Topic 1 Cell Biology 1 1 1 2

Topic 1: Cell Biology 1. 1 -1. 2 IB Biology Junior Year

Cell Theory • 1. All organisms are composed of one or more cells. • 2. Cells are the smallest units of life • 3. All cells come from pre-existing cells

Functions of Life • • • Metabolism Growth Reproduction Response Homeostasis Nutrition Excretion

Cells and Sizes • Light Microscope – Inexpensive and easy to operate – Simple specimen preparation – Magnifies up to 2000 x – Specimens may be living or dead • Electron microscope – Expensive to purchase and operate – Complex specimen preparation – Magnifies over 50, 000 x – Specimens are dead and fixed in a plastic material

Microscopes

Limiting Cell Size • Surface to volume ratio – Limits cell size – Processes dependent on volume: • • Heat production Waste production Resource consumption Rate of chemical reactions • More surface area/volume, moves more materials in and out • Large cell: less SA than smaller one • Large animals do not have large cells, just more cells.

Cell Reproduction and Differentiation • Facilitates growth of organism • Replaces dead or damaged cells – Nerve cells and muscle cells do not reproduce • Multicellular organisms begin from one cell as a result of sexual reproduction • Unicellular- binary fission • Cell Differentiation – Result of gene expression regulated by DNA – Specificity of cell depends on area of DNA that is activated

Cell Reproduction

Emergent Concept • Multicellular organisms can carry out more functions collectively than the sum of each cell’s specialty • Non-living molecules function together living organism

Stem Cells • 1. Pluripotentembryonic • 2. Tissue specific • Stem cells can divide and differentiate into any kind of cell • Plants: meristematic tissue – Root and stem tips • Stem cells divide produce other stem cells, as well. – Continual production of specialized cells and stem cells

Germ Layer Derivatives

Stem Cell Research • Embryonic stem cells – Grown in culture – Can replace cells that are injured or diseased – Therapeutic cloning • Parkinson’s • Alzheimer's • Diabetes • Tissue specific: – Blood cells- replace damaged bone marrow – Stargardt’s disease • Inherited • Defective vitamin A processing – Retinal function – 20 years: loss of vision – March 2010: use of embryonic stem cells designed to protect and regenerate retinal cells

Ethics of Stem Cell Research • Pluripotent: controversial – From embryos in IVF clinics – Harvesting requires death of embryo • Cultural and religious traditions: – Many nations ban practice What are the opposing views?

Stem Cell Videos • http: //www. nyscf. org/about-us/watch-nyscfvideos/item/16 -video-stem-cells-developingnew-cures • https: //www. youtube. com/watch? v=EWUq. Cl H 8 oos

1. 2 Ultrastructure of Cells • Prokaryotes: – Much smaller than eukaryotic cells- less than 1 um in diameter – “First” cells – Features: • • • Cell wall Plasma membrane Flagella Pili Ribosomes Nucleoid

Features of Prokaryotic Cells • Cell wall and cell membrane: – Cell wall- protects and maintains shape of cell • Made of peptidoglycan; a carb-protein complex • Some also have extra layer- LPS (lipo-poly saccharide) Induces strong immune response – Fever – Shock • Plasma membrane: – Similar composition to eukaryotes – Controls what enters and leaves – Role in binary fission – Contains cytoplasm – Role in cell metabolism

Gram + and Gram – Bacterial Cells

Pili and Flagella • Pili- • Flagella- – Hair-like growths used for attachment – Role in joining bacterial cells in preparation for sexual reproduction • DNA transfer from one to another through conjugation tube – Flagellum (singular) – Role in movement

Ribosomes & Nucleoid • Ribosomes– Size: 70 s – Protein synthesis • Nucleoid– Non compartmentalized – Long circular strand of DNA – Plasmids • Not connected to chromosome • Confer virulence, antibiotic resistance • Increase survival advantage of cell

Reproduction: Binary Fission • DNA copied – Daughter chromosomes attach to opposite ends of plasma membrane – Result is 2 identical daughter cells – Process includes partitioning of new DNA by microtubule fibers called Fts. Z

Harvard’s “Inner Life of the Cell” • Non-narrated version: • https: //www. youtube. com/watch? v=w. Jy. Utbn 0 O 5 Y • Narrated version: • https: //www. youtube. com/watch? v=Fzc. Tgrx Mz. Zk

Eukaryotic Cells • Protozoans, algae, fungi, plant and animal • 5 -100 um in size • Organelles: – Non-cellular membrane bound structures that carry out specific functions to allow the cell to function as a whole • Compartmentalization: – Allows for: • Incompatible chemical reactions to occur • Isolation of certain chemical reactions • Result: increased efficiency

Animal and Plant

Eukaryotic Organelles • Endoplasmic reticulum- – Most cells have both rough and smooth – Transport throughout cell – Smooth: no ribosomes • Production of membrane phospholipids, cellular lipids • Detoxification in liver • Stores Ca 2+ in muscle cells • Transports lipid based compounds • Helps liver release glucose • Rough E. R. – Ribosomes (80 s) on exterior channels • Protein synthesis • Protein transport • Proteins synthesized here are transported out of the cell

Ribosomes • • 80 s No exterior membrane On surface of rough E. R. Free in cytoplasm – Proteins synthesized here are used inside the cell Composed of 2 sub-units Sub-units not assembled until there is a protein to be translated

Lysosomes • Intracellular digestive centers • Arise from Golgi • No internal structures • Single membrane sacs with as many as 40 different hydrolytic enzymes • Break down carbs, lipids, proteins, nucleic acids • Fuse with old and damaged organelles from within cell to break them down

Golgi Apparatus • Made of flattened sacs called cisternae • Collects, packages, modifies and distributes materials made in the cell – Cis side- near the rough E. R. , receives products from the E. R. • Trans side- side opposite cis where materials are discharged – Vesicles filled with products exit to where they are needed • Golgi prevalent in glandular cells (pancreas) that manufacture and secrete substances

Mitochondria • • Mitochondria- plural Mitochondrian- singular Rod shaped Close in size to bacterial cell Have own DNA Has own ribosomes (70 s) Circular chromosome Double membrane – Outer- smooth – Inner- folded into cristae • High surface area • Filled with semi-fluid matrix • Has inner membrane space • Most reactions ATP • Cells with high energy requirements have more mitochondria • Mitochondria are inherited from your mother only

Mitochondrion

Nucleus • Isolated region where DNA resides • Double membranenuclear envelope – Has pores that allow communication from the cell • DNA functions are isolated from the rest of the cell • DNA in form of chromosomes – Vary in number • Not dividing? –DNA in form of chromatin – Chromatin wound around histone proteins – Nucleosome=strand of DNA + 9 histone proteins – Chromosomes are highly coiled structure of nucleosomes

Nucleus, cont. • Usually centrally located • Contains nucleolus except in plant cells – Ribosome manufacture – Large central vacuole • Can have single nucleus, multiple nuclei, or no nucleus at all – RBC- anucleate, don’t need to reproduce, generated in bone marrow

Chloroplasts Plant cells and algae only Double membrane Same size as bacterial cell Has own DNA, circular Can reproduce independently • Has 70 s ribosomes • Interior: • • • – Grana, thylakoids, stroma • Grana: – Thylakoids stacked like pile of coins • Thylakoids: – Flattened membrane sacs containing chlorophyll • Stroma: – Fluid filled area full of enzymes and chemicals for photosynthesis

Chloroplast

Centrosome • Pair of centrioles • Assembly of microtubules – Structure and movement of cell – Plants do have microtubules but no centrioles • Located close to the nucleus

Vacuoles • Storage organelles that arise from Golgi • Membrane bound • Can store: – Food and water – Metabolic waste – Toxins • Enable cells to increase SA: V ratio • Plants: – Store water – Provide structure to plant

Cell Walls • Plants: – Cell wall of cellulose (fiber) – Humans cannot digest cellulose because we lack cellulase • Fungi: – Cell wall of chitin – Water uptake and structure

Cell Membrane • Phospholipid bilayer • Hydrophobic and hydrophyllic components • ECM (extra cellular matrix) of collagen and glycoproteins – Strengthens cell membrane and anchors it to adjacent cells • ECM: – Allows cell-cell interactions – Could alter gene expression – Enable coordination of cell actions within tissue – Directs stem cells to differentiate – Directs cell migration and movement

Cell Membrane