Nature of Biology and Introduction to the Cell.pdf

BIO 14 LECTURE Nature of Biology and Introduction to the Cell A.Y. 2024-2025 | 1st Semester Characteristics of Life 1. It responds to the environment/stimuli ○ Internal and external stimuli 2. It grows and develops 3. It produces offspring 4. It maintains homeostasis...

BIO 14 LECTURE Nature of Biology and Introduction to the Cell A.Y. 2024-2025 | 1st Semester Characteristics of Life 1. It responds to the environment/stimuli ○ Internal and external stimuli 2. It grows and develops 3. It produces offspring 4. It maintains homeostasis ○ Temperature, water content ○ Feedback system 5. It has complex chemistry ○ Metabolism → accumulated total of all biochemical reactions ○ Photosynthesis → autotrophs ○ Digestion of glucose to create ATP 6. It consists of cells aka organization ○ Cell → basic unit of structure and function ○ Cell, tissue, organs, organ system 7. Evolution ○ Self-sustaining system capable of Darwinian evolution ○ Gene frequencies change in populations over time such as in natural selection ○ Adaptations for evolution Origin of Life Basic Necessities of Life Forms Hydrogen, phosphate, nitrogen, carbon dioxide, methane, ammonia Water as a liquid solvent to bond the elements Source of energy is needed Classifications Autotroph ○ Generating own energy through the sun or chemical gradients ○ Places on land or near ocean have access to sunlight, but UV radiation before was too harsh → hydrothermal vents on ocean Heterotroph Hydrothermal Vents Fissure in crust, where seawater seeps into magma chambers Water is ejected out at high temperatures with minerals simple chemical compounds ○ Iron, barium, calcium, silicon, H2, CO2, CH3 ○ Energy is concentrated at the steep chemical gradient of hydrothermal vents BIO 14 LECTURE Nature of Biology and Introduction to the Cell A.Y. 2024-2025 | 1st Semester LUCA - Last Universal Common Ancestor As far back as we can trace; however, its appearance is unknown Identified through genes present in all three domains of life: archaea, bacteria, eukarya LUCA lived in a hot, oxygen-free space and harvested energy from a chemical gradient → such as in hydrothermal vents Classification of Hydrothermal Vents 1. Black Smokers ○ Release acidic, carbon-dioxide-rich water ○ Heated at high temperatures and packed with sulfur, iron, copper, and other metals essential for life ○ However, were deemed as too hot for LUCA 2. White Smokers ○ Alkali, CH4, Ca ○ Lost City → field of vents on the mid-Atlantic Ridge Candidate for the cradle of life / habitat of LUCA Water is alkali and lacks carbon dioxide, rich in methane ○ More hospitable temperature ○ Adjacent black smokers → may have contributed to CO2 necessary for life to evolve Biological Cell Types, Ultrastructure, and Function Cell Theory History Living things are made up of cells Microscopes → used to view and magnify individual cells Robert Hooke → first person to observe cells; British scientist, 1665 ○ Gave cells their name due to their box-life structures ○ However, the cells observed were from dead tissue ○ Published Micrographia Antonie van Leeuwenhoek → first person to observe living cells; Dutch shopkeeper and lens crafter ○ Inspired by Hooke’s book, in the 1670s ○ Observed living single-celled organisms (protists) and sperm cells ○ He called them animalcules Matthias Schleiden and Theodor Schwann → all different parts of plants and animals are made up of cells, and cells can be produced from other cells ○ Lay foundation for modern cell theory ○ Botanist and zoologist, 1830s Rudolf Virchow → all cells must come from other cells, 1858 ○ German scientist BIO 14 LECTURE Nature of Biology and Introduction to the Cell A.Y. 2024-2025 | 1st Semester ○ However, idea stolen from Polish scientist Robert Remak Modern Cell Theory All living things are composed of one or more cells The cell is the basic unit of life New cells arise from pre-existing cells Where did the first cell come from? 1. Phospholipids ○ Naturally former bilayers, forming spherically membranes 2. Self-replicating RNA molecules or proteins ○ After long period of time, evolved to have more complex machinery Kinds of Microscopy 1. Light microscopy ○ Use normal light and can magnify transparent things 1000 times 2. Transmission electron microscopy (TEM) ○ More detailed view of internal organization of cells and organelles ○ Use electronic beam that kills objects as it passes through ○ Specimens are stained with heavy metals like osmium ○ Magnifies 10,000,000 times 3. Scanning electron microscopy (SEM) ○ Specimens stained with gold → highly reflective for electronic rays ○ Show image of the surface of cells and organisms using reflected electronic beam ○ Magnifies 1,000,00 times ○ Possible to see atoms under this microscope Basic Requirements for a Cell 1. Protein-synthesizing apparatus → DNA, RNA, proteins 2. Space designated for chemical reactions → jelly-like cytoplasm 3. Oily film separating cell from environment → membrane Cell Membrane Membrane of all cells has two layers ○ Hydrophobic and hydrophilic ends of each layer Layers made with phospholipids ○ Have polar head with phosphoric acid and two hydrophobic, non-polar tails Contains embedded other lipids ○ Proteins and carbohydrates ○ Cholesterol → animal cells BIO 14 LECTURE Nature of Biology and Introduction to the Cell A.Y. 2024-2025 | 1st Semester ○ Chlorophyll → in some plant membranes Proteins are important for allowing large hydrophilic molecules and ions to come through Classification of Cells 1. Eukaryotic ○ DNA in a membrane-bound nucleus ○ DNA in a nucleus, separating it from the cytoplasm ○ DNA in multiple strands ○ Karyote → nut or kernel ○ Has other membrane-bound structures Mitochondria, Golgi apparatus, nucleolus ○ Tend to be larger ○ Examples Multicellular organisms (animals, plants, protists, etc.) 2. Prokaryotic ○ DNA not in a membrane-bound nucleus, may be in a nucleoid ○ DNA is surrounded by cytoplasm ○ DNA is circular ○ Some have prokaryotic flagella, cell wall, vesicles, and membrane folds/ pockets Flagella → rotating protein structure ○ Tend to be smaller and simpler ○ Examples Bacteria, archaea Partsof the Eukaryotic Cell 1. Nucleus → contains DNA and proteins 2. Nucleoli → in the nucleoplasm, where ribosomal RNAs assemble 3. Ribosomes → in cytoplasm, synthesize proteins 4. Endoplasmic reticulum → found near cell edge, is where proteins are synthesized, packacked, transported ○ In many cells, is connected with nucleus membrane 5. Golgi apparatus → directs proteins and other substances to needed areas of the cell 6. Mitochondria or Choloroplasts → originated via symbiogenesis ○ Mitochondria → covered with two membranes; inner membrane has intrusion called cristae ○ Breaks down organic molecules into carbon dioxide and weather through oxidative respiration Mitochondria Theory First evolved as prokaryote living in symbiosis inside of a larger eukaryotic cell Cell Membrane Chemistry BIO 14 LECTURE Nature of Biology and Introduction to the Cell A.Y. 2024-2025 | 1st Semester Cell membranes are semi-permeable ○ Allow small and non-polar molecules through ○ while big and polar will stay outside or inside forever, or until specific pore opens Osmosis ○ Water wants to equalize concentrations on both sides of the membrane ○ Water flows from high concentration to low concentration of water Or flows towards higher concentration of molecules, such as salts and acids Cell Wall Common in plants and fungi Surrounds cell and limits expansion due to osmosis ○ Osmosis may cause uncontrollable cell expansion, cells without cell walls pump out excess water through vacuoles ○ Vacuoles → large vesicle for multiple functions: store nutrients, accumulate ions, store wastes, as well as playing a role in turgor