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Parts of Microscope 1. Arm It is in the back of the microscope and supports the objectives and ocular. Also, it is the part that we use to carry or lift it. 2. Base It’s the bottom of the scope. In addition, it houses the light source and the back section of base acts as a handle to carry the scope. 3. Course Focusing Knob We use it to adjust the position of objective lenses. Also, this should be done keeping in mind that the objective should not hit the slide. In addition, it should be stopped when the object is completely visible through the ocular. 4. Fine Focusing Knob We use it to bring the specimen in perfect focus once the specimen is visible through the course-focusing knob. Also, focus slowly to avoid contact between the objective and the specimen. 5. Illuminator It is the light source of the microscope. 6. Numerical Aperture or Objective lens It is found in a compound scope and is the lens that is closest to the specimen. 7. Ocular Lens This is the lens closest to the viewer in a compound light microscope. 8. Oil immersion Lens This is a 100x (100 times) objective lens. Also, this lens is small in order to attain high resolution and magnification. Furthermore, due to its size, it is important for the lens to get as much light as possible. Moreover, by immersion of lens in oil it eliminates the refraction of light, it happens because the glass and oil have almost the same refractive index. Most noteworthy, in this way the light is maximized and gives the clearest image. Besides, It oil immersion lens is used without oil then the produced Image will become unclear and has a poor resolution.

Energy is very useful to us. We have proved it in our previous lessons. But do you know that, energy can also be harmful? Yes, energy can harm or cause different health problems if we expose ourselves too much to it. Too much exposure to the bright light of the sun and other artificial lights can cause… a. damage to our eyes that may lead to blindness b. skin allergies that may lead to skin cancer c. sunburn We can prevent the above health problems by… a. avoiding looking directly to the source of bright light such as the sun. b. wearing hat or using umbrella when going out of the house during the hottest part of the day which is from 10 am to 2 pm. c. putting on sunblock to protect your skin Too much heat can cause… a. dehydration or loss of body fluids because of perspiration b. burns These can be prevented by… a. drinking plenty of water b. using pot holders when handling hot objects SCIENCE 2 – MODULE 6 SEIBO COLLEGE 29 Too much exposure to loud sounds can cause… a. hearing difficulty that may lead to deafness b. nervousness We can avoid these health problems if… a. we talk softly especially when the person we are talking to is near us b. we avoid places which have loud sounds. Electrical energy can give us a comfortable life, but it can cause great danger to us. So to avoid accidents that may harm us in handling electrical devices we need to practice safety precautions. Below is a list of the things that we should do. Study it carefully. Safety Precautions in Handling Electrical Devices 1. Never play with live wires and electrical plug. 2. Never touch any electrical device with wet hands. 3. Do not overload electrical sockets. 4. Do not play or insert things especially metals into electrical outlets. 5. Never play with the switch of any electrical device

PHOTOSYNTHESIS LIGHT DEPENDENT REACTION 1. Photosystem II (PSII) – Light Absorption & Water Splitting • Light energy (photons) excites electrons in chlorophyll molecules. • These high-energy electrons leave PSII and are passed into the electron transport chain (ETC). • Meanwhile, water molecules are split (photolysis) into: o O₂ (released as a by-product into the atmosphere) o H⁺ ions (protons, which build up inside the thylakoid) o Electrons (e⁻), which replace the ones lost by PSII. 2. Electron Transport Chain (ETC) • Excited electrons move through protein carriers embedded in the thylakoid membrane. • As they move, their energy pumps H⁺ ions into the thylakoid space, creating a proton gradient (high H⁺ inside, low outside). 3. ATP Production (ATP Synthase) • The buildup of H⁺ ions acts like a “waterfall” of potential energy. • These protons flow back across the membrane through ATP synthase, a protein complex that acts like a turbine. • This flow drives the conversion of ADP + Pi → ATP, which provides energy for the Calvin cycle. 4. Photosystem I (PSI) • Electrons arriving from the ETC enter PSI. • Sunlight excites them again, boosting them to a higher energy level. 5. NADPH Production • The energized electrons are transferred to NADP⁺. • Along with a proton (H⁺), this forms NADPH, another energy carrier. • NADPH is then delivered to the Calvin cycle to help build glucose. End Products of Light-Dependent Reactions: • ATP (energy source for Calvin cycle) • NADPH (reducing power for glucose synthesis) • O₂ (released into the atmosphere as waste) Light-Independent Reactions (Calvin Cycle) • These reactions do not directly require sunlight. • They occur in the stroma of the chloroplast (the fluid-filled space surrounding the thylakoids). • The inputs are ATP and NADPH (from light-dependent reactions) and CO₂ (from the atmosphere). • The outputs are glucose (C₆H₁₂O₆) and other carbohydrates. Think of the Calvin cycle as a factory that uses the energy and “raw materials” made in Stage I (ATP & NADPH) to build sugars. The 3 Main Steps of the Calvin Cycle 1. Carbon Fixation • CO₂ from the atmosphere enters the chloroplast and diffuses into the stroma. • Each CO₂ molecule attaches to a 5-carbon sugar called RuBP (ribulose-1,5-bisphosphate). • This reaction is catalyzed by the enzyme RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase — the most abundant enzyme on Earth!). • The result is a short-lived 6-carbon compound, which immediately splits into two 3-carbon molecules called 3-PGA (3-phosphoglycerate). Summary: CO₂ + RuBP → 2 × 3-PGA 2. Reduction Phase • The 3-PGA molecules are “energized” and converted into G3P (glyceraldehyde-3-phosphate), a more energy-rich 3-carbon sugar. • This transformation requires: o ATP (provides energy) o NADPH (provides high-energy electrons and hydrogen atoms). • Some of the G3P molecules will eventually be combined to form glucose and other sugars. Summary: 3-PGA + ATP + NADPH → G3P 3. Regeneration of RuBP • Not all G3P molecules leave the cycle. Most of them are used to regenerate RuBP so the cycle can continue. • This regeneration also requires ATP. • For every 3 turns of the cycle, 5 G3P molecules are recycled to regenerate 3 molecules of RuBP. Summary: G3P + ATP → RuBP The Full Cycle Balance • To make one G3P molecule that can exit the cycle (and later form glucose), the cycle must run 3 times, fixing 3 molecules of CO₂. • To make one glucose molecule (C₆H₁₂O₆), the cycle must run 6 times (since glucose needs 6 carbon atoms). Inputs (for 1 glucose): • 6 CO₂ • 18 ATP • 12 NADPH Outputs: • 1 glucose (C₆H₁₂O₆) • 18 ADP + 18 Pi • 12 NADP⁺ Day vs Night Clarification • The Calvin Cycle is called light-independent, but that doesn’t mean it only happens at night. • It usually happens during the day because it depends on ATP and NADPH, which are only produced in light-dependent reactions (when sunlight is available). Simplified Analogy • Carbon fixation = The factory brings in CO₂ as raw material. • Reduction = Workers use energy (ATP & NADPH) to shape the raw material into useful products (G3P). • Regeneration = Some products are recycled to keep the factory running (RuBP is re-formed). • Output = After enough cycles, the factory produces glucose, the “food” of the plant.

Orchard / fruit trees Importance of fruit trees • Fruit trees are important for the following uses: They are a source of food, they produce fruits Some are used for making medicines Others provide shade and can also act as wind breakers. Those with beautiful flowers are very decorative. They contain vitamins which means they have nutritional value. Classification of fruit trees • Fruit trees are classified as indigenous and exotic. Indigenous fruit trees • are those that natural grow in a country. • They take longer to grow. • Examples of indigenous fruit trees are: English name Shona Name Snot apple Water berry Red ivory Fig Monkey orange Wild custard apple Mobola fruit Exotic fruit trees • These are trees that were brought from other countries. • They are commercially grown in orchards. • Common exotic fruit trees include: • Exotic fruit trees grow faster than indigenous. Ornamental horticulture • It deals with the growing of decorative plants. • Decorative plants are collectively called ornamental plants. • They include trees, shrubs, flowers and lawn grasses. Importance of ornamental plants They beautify the environment. Flowers often produce a pleasing fragrance. Flowers attract insects like bees that are responsible for pollination. Plants produce oxygen that we need for breathing. • Some are used for making medicines. • Lawn grasses prevent soil erosion. • Plants provide shelter for birds and insects. Classification of ornamental plants • There are four classes of ornamental plants. Trees Shrubs Flowers Lawn Trees: • Ornamental trees are very useful as decorative plants. • This is because most of these trees produce beautiful flowers and some are ever green. • Examples of decorative trees include flamboyant, jacaranda, pines, Cyprus. Shrubs: • A shrub is a woody plant with many branches but smaller than a tree. • Some of them are ornamentals because they produce beautiful flowers. • Others can be cut into decorative shapes. • The golden duranta is good example because it can be cut into nice shapes. • The bougainvillea is another example of a decorative plant because: It can act as a climbing plant. It produces decorative flowers. It can also be cut into any shape using a hedge shear. Flowers: • Flowers have the following functions: They are used for decorations at weddings, hotels and parties. They are used as an expression of love and appreciation such as valentine’s day and get well soon messages. They are useful in bee farming called apiculture as they are a source of nectar used for making honey. Flowers produce a pleasant fragrance used in the production of soaps and scents for perfumes, deodorant and lotions. Lawn: • A lawn is an area of grass that is kept cut short and is usually part of someone's garden or backyard, or part of a park. • Some lawn grasses grown in Zimbabwe are Durban, kikuyu, couch and buffalo lawn. • They prevent soil erosion. • They also provide a comfortable outdoor resting place. Forestry Importance of trees • Trees are important to us and animals. • The Forestry Commission is responsible for taking care of trees in Zimbabwe. • Trees are also important to the environment because: They are a source of fuel in the form of firewood. They are used for making most of the furniture we use. Most medicines come from both exotic and indigenous trees, for example pine trees and gum trees are used for making cough medicines. Trees provide browsing animals like the kudu and giraffe with food. Fruits from both exotic and indigenous fruit trees are a rich source of vitamins Trees give out oxygen which we need for breathing. Trees provide timber that can be used for roofing. • Trees are grouped according to where they come from. • The groups are indigenous and exotic. 1 . Indigenous trees : • These are local trees that have always been grown in their country. Shona name English name Mutohwe Snot apple Mususu Yellow wood Mubvamaropa Blood wood Muuyu Baobab Muonde Fig tree Musasa msasa Characteristics of indigenous trees  take longer to mature  Do not produce straight poles  Grow on their own  Hard wood 2 .Exotic trees : • These are trees that have been brought from another country to be grown in Zimbabwe. Characteristics of exotic trees  They are brought in a country from another country. Grow very fast.  Have soft woods  Usually grow straight  Usually grown in orchards and plantations Common exotic trees in Zimbabwe are: Gum trees Pine trees Wattle Cyprus Date palm Mango Apple pawpaw Causes of plant damage • plant damage is when cultivated crops are kept from normal growth that leads to reduced yields. • plant damage is caused by both living and non living things. • Some of the common causes of crop damage are: (a)Pests • These are living organisms that cause physical damage to crops. • Examples of pests are weevils, army worm, aphids, cutworms and locusts. (b) Diseases • Plant diseases are caused by living organisms called pathogens. • These pathogens infest the plant and take away nutrients. • Fruit rot and bacteria spot are some of the examples of plant diseases. (c) Weeds • these are plant which grow where they are not wanted. • For example if black jack grows in a groundnut field, it is a weed. • Weeds compete for nutrients with cultivated plants. (d) Very high temperatures • High temperatures may cause crops to wither. • High temperatures may also lead to lightning and fires. • This can burn up crops. ( e) Frost • Frost damages crops in winter. • Tomatoes, potatoes, and beans are easily damaged by frost. (f) Drought • drought is when there is no rainfall in a season where it supposed to be raining. • It is one of the most serious forms of crop damage. • Plants wither and die if there is no rainfall. ( g) Animals • Wild animals like baboons often eat maize crops before they mature. • Birds also are a problem to crops like sorghum. Signs of plant damage • There are various signs that show plant damage. • Some can be corrected but some lead to total loss. • Some signs of plant damage include: Lodged plants Flowers and small fruits blown to the ground Dull leaf color Wilted plants Stunted growth

CARBOHYDRATES Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen in a ratio of about one carbon atom to two hydrogen atoms to one oxygen atom. The number of carbon atoms in a carbohydrate varies. Some carbohydrates serve as a source of energy. Other carbohydrates are used as structural materials. Carbohydrates can exist as monosaccharides, disaccharides, or polysaccharides. Monosaccharides A monomer of a carbohydrate is called a monosaccharide (MAHN-oh-SAK-uh-RIED). A monosaccharide—or simple sugar— contains carbon, hydrogen, and oxygen in a ratio of 1:2:1. The gen- eral formula for a monosaccharide is written as (CH2O)n, where n is any whole number from 3 to 8. For example, a six-carbon mono- saccharide, (CH2O)6, would have the formula C6H12O6. The most common monosaccharides are glucose, fructose, and galactose, as shown in Figure 3-6. Glucose is a main source of energy for cells. Fructose is found in fruits and is the sweetest of the monosaccharides. Galactose is found in milk. Notice in Figure 3-6 that glucose, fructose, and galactose have the same molecular formula, C6H12O6, but differing structures. The different structures determine the slightly different properties of the three compounds. Compounds like these sugars, with a single chemical formula but different structural forms, are called isomers (IE-soh-muhrz). SECTION 2 OBJECTIVES ● Distinguish between monosaccharides, disaccharides, and polysaccharides. ● Explain the relationship between amino acids and protein structure. ● Describe the induced fit model of enzyme action. ● Compare the structure and function of each of the different types of lipids. ● Compare the nucleic acids DNA and RNA. VOCABULARY carbohydrate monosaccharide disaccharide polysaccharide protein amino acid peptide bond polypeptide enzyme substrate active site lipid fatty acid phospholipid wax steroid nucleic acid deoxyribonucleic acid (DNA) ribonucleic acid (RNA) nucleotide C HO H C H OH C OH H C CH2OH H C H OH O Glucose C OH C O H OH C OH H CH2OH C H CH2OH Fructose C H HO C OH H C OH H C CH2OH H C H OH O Galactose Glucose, fructose, and galactose have the same chemical formula, but their structural differences result in different properties among the three compounds. FIGURE 3-6 Copyright © by Holt, Rinehart and Winston. All rights reserved. 56 CHAPTER 3 Disaccharides and Polysaccharides In living things, two monosaccharides can combine in a condensa- tion reaction to form a double sugar, or disaccharide (die-SAK-e-RIED). For example in Figure 3-4, the monosaccharides fructose and glu- cose can combine to form the disaccharide sucrose. A polysaccharide is a complex molecule composed of three or more monosaccharides. Animals store glucose in the form of the polysaccharide glycogen. Glycogen consists of hundreds of glucose molecules strung together in a highly branched chain. Much of the glucose that comes from food is ultimately stored in your liver and muscles as glycogen and is ready to be used for quick energy. Plants store glucose molecules in the form of the polysaccha- ride starch. Starch molecules have two basic forms—highly branched chains that are similar to glycogen and long, coiled, unbranched chains. Plants also make a large polysaccharide called cellulose. Cellulose, which gives strength and rigidity to plant cells, makes up about 50 percent of wood. In a single cellu- lose molecule, thousands of glucose monomers are linked in long, straight chains. These chains tend to form hydrogen bonds with each other. The resulting structure is strong and can be broken down by hydrolysis only under certain conditions. PROTEINS Proteins are organic compounds composed mainly of carbon, hydrogen, oxygen, and nitrogen. Like most of the other biological macromolecules, proteins are formed from the linkage of monomers called amino acids. Hair and horns, as shown in Figure 3-7a, are made mostly of proteins, as are skin, muscles and many biological catalysts (enzymes). Amino Acids There are 20 different amino acids, and all share a basic structure. As Figure 3-7b shows, each amino acid contains a central carbon atom covalently bonded to four other atoms or functional groups. A single hydrogen atom, highlighted in blue in the illustration, bonds at one site. A carboxyl group, —COOH, highlighted in green, bonds at a second site. An amino group, —NH2, highlighted in yel- low, bonds at a third site. A side chain called the R group, high- lighted in red, bonds at the fourth site. The main difference among the different amino acids is in their R groups. The R group can be complex or it can be simple, such as the CH3 group shown in the amino acid alanine in Figure 3-7b. The differences among the amino acid R groups gives different proteins very different shapes. The different shapes allow pro- teins to carry out many different activities in living things. Amino acids are commonly shown in a simplified way such as balls, as shown in Figure 3-7c. (a) Many structures, such as hair and horns are made of proteins. (b) Proteins are made up of amino acids. Amino acids differ only in the type of R group (shown in red) they carry. Polar R groups can dissolve in water, but nonpolar R groups cannot. (c) Amino acids have complex structures, so, in this and other textbooks, they are often simplified into balls. FIGURE 3-7 (b) Alanine (an amino acid) (c) Simplified version of amino acid CH3 H N OH C C H O H (a) Copyright © by Holt, Rinehart and Winston. All rights reserved. BIOCHEMISTRY 57 H H N C C OH H O H CH3 H2O Glycine Alanine H N OH C C H O H H H N C C H O H CH3 N OH C C H O H (a) (b) (a) The peptide bond (shaded blue) that binds amino acids together to form a polypeptide results from a condensation reaction that produces water. (b) Poly- peptides are commonly shown as a string of balls in this textbook and elsewhere. Each ball represents an amino acid. FIGURE 3-8 Substrate Products Enzyme 1 2 3 In the induced fit model of enzyme action, the enzyme can attach only to a substrate (reactant) with a specific shape. The enzyme then changes and reduces the activation energy of the reaction so reactants can become products. The enzyme is unchanged and is available to be used again. 3 2 1 FIGURE 3-9 Dipeptides and Polypeptides Figure 3-8a shows how two amino acids bond to form a dipeptide (die-PEP-TIED). In this condensation reaction, the two amino acids form a covalent bond, called a peptide bond (shaded in blue in Figure 3-8a) and release a water molecule. Amino acids often form very long chains called polypeptides (PAHL-i-PEP-TIEDZ). Proteins are composed of one or more polypep- tides. Some proteins are very large molecules, containing hun- dreds of amino acids. Often, these long proteins are bent and folded upon themselves as a result of interactions—such as hydrogen bonding—between individual amino acids. Protein shape can also be influenced by conditions such as temperature and the type of solvent in which a protein is dissolved. For exam- ple, cooking an egg changes the shape of proteins in the egg white. The firm, opaque result is very different from the initial clear, runny material. Enzymes Enzymes—RNA or protein molecules that act as biological catalysts—are essential for the functioning of any cell. Many enzymes are proteins. Figure 3-9 shows an induced fit model of enzyme action. Enzyme reactions depend on a physical fit between the enzyme molecule and its specific substrate, the reactant being catalyzed. Notice that the enzyme has folds, or an active site, with a shape that allows the substrate to fit into the active site. An enzyme acts only on a specific substrate because only that substrate fits into its active site. The linkage of the enzyme and substrate causes a slight change in the enzyme’s shape. The change in the enzyme’s shape weakens some chemical bonds in the substrate, which is one way that enzymes reduce activation energy, the energy needed to start the reaction. After the reaction, the enzyme releases the products. Like any catalyst, the enzyme itself is unchanged, so it can be used many times. An enzyme may not work if its environment is changed. For example, change in temperature or pH can cause a change in the shape of the enzyme or the substrate. If such a change happens, the reaction that the enzyme would have catalyzed cannot occur.

By the late 1800s, the Spanish were losing control of Cuba. Concerned about insurrection in the countryside, they moved rural Cubans to “reconcentration” camps where the Spanish claimed they would be better able to protect them. U.S. Consul-General Fitzhugh Lee forwarded the following account of the conditions of the camps to the U.S. Assistant Secretary of State on November 27, 1897. Lee said the author of the note was “a man of integrity and character.” “[W]e will relate to you what we saw with our own eyes: “Four hundred and sixty women and children thrown on the ground, heaped pellet-mell as animals, some in a dying condition, others sick and others dead. . . . “There is still alive the only living witness, a young girl of 18 years, whom we found seemingly lifeless on the ground; on her right-hand side was the body of a young mother, cold and rigid, but with her young child still alive clinging to her dead body; on her left-hand side was also the corpse of a dead woman holding her son in a dead embrace. . . . “The circumstances are the following: complete accumulation of bodies dead and alive, so that it was impossible to take one step without walking over them; the greatest want of cleanliness, want of light, air, and water; the food lacking in quality and quantity what was necessary to sustain life. . . . From all this we deduct that the number of deaths among the reconcentrados has amounted to 77 per cent.” Source: Unsigned note that was included in a telegram sent by Fitzhugh Lee, U.S. Consul-General in Cuba, to the U.S. Assistant Secretary of State November 27, 1897. consul-general: a government official living in a foreign country charged with overseeing the protection of U.S. citizens and promoting trade pell-mell: state of disorder accumulation: pile want: lack reconcentrados: the reconcentration camp prisoners; The following is an excerpt from Albert J. Beveridge’s speech, delivered September 16, 1898. Beveridge gave this speech while he was campaigning to become a senator for Indiana. The speech helped him win the election and made him one of the leading advocates of American expansion. “Fellow citizens, it is a noble land that God has given us; a land that can feed and clothe the world;. . . . It is a mighty people that he has planted on this soil . . . It is a glorious history our God has bestowed upon his chosen people; . . .a history of soldiers who carried the flag across the blazing deserts and through the ranks of hostile mountains, even to the gates of sunset. . . . “The Opposition tells us that we ought not to govern a people without their consent. I answer: The rule of liberty that all just government derives its authority from the consent of the governed, applies only to those who are capable of self-government. I answer, We govern the Indians without their consent, we govern our territories without their consent, we govern our children without their consent. “They ask us how we will govern these new possessions. I answer: If England can govern foreign lands, so can America. If Germany can govern foreign lands, so can America. . . . “What does all this mean for every one of us? It means opportunity for all the glorious young manhood of the republic, the most virile, ambitious, impatient, militant manhood the world has ever seen. It means that the resources and the commerce of these immensely rich dominions will be increased. . . . “In Cuba, alone, there are 15,000,000 acres of forest unacquainted with the axe. There are exhaustless mines of iron. . . . There are millions of acres yet unexplored. . . . It means new employment and better wages for every laboring man in the Union. . . .

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