2 weeks of notes, CH 5 and 6
2 weeks of notes, CH 5 and 6 Biology 1010 (Anderson)
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This 15 page Bundle was uploaded by Emily Johnson on Saturday October 1, 2016. The Bundle belongs to Biology 1010 (Anderson) at Austin Peay State University taught by Kelly Anderson in Fall 2016. Since its upload, it has received 8 views. For similar materials see Principles of Life 1 in Biology at Austin Peay State University.
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Date Created: 10/01/16
Biology 1010 Notes: Weeks of 9/19-9/23 and 9/26-9/30 (Test 2 Material) I’m sorry these are late!!! I had the flu, so I just combined both weeks. Monday 9/19: The Working Cell: Basic Concepts of Energy: ● Energy is defined as the capacity to cause change. ● Work is performed when an object is moved against an opposing force ○ Ex: gravity ● Kinetic energy is the energy of motion. ● Conservation of energy states that energy cannot be created or destroyed. ● Like matter, energy can only be converted. ● Potential energy is energy that an object has because of its location/structure. ● Entropy is the measure of disorder or randomness in a system. ● Heat (a type of kinetic energy) involves random motion of atoms and molecules. ● Although heat production does not destroy energy, it does make it less useful. ● Life depends on the conversion of one energy to another. ● Forms of energy: ○ Kinetic energy ○ Potential energy ○ Heat ○ Entropy ● Molecules of food, gasoline, and other fuels contain a special form of potential energy called chemical energy which is stored in the chemical bonds of these molecules. ● Carbohydrates, fats, and gasoline have structures that make them especially rich in chemical energy. ● In life, organic fuel is broken down into smaller waste molecules, which releases energy that can be used for work. ● Cells use oxygen in reactions that release energy from fuel molecules. Food Calories: ● The combustion of fuel in cells is called cellular respiration. ○ Cellular respiration is the energy- releasing chemical breakdown of fuel molecules and the storage of that energy in a form the cell can use to perform work. ● A calorie is the amount of energy that can raise the temperature of 1 gram of water by 1 degree Celsius. ● Calories on food packages are actually kilocalories. 1kcal=1,000 calories. ● Calories are a very small unit of measurement, which is why food is measured in kilocalories. Chemical Energy and Food Calories: ● Chemical energy of organic fuel is harvested using oxygen. ● Entropy increases when energy changes form. ● A gasoline engine is only about 25% efficient due to the entropy caused by chemical energy. ATP and Cellular Work: ● The carbs, fats, and other fuel we obtain from food do not drive work in our cells directly. Instead, the chemical energy is released by the breakdown of organic molecules during cellular respiration is used to generate molecules of ATP. ● The molecules of ATP power work in our cells. ● ATP stores energy obtained from food and releases it when needed. ● ATP consists of: ○ An organic molecule called adenosine ○ A tail of three phosphate groups ■ Each phosphate group is negatively charged. Negative charges repel each other. ● The crowding of negative charges on the tail causes 1 phosphate to be released, making energy available to the cell. ● What is left is ADP (adenosine diphosphate), with 2 phosphate groups instead of 3. ● When ATP does work in cells, the phosphate groups serve the purpose of providing energy to other molecules. ATP energizes molecules by transferring phosphates to them. ○ This transfer allows for 3 kinds of work: ■ Mechanical ■ Transport ■ Chemical ● All work occurs when target molecules accept a phosphate group from ATP. The ATP Cycle: ● Your body naturally renews ATP continuously. ● ATP can be restored by adding another phosphate group to ADP. (Essentially, turning a diphosphate back into a triphosphate.) ○ This restoration takes energy and is where the harvested energy from cellular respiration comes in. ● Cellular work spends ATP, which is recycled when ADP is combined with a phosphate. Enzymes: ● Enzymes are proteins that speed up chemical reactions without being consumed by the reaction. ● The total of all chemical reactions in an organism is called a metabolism. ● Most reactions require the assistance of enzymes. ● All living organisms contain enzymes. Each enzyme assists a different reaction. Enzymes and Chemical Reactions: ● To begin a chemical reaction, chemical bonds must be broken. The energy needed to activate the reactants and cause the chemical reaction is called activation energy. ● Enzymes are selective in the reactions they catalyze. An enzyme’s substrate is its ability to recognize a reactant molecule. An enzyme’s ability to bind to its substrate depends on the enzyme’s shape. ● Active site: the region of the enzyme that has the shape and chemistry needed to fit its substrate molecule. ● Induced fit: when a substrate falling into the active site changes its shape slightly to embrace the substrate and catalyze the reaction. ● After the products are released from the active site, the enzyme can accept another molecule of its substrate. The ability to function repeatedly is a key characteristic of enzymes. ● Many enzymes are named for their substrates but have an -ase ending. ● An enzyme inhibitor is a chemical that interferes with an enzyme’s activity by changing its shape. As a result, the enzyme will no longer accept its substrate. ● Enzyme inhibition is key to many drugs. Antibiotics in particular work by inhibiting disease-causing bacteria. ○ An example of an enzyme-inhibiting drug is ibuprofen. It inhibits an enzyme that is involved in the sending of pain signals. ● Toxins and poisons are irreversible inhibitors. They bind to the active site that is vital to transmitting nerve impulses. The inhibition leads to paralysis of vital functions. Membrane Function: ● Cells regulate the flow of materials between the environment with the help of a plasma membrane. ● A plasma membrane is selectively permeable, meaning that it only allows certain substances in and out of the cell. ● 3 types of membrane proteins: ○ Attachment to the cytoskeleton and extracellular matrix: helps maintain cell shape and coordinate changes ○ Enzymatic activity: enzymes ○ Transport: move substances across a cell membrane by providing a channel for solutes to pass through Passive Transport: Diffusion ● Molecules are always moving, they are restless. This movement causes diffusion. Diffusion is the movement of molecules into an available space. ● Diffusion of molecules is directional, moving from high concentration to low concentration. ● Diffusion across a membrane is passive transport. Passive transport is when a substance diffuses down its concentration gradient, meaning it moves from where the substance is more concentrated to where it is less concentrated. It is passive because the cells aren’t using energy to move the molecules. ● Facilitated diffusion is a kind of passive transport that transports substances via proteins that act as corridors to move larger molecules. ● Size and charge affect the rate of diffusion across a membrane. ● Some molecules move independently, others need transport proteins. Osmosis: ● Solute: substance dissolved into a solvent ● Solvent: dissolving agent. ● Solution: a liquid mixture of 2 or more substances. ● Hypotonic solutions have a lower concentration of the solute. Less solute, more water. ● Hypertonic solutions have a higher concentration of the solute. More solute, less water. ● Solutions with equal amount of the solute and solvent are isotonic. ● During osmosis, water diffuses across the membrane down its concentration gradient, meaning that it is moving from an area of higher water concentration to an area of lower water concentration. It reduces the difference in solute concentrations, and changes the volume of the two solutions as a result. ● In a hypertonic environment, the water will move out of the cell and shrink. ● In a hypotonic environment, the water will move into the cell and swell or burst. This is known as lysis when it occurs in animal cells. ● In an isotonic environment, there is no net movement of water molecules. ● For an animal to survive this osmosis, they have to have a way to balance the uptake and loss of water. This is called osmoregulation. ● Humans can suffer consequences if osmoregulation fails. An example of this is dehydration. ● In plant cells, the water balance issues are different because of their rigid cell walls. ● If a plant cell comes in contact with an isotonic solution, the plant cell will turn floppy and the plant wilts. Water is lost in the process which is bad for plants. ● If a plant cell comes in contact with a hypotonic solution, the plant cell will be turgid due to a net inflow of water. ● If a plant cell comes in contact with a hypertonic solution, the plant cell will lose water, shrivel and its plasma membrane will pull away from the cell wall. This is called plasmolysis, and it kills the cell. ● Turgor is necessary for plants to retain their upright structure. ● Plants do best in a hypotonic solution. Active Transport: ● Active transport requires a cell that spends energy to move molecules across a membrane. ● A cell can use energy from ATP and get help from transport proteins to pump a solute against its concentration gradient, meaning it is going from regions of low concentration to regions of high concentration. ● Active transport allows for cells to maintain their internal concentration of small solutes. ● Exocytosis is the movement of materials out of the cytoplasm via vesicles. Transport vesicles fuse with the cell membrane. ● Endocytosis is the movement of materials from the external environment into the cytoplasm via vesicles. The cell membrane folds in to become transport vesicles. 9/23, 9/26, 9/28: Chapter 6: Cellular Respiration: The Importance of Photosynthesis: ● Photosynthesis is the conversion of light energy into chemical energy. It provides sustenance for plants, which in turn provides food for animals. Humans and other animals depend on photosynthesis for food, cotton, lumber, paper, etc. ● Plants, algae, and photosynthetic bacteria are autotrophs. Autotrophs make their own food from inorganic ingredients, via photosynthesis. ○ “Food” in the form of organic matter: carbohydrates, lipids, proteins, and nucleic acis. ○ “Inorganic ingredients”: CO2, water, and minerals from soil. ● Autotrophs are referred to as producers because they support all others in a food chain. ● Humans and animals are heterotrophs. Heterotrophs rely on consuming food to obtain energy. They cannot make their own organic food molecules from inorganic ingredients. Heterotrophs are called consumers because they eat plants or animals that have eaten plants. ○ Heterotrophs depend on autotrophs for organic fuel and raw organic materials needed to build cells and tissues. ● Producer=autotroph, consumer=heterotroph. ● In plant cells, chloroplasts use light energy to produce sugars, most importantly glucose. ○ Both animals and plants use the organic products of photosynthesis as sources of energy. ● Cellular respiration uses oxygen to convert energy stored in chemical bonds of organic fuels to ATP. Cells use ATP for almost all of their work. ● In both plants and animals, the production of ATP occurs in the mitochondria. ● The waste products of cellular respiration are carbon dioxide and water, which are the same ingredients used for photosynthesis. Cellular Respiration and Breathing: ● Breathing and cellular respiration are closely related. Breathing results in the exchange of gases between your blood and the air. ● When you inhale, the oxygen is sent to your cells and used for cellular respiration. The carbon dioxide that is the waste from cellular respiration then diffuses from your cells into your blood and travels to your lungs, where it’s exhaled. Every molecule of carbon dioxide that you exhale was formed in one of the mitochondria in your body’s cells. ● Cellular respiration requires a cell to exchange gases with its surroundings. It is an aerobic process, meaning it requires oxygen. The cell takes in oxygen and gets rid of waste in the form of carbon dioxide. ● Cellular respiration is the aerobic harvesting of chemical energy from organic fuel molecules. ● Equation for cellular respiration: ○ C6H12O6 (glucose) + 6O2 (oxygen) yields 6CO2 (carbon dioxide) + 6H20 (water) + ATP (energy) ● Cellular respiration is an example of a metabolic pathway, meaning that it is a series of chemical reactions, not just one. ● The main function of cellular respiration is to generate ATP that can be used for cellular work. Cellular respiration forms about 32 ATP molecules for every 1 glucose molecule consumed. ● Cellular respiration transfers hydrogen atoms from glucose to oxygen, forming water. (Takes the H12 from C6H12O6 and combines it with the O2 to make 6H2O). This hydrogen transfer is why oxygen is vital to the harvest of energy during cellular respiration. ● Chemical reactions that transfer electrons from one substance to another are oxidation-reduction reactions. ○ The loss of electrons during a redox reaction is called oxidation. An example of this is glucose; it is oxidized during cellular respiration, losing its electrons to oxygen. ● The acceptance of electrons during a redox reaction is called reduction. Oxygen is reduced during cellular respiration, because it accepts the electrons lost from glucose. It is called reduction since the addition of negatively charged electrons reduces the amount of positive charge in the atom. ● There are more than 24 reactions involved in cellular respiration. They are grouped into metabolic stages. ○ Stage 1: glycolysis. occurs in the cytoplasm. ○ Stage 2: citric acid cycle(also known as the Krebs cycle). occurs in the matrix of the mitochondria. ○ Stage 3: electron transport(also known as electron transport chain or ETC). occurs in the inner membranes of the mitochondria. ● During glycolysis, glucose is split into two molecules called pyruvic acid. ● During the citric acid cycle, glucose is broken down even further into CO2 (carbon dioxide). ● During electron transport, electrons are transferred to produce large amounts of ATP. ● Some reactions can release too much energy at once. In cellular respiration, NADH solves this problem. Its electrons are transported to oxygen, which releases the energy your cells use to make most of their ATP. Stages of Cellular Respiration In-Depth: ● Stage 1: Glycolysis: ○ Glycolysis means “splitting of sugar”. ○ Glycolysis does not need oxygen to begin. ○ Step 1: A 6-carbon glucose molecule is broken in half, forming two 3-carbon molecules. ○ The initial split requires an energy investment of 2 ATP molecules. ○ Step 2: The 3-carbon molecules donate high-energy electrons to NAD+, forming NADH. ○ NAD+ is a positively charged electron acceptor. Cells make this molecule from niacin, a type of B vitamin. The transfer of electrons from pyruvic acid to the NAD+ reduces it to form NADH. ○ Step 3: In addition to NADH, glycolysis also makes 4 ATP molecules directly when enzymes transfer phosphate groups to fuel molecules to ADP. ○ At the end, glycolysis produces a net gain of 2 ATP molecules per molecule of glucose. What is left is 2 molecules of pyruvic acid. Pyruvic acid still holds most of the energy from glucose, which will be used in the citric acid cycle. ● The 2 molecules of pyruvic acid are not ready for the citric acid cycle. They have to be converted to a form that the citric acid cycle can use. ● First, each pyruvic acid loses a carbon in the form of CO2. This is the first waste product in the breakdown of glucose. The remaining fuel molecules are acetic acid (the same acid in vinegar). ● Next, electrons are transferred from acetic acid to NAD+, forming NADH. Finally, each acetic acid is attached to a molecule called coenzyme A (CoA), forming Acetyl CoA. This CoA is removed from acetic acid in the first step of the citric acid cycle. ● Stage 2: The Citric Acid Cycle ○ This cycle finishes extracting energy by breaking down acetic acid molecules, all the way to CO2. ○ Step 1: Acetic acid joins a 4-carbon acceptor molecule to form a 6-carbon product called citric acid. An acceptor molecule is a molecule that accepts electrons from another compound. ○ Step 2: For every acetic acid molecule that enters the cycle, two CO2 molecules exit as waste products. ○ Step 3: Along the way, the citric acid cycle harvests energy from the fuel. Some of the energy is used to produce 2 molecules of ATP. ○ Step 4: The cycle captures much more energy in the form of NADH. ○ Step 5: The cycle captures energy in the form of FADH2 as well. ○ Step 6: All of the carbon atoms that entered the cycle as fuel are accounted for as CO2 waste and the 4-carbon acceptor molecule is recycled. ○ Since there are 2 acetic acid molecules following glycolysis, the citric acid cycle happens twice for each molecule. ● Stage 3: Electron Transport ○ The molecules of electron transport chains are built into the inner membranes of mitochondria. Each chain functions as a chemical machine that uses the energy released by the fall of electrons to pump hydrogen ions across the inner mitochondrial membrane. This causes ions to become more concentrated on one side of the membrane, and this imbalance stores potential energy. ○ The energy stored by electron transport is like water behind a dam. The hydrogen ions tend to gush back to where they are less concentrated. The inner membrane temporarily dams the hydrogen ions. ○ ATP synthase works as a turbines, so when hydrogen flows to an area of less concentration, the ATP synthase turns, and creates energy. ○ Step 1 & 2: NADH and FADH2 transfer electrons to the top of the electron transport chain. ○ Step 3: The electron transport chain uses this energy supply to pump hydrogen across the inner mitochondrial membrane. ○ Step 4: Oxygen pulls electrons down the chain, forming water. ○ Step 5: The hydrogen concentrated on one side of the membrane rushes back downhill through ATP synthase, causing it to spin. ○ Step 6: The rotation of ATP synthase allows it to attach phosphate groups to ADP, which forms ATP molecules. About 28 molecules of ATP per glucose molecule is formed during electron transport. ● Oxygen’s Role in Electron Transport ● Oxygen makes the release of chemical energy and formation of ATP possible. ● Electron transport ○ Input: NADH, FADH2, O2 and ADP+P ○ Output: Water and many ATPs. ○ Roll of ATP synthase ● Summary of Cellular Respiration: ○ It generates about 32 net ATP per molecule of glucose ○ Glycolysis and the citric cycle contribute 2 ATP each directly. ○ The rest is produced by electron transport Food Diversity and ATP Production: ● Fermentation: the anaerobic harvest of food energy. (anaerobic=without oxygen). ● Fermentation relies on glycolysis (remember that glycolysis does not require oxygen!). ● Under anaerobic conditions, your cells have to consume more glucose per second due to less ATP being generated. Glycolysis isn’t very efficient in comparison to cellular respiration, but it can still energize muscles for a short burst. ● 2 examples of fermentation: ○ Lactic acid fermentation (occurs in muscle cells) ○ Alcoholic fermentation (occurs in yeast) Lactic Acid Fermentation: ● Under strenuous conditions, your muscles spend ATP faster than your bloodstream can deliver oxygen, so your muscle cells begin to work anaerobically. After functioning anaerobically for about 15 seconds, muscle cells will begin to generate ATP through fermentation. ● To harvest energy during glycolysis, NAD+ must be present as an electron acceptor. Under anaerobic conditions, the cell regenerates NAD+ when NADH drops off electrons at the top of the electron transport chain. ● The recycling of NAD+ cannot occur under anaerobic conditions because there is no oxygen to accept the electrons at the bottom of the chain. Instead, NADH disposes of electrons by adding them to pyruvic acid. This restores NAD+ and keeps glycolysis working. ● The addition of electrons to pyruvic acid produces a waste called lactic acid. Lactic acid is what causes soreness in your muscles. Alcoholic Fermentation: ● Yeast plays a big role in alcoholic fermentation. Yeast is used in food to create soy sauce, olives, cabbage, salami, etc. ● During yeast fermentation, sugars are converted to CO2 and ethyl alcohol as waste products.
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