Presentation on theme: "Lecture 2 OrR. Overview: Inquiring About the World of life Evolution is the process of change that has transformed life on Earth. Biology is the scientific."— Presentation transcript:
Lecture 2 OrR
Overview: Inquiring About the World of life Evolution is the process of change that has transformed life on Earth. Biology is the scientific study of life Biologist ask questions such as: How does a single cell develop into an organism? How does the human brain work? How do living things interact in communities?
Evolution, the Overarching Theme of Biology Evolution makes sense of everything we know about living organisms Organisms living on Earth are modified descendents of common ancestors
The Biological Hierarchy The study of life can be divides into different level of biological organization
Life, Chemistry and Water Biology is a multidisciplinary science Living organisms are subject to basic laws of physics and chemistry
Organisms are composed of matter Matter – anything that takes up space and has mass Mass measures the quantity of matter in an object and is defined by: Volume is how much space it takes up Density measure concentration of matter Matter is made up of elements An element is a substance that cannot be broken down to other substances by chemical reactions A compound is a substance consisting of two or more elements in a fixed ratio. A compound has characteristics different from those of its elements Matter, Elements & compounds
Is oxygen an element or a compound? What about iron? Water? Carbon di oxide? Sodium (Na)Chlorine (Cl) Table Salt Sodium Chloride(NaCl)
Essential Elements of Life About 25 of the 92 elements are essential of life Carbon (C), hydrogen (H), oxygen (O), and nitrogen make up 96% of living matter. Most of the remaining consist of calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl) and magnesium (Mg). Trace elements are those required by an organism in minute quantities. Example: selenium, Zinc
Atomic Structure Each elements consists of one type of atom Each atom consists of an atomic nucleus surrounded by fast moving, negatively charged electrons Atomic nuclei contain positively charged protons – the number of protons (atomic number) identifies an element The nuclei of all atoms (except hydrogen) also contain uncharged neutrons
Isotopes Makes atomic number not as simple as it may seem Protons and Neutrons in the nucleus Neutrons can vary independently of the number of protons Neutrons add weight to the atom Isotopes have the same number of protons, different number of neutrons ISOTOPES OF CARBON
Isotopes in Research Radioisotopes decay can be used to estimate the age of organic material, rocks, or fossils that contain them. Isotopes are used in biological research as tracers Radioisotopes such as 14 C, 32 P, and 25 S Stable, nonradioactive isotopes such as 15 N (heavy nitrogen)
123 I can be used to visualize the thyroid gland Scans of human thyroid glands after 123 I was injected into the blood stream Radioactive iodine becomes concentrated in the thyroid gland
Chemical Bonds and Chemical Reactions Atoms of reactive elements tend to combine into molecules by forming chemical bonds The four most important chemical linkages in biological molecules are ionic bonds, covalent bonds, hydrogen bonds and van der Waals forces. Chemical reactions occur when atoms or molecules interact to form new chemical bonds or break old ones
Chemical Bonds and Chemical Reactions Forces: 1.Covalent bonds 2. Hydrogen bonds 3. Ionic bonds 4. van der Waals bonds 5.Hydrogen bonds Macromolecules 1.Carbohydrate 2.Proteins 3.Nucleic acids 4.Lipids
Covalent Bonds Principle form to hold atoms together based on sharing electrons very strong
to break a C-C bond require 83 kcal/mole the bond cant be break with any physiological condition The bond can only be bend, stretch or rotate Enzymes: Biological catalysts that enable specific bonds to be broken or formed under physiological conditions
Types of covalent bonds: Single bonds C-C Double bondsC=C Triple bondsC=C Stronger unsaturated saturated rotate Can’t rotate Other molecules: Oxygen molecule O=O Nitrogen molecule N=N Nitrogen is strong molecule, cant be broken by any organism, but by bacteria which produce enzyme name nitrogenase
Chirality characteristics of covalent bond Carbon can make 4 COVALENT bonds comes out as tetrahedron
Chirality characteristics of covalent bond Mirror image Molecules are known as Optical isomer Important concept: At molecular level much of biology relies on interaction of complementary 3d surfaces
Sharing of electron C-C or C-H equal sharing (non-polar bond) N-H, O-H unequal sharing (polar bond) Electronegativity
Two Types of Covalent Bonds Nonpolar Covalent Bond Nonpolar Covalent Bond sharing electrons equally – The atoms participating in the bond are sharing electrons equally. There is no difference in charge between the two ends of such bonds. Polar Covalent Bond Polar Covalent Bond do not share electrons equally. – Atoms participating in the bonds do not share electrons equally. – One atom pulls the electrons a little more toward its "end" of the bond, so that atom bears a slightly negative charge. The atom at the other end of the bond bears a slightly positive charge.
Polar Covalent Bond Polarity occurs when atoms electrons unequally due to differences in electronegativities. This is seen in water (H 2 O). More electronegative atoms tend to pull electrons toward them creating a polar molecule.
The polarity of water molecules results in hydrogen bonding
Ionic Bonding Sodium chloride (table salt) is an example of ionic bonding, that is, electron transfer among atoms or redox reaction.
Ionization Molecules formed by ionic bonding breakup (ionization) when dissolved in water (solvent), producing separate positive (cation) and negative (anion) ions. These ions conduct electricity and thus called electrolytes.
Hydrogen Bonds a weak attractionhydrogen atom another atom a separate polar covalent bond A hydrogen bond is a weak attraction between a hydrogen atom and another atom taking part in a separate polar covalent bond Like ionic bonds, hydrogen bonds form by the mutual attraction of opposite charges. Unlike ionic bonds, hydrogen bonds do not make molecules out of atoms, so they are not chemical bonds Hydrogen bonds form and break much more easily
Hydrogen Bond Hydrogen bonding is formed between the partially positive (hydrogen) end of a polar molecule and the negative end of another (e.g. O 2 or N 2 ). Example : Water molecules
Summary: From Atoms to Molecules
Water: The Molecule That Supports All of Life Water is the biological solvent on Earth All living organisms require water more than any other substance Most cells are surrounded by water, and cells themselves are about 70-95% water The abundance of water is the main reason the Earth is habitable.
Water unique properties Water: Polar covalent bonds gives water its unique properties that make life possible Water is an excellent solvent Water is an excellent solvent – Hydrophilic substances – Hydrophobic substances Water is stable in high temperature Water is stable in high temperature – Why ice floats on water Water has cohesive properties Water has cohesive properties Water evaporates Water evaporates
OSMOSIS Osmosis is the net diffusion of water down its own concentration gradient Water molecules can readily permeate the plasma membrane Slower Process Aquaporins One molecule of solute can displace one molecule of water
Osmosis when pure water is separated from a solution containing a nonpenetrating solute. The net diffusion of water down its concentration gradient through a selectively permeable membrane is known as osmosis OSMOSIS
MOVEMENT OF WATER AND SOLUTE WHEN A MEMBRANE SEPARATES UNEQUAL SOLUTIONS OF A PENETRATING SOLUTE Solutes that can penetrate the plasma membrane do not contribute to osmotic differences between the ICF and ECF and do not affect cell volume (although before equilibrium is achieved, transient changes in volume may occur as a result of differing rates of diffusion of water and the solute across the membrane
Tonicity The effect of a solution on the osmotic movement of H 2 0. The tonicity of a solution has no units and is a reflection of its concentration of nonpenetrating solutes relative to the cell’s concentration of nonpenetrating solutes Isotonic – Equal tension to plasma. – RBCs will not gain or lose H 2 0. Hypotonic: – Osmotically active solutes in a lower osmolality and osmotic pressure than plasma. – RBC will hemolyse. Hypertonic: – Osmotically active solutes in a higher osmolality and osmotic pressure than plasma. – RBC will crenate.
MOVEMENT OF WATER WHEN A MEMBRANE SEPARATES EQUAL AND UNEQUAL SOLUTIONS OF A NONPENETRATING SOLUTE
Acids and Bases What is pH Acids: Fossil fuel, N 2 containing fertilizers, Acid rain Bases Buffers Hydrogen ions contribute to pH. Acids release hydrogen ions in water; bases accept them. Salts release ions other than H + and OH -. Hydrogen ions contribute to pH. Acids release hydrogen ions in water; bases accept them. Salts release ions other than H + and OH -. Buffers keep the pH of body fluids stable. They are part of homeostasis. Buffers keep the pH of body fluids stable. They are part of homeostasis.