As humans, we are the most dominant species in the world. We have the ability to walk upright, grasping thumbs, and large brains. This helps us to live and be successful on earth. But, these advantages we have didn’t happen overnight, they occurred during the hominine evolution. The skull, neck, spiral column, hip bones, and leg bones of the early hominine species changed shape in ways that later enabled species to walk upright. The evolution of dipedal, or two-footed, locomotion was very important, because it freed both hands to use tools. The hominine hand evolved opposable thumbs that could touch the tips of fingers, enabling the group of objects and the use of tools. Hominine’s evolved much larger brains. Most of the difference in brain size results from an expanded cerebrum, which is, as you recall the “thinking” part of the brain. It’s really extraordinary how humans came to be, it all started from atoms, a strike of lightning and macromolecules. Carbon atoms have four valence electrons allowing them to form strong covalent bonds with many other elements, including hydrogen, oxygen, phosphorus, sulfur, and nitrogen. Living organisms are made up of molecules that consist of carbon and these three other elements. Carbon atoms can also bond to each other, which gives carbon the ability to form millions of different large and complex structures. Many of the organic compounds in living cells are macromolecules or “giant molecules”, made from thousands or even hundreds of thousands of smaller molecules. Most macromolecules are formed by a process known as polymerization, in which large compounds are built by joining smaller ones together. The smaller units, or “monomers”, join together to form polymers. Biochemists sort the macromolecules found in living things into groups based on their chemical composition. The four major macromolecules in all living things are carbohydrates, lipids, proteins, and nucleic acids. Each of these macromolecules has a specific function to carry out, and is crucial to not only humans, but every living organism on earth. Carbohydrates are compounds made up of carbon, hydrogen, and oxygen atoms. Living things use carbohydrates as their main sources of energy. The breakdown of sugars, such as glucose, supplies immediate energy for cell activities. Plants, some animals, and other organisms also use carbohydrates for structural purpose. Single sugar molecules are also known as monosaccharides. Besides glucose, monosaccharides include galactose, which is a component of milk, and fructose, which is found in many fruits. Ordinary table sugar, sucrose, is a disaccharide, a compound made by joining glucose and fructose together. The large macromolecules formed from monosaccharides are known as polysaccharides. Many organisms store extra sugar as complex carbohydrates known as starches. Starches are made by plants and digested by animals. The monomers in starch polymers are sugar molecules, such as glucose. Plants also make an important polysaccharide called cellulose (fiber) which is used to give plants strength and support and cannot be digested by animals. Many animals store excess sugar in a polysaccharide called glycogen. When the level of glucose in your blood runs low, glycogen is broken down into glucose, which is then released into the blood. The glycogen stored I your muscles supplies energy for muscle contraction. Carbohydrates are an important source of energy for the cell, there are two ways the cell uses energy it stores and releases it. One of the most important compounds that cells use to store and release energy is adenosine triphosphate (ATP). ATP consists of adenine a 5- carbon sugar called ribose, and three phosphate groups. Adenosine diphosphate (ADP) looks almost like ATP, except that it has two phosphate groups instead of three. ADP contains some energy, but not as much as ATP. When a cell has energy available, it can store small amounts of it by adding phosphate groups to ADP, producing ATP. ADP is like a rechargeable battery that powers the machinery of the cell. Cells can release energy stored in ATP by breaking the bonds between the second and third phosphate groups. Because a cell can add or subtract these phosphate groups, it has an efficient way of storing and releasing energy as needed. One way cells use the energy provided by ATP is to carry out active transport. Many cell membranes contain sodium-potassium pumps. ATP provides the energy that keeps these pumps working, maintaining a balance of ions on both side of the cell membrane. Energy from ATP powers the synthesis of proteins and responses to chemical signals at the cell surface. ATP is not a good molecule for storing large amounts of energy over the long term. Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose. Organisms that obtain food by consuming other organisms are known as heterotrophs. Some heterotrophs get their food by eating plants. Other heterotrophs, such as a cheetah, obtain food from plants indirectly by feeding on plant-eating animals. Still other heterotrophs, such as mushrooms, obtain food by decomposing other organism. Organisms that make their own food are called autotrophs. Plants, algae, and some bacteria use light energy from the sun to produce food. The process by which autotrophs use the energy of sunlight to produce high-energy carbohydrates that can be used for food is known as photosynthesis. Photosynthesis is when organisms produce glucose (food) and oxygen gas from the reactants of water, carbon dioxide, and light. Chlorophyll acts like a solar panel. Chlorophyll is a pigment which captures light energy in plants, algae, and some bacteria. The energy it collects is used to make glucose. Glucose can then be used to make more complex sugars like starch and cellulose. Food provides living things with the chemical building blocks they need to grow and reproduce. Food molecules contain chemical energy that is released when its chemical bonds are broken. Energy stored in food is expressed by units of calories. A calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius. 1,000 calories=1 kilocalorie, or calorie. Cells use all sorts of molecules for food, including fats, proteins, and carbohydrates the energy stored in each of these molecules varies because of their chemical structures, and therefore their energy-storing bonds, differ. Cells break down food molecules gradually and use the energy stored in the chemical bonds to produce compounds such as ATP that powers the activities of the cell. All organisms carry out some form of cellular respiration. Cellular respiration provides organism the energy needed to carry out life processes. The process occurs in the mitochondria. Cellular respiration is where cells use oxygen to break down large organic food molecules into simpler molecules. Chemical energy stored in food molecules is converted into another form of chemical energy (ATP). Cells in both plants and animals then use ATP as their main energy supply. The three main stages of cellular respiration are glycosis, the Krebs cycle, and the electron transport chain. During the first stage, glycosis, which occurs in the cytoplasm does not require energy and produces 2 ATP molecules. The next two stages, Krebs cycle and the electron transport chain do require energy and produce 34 ATP molecules. The overall reaction of cellular respiration produces 36 total ATP molecules. If there is not enough oxygen present, glycosis is followed by anaerobic respiration. Some cells can create energy without oxygen through anaerobic respiration. Fermentation is a process that makes ATP with no oxygen. But it produces no additional ATP. When oxygen is not present there is an overall net gain of 2 ATP per glucose molecule. There are two major types of fermentation which are lactic and alcoholic fermentation. Some organisms thrive in environments with little or no oxygen in places such as marshes, bogs, guts of animals, and sewage treatment ponds. Lactic acid fermentation occurs in muscle cells when oxygen supply is too low. Cellular respiration continues but fermentation is main ATP source. This results in muscle soreness after strenuous exercise, buts its relieved after oxygen supply is restored. On the other hand there is alcoholic fermentation, you can think of it as the yeast that causes bread to rise. This fermentation is used in the brewing industry, released co2 makes champagne and beer bubbly, and as I’ve stated before is used by bakers to make bread rise. Fungi and bacteria produce lactic acid like muscle cells. Human muscle cells make ATP with and without oxygen. They have enough ATP to support activities such as quick sprinting for about 5 seconds. A second supply of energy (creatine phosphate) can keep muscle cells going for another 10 seconds. Overall, plants do photosynthesis, and animals as well as humans do cellular respiration. Photosynthesis and cellular respiration are opposite processes. Photosynthesis in plants is mad possible by plants structure and function. Plants organs such as leaves, stems, and toots. Shoot systems that include leaves and stems, and a root system that includes taproots and fibrous roots help carry water minerals through the stem that feeds and provides nutrition for the plant. Plant leaves consist of a blade and petiole, the leaf exposes surface to sunlight, and conserves water. The stoma which is an opening in the leaf is for gas exchange and water evaporation. The stem holds leaves up to light, and transports substances through vascular tissue. The roots (fibrous and taproots) anchors plants in soil, and takes up water and minerals from the soil. There are also three types of plant tissues. Vascular tissue transports and supports, ground tissue is responsible for the synthesis of sugar, storage, and support, and finally dermal tissue is for protection. Overall, photosynthesis and cellular respiration are opposite processes. The energy flows in opposite directions. Photosynthesis “deposits” energy, and cellular respiration “withdraws” energy. The reactants of cellular respiration are the products of photosynthesis and vice versa. In the same sense matter flows just like energy, but unlike the one-way flow of energy, matter is recycled within and between ecosystems. Elements pass from one organism to another among parts of the biosphere through closed loops called biogeochemical cycles which are powered by the flow of energy. As matter moves through these cycles, it is never created or destroyed ---- just changed. Biological processes consist of any and all activities performed by living organisms. These processes include eating, breathing, “burning” food, and eliminating waste products. Geological processes include volcanic eruptions, the formation and breakdown of rock, and major movements of matter within and below the surface of the earth. Chemical and physical processes include the formation of clouds and precipitation, the flow of running water, and the action of lightning. One cycle is the nutrient cycle. The chemical substances that an organism needs to sustain life are called nutrients. Every organism needs nutrients to build tissues and carry out life functions. Nutrients pass through organisms and the environment through biogeochemical cycles. Oxygen participates in parts of carbon, nitrogen and phosphorus cycles by combining with these elements and cycling them through parts of their journeys. Oxygen gas in the atmosphere is released by one of the most important biological activities: photosynthesis. Oxygen is used in respiration by all multicellular forms of life, and many single celled organisms as well. Now the carbon cycle is a little different. Carbon is a major component of all organic compounds, including carbohydrates, lipids, proteins, and nucleic acids. Carbon dioxide is continually exchanged through chemical and physical processes between the atmosphere and oceans. Plants take in carbon dioxide during photosynthesis and use the carbon the build carbohydrates. Carbohydrates then pass through the food web to consumers. Organisms release carbon in the form of carbon dioxide gas by respiration. When organisms die, decomposers break down the bodies, releasing carbon the environment. Geological forces can turn accumulated carbon into carbon-containing rocks or fossil fuels. Carbon dioxide is released into the atmosphere by volcanic activity or by human activities, such as the burning of fossil fuels and the clearing and burning of forests. The final cycle of matter is the water cycle. Water molecules typically enter the atmosphere as water vapor when they evaporate from the ocean or other bodies of water. Water can also enter the atmosphere by evaporating from the leaves of plants in the process of transpiration. If the air carrying it cools, water vapor condenses into tiny droplets that form clouds. When the droplets become large enough, they fall to earth’s surface as precipitation in the form of rain, snow, sleet, or hail. On land, some precipitation flows along the surface in what scientists call runoff, until it enters a river or stream that carries it into an ocean or lake. Precipitation can also be absorbed into the soil, and then is called groundwater. Ground water can enter plants through their roots, or flow into rivers, streams, lakes, or oceans. Some groundwater penetrates deeply enough into the ground to become a part of water reservoirs. Water is a very crucial element to an ecosystem. Water is made up of three atoms --- one oxygen and two hydrogen. Water has many unique properties such as cohesion, adhesion, high specific heat, high heat of vaporization, and being less dense as a solid. Because of these many characteristics water is able to support life. 75% of the earth is covered by water. This includes freshwater ecosystems, wetlands, estuaries, marine ecosystems, costal ocean, coral reefs, and the open ocean. These aquatic ecosystems support various unique aquatic life. Lipids are another macromolecule. Lipids are a large and varied group of biological molecules. Lipids are made mostly from carbon and hydrogen atoms and are generally not soluble in water. The common categories of lipids are fats, oils, and waxes. Lipids can be used to store energy. Some lipids are important parts of biological membranes and waterproof coverings. Steroids synthesized by the body are lipids as well. Many steroids, such as hormones, serve as chemical messengers. Many lipids are formed when a glycerol molecule combines with the compounds called fatty acids. If each carbon atom in a lipids fatty acid chain is joined to another carbon atom by a single bond, the lipid is said to be saturated. If there is at least one carbon-carbon bond in a fatty acid, the fatty acid is said to be unsaturated. Lipids whose fatty acids contain more than one double bond are said to be poly-saturated. Lipids that contain unsaturated fatty acids, such as oil, tend to be liquid at room temperature. Lipids that contain saturated fatty acids such as butter tend to be solid at room temperature. For a cell, lipids serve as waterproof coverings for the cell membrane that protects the cell. The cell membrane is responsible for passive and active transport which move substances across a membrane. In a cell, is a constant regeneration of new cells through mitosis, and on the other hand there’s meiosis. Meiosis produces sex cells that are vital to both male and female reproductive systems and fetal development. The function of reproductive systems is to ensure the survival of a species. The male’s consists of a pair of testes, a network of excretory ducts, seminal vesicle, prostate, urethra, and the penis. Its functions are to produce, maintain and transport sperm and semen, and to produce and secrete male sex hormones responsible for maintaining the male reproductive system. The female reproductive system consists of a vagina, uterus, ovaries, and fallopian tubes. Its functions are to produce female sex egg cells, transports the eggs to the site of fertilization, and the fertilization occurs in the fallopian tubes. Fertilization begins with 46 pair of chromosomes, splits off to 23 then combines for a unique new 46 pair. The stages of development are zygote, 2-cell stage, 4-cell stage, 8-cell stage, morula, blastula, early gastrula, and late gastrula. During pregnancy there are 3 trimesters, each one is an upgrade all the way until birth. Last but not least, proteins are macromolecules that contain nitrogen as well as carbon, hydrogen, and oxygen. Proteins are polymers of molecules called amino acids. Proteins preform many varied functions, such as the rate of reactions and regulating cell processes, forming cellular structures, transporting substances into or out of cells, and helping to fight disease. One protein is enzymes. Some chemical reactions are too slow for living tissues. Enzymes are proteins that speed up chemical reactions that take place in cells by acting as a catalyst. A catalyst is a substance that speeds up the rate of reaction. Enzymes speed up the rate of reaction by lowering the activation energy level. Proteins help fight diseases. Diseases are spread through coughing, sneezing, physical contact, and the exchange of body fluids. Some diseases are spread through contaminated water or food, and infected animals. An infectious disease is one that causes physiological changes that disrupt normal body functions. Our body provides its own defense against infection both specific and non-specific. Non-specific defenses include skin, tears, other secretions, inflammatory response, interferon, and fever. Specific defenses are immune response. The immune systems specific defenses inactivate or kill any foreign substance or cell that enters the body. Finally, the last macromolecules are nucleic acids. Nucleic acids store and transmit hereditary or genetic, information. They contain hydrogen, oxygen, nitrogen, carbon, and phosphorus. Individual nucleotides can be joined by covalent bonds to form a polynucleotide, or nucleic acid. There are two kinds of nucleic acids: ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). RNA contains the sugar ribose and DNA contains the sugar deoxyribose. Genes contain coded DNA instructions that tell cells how to build proteins. The first step in decoding these genetic instructions is to copy part of the base sequence from DNA into RNA. RNA and DNA are different in 3 major ways. The sugar in RNA is ribose instead of deoxyribose. RNA is generally single stranded and not double stranded, and RNA contains uracil in place of thymine. There are 3 types of RNA, messenger RNA, ribosomal RNA, and transfer RNA. They make protein through transcription and translation. Changes in the nucleotide sequence in DNA can cause mutations. Most mutations are neutral and they happen regularly. But some can be harmful, while others may improve an organism’s survival (beneficial). Other benefits can result from natural selection, which is best described as “survival of the fittest”. When genetic drift takes place mutations can make or break a species. Mutations may cause one species to adapt easier than another, giving them an advantage to thrive in an environment. We originated from the very first cells, and evolved from the hominine evolution into the humans we are today. The four major macromolecules carbohydrates, proteins, lipids, and nucleic acids, have various functions that help carry out many life functions. We are interconnected from the smallest atom to the vastness of the universe that fit perfectly together like pieces of a puzzle.
