Keystone Study Guide Module A: Cells and Cell Processes

Transcription

1 Keystone Study Guide Module A: Cells and Cell Processes Topic 1: Biological Principles Cells and the Organization of Life Characteristics of Life all living things share the following characteristics: 1. Made of cells 2. Based on universal genetic code 3. Obtain and use energy 4. Change over time 5. The ability to reproduce 6. The ability to grow and develop 7. Respond to stimuli in the environment 8. Maintain stable internal environment Cell Theory 1. The cell is the most basic unit of life 2. Living organisms are composed of one or more cells 3. All cells arise from pre-existing, living cells Prokaryotic Cells Lack a nucleus and the membranous organelles found in complex cells; DNA is a circle Example: bacteria, including cyanobacteria Plasma Membrane - Membrane surrounding the cytoplasm of both prokaryotic and eukaryotic cells that consists of a phospholipid bilayer with embedded proteins; functions to regulate the entrance and exit of molecules from cell Eukaryotic Cells Have a nucleus and the other membranous organelles of complex cells; DNA is linear Example: animal cells, plant cells Organelles - Specialized structure within cells (e.g., nucleus, mitochondria, and endoplasmic reticulum) o Nucleus - The distinctive organelle of a eukaryotic cell, consisting of a membranous envelope in which the chromosomes reside o Endoplasmic Reticulum - Membranous system of tubules, vesicles, and sacs in cells, sometimes having attached ribosomes. Rough ER has ribosomes; smooth ER does not o o o Mitochondria - Membranous organelle in which aerobic cellular respiration produces the energy carrier ATP Ribosomes - Minute particle that is attached to endoplasmic reticulum or occurs loose in the cytoplasm and is the site of protein synthesis Golgi apparatus Stacked set of membranes that modifies, transports, and packages materials for export

2 Plant Cells Eukaryotic cells that have features and organelles not present in animal cells: Cell Wall - Protective barrier outside the plasma membrane of plant and certain other cells Vacuole - Membranous cavity, usually filled with fluid Chloroplasts - Membranous organelle that contains chlorophyll and is the site of photosynthesis Organization of Life Life is organized from the simplest to the complex: 1. Cells 2. Tissues 3. Organs 4. Organ Systems 5. Organism Properties of Water Topic 2: The Chemical Basis for Life Life could not exist without water. Most of an organism s cells are made up of water. Water makes up over 65% of the human body. One side of the water molecule is positively charged and the other is negatively charged. These opposite charges make water a polar molecule. The negative oxygen of one water molecule is attracted to the positive hydrogen of another molecule forming a hydrogen bond. In other words water likes to stick to itself. Water sticking to water is called cohesion. Water sticking to something else is called adhesion. Hydrogen bonds give water a high specific heat and also cause water to expand upon freezing. When water expands it becomes less dense than when in the liquid state, allowing ice to float. Because water is a polar molecule, it can dissolve ionic compounds, like NaCl (table salt) and other polar molecules. Water is known as the universal solvent. 2

3 Carbon Organic compounds contain carbon. Carbon has four electrons in its outer shell to share with other atoms. When electrons are shared, they form a covalent bond. Carbon is special because it can form four covalent bonds with atoms of other elements or other carbon atoms. Carbon s structure allows the formation of large, complex molecules called macromolecules, or polymers, which are made of chains of smaller molecules called monomers. Dehydration synthesis reactions remove water molecules to join monomers together into polymers Hydrolysis reactions add water molecules to break polymers apart into monomers Macromolecules Four major classes of macromolecules exist, shown in the table below: Carbohydrates Lipids Nucleic Acids Proteins Elements C, H, O in 1:2:1 ratio C, H, and a little O C, H, O, N, P C, H, O, N, S Monomer Monosaccharide Fatty Acids, Glycerol Nucleotide Amino Acid Polymer Polysaccharide Fats, Oils, Waxes Polynucleotide chain Polypeptide chain Examples Glucose, Galactose, Sucrose, Fructose, Starch, Cellulose Functions Short-term energy storage, Structure of cell walls Monomers of macromolecules: Triglycerides, Phospholipids, Steroids Long-term energy storage, cell membranes, insulation DNA, RNA Encode genetic information, Protein synthesis Fibrous proteins, Globular proteins Cell structures, Animal structures, Cell function, Enzymes Carbohydrate (glucose) Lipid (phospholipid) Nucleic Acid (nucleotide) Protein (amino acid) 3

4 Enzymes Some proteins function as enzymes, which are catalysts that allow reactions to occur at rates thousands of times per second. Enzymes lower the activation energy of a chemical reaction. With lowered activation energy, the reactants can be changed to products at a much faster rate. The substrate is the substance that the enzyme helps to react. The active site is the region on the enzyme to which the substrate binds, which catalyzes the change from substrate to product. Enzymes are substrate specific and are compared to a lock-and-key fit: The reaction rate refers to how fast or slow the reaction occurs. Enzymes function best at an optimal temperature, ph, and enzyme concentration. The reaction rate will slow if the enzyme is in less than optimal conditions. Denaturation is the process of an enzyme becoming inactive due to factors that alter the enzyme s structure. A denatured enzyme does not catalyze a reaction. ATP Topic 3: Bioenergetics Adenosine triphosphate, or ATP, is a small molecule that provides energy to reactions throughout the cell. For this reason, ATP is known as the energy currency of cells. When a phosphate group is removed from ATP by hydrolysis, energy is released. When a phosphate group is added to ATP by dehydration synthesis, energy is stored. Autotrophs(producers) make their own energyfrom the Sun through photosynthesis; plants, some bacteria Heterotrophs(consumers) must get their energy from other sources; animals 4

5 Photosynthesis Process by which plants convert Sun s energy, H 2 O and CO 2 into glucose and oxygen Takes place in the chloroplasts of plant cells Chlorophyll is the molecule that receives the Sun s energy Two major reactions in photosynthesis: 1. Light Dependent Reactions a. Light energy is absorbed by chlorophyll, which uses the energy to split water; Oxygen is released to the outside b. Some ATP is made, which will be used in the Light Independent Reactions 2. Light Independent Reactions (also called the Calvin Cycle) a. CO 2 is usedto make glucose b. ATP is used Cellular Respiration Process by which glucose is broken down to release ATP (energy) Takes place in the mitochondria of plant and animal cells Three major reactions in cellular respiration: 1. Glycolysis; occurs in cytoplasm; glucose is split apart and small amount of energy released 2. Kreb s cycle; occurs in mitochondria; glucose subunits are broken down into CO 2 and released 3. Electron Transport Chain (ETC); occurs in mitochondria; creates ATP Photosynthesis and Cellular Respiration Photosynthesis and cellular respiration complement each other: they are the same reactions, but occurring in reverse (the reactants of one are the products of the other) Photosynthesis equation: 6CO 2 + 6H 2 O + light C 6 H 12 O 6 + 6O 2 Cellular Respiration equation: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + energy (ATP) Fermentation In the absence of oxygen, some organisms will use the products of glycolysis and go through fermentation Alcoholic fermentationmakes alcohol and CO 2 as the byproducts Lactic acid fermentationmakes lactic acid as the byproduct 5

6 Topic 4: Transport and Homeostasis Membranes of the Cell The cell membrane, or plasma membrane, is made up of two layers of phospholipids and is called a phospholipid bilayer. It surrounds the cytoplasm of a cell, controlling what enters and exits. The cell membrane is semi-permeable, meaning some substances cross more easily than others and some substances cannot move across it at all. Passive Transport Does not use energy Moves from a high concentration to a low concentration Examples: 1. Diffusion: The movement of particles from regions of higher density to regions of lower density 2. Facilitated Diffusion: Transport proteins help molecules diffuse through the membrane 3. Osmosis: The diffusion of water across a selectively permeable membrane Diffusion Facilitated Diffusion A solution with higher solute concentration is hypertonic relative to one with lower solute concentration. Conversely, a solution with lower solute concentration is hypotonic relative to one with higher solute concentration. If two solutions have the same concentration they are isotonic. Water will move from a hypotonic to a hypertonic solution. Solute - substance dissolved in a solvent to form a solution Hypertonic - solution with a higher concentration of solute and a lower concentration of water Hypotonic - solution with a lower concentration of solute and a higher concentration of water Isotonic solution with equal concentration of solute and water 6

7 Active Transport Requires energy (ATP) Moves from a low concentration to a high concentration Examples: 1. Sodium-Potassium Pump: Moves sodium ions out of the cell and potassium ions into the cell 2. Endocytosis: The movement of a large substance into a cell by means of a vesicle 3. Exocytosis: The movement of material out of a cell by means of a vesicle Homeostasis Homeostasis refers to the maintenance of a constant internal state. Glucose, water, temperature, and ph levels in the blood are maintained at constant levels Homeostatic mechanisms are processes by which organisms monitor and maintain constant states Internal conditions are not perfectly constant. They vary slightly as the body returns them to set points through dynamic equilibrium Negative feedback loop any change in a system causes the system to return to its original state Positive feedback loop amplifies a change to the system, causing it to move farther from its original state 7

8 Biology Keystone Module A Review Questions: 1. Describe the characteristics of life shared by all prokaryotic and eukaryotic organisms. 2. Compare cellular structures and their functions in prokaryotic and eukaryotic cells. 3. Describe and interpret relationships between structure and function at various levels of biological organization (i.e., organelles, cells, tissues, organs, organ systems, and multicellular organisms). 4. Describe the unique properties of water and how these properties support life on Earth (e.g., freezing point, high specific heat, cohesion). 5. Explain how carbon is uniquely suited to form biological macromolecules. 6. Describe how biological macromolecules form from monomers. 7. Compare and contrast the structure and function of carbohydrates, lipids, proteins, and nucleic acids in organisms. 8. Describe the role of an enzyme as a catalyst in regulating a specific biochemical reaction. 9. Explain how factors such as ph, temperature, and concentration levels can affect enzyme function. 10. Describe the fundamental roles of plastids (e.g., chloroplasts) and mitochondria in energy transformations. 11. Compare and contrast the basic transformation of energy during photosynthesis and cellular respiration. 12. Describe the role of ATP in biochemical reactions. 13. Describe how the structure of the plasma membrane allows it to function as a regulatory structure and/or protective barrier for a cell. 14. Compare and contrast the mechanisms that transport materials across the plasma membrane (i.e., passive transport -- diffusion, osmosis, facilitated diffusion; active transport -- pumps, endocytosis, exocytosis). 15. Describe how endoplasmic reticulum, Golgi apparatus, and other membrane-bound cellular organelles facilitate transport of materials within cells. 16. Explain how organisms maintain homeostasis (e.g., thermoregulation, water regulation, oxygen regulation). 8