Chapter 2 Lecture 1 _ 2.pptx

The Chemistry of Life Chapter 2: Lecture 1 & 2 Lecturer: Ms. Thabisa Mdlangu BCB Department, Life Sciences Building Core 2, 5th floor [email protected] A living body is a mixture of thousands of different types of interacting chemicals Some of these would be familiar nutritional food labels: Sugars...

The Chemistry of Life Chapter 2: Lecture 1 & 2 Lecturer: Ms. Thabisa Mdlangu BCB Department, Life Sciences Building Core 2, 5th floor [email protected] A living body is a mixture of thousands of different types of interacting chemicals Some of these would be familiar nutritional food labels: Sugars, proteins, fats… Some of these are substances you may never have thought of as chemicals: protein that helps form hair on your head (keratin) , hormones in your blood stream (e.g. insulin), red pigment in you blood cells (haemoglobin) Not just animals - but all organelles are made up of chemicals Some chemicals are the same as in animals, and some are unique to the plant kingdom Some of the most interesting chemicals are those that plants deploy in their never-ending fight against herbivores and competitors Most plants use chemical warfare to defend themselves Example Black walnut tree releases chemicals that inhibit the growth of other trees Landscapes find it difficult to establish other plants around this tree This reduces competition for vital resources: Light, Water, Soil nutrients https://www.thespruce.com/thmb/5aBICPU39d-Xx2k6WgRVlgPGLcw=/2121x1414/filters:no_upscale():max_ bytes(150000):strip_icc()/Blackwalnut-GettyImages-597273616-75d1dad619504bebba0b8634f713d46c.jp g Plants also release chemicals that limit damage from animals that might otherwise dine on their foliage, flowers, fruits, seeds, Another example chili pepper tree Most animals cannot stand it, so they leave it alone Some reptiles use pheromones to mark territory These pheromones protect their territory even in their absence Can also be used by predators to locate these animals Picture source: https://www.thefactsite.com/wp-content/uploads/2019/08/lizardfacts.webp Chemicals are also used by foraging animals e.g. Trail pheromone in ants Image source: https://www.chemistryviews.org/wp-content/uploads/legacy/common/images/thumbnails/source/17724 Herbivory induces the release of volatiles in Lantana camara Image source: https://planthouseaesthetic.com/wp-content/uploads/2023/02/Common-Lantana-1536x1024.jpg?ezimgfmt=ng:w cb2 Some of the chemicals protect the owners against competitors, predators, and diseases -The monarch butterfly on milkweed https://bloximages.chicago2.vip.townnews.com/greensburgdailynews.com/content/tncms/assets/v3/e ditorial/b/98/b98dd46b-8d1c-5cb4-bff9-eef4023619f1/59926f0be9e05.image.jpg Majority of a cell consists of water and four classes of organic compounds and defensive chemicals make up relatively small proportion of any organism’s body Carbohydrates, Proteins, Lipids, Nucleic acids Atoms make up all matter For plants – living plants are different from plastic plants that are fake and stiff All objects in the universe are composed of matter and energy Matter- any material that takes up space and has mass Heat, light, and chemical bonds are all forms of energy Matter- any material that takes up space and has mass Elements are fundamental types of matter The matter that makes up every object in the universe consists of one or more elements Chemical element: A pure substance that cannot be broken down by chemical means into other substances O, N, C, Na, H Periodic table Russian chemist, Dmitry Mendeleyev invented the chart we still use to this day Have 54 elements – each with a unique atomic number and symbol About 25 elements are essential to life, of these elements, bulk are required in the largest amounts because they make up vast majority of every living cell The four most abundant bulk elements in life are Carbon, Hydrogen, Oxygen, Nitrogen Other bulk elements include Phosphorus (P), Sulfur (S), Sodium (Na), Magnesium (Mg), Potassium (K), Calcium (Ca) Trace elements such as Iron (Fe) and Zinc (Zn), are required in small amounts A person whose diet is deficient can become ill or die Thyroid gland – Iodine deficiency (trace element), if a person’s diet is iodine deficient, their thyroid gland might be enlarged, forming a growth called a goiter in the neck Red blood cells require Iron to carry Oxygen to the body’s tissues Iron poor diet can cause anemia (decline in red blood cells) Atoms are particles of elements Atom: the smallest possible piece of an element that retains the characteristics of the element Composed of three types of subatomic particles: Protons Neutrons Electrons http://www.word-buff.com/vocabulary-word-list-particles. html For simplicity, most drawings of atoms will show electrons circling the nucleus in tight, orbitlike rings – in reality, electrons move in every direction within a large electron cloud Most of an atom’s mass is concentrated in the nucleus, while the electron cloud virtually occupies all of its volume Protons (positively charged ) and neutrons (neutral) together form a central nucleus http://www.word-buff.com/vocabulary-word-list-particles.html - Each element has a unique atomic number, the number of protons in the nucleus - Elements are arranged sequentially in the periodic table by atomic numbers When the number of protons equals the number of electrons, the atom is electrically neutral – it has no net charge An ion is an atom (group of atoms) that has gained or lost electrons and therefore has a net negative or positive charge Cation is a positively charged ion e.g. H+ (Hydrogen) Na+ (Sodium) K+ (Potassium) Anion a negatively charged ion (Include Hydroxide OH- and Chloride Cl-) Ions participate in many biological processes, including the transmission of messages in the nervous system They also form ionic bonds Isotopes have different number of atoms An atom’s mass number is the total number of protons and neutrons in its nucleus. Protons and neutrons have the same mass, so subtracting the atomic number from the mass number yields the number of neutrons in an atom All atoms in an element have the same number of protons but not necessarily the same number of neutrons Mass number – atomic number = Number of neutrons in an atom An isotope is any of the different forms of a single element Often one isotope of an element is very abundant and others are rare Atomic weight: is the average mass of all atoms of an element It is typically close to the mass number of the most abundant isotope Most atoms have both stable (nonradioactive) isotope and non-stable (radioactive) – which emit energy as rays of particles when they break down into more stable forms A radioactive isotope is an atom that emits particles or rays as it disintegrates Every radioactive isotope has a characteristic half-life: the time it takes for half of the atoms in a sample to emit radiation, or decay to a different, more stable form Scientists have determined the half-life of each radioactive isotope experimentally Depending on the isotope, the half-life might range from a fraction of a second to millions or even billions of years Radioactive isotopes have many uses in medicine and science – from detecting broken bones to determining the age of fossils The same properties that can make them useful, can also make them dangerous Exposure to excessive radiation can lead to radiation sickness and radiation-induced mutations of a cell’s DNA Lead containing bib that a dentist places on your chest during mouth x-ray protects you from radiation Chemical bonds link atoms Like all organisms, you are composed mostly of Carbon, Hydrogen, Oxygen, and Nitrogen The arrangement of these atoms is not random – your atoms are arranged into molecules Molecule: Two chemically joined atoms Some molecules such as the gases H2, O2, N2 consist of two atoms of the same element More often the elements in a molecule are different Compound: a molecule composed of two or more different elements - CO Carbon monoxide, H2O these are compounds Many large biological compounds – including DNA and proteins, consist of tens of thousands of atoms A compound’s characteristics can differ strikingly Na – silvery, highly reactive solid metal Cl – Yellow corrosive gas Together they form NaCl: A crystal white table salt Molecular formula: representation of the atoms in a compound CH4 molecular formula for Methane NaCl, H2O, CO2 What forces hold together the atoms that make up each of these molecules? Electrons determine bonding They occupy distinct energetic regions around the nucleus They are constantly in motion so it is impossible to determine the exact location around the nucleus at any given moment Orbital: a term used by chemists to describe the most likely location for an electron relative to its nucleus Each orbital can hold up to two electrons – the more electrons in an atom, the more orbitals they occupy An atom’s orbitals are grouped into a series of concentric energy shells – each having a higher energy level than the one inside it The number of orbitals in each shell determines the number of electrons the shell can hold The lowest energy shell contains just one orbital and can therefore hold only electrons The next shells will each contain four orbitals – meaning they can each carry up to eight electrons Electrons occupy the lowest energy level available to them, starting with the innermost one As each energy shell fills, any additional electrons must reside in higher energy shells Valence shell: An atom’s outermost occupied shell Atoms are most stable when their valence shells are occupied Periodic Table of Elements Vertical columns indicate number of electrons in outermost shell I Horizontal periods indicate total number of electron shells 1 2 3 4 VIII 1 2 H II 1.008 III IV V VI VII He 4.003 3 4 5 6 7 8 9 10 Li Be B C N O F Ne 11 12 13 14 15 16 17 18 Na Mg Al Si P S Cl Ar 19 20 21 22 23 24 25 26 K Ca Ga Ge As Se Br Kr 6.941 9.012 10.81 12.01 14.01 16.00 19.00 20.18 22.99 24.31 26.98 28.09 30.97 32.07 35.45 39.95 39.10 40.08 69.72 72.59 74.92 78.96 79.90 83.60 Glossary of terms Matter Chemical element Bulk elements Trace elements Atom Protons Neutrons Electrons Atomic number Ion Anion Cation Mass number Isotope Atomic weight Radioactive isotope Characteristic half-life of a radioactive isotope Molecule Compound Molecular formula Orbital Valence shell