Bio Outcome 2 2023 Key (Complete) - PDF

Science 10 - BIOLOGY Outcome 2 Cell Transport Answer Key Name: _______________________ Teacher: ______________________ Class: ____________...

Science 10 - BIOLOGY Outcome 2 Cell Transport Answer Key Name: _______________________ Teacher: ______________________ Class: ____________ Essential Understandings: 1. What is the structure of a cell membrane? 2. How do cells transport materials across the cell membrane? 3. What is the relationship between cell size and shape and surface area-to-volume ratio? 1 Cell Survival To survive, all cells must: Obtain energy for food Rid themselves of waste Nearly all cells require oxygen to metabolize the energy in their food into ATP through cellular respiration in the mitochondria. glucose + oxygen ➜ carbon dioxide + water All molecules must pass through the cell membrane to enter or exit the cell. Membrane Function Some of the main functions of the cell membrane are: contain the cytoplasm selectively allow substances to enter and exit the cell be flexible to allow the cell to change shape adhere (stick) to other cells use identification tags (proteins) that are recognized by other cells Membrane Structure [attracted to water] Phospholipids form thin bilayers (2 layers) because of their hydrophilic heads and hydrophobic tails. [repelled by water] Label the phospholipid and the phospholipid bilayer. [outside cell] phosphate head (hydrophilic) bilayer lipid tail (hydrophobic) [inside cell] hydrophilic hydrophobic (not touching cytoplasm (touching water) 2 water)  Membrane Proteins Proteins are embedded in the phospholipid bilayer. They function to: transport substances across the membrane carry out chemical reactions provide cell recognition protect cells from infection provide intercellular communication (between cells) Label the model of the phospholipid bilayer below. Include: integral protein, peripheral protein, cholesterol, carbohydrate, hydrophobic, hydrophilic. carbohydrate attached to glycolipid (lipid + sugar) integral protein hydrophobic (lipid tails) cholesterol peripheral hydrophilic holds phospholipids still and protein (phosphate heads) can stiffen the membrane 3 Semi-Permeable Membranes Cell membranes are selectively (or semi-) permeable. They allow some substances to pass through, but not others. Factors Affecting Semi-Permeability small molecules (e.g. water & gases) can pass through easily; large molecules Size: need to use proteins protein channels have sites (like a lock) that only allow certain molecule Shape: shapes to bind and open the protein hydrophobic tails inside membrane do not allow polar or charged molecules to Charge: pass through; these particles use proteins to enter/exit the cell Concentration Gradients Concentration is the amount of a substance in a given volume. The difference in concentration between two areas is called the concentration gradient. No concentration gradient: same number of particles in a given volume throughout Concentration gradient: different numbers of particles in a given volume throughout up/against concentration gradient high low concentration concentration down / with / along concentration gradient 4  Dynamic = particles are still moving! Dynamic Equilibrium no net change in concentration Cells must exist in a steady state (homeostasis) to survive. For this to occur, the cell must be in dynamic equilibrium with its environment. Dynamic equilibrium exists when: The concentration inside the cell is equal to the concentration outside the cell The movement of molecules into and out of the cell occurs at the the same rate o molecules entering cell = molecules exiting cell no net movement Passive Transport – Diffusion & Osmosis & Facilitated Diffusion Movement down/with/along a concentration gradient Requires no energy input 5 Diffusion Diffusion is the net movement of particles from an area of high concentration to an area of low concentration. There are two types of diffusion: simple diffusion - no proteins required facilitated diffusion - proteins required Simple Diffusion Substances that diffuse across a cell membrane include gases like O2 and CO2 and water. High concentration dynamic equilibrium Low concentration down gradient Facilitated Diffusion Membrane uses transport proteins to aid (assist) in the diffusion of particles that cannot pass through the membrane due to size or charge high Particles move from high concentration to low concentration. low 6 Carrier Proteins A carrier protein is a transport protein that is specific for an ion, molecule, or group of substances. Carrier proteins "carry" the ion or molecule across the membrane by changing shape after the binding of the ion or molecule Example: When glucose binds to a carrier protein the protein: o changes shape - the side that is ‘open’ changes o allows the molecule to pass through the membrane Channel Proteins A channel protein is a transport protein that acts like a water-filled pore or tunnel in the membrane and lets small ions through quickly When the protein is open they allow charged ions into and out of the cell Channel proteins for positive ions are negatively charged Channel proteins for negative ions are positively charged opposite charges attract 7 Osmosis [uses protein pores] Diffusion of water across cell membrane Water will flow from high water concentration to low water concentration. Water moves from areas of low solute concentration to areas of high solute concentration This is against the solute concentration gradient low high equal solute solute solute conc. conc. conc. high solute low solute conc. conc. water dilutes solute to reach dynamic equilibrium Tonicity – Understanding the Movement of Water Water moves from a hypotonic to a hypertonic environment Hypotonic solutions have low solute concentrations; these solutions lose water through osmosis (compared to another solution / cell) Hypertonic solutions have high solute concentrations; these solutions gain water through osmosis Isotonic solutions neither gain nor lose water. Their solutions are in dynamic equilibrium. Water is entering and leaving the cell at the same rate. Isotonic Hypertonic solution; Hypotonic solution; solution & cell hypotonic cell hypertonic cell Cell doesn’t H 20 H 20 Cell gets H 20 Cell gets larger change size H 20 H 20 H 20 smaller Rate of water leaving cell = Rate of water leaving cell > Rate of water entering cell Rate of water entering cell Rate of water entering cell > Rate of water leaving cell 8  (burst) Cell wall prevents plant cell from changing shape/ (central vacuole puts (cell membrane detaches size pressure on cell wall) from cell wall) Active Transport Low Movement against a concentration gradient concentration of diamonds Particles move from low concentration to high concentration. Requires energy in the form of ATP (ATP attaches to protein, allowing it to change shape) Always uses a transport protein. (carrier protein) High concentration of diamonds 9 Endocytosis (Active Transport) Process by which cells take in substances which cannot be moved by diffusion or carrier/channel proteins. Phagocytosis: food or solids are engulfed by by plasma membrane and brought into the cell in a food vacuole (used by immune cells to engulf and destroy bacteria) drops of fluid are engulfed by the Pinocytosis: plasma membrane and brought into the cell in a vesicle (used by kidney cells to separate nutrients and fluids from urine) Receptor-mediated endocytosis: receptor (protein) identifies an item for transport then binds to it and forms a vesicle (proteins bind to cholesterol in the blood and bring it into the cell through receptor-mediated endocytosis) Exocytosis (Active Transport) Process by which cells expel substances which cannot be moved by diffusion or carrier / channel proteins. Removes waste from cells Specializes in the release of enzymes and hormones 10 Surface Area and Volume Cells must maximize surface area (membrane diffusion) [driven by and limit volume (cytoplasm diffusion) concentration gradient] o Diffusion into cell is relatively fast o Diffusion within cell is relatively slow [driven by Brownian motion] Nutrients must get from the cell membrane to the organelles where they are required. As cell size increases, o Cell surface area increases as a square (r2) o Cell volume increases as a cube (r3) As cell size increases, the surface area to volume ratio decreases. Surface Area 6r2 (for cube- SA:V = Volume r3 shaped cells) slower diffusion into and through cell Smaller surface area-to-volume ratio ⇒ cell can’t get nutrients or eliminate waste quickly enough and dies. 11 Maximizing SA:V Multicellular organisms: large organisms are made up of many specialized cells that work together to carry out the functions of life Cellular structures: some cells (e.g. plant roots or intestinal cells) have hair-like or finger-like structures that maximize surface are for maximum uptake 12 Outcome 2 Practice 1. Below are three diagrams that show three identical cells in three separate beakers of solution. The relative concentration of water and solute molecules is given for the cell in each beaker. Complete the diagrams by drawing the molecules of water and solution required to make the external fluid in each beaker hypertonic, isotonic, or hypotonic, as indicated. Use arrows to show the direction of water flow, with a thicker arrow indicating more molecules moving in one direction. Hypertonic Solution Isotonic Solution Hypotonic Solution X X X X X X X X X X X X X X X X X X X X X X X X X X X X XX X Water Solute A Solute B 2. Fill in the blanks on the diagram, using the following terms: cell membrane, vesicle, solid, solute, phagocytosis, pinocytosis, secreted solute, exocytosis. You may need to use some terms more than once. cell solid membrane solute secreted solute vesicle vesicle phagocytosis pinocytosis exocytosis Describe the processes shown in the picture above: A B C The solid adheres to the The solute molecules are membrane and is engulfed. The Digested substances, enzymes, surrounded by the membrane, or hormones that need to be membrane pinches off a vesicle which pinches off a vesicle containing the solid. expelled are carried to the containing the solute molecules. membrane in a vesicle, which merges with the membrane, secreting the substances. 13