BIOL 302 Lecture 1Outline of Current Lecture II. What is a cell?A. Unity and diversity of cellsB. How to observe/study cellsC. Classification of cells III. Prokaryotes , EukaryotesA.Cytoplasm vs. cytosolB.Endosymbiotic theoryC.Cytoskeleton IV. Chemical components of cellsA. Organic compoundsB. AtomsC. Molecules in cells Current LectureChapter 1 Introduction to Cells What is a Cell?Cells: are the structural and functional units of all living organisms and the most basic unit of lifefrom which living organisms are made. They consist of an aqueous solution of organic moleculesenclosed by a membrane.All cells arise from pre-existing cells (usually by a process of cellular division). Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, aremulticellular, or have many cells. Each cell can take in nutrients, convert these nutrients into energy, and carry out specialized functions, and reproduce as necessary. Each cell stores its own set of instructions for carrying out each of these activities. Unity and diversity of cells:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Cells vary enormously in appearance (morphology) and function. However, living cells all have a similar basic chemistry for passing on genetic information. Genes provide the instructions for cellular form, function, and complex behavior.How do we observe/study cells? Early technology: 17th century-invention of first light microscope. Robert Hooke (1665) used a primitive microscope to examine cork- and he found it to be composed of discrete units (he called these “cells”). Antoni van Leeuwenhoek (1674) used a simple magnifying lens to look at pond water and saw the first living microorganisms (protozoa).The field of cell biology would not exist were it not for the invention of the microscope. Technology has since progressed: Electron microscope was invented in 1930s. It uses beams of electrons, magnification and resolution limits are greatly increased, cannot view living samples. Two types: 1. Transmission electron microscopy (TEM)- fine structure from thin sections of tissue. 2. Scanning electron microscopy (SEM)- allows the user to view the surface features of a sample (3-D images). Classification of Cells Two major classifications of cells: Eukaryotes: contains a nucleus Prokaryotes: lacking a nucleus, no membrane bound nucleus, relatively “simple” life form (structurally), but can be very distinct chemically The eukaryotic cell is much more structurally and functionally complex, It contains a nucleus which is the information store of the cell (houses DNA). Mitochondria generate usable energy from food to power the cell. Intracellular membrane- bound compartments (organelles) with different functions. Contains a very dynamic cytoplasm (intracellular aqueous solution). Nucleus- large structure that contains DNA organized into chromosomes, enclosed by a double membrane (nuclear envelope). Plasma Membrane: this is what encloses the cell and separates the inside of the cell from the outside of the cell. The plasma membrane consists of a lipid bilayer, which contains proteins andsterols (5 nm thick). Cytoplasm vs. Cytosol?Inside of the plasma membrane is the cytoplasm. The cytoplasm contains various organelles (does not contain the nucleus). The cytoplasm is a viscous fluid or gel in the interior of the cell; transparent, mostly water and solutes. Cytosol- contents of the main compartment of cytoplasm, excluding the membrane-bound organelles.The mitochondria is considered the “powerhouse” of the cell, site for energy generation (ATP production) Double-membrane organelle, contains its own DNA. Endosymbiotic theory: suggests that the origins of this organelle developed from an engulfing event, where an ancestral eukaryotic cell engulfed a bacterium leading to a symbiotic relationship between the cell and bacterium. This theory is also adapted to chloroplasts in plants (double membrane and contain own DNA). Other evidence of support comes from the fact that mitochondria and chloroplasts can divide on their own. Basic components of all eukaryotic cells: The cytoplasm is NOT a structureless “soup” of chemicals and organelles. Cytoskeleton- molecules that give the cell a structure, these molecules are polymers that can undergo polymerization (to get bigger) or depolymerization (to shrink), these are long filamentous strands of protein. Chapter 2: Chemical Components of Cells The chemistry of life, organic chemistry, is special in that it deals with “organic” compounds, Organic Compounds=carbon-containing compounds.All reactions take place in aqueous solution. All reactions take place in a narrow temp range (often narrow pH range). Many are very complex, with multiple steps and multiple catalysts. Dominated by large polymers - chains of molecules linked end to end. Organic matter, like all matter, is made of elements. Can’t be broken down or changed by chemical means. Living organisms use only a small number of elements; there are 92 naturally occurring elements. Diameter of cloud 0.1-0.4nm Diameter of nucleus 0.00002 nm, Cell diameter ~ 20,000 nm (20μm).The smallest particle of an element is an atom, the centrally located nucleus is a less dense continuous cloud of electrons. The nucleus provides most of the atom’s mass and contains protons (+) and neutrons (neutral). Electrons move rapidly around the nucleus The “Cloud” shows probability that an electron will be located within that area.The number of protons = Atomic Number. Atomic weight = protons + neutrons. The number of neutrons can vary, equal proton and neutron number is the most stable form, Ex: C14 exists, butis unstable: isotope. Electron Orbitals and Chemical bonds: Atoms with more than 4 orbitals are rare in biological molecules. Electrons tend to frequent discrete regions, or orbitals (electron shells) maximum of 18 electrons. Atoms are most stable with electrons in innermost shells, so innermost shells fill first. When the outermost shell is completely filled, the atom is very stable (chemically unreactive). Valence - the # of electrons an atom must acquire or lose to fill its outer shell. Hydrogen is quite reactive because the outer orbital is not full (1e: half-filled shell). Because unfilled shells are less stable than filled shells, atoms tend to either gain