Study Guide for Midterm (General Biology) PDF

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General Biology 101. Study guide for Midterm. Professor Pathapadu of Northern Virginia Community College....

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Study Guide for Midterm 1. Scientific Investigation i) SPONTANEOUS GENERATION - Aristotle, a great philosopher of 4th Century BC, proposed spontaneous generation (Non-living objects can give rise to living organisms). ii) Experiments to disprove Spontaneous Generation - Francesco Redi(16th Century) and Louis Pasteur(18th Century) used ‘Scientific Method’ to disprove the idea of spontaneous generation. Louis Pasteur’s Experiment - Francesco disproved spontaneous generation for larger organisms. Lois Pasteur disproved theory of spontaneous generation for microorganisms. iii) Scientific Method - Method of research in which a problem is identified, relevant data are gathered, a hypothesis is formulated from these data, and the hypothesis is empirically tested. 2. Steps in Scientific Method – a) Observation and Questioning b) Preparing a Hypothesis c) Testing (using control and experimental group) d) Data collection e) Analysis and Conclusion (1) Hypothesis - is a tentative explanation for the observation based on previous knowledge, facts, and general principles. Multiple hypotheses should be proposed whenever possible. Hypotheses should be testable. Hypotheses can be proven wrong/incorrect (2) Variables(a) Constants are controlled variables, (b) Independent variables are the changes made by the experimenter (c) Dependent variables depend on the independent variables. 3. Different Levels of Organization – Life is highly organized into different levels a) Biosphere - The biosphere is the biological component of earth systems, which also include the lithosphere, hydrosphere and atmosphere. b) Ecosystem - An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment interacting as a system. Ex. Desert ecosystem c) Community- Community includes all the living components of a specific region d) Population - A population is a group of organisms which belong to the same species that interbreed and live in the same geographical area. Ex. Pack of wolves e) Organisms - Organism is an individual constituted to carry on the activities of life by means of organs separate in function but mutually dependent : a living being f) An organ systems is a group of organs that work together to perform a certain task. Ex. Respiratory system, excretory system g) Organs - An organ is a collection of tissues joined in a structural unit to serve a common function. Ex. Heart ;

h) Cell- Cells are the building blocks of all plants and animals. Cell is the fundamental unit, functional and structural unit of life. i) Organelles - Within cells there are organelles which allow it to function properly j) Molecules - Each organelle is made up of molecules which are in turn made up of atom 4.

Characteristics of Life – 1) Organization of Life - Organisms have an enormously complex organization from organism level to molecular and atomic level. 2) Evolutionary Adaptations - Life can adapt and respond to the demands placed on it by the environment. Change in the climate forces organisms to adapt. Adapting often means changing one's behavior to suit the circumstances. 3) Response to the environment - Life is characterized by this response to stimuli. 4) Reproduction- Life can only come from other living creatures. 5) Growth and development - Life grows and develops. This means more than just getting larger in size. 6) Metabolism - Energy, in the form of food, is transformed to maintain metabolic processes and for survival. 7) Osmoregulation - The process of regulating water potential in order to keep fluid and electrolyte balance within a cell or organism relative to the surrounding.

5. Chemistry of Life- Atomic Structure and Bonding – a) An atom is the smallest stable form of matter. A cell is the smallest form of life. Cells are made up of molecules and molecules are made up of atoms. All living and nonliving things are ultimately made up of atoms. b) Element - Element is a substance that consists of just one type of atoms c) Latest periodic table shows a total of 118 elements. There are 98 Naturally occurring elements. Others are Radio-active elements. Carbon, Hydrogen, Oxygen and Nitrogen major elements found in organic molecules d) Branches of Science which study the relationships between Biology and Chemistry e) Organic Chemistry - Study of compounds containing Carbon. All organic/biological compounds contain Carbon and Hydrogen f) Biochemistry - It is the study of chemical processes in living organisms g) Essential Elements of Life – Carbon, Hydrogen, Oxygen and Nitrogen constitute 96% of living matter. Calcium(Ca), phosphorus(P), potassium(K), sulfur(S) and some other elements form the remaining 4% of an organism’s mass h) Atomic structure - Atom is the smallest unit having all the properties of an element. i) It is composed of sub atomic particles like neutrons and protons in the nucleus and electrons in the periphery. j) Mass of neutron and proton is identical. Mass of electron is negligible k) Atomic number = no. of protons or electrons l) Mass number = no. of protons + no. of neutrons

m) Isotopes - Atoms of the same element can have different numbers of neutrons. The different possible versions of each element are called isotopes. For example, the most common isotope of hydrogen has no neutrons at all; there's also a hydrogen isotope called deuterium, with one neutron, and another, tritium, with two neutrons. a) Electronic orbitals - Electrons revolve around nucleus in their orbitals. Orbitals are 4 types depending on the shapes -s,p,d,f. b) Energy levels of the shell - Orbitals form shells, KLMN. Energy increases from inner shell towards outer shell. Electrons gain or lose energy when they jump from one level to another c) Molecule and Compound - A molecule is formed when two or more similar or different atoms join together chemically. Ex. Hydrogen (H2), Carbon monoxide (CO). A compound is a molecule that contains at least two different elements. Ex. H2O (water with H and O), CO2 (Carbon dioxide with C and O). All compounds are molecules but not all molecules are compounds. Organic molecules are composed of carbon and hydrogen and often contain other elements such as oxygen, nitrogen, phosphorus, and sulfur d) Chemical Bonding between atoms - Atoms with incomplete valence shells can interact with certain atoms. They share or transfer valence electrons resulting in atoms staying close by chemical bonds. Strongest chemical bonds are covalent and ionic bonds. Weak bonds are hydrogen bonds and van der Waal's interactions e) Ionic bond in NaCl - formed due to transfer of electrons. When chemically bonded together, these two dangerous substances (Na and Cl) form the compound sodium chloride, common table salt! f) Covalent bonds – Non- Polar Covalent – Formed between two similar atoms. Ex.H2 and Polar Covalent -Formed between two dissimilar atoms. Ex.H2O g) Hydrogen Bonds - Polar molecules such as water show partial positive and negative charges. The partial positive charge on a covalently bonded hydrogen atom attracts a different electronegative atom to form a hydrogen bond. For ex. hydrogen atom of water (partially +ve) attracts nitrogen from ammonia (partially –ve) and forms hydrogen bond. Hydrogen bonds can be formed between water molecules also. h) Van der Waal’s forces - The ever changing regions of positive and negative charge enable all atoms and molecules to stick together by van der Waal’s interactions. A gecko lizard can walk on the wall due to the Van der Waal's forces in the projections at the tip of numerous tiny hairs on its toes which together can support the weight of gecko’s body

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6. Water – The formula for water is H2O, The covalent bonds between H and O are polar and give a partial negative charge to oxygen atom and a partial positive charge to hydrogen atom Unique properties of water a. Versatility as a solvent Water is called the "universal solvent" because it dissolves more substances than any other liquid. Hydrophilic substances has an affinity for water. They may not actually dissolve, but only suspended in water. Ex. Molecules in cell, cotton Hydrophobic substances are nonionic and nonpolar and repel water. Ex. Oil

a. Cohesion of water molecules Cohesion and adhesion are the "stickiness" that water molecules have Cohesion - for each other, causes transport of water and dissolved nutrients against gravity in plants • Adhesion - for other substances, attraction of water to cell walls counter the downward pull of gravity • Surface tension of water when interacting with air is an ordered arrangement of water and behaves as if coated with an invisible film. This makes the water behave as though coated with an invisible film. b. Ability to modify temperature Water moderates air temperature by absorbing heat from warm air or releasing stored heat to cool air. •

Around small water bodies it is cool in summer because of evaporative cooling effect Around large bodies of water there cannot be sudden rise or fall in temperatures because of high specific heat of water c. Water expands on freezing d. Water expands on freezing and ice occupies more space than liquid water. That’s why the pipes with flowing water break during the winter if they are not provided for the expansion e. Water freezes at zero degree Celsius temperature by locking the molecules into crystalline lattice. Water is less dense as a solid than liquid, so ice floats on water Acids and Bases f. Sometimes water molecules break down to release an H+ (hydrogen) ion and an OH(hydroxide) ion. When more hydrogen ions are released, the solution becomes acidic. When more hydroxide ions are released, the solution becomes basic. 2H2O --> H3O+ + OHg. When sodium chloride is placed in water, sodium and chloride ions are exposed to hydrogen and oxygen ions of water. Anions of water molecules attract cations of sodium. h. pH Scale focuses on concentrations of hydrogen ions (H+) and hydroxide ions (OH-). The scale measures values from 0 all the way up to 14. Body fluids and Pure water are pH 7 (neutral). pH of acids is between 0 and 7. Bases between 7 to 14 i. Buffer is a substance that can minimize changes to the concentration of the solution by accepting hydrogen ions when excess or donating hydrogen ions when depleted. Ex.Blood j. Burning of fossil fuels release carbon dioxide, sulfur oxide and nitrogen oxides, which can cause ocean acidification & acid precipitation. k. Carbon dioxide can react with water to form carbonic acid and cause ocean acidification l. Acid precipitation refers to acidic rain, fog or snow which can affect plants on earth by changing soil chemistry. • •

7. Carbon- backbone of life a. Carbon skeleton accounts for the variations in organic molecules like proteins, lipids, carbohydrates and nucleic acids. Organic compounds form simplest structure like methane (CH4) to most complex protein structures. Hydrocarbons can store large amounts of energy. Ex. Fossil fuels like petroleum, tails of fat molecules. Monomers

bond together and form polymer of organic molecules by dehydration (losing water molecule) and vice versa is possible by hydrolysis (addition of water molecule). All biological molecules are polymers with repeated units of monomers bonded together. The four types of bio-molecules are Carbohydrates, lipids, proteins and nucleic acid. Monomers for these polymers are as follows: carbohydrates-monosaccharides, proteins-amino acids, lipids- fatty acids and glycerol and nucleic acids – nucleotides. 8. Biological Molecules: Four types of biological molecules include i. Carbohydrates – Monosaccharides, Ex. glucose are broken down by the cell to release energy, they form polysaccharides (glycogen in liver) if not utilized immediately. Polysaccharides can be structural (like cellulose in plants forming cell wall) or storage (like glycogen in liver of animals or starch in potato tubers) ii. Lipids – monomers are fatty acids and glycerol. Hydrophobic and are the only biomolecules which are not macro. They are three types-fats (unsaturated (plant-oils), saturated (animal-fats) and Trans fats(synthetic), phospholipids (form cell membrane) and steroids (in animals as cholesterol and sex hormones). iii. Proteins – Instrumental in almost all the functions of organisms are formed from 20 amino acids. They are polypeptide chains with 3D structure. The structure includes-primary, secondary, tertiary and quaternary structure. One end with amino group and other end with carboxyl group. They are called polypeptides as these amino acids are joined by peptide bonds. Proteins are instrumental in almost all the functions of organisms. They speed up reactions; play a role in defense, storage (in seeds, milk and eggs), transport (Cellular transport and hemoglobin transport in blood), cellular communication, movement (Muscles) or structural support (appendages of skin). Enzymes (Ex. Maltase), hormones (Ex. Insulin), antibodies (Lysozyme), are all proteins. Enzymes are specific for each chemical reaction. Enzyme substrate complex is formed when substrate binds with active site of enzyme. The names of the enzymes always end with ___ ase. iv. Nucleic Acids – DNA is the genetic material which is inheritable. It is double stranded, helical in structure and formed by polymers of nucleotides. A nucleotide is composed of N base, pentose sugar and phosphate groups. Back bone in both RNA and DNA backbone is made up of Sugar and phosphate. RNA is single stranded. Sugar in DNA is deoxyribose, sugar in RNA is ribose. In both nucleic acids Purines (AG) always pair with Pyramidines (CT/U). Thymine in DNA is replaced by Uracil in RNA. 9. Metabolism: It includes two processes, Anabolism (forming large molecules from small molecules) and catabolism (breaking large molecules to form small molecules). Anabolism + Catabolism = Metabolism

a) Exergonic reaction (Catabolism). A reaction where energy is released. The example of exergonic reaction that occurs in our body is cellular respiration, which releases energy that is used for cell activities. C6H12O6 (glucose) + 6 O2 -> 6 CO2 + 6 H2O b) Endergonic reaction (Anabolism) energy is absorbed as the reaction proceeds. Examples of endergonic reaction are muscle contraction and protein synthesis. c) ATP powers cellular work by coupling exergonic reactions to endergonic reactions d) Energy is the capacity to cause change and is needed to do work. Potential energy is associated with the location of the matter. Kinetic energy is associated with relative motion of objects. Ex. Heat. Chemical energy is potential energy available for release in a chemical reaction, breaking and forming bonds between atoms is a form of energy. e) First law of Thermodynamics states that “Energy can neither be created nor destroyed it can only be transferred and transformed from one form to another”. Energy flows into the ecosystem in the form of light energy and exits in the form of heat energy. i) Photosynthesis: The process of conversion of energy from the sunlight into chemical energy by chloroplast. Plants feed the entire living world directly or indirectly (a) Chloroplasts- are the sites of photosynthesis. It has two membranes surrounding fluid like stroma. Inner membrane forms sacs called thylakoids which are stacked to form granum. Chlorophyll resides in thylakoid membrane which absorbs light energy and undergoes photosynthesis. . (b) Stages of Photosynthesis - Photosynthesis involves two stages: Light reactions (photo) & Calvin cycle (synthesis) (i) Light reaction converts solar energy into chemical energy after photophosphorylation (ii) Calvin Cycle includes carbon fixation, incorporation of CO2 into organic molecules (sugars) ii) Cellular Respiration: The most efficient way for cells to harvest energy stored in food is through cellular respiration, a catabolic pathway for the production of adenosine triphosphate (ATP). Cellular respiration occurs in both eukaryotic and prokaryotic cells. It has three main stages: (1) Glycolysis (breaks down glucose into two molecules of pyruvate, occurs in cytoplasm) (2) The citric acid cycle/Krebs Cycle (completes the breakdown of glucose, releases CO2). (3) Oxidative phosphorylation (Includes electron transport and chemiosmosis, accounts for most of the ATP synthesis) Substrate level phosphorylation occurs in glycolysis and citric acid cycle releasing some ATP. For each molecule of glucose the cell makes 30-38 molecules of ATP iii) Anaerobic respiration and Fermentation: The two mechanisms by which certain cells can generate ATP without oxygen: Anaerobic respiration and fermentation. (a) Anaerobic respiration occurs in prokaryotes does not need oxygen to complete the process. In this case electron acceptor is not oxygen, it can be nitrate, sulfate or carbonate, energy is gained from electron transport

(b) Fermentation allows continuous generation of ATP by substrate level phosphorylation of glycolysis. Two common types are alcohol fermentation (CO2 is released and end product is ethanol, Ex. Yeast in brewing, wine making) and lactic acid fermentation (Ex. fungi and bacteria used to make cheese and yogurt and Human muscle cells)....