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BIOLOGY Ch-2 Chemistry of life Nature of matter An __________is the smallest unit of matter that cannot be broken down by chemical means. Subatomic particles: Protons – Electrons – Neutrons – Draw the model of an Atom. An _________________is a pure substance made of only one kind of atom. Number of known elements now is ____________ e.g. Atoms of an element that contain different numbers of neutrons are called __________________. e.g. CHEMICAL BONDING Atoms can join with other atoms to form stable substances through a _____________ ________. A _____________ is a substance made of the joined atoms of two or more different elements. e.g. Covalent Bonds A , molecule is a group of atoms held together by covalent bonds. e.g Covalent bonds form when two or more atoms share electrons to form a molecule. e.g. Hydrogen bonds Molecules with an unequal distribution of electrical charge, such as water molecules, are called __________ molecules. This attraction between two water molecules is an example of a hydrogen bond—a weak chemical attraction between polar molecules. Ionic Bonds Sometimes atoms or molecules gain or lose electrons. An atom or molecule that has gained or lost one or more electrons is called an _______. An atom that has lost electrons is _____________charged, whereas an atom that has gained electrons is ___________ charged. Ions of opposite charge may interact to form an _________ bond. e.g. Water and Solutions Properties of water: Storage of heat – Cohesion – Surface tension – Adhesion – Aqueous Solutions A _____________ is a mixture in which one or more substances are evenly distributed in another substance. What is Polarity? Give an example of a polar substance. Give an example of a non polar substance. Acids and Bases H2O --------------- H+ + OH– Pure water always has a low concentration of hydrogen ions and hydroxide ions, which are present in equal numbers. Compounds that form hydrogen ions when dissolved in water are called ______________. When an acid is added to water, the concentration of hydrogen ions in the solution is increased above that of pure water. Compounds that reduce the concentration of hydrogen ions in a solution are called __________. Many bases form hydroxide ions when dissolved in water. pH scale Carbon Compounds Organic compounds contain _________ atoms that are covalently bonded to other elements—typically hydrogen, oxygen, and other carbon atoms. Four principal classes of organic compounds are found in living things: Carbohydrates, lipids, proteins, and nucleic acids CARBOHYDRATES Properties and uses: Made of carbon, hydrogen, and oxygen atoms in the proportion of 1:2:1 Key source of energy, and they are found in most foods—especially fruits, vegetables, and grains Classification: LIPIDS Properties and uses: They are nonpolar molecules that are not soluble in water. They include fats, phospholipids, steroids, and waxes. They are an important part of the structure and functioning of cell membranes. Phospholipids make up the lipid bilayer of cell membranes. Steroids include cholesterol, which is found in animal cell membranes. Other lipids include some light-absorbing compounds called pigments, such as the plant pigment chlorophyll. Fats are lipids that store energy Fat = Glycerol + 3 fatty acids Classification: PROTEIN is a large molecule formed by linked smaller molecules called amino acids. 20 types of amino acids are found. They may be polar, non polar or electrically charged. Proteins tend to fold into compact shapes determined by how the protein’s amino acids interact with water and one another. Uses: Some proteins are enzymes and they promote chemical reactions Structural functions Antibodies help fight infections Help muscle contraction Carry oxygen in blood - NUCLEIC ACIDS are long chain of smaller molecules called nucleotides. A has three parts: a sugar, a base, and a phosphate group, which contains phosphorus and oxygen atoms. There are two types of nucleic acids— DNA and RNA—and each type contains four kinds of nucleotides. DNA - ________________________ consists of two strands of nucleotides that spiral around each other. Chromosomes contain long strands of DNA, which stores hereditary information RNA - _____________________ consists of a single strand of nucleotides. RNA plays many key roles in the manufacture of proteins. RNA can also act as an enzyme, promoting chemical reactions that link amino acids to form proteins. Other important compounds ATP _____________________________ is a single nucleotide with two extra energy-storing phosphate groups. Energy and chemical reactions __________________ is the ability to move or change matter. Energy exists in many forms—including light, heat, chemical energy, mechanical energy, and electrical energy—and it can be converted from one form to another. A _____________ ______________is a process during which chemical bonds between atoms are broken and new ones are formed, producing one or more different substances Reactants -------- e.g. ENERGY AND CHEMICAL REACTIONS (Refer to figure ___ in textbook) Energy releasing reactions e.g. When water freezes, the process that leads to the formation of ice crystals causes heat energy to be released. Energy absorbing reactions e.g. When you remove ice cubes from the freezer, the ice begins to melt. When ice melts, it absorbs heat from the environment. ________________ is the term used to describe all of the chemical reactions that occur within an organism Activation Energy The energy needed to start a chemical reaction is called _______________ __________. Activation energy is simply a chemical “push” that starts a chemical reaction Enzymes – Enzymes are catalysts, which are substances that reduce the activation energy of a chemical reaction Enzymes help organisms maintain homeostasis. Without enzymes, chemical reactions would not occur quickly enough to sustain life. (Refer to figure ___ in textbook) e.g. Enzyme Specificity A substance on which an enzyme acts during a chemical reaction is called a_________________. Enzymes act only on specific substrates. e.g. starch------------ e.g. 2H2O2 ----------------- 2H2O + O2 An enzyme’s shape determines its activity. Typically, an enzyme is a large protein with one or more deep folds on its surface. These folds form pockets called_______ ________ An enzyme acts only on a specific substrate because only that substrate fits into its active site. (Refer to figure ___ in textbook) Factors in Enzyme Activity Temperature pH Chemicals