ThatBioTutor Biology Notes (6093)

1. Cells Learning Outcomes: 1. Identify and state the functions of plant and animal cell organelles 2. State the relationship between cell structure and function (w.r.t. RBC, root hair cell, muscle cell) 3. Compare structures of plant and animal cells Keywords: • Organelle, membrane, cellular activities • Steroids, detoxification, protein synthesis • Small and temporary, large central, cell sap • Modifies, sorts and packages • Partially permeable, fully permeable • Biconcave, surface area to volume ratio, flexible, bell-shaped, long, narrow protrusion If you're our student: Cells Crash Course Clips 1. Identifying structures Component/OrganelleFunction Visible under Light Microscope? Nucleus • Contains (in the form of chromatin) • Controls DNA cellular activities Y Nuclear envelope Separates nucleus from cytoplasm Y Rough Endoplasmic Reticulum • Studded with • Ribosomes (for transport out of the cell) ribosomes synthesise proteins N Smooth Endoplasmic Reticulum • Synthesises and **Pro Tip: A class of molecules, including sex hormones • Carries out where harmful substances are converted to harmless ones fats steroids detoxification: N Cytoplasm • Place where most occur • Contains • Site of cellularactivities organelles anaerobic respiration Y Vacuole Animals: • Several and vacuoles • Store food and water Plants: • Have a vacuole • Stores (water + dissolved substances such as: sugars, amino acids, mineral salts) small temporary large central cell sap Y (plants) N (animals) Golgi body/apparatus• odifies, orts and ackages substances into for secretion out of cell M S P vesicles N Mitochondria • Site of , where food substances (such as glucose) are broken down to aerobic respiration release energy N Chloroplast (plants only) • Site of photosynthesis Y Cell surface membrane/plasma membrane • • Controls movement of substances in and out of the cell Partially permeable Y Cell wall (plants only) • Fully permeable • Made of • Gives cell its shape cellulose Y Ribosomes • Protein synthesis N [Memory Hacks] • Golgi Body: ◦ When receiving vesicles from ER, says "Majulah SingaPura" ◦ Modifies, Sorts and Packages substances into vesicles for secretion out of cell • Rough ER: ◦ Proteins --> Meat. When you bite into meat patty, has a rough texture ◦ Rough ER synthesises proteins • Smooth ER: ◦ Lipids --> Oil. Oil is smooth and slippery. ◦ Smooth ER synthesises lipids 2. Linking Structure to Function Cell Structure Red Blood Cell How it is adapted to its function • , increases , so oxygen can in/out of it faster Biconcave surface area to volume ratio diffuse • Lacks a nucleus hence has for more to transport more oxygen more space haemoglobin, • , so it can squeeze through tiny Flexible capillaries • Can become in capillaries, further increasing bell-shaped surface area to volume ratio Root Hair Cell • Has a (root hair), that increases , for faster absorption of water and mineral salts long, narrow protrusion surface area to volume ratio • Have to generate a lot of via many mitochondria energy aerobic respiration ◦ As they need to pump in mineral salts from the surrounding soil into their via large central vacuolesactive transport Muscle Cell • , shapeElongatedcylindrical • Contains many nuclei • Have to generate a lot of via for many mitochondria energy aerobic respiration muscular contractions 3. Comparing Plant and Animal Cells Comparison Animal Cell Plant cell Chloroplasts No Yes (sometimes) Cell wall No Yes (always) Mitochondria Yes (mostly) Yes (mostly) Vacuole Small, temporary Large, permanent Need personalised guidance for O Level Pure Bio? Learn more here: www .thatbiotutor .com 2025 ThatBioTutor Pte. Ltd. All Rights Reserved. 3/23/25, 11:57 PM 1. Cells https://fabulous-brie-43b.notion.site/1-Cells-2c3529cd01d542c3ad796416930fcb25 1/2

2. Movement of Substances Learning Outcomes: 1. Define Diffusion, Osmosis and Active Transport 2. Movement of substances in nutrient uptake and gas exchange 3. Effects of osmosis on plant and animal tissues 4. Bonus: Factors affecting rate of diffusion Keywords: • Diffuse, osmosis, active transport • Water potential, down/against concentration gradient, steepness • Partially permeable membrane • Crenated, lyse/burst • Plasmolysed, flaccid, turgid, turgor pressure If you're our student: Movement of Substances Crash Course Clips 1. Definitions 1. Diffusion: The movement of particles from a region of higher concentration to a region of lower concentration, . net down a concentration gradient 2. Osmosis: The movement of from a region of higher to a region of lower , through a membrane. net water molecules water potential water potential partially permeable 3. Active Transport: The movement of particles, using , from a region of lower concentration to a region of higher concentration, , through a membrane. energy against a concentration gradient partially permeable *Pro Tip: When explaining these processes in contexts of questions, replace' substances' with the molecule in the question, e.g. CO2 Process Diffusion Osmosis Active transport Type of molecule Any Water molecules Dissolved molecules/ions Partially permeable membrane needed? No Yes Yes Energy needed? No No Yes Direction w.r.t. Concentration gradient Down (higher to lower) Down (higher to lower) Against (lower to higher) 2. Movement of substances in nutrient uptake and gas exchange Example How substances are moving • Digested food substances such as glucose, and amino acids into epithelial cells of villi in the small intestinediffuse • After no longer occurs, these substances are transported in via diffusion active transport • Mineral salts are transported from the soil into root hair cells , to maintain a high concentration of mineral salts in their vacuoles via active transport • This creates a region of lower than the surrounding soil, so that water molecules flows in by water potential osmosis • O2 into the thin film of moisture lining the , then into the dissolves alveolar air spacediffuses blood plasma • Conversely, CO2 from the into the diffuses blood plasma alveoli air space • O2 from the of the leaf to the surrounding air, through the diffuses intercellular air spaces stomata • CO2 from the surrounding air into the of the leaf, through the diffuses intercellular air spaces stomata 3. Effects of osmosis on plant and animal tissues Water Potential of Solution Effect on Animal Cell Effect on Plant Cell High Bursts/Lysed Turgid Low Crenated Flaccid Very Low Crenated Plasmolysed How plasmolysed is different from flaccid: • During , as a lot of water molecules have left the from the to the outside of the cell by , plasmolysis cell sap large central vacuole osmosis • of the plant cell so much that the pulls away from the . cytoplasm shrinks plasma membrane cell wall *Pro Tip: Turgidity in plant cells is important as it allows the plant to remain upright and reach for sunlight, especially if it has a non-woody stem. 4. Bonus: Factors affecting rate of diffusion • Surface area to volume ratio: The higher the SA:V, the higher the diffusion rate • Temperature: Higher temperature, molecules have more , hence move faster and diffuse down the concentration gradient faster kinetic energy • Steepness of concentration gradient: The steeper the gradient, the higher the diffusion rate • Distance: The shorter the distance that molecules need to travel/diffusion distance, the higher the diffusion rate • Molecule size: Smaller molecules diffuse faster (e.g. glucose diffuses faster than sucrose) Need personalised guidance for O Level Pure Bio? Learn more here: www .thatbiotutor .com 2025 ThatBioTutor Pte. Ltd. All Rights Reserved. 3/23/25, 11:58 PM 2. Movement of Substances https://fabulous-brie-43b.notion.site/2-Move