains the cell's genetic material (naked DNA) Binary Fission Prokaryotic cells divide by binary fission Asexual splits directly into two equal-sized

offspring, each with a copy of the parent's genetic material. Identify parts of a Prokaryote Using an Electron Micrograph Harvard Animation Why are cells cool? Eukaryotic Cells Draw a diagram to show the

ultrastructure of a generalized animal cell (liver cell) as seen in electron micrographs. Should include free ribosomes, rough and smooth ER, lysosome, Golgi apparatus, mitochondria, and nucleus. An Animal Cell Liver cell electron micrographs (objective 1.2)

1. Nucleus 2. Mitochondria 3. Cell border 4. Nucleoli 5. Red blood cell Define organelle. An organelle is a discrete structure within a cell, and has a specific function. Describe the functions of the

following organelles: (see p. 114/ch.7 of Campbell) mitochondrion golgi body endoplasmic reticulum vacuole lysosome ribosome In contrast to the other organelles, they are not surrounded by a membrane. centriole (Unique to animal cells) chloroplast EUKARYOTE CELL ULTRASTRUCTURE Practice: What are the respective

magnifications of the cell as a whole and of each of its organelles in the following cell picture? Summary of the major cell organelles: ORGANELLE MAIN FUNCTIONS DIMENSIONS Nucleus Cell division, protein

synthesis 10 m diameter Mitochondrion Respiration pathways Chloroplast Photosynthetic pathways Lysosome Digestion, recycling &

isolation Golgi apparatus Secretion, reprocessing, lysosome synthesis Cisternae: 0.5m thick, l3m diameter Endoplasmic Reticulum (ER) Support, Golgi apparatus synthesis.

26 to 56 nm thick Ribosome Protein synthesis 1.0 to 12.5 m 5 to 10 m diameter 0.5 to 3.0 m diameter 20 nm diameter State one function of each of these

organelles: ribosomes, rough endoplasmic reticulum, lysosome, Golgi apparatus, mitochondrion and nucleus. Ribosomes: protein synthesis Rough endoplasmic reticulum (rER): Packages proteins Lysosome: digests old cell parts, macromolecules (food) and

engulfed viruses/bacteria Golgi apparatus: Modifies, stores and routes products of the endoplasmic reticulum. Mitochondrion: cellular respiration. Nucleus: contains genetic material Prokaryotic cells vs. Eukaryotic cells Contain naked DNA vs. DNA associated with protein DNA in cytoplasm vs. DNA enclosed in a nuclear envelope No membrane-enclosed organelles vs. membraneenclosed organelles (e.g., mitochondria, chloroplasts) 70S vs. 80S ribosomes Describe three differences between plant

and animal cells. Only plant cells have: Cell walls Chloroplasts Large central vacuoles and tonoplast Plasmodesmata Starch granules for storage of carbohydrates Only animal cells have:

Centrioles Lysosomes Glycogen for storage of carbohydrate Also: Plant cells usually have much less cholesterol in their plasma membranes. Roles of extracellular components (2.3.6) Animal cells Extracellular matrix (secreted glycoproteins) Support Adhesion Movement

Plant cell wall (see next slides) Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll cells (1.2) and within palisade mesophyll cells (1.2) Plant cell wall Main component= cellulose Cellulose molecules are arranged in bundles called microfibrils.

give the cell wall great tensile strength and allow high pressures to develop inside the cell. Functions= structure, support, protection. Draw a diagram of the fluid mosaic model. http://www.youtu Qqsf_UJcfBc Diagram should show

the phospholipid bilayer, cholesterol, glycoproteins, Integral proteins peripheral proteins. Membranes Explain how the hydrophobic and

hydrophilic properties of phospholipids help to maintain the structure of cell membranes. Hydrophilic -water loving -phosphate heads Hydrophobic -water-fearing -fatty acid tails Functions of membrane proteins Hormone binding sites. Enzymes Cell adhesion Attachment to the cytoskeleton and

extracellular matrix Cell communication Signal transduction Cell-cell recognition Channels for passive transport Pumps for active transport. Electron carriers Define diffusion Diffusion: the passive

movement of particles from a region of higher concentration to a region of lower concentration, as a result of the random motion Animation of particles. s/lecgraphics/diffusion2.gif Define Osmosis Osmosis: the passive movement of water molecules, across a selectively permeable membrane, from a region of lower solute

concentration to a region of higher solute concentration. (i.e. the diffusion of water) Remember: Lowers solute concentration = higher water concentration!!! Hypertonic (hyperosmotic) Hypotonic (hypoosmotic) Isotonic (isoosmotic) nce/sbi3a1/Cells/Osmosis.htm effect of osmosis on cell animation Explain passive transport across membranes in terms of diffusion. Simple

diffusion facilitated diffusion. No ATP used Channel proteins (integral membrane proteins) Down concentration/electrochemical gradient Specific ex. Ion Channels in neurons Explain the role of protein pumps and ATP in active transport across membranes. Active transport is the movement of substances

across membranes using energy from ATP. moves substances against a concentration gradient. Active transport animations: Carrier proteins protein pumps Types of transport

Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus, and plasma membrane. Proteins synthesized by ribosomes

enter the rough endoplasmic reticulum. Vesicles bud from rER and carry the proteins to the Golgi apparatus. Golgi apparatus modifies the proteins. Vesicles bud off from the Golgi apparatus and carry the modified proteins to the plasma membrane. Describe how the fluidity of the membrane allows it to change shape, break and reform during exocytosis. In exocytosis vesicles fuse with the plasma membrane. The contents of the vesicles are then expelled. The membrane flattens out again.

animations: In Describe how the fluidity of the membrane allows it to change shape, break and reform during endocytosis endocytosis part of the plasma membrane is pulled inwards. A droplet of fluid becomes enclosed when a vesicle is pinched off. Vesicle can then

move through the cytoplasm carrying its contents. Cell Division State that mitosis is division of the nucleus into two genetically identical daughter nuclei. New cells are produced by the division of existing cell, remember the cell theory.

Interphase: DNA replication and transcription occurs. Also, normal cell life. Mitosis: Cell begins to divide. Cytokinesis: The cell finishes dividing and the cytoplasm splits between them. Mitosis olcweb/cgi/pluginpop.cgi? it=swf::535::535::/sites/dl/free/

0072437316/120073/ bio14.swf::Mitosis%20and %20Cytokinesis Beginning of Cell Cycle Interphase is an active period in the life of a cell when many biochemical reactions occur: protein synthesis (transcription and translation) DNA Replication Increase in number of mitochondria and/or chloroplasts etc. Interphase continued

Phases of Interphase G1 = growth, protein synthesis, increase mitochondria/ chloroplasts S = DNA Replication G2 = growth, increase in organelles, preparation for cell division. What controls Cell Cycle?

Cyclins Control Cell Cycle Proteins that ensure that tasks within the Cell Cycle are performed at the correct time and moves the cell on to the next stage of the cycle when appropriate Four groups of Cyclins (1 per stage) How do they do it? Cyclins bind to enzymes called cyclin-dependent kinases These kinases become active and attach phosphate groups to other proteins which triggers a reaction that carries out tasks specific to one of the phases of the cell cycle Unless these cyclins reach a threshold concentration, the cell does not progress to the next phase in the cell cycle. Describe the events that occur in the four

phases of mitosis Prophase the mitotic spindle (made from microtubules) starts growing (going from pole to pole). Condensation of Chromosomes Chromatin coils up to form distinct chromosomes. Process is called Supercoiling (Each chromosome contains two identical sister chromatids, attached

to each other at the centromere region.) The nuclear envelope starts breaks down. Describe the events that occur in the four phases of mitosis each chromosome attaches to two spindle microtubules (one going

to each pole) at the centromere. line up at the equator mitotic spindle is fully developed some microtubules are attached to chromosomes and reach to the equator; others go from pole to pole. Describe the events that occur in the four phases of mitosis Anaphase the spindle microtubules

pull the sister chromatids to opposite poles each sister chromatid becomes one new chromosome of the daughter cell. Telophase each sister chromatid reaches its pole (becoming a chromosome). nuclear envelope starts to reform. Spindle microtubles

deteriorate. Cytokinesis (division of the cytoplasm) takes place. Summary of Mitosis Summary of mitosis continued In your journal Explain how mitosis produces two genetically identical nuclei. (an IB standard) Outline the differences in

mitosis and cytokinesis between animal and plant cells. (limit this to the lack of the centrioles in plant cells and the formation of the cell wall.) Animals: Centrioles No cell wall Plants: No centrioles Cell wall (cell plate) is

formed between cells as vesicles transport cell wall materials to middle. State that mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumors. Cancer cells do not respond to cell cycle regulation

Mutagens Agents that produce changes in genes involved in controlling the cell cycle Produce Oncogenes that cause uncontrolled Cell Division Tumor: benign (dont spread) or malignant (do spread) Result from uncontrolled cell division Metastasis spreading of cancer cells to other areas (Cancer Warrior angiogenesis resources) (Video: Cancer Warrior-- angiogenesis) Cancer cancer/ (Cancer Warrior angiogenesis resources) nova/cancer/program.html (Video: Cancer Warrior-angiogenesis) cancer/grows.html State that a virus is a non-cellular structure consisting of DNA or RNA surrounded by a protein coat.

Characteristics of Viruses not considered living no metabolism. Unable to reproduce without a host Others? Explain three advantages of using light microscopes.

color instead of monochrome (black and white) images. large field of view. Facilitate preparation of sample material. Allow for the examination of living material and the observation of movement. Relatively inexpensive Outline the advantages of using electron microscopes.

1) higher resolution and magnification than light microscopes. Resolution refers to the ability to distinguish two objects as seperate entities. Magnification refers to the ability to increase the size of a viewed object. 2) May provide a three dimensional view. Scanning Electron Microscopes (SEM) provide images of the specimen's surface Transmission Electron Microscopes (TEM) provide images of a sample's interior. The resolution of an SEM is approximately half that of a TEM. TEM SEM

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