Unit 4 ~ Learning Guide Name: INSTRUCTIONS Complete the following notes and questions as you work through the related lessons You are required to have this package completed BEFORE you write your unit test Do your best and ask questions about anything that you don't understand BEFORE you write the unit test U4L1 NOTES: INTRODUCTION (web notes and video) Cell Membrane Structure YOU SHOULD WATCH THE OSMOSIS LAB VIDEO BEFORE PROCEEDING ANY FURTHER! Early Theory: Proteins were sandwiched between 2 layers of phospholipid molecules Problem: Since the phospholipid tails are hydrophobic (hate water) this theory did not explain how water can travel freely through membranes Fluid Mosaic Model: Accepted Theory: There is a double layer of phospholipids but the Water travels through the pores formed by the proteins YOU SHOULD WATCH THE FLUID MOSAIC MODEL VIDEO BEFORE PROCEEDING ANY FURTHER! The proteins have, which accounts for their placement among the Some of the proteins and phospholipids have carbohydrate chains attached to them Protein + Carbohydrate chain = Phospholipid + Carbohydrate chain = 1
These carbohydrate chains function as A body will cells with the wrong markers Example: Organ rejections in transplants YOU SHOULD WATCH THE CELL MEMBRANE AND STRUCTURE VIDEO BEFORE PROCEEDING ANY FURTHER! 2
U4L1 PRACTICE: INTRODUCTION 1 Describe the fluid mosaic model 2 What prefix is used to indicate a protein or lipid that has a carbohydrate chain attached? 3 Please label the following cell membrane diagram with as much detail as possible 3
U4L2 NOTES: CELL MEMBRANE FUNCTION (web notes and video) Following are some definitions you should understand: Impermeable - Permeable - Semi-permeable - **SELECTIVELY PERMEABLE** - Certain smaller and certain large molecules can pass through Cell Membranes are selectively permeable (also called differentially permeable) YOU SHOULD WATCH THE MOVEMENT ACROSS THE CELL MEMBRANE VIDEO BEFORE PROCEEDING ANY FURTHER! Movement Across Membranes: 4 main ways: 1 DIFFUSION: from an area of high concentration to an area of low concentration until evenly distributed No membrane, carrier, or ATP required *A Solute is made up of solid particles or molecules suspended in air or liquid* Diffusion Example: A foul odour in the corner of a room will spread out until it is evenly distributed Diffusion Example: Cream in coffee will diffuse until concentration are balanced Diffusion refers to the process by which molecules intermingle as a result of their of random motion Consider two containers of gas A and B separated by a partition The molecules of both gases are in constant motion and make numerous collisions with the partition If the partition is removed as in the illustration, the bases will mix because of the random velocities of their molecules In time a 4
produced in the container of A and B molecules will be 2 OSMOSIS: Pressure caused by the between two different solutions is called Hydrostatic pressure offsets osmotic pressure (Gravity) The solute cannot spread out because it is the membrane Therefore, water moves across the membrane from [high water] to [low water] Recall: square brackets represent the term "concentration" as in [high salt] = high salt concentration Water moves through the protein-lined pores of the cell membrane Hypertonic, Hypotonic and Isotonic Solutions Hypertonic Solutions: Hypotonic Solutions: Isotonic Solutions: Water will always move from a solution to a solution There is no net movement of water between solutions Tonicity: 5
You should watch the OSMOSIS videos and animations and identify the hypertonic and hypotonic solutions in the video before proceeding any further! 3 FACILITATED TRANSPORT: ( ) Solutes move across a membrane from an area of [ ] to and area of [ ] with the help of a carrier molecule (protein) Example of Solute: Glucose Molecules needed by the cell such as glucose, enter through from the blood 4 ACTIVE TRANSPORT: Solutes move from an area of across a membrane with the aid of Example of Solute: Ions such as Na+ Since the movement is against the concentration gradient, is required o Example: is removed from the urine, by active transport, into the blood Since there is already a lot of glucose in the blood, it is traveling the concentration gradient o Example: Found in nerve and muscle cells Same carrier, but changes shape to fit Na + and K + 6
Transport Across the Membrane Summary There are always four points to consider when comparing the types of movement across a membrane Is a membrane, carrier, or energy in the form of ATP required, and is transport with or against the concentration gradient Factors Affecting Diffusion Surface Area Vs Volume Nutrients ( ) enter a cell while wastes (carbon dioxide and urea) exit a cell across the cell membrane The amount of cell membrane - = Inside the cell, organelles use up nutrients and produce The larger the cell, the more The size of the cell (# of organelles) = Small cells have a high SA:Volume ratio They can supply the organelles with plenty of nutrients and remove wastes Large cells have a because volume increases faster than surface area If a cell gets too big, wastes will build up and nutrients will run out Therefore, cells are limited in size Active cells must be than less active cells Active cells need more Cells reproduce by mitosis to become smaller Some cell are able to get larger than they should be able to by producing These folds allow the cell to gain more surface area without a large increase in volume 7
Factors That Will Increase Diffusion Movement of the medium - Example: Stirring cream in coffee Endocytosis versus Exocytosis Endocytosis - process in which large materials enter a cell Phagocytosis - --"Cell eating" -very large pieces Pinocytosis - A type of endocytosis in which molecules such a proteins are taken in (liquid) --" " -smaller "larger" pieces Exocytosis Exocytosis - A process by which products or wastes exit a cell YOU SHOULD WATCH THE FACILITATED TRANSPORT VIDEO BEFORE PROCEEDING ANY FURTHER! 8
U4L2 PRACTICE: CELL MEMBRANE FUNCTION BCLN BIOLOGY 12 Rev July 2014 1 Please define the following terms and provide one example where it is involved in transporting a substance in the human body: a diffusion b osmosis c facilitated transport d active transport 2 There are several ways to transport substances across the cell membrane Please complete the table below, indicating whether the form of transport requires a membrane, carrier, energy in the form of ATP, and is with the concentration gradient Type Transport of Membrane Required (ü or û ) Carrier Required (ü or û ) Energy/ATP Required (ü or û ) With concentration Gradient (ü or û ) Diffusion Osmosis Facilitated Transport Active Transport 9
3 Which mode of transport is used to move the following molecules across the cell membrane? a oxygen molecules b water c sodium ions d glucose 4 Why is the cell membrane important to the cell? 5 What factors influence the rate at which specific molecules diffuse across the cell membrane? 6 Why does winter road salt cause damage to plants on the roadside? 7 Salting fish was a common practice How did this practice prevent the fish from rotting? 8 Compare and contrast endocytosis, including both phagocytosis and pinocytosis,and exocytosis Include an example of the use of each process in the body ~ END OF BIOLOGY 12 UNIT 4 LEARNING GUIDE ~ 10
UNIT 4 ANSWER KEY U4L1 PRACTICE: INTRODUCTION 1 Describe the fluid mosaic model (2 marks) = states that the cell membrane (aka the plasma membrane) is made up of a semifluid (dynamic and changing) phospholipid bilayer with a variety of proteins floating within that bilayer 2 What prefix is used to indicate a protein or lipid that has a carbohydrate chain attached? (1 mark) = glycol as in glycoprotein or glycolipid 3 Please label the following cell membrane diagram with as much detail as possible (5 marks) 11
U4L2 PRACTICE: CELL MEMBRANE FUNCTION 4 Please define the following terms and provide one example where it is involved in transporting a substance in the human body: a diffusion (2 marks) = the movement of particles from areas of higher concentration to areas of lower concentrations until equilibrium is met b osmosis (2 marks) = the movement of water molecules from areas of lower concentration (note lower concentration of solution actually means greater amounts of water) to areas of higher concentrations (note higher concentration of solution actually means greater amounts of water) across a semi-permeable membrane until equilibrium is met instead of concentration simply think of the movement of water from areas with greater/higher amounts of water to areas of lesser/lower amounts of water c facilitated transport (2 marks) = any form of diffusion that requires the assistance of a carrier or channel protein, the protein's assistance is generally required to either limit the transported substance's interactions with the cell membrane (such as with negative ions that would be repelled by or positive ions that would be attracted to the negative membrane without the assistance ) or because the transported substance is simply too large to diffuse directly across the membrane, process is energy-independent as it is diffusion and particles are moving along their concentration gradient from high to low d active transport (2 marks) = any form of transport that requires energy (typically supplied in the form of ATP) such as when substances are moved against their concentration gradients (from lower concentrations to higher concentrations) of moved within vesicles 5 There are several ways to transport substances across the cell membrane Please complete the table below, indicating whether the form of transport requires a membrane, carrier, energy in the form of ATP, and is with the concentration gradient (8 marks) Type of Transport Membrane Required (ü or û ) Carrier Required (ü or û ) Energy/ATP Required (ü or û ) With concentration Gradient (ü or û ) Diffusion û û û ü Osmosis Facilitated Transport Active Transport ü û û ü (with respect to water moving from areas of higher water to areas of lower water) ü ü (or channel) û ü ü ü ü û 12
6 Which mode of transport is used to move the following molecules across the cell membrane? (4 marks) a oxygen molecules _ b water _ c sodium ions d glucose _ 4 Why is the cell membrane important to the cell? (2 marks) = defines the boundaries of the cell from the surrounding environment = controls what enters and exits the cell 5 What factors influence the rate at which specific molecules diffuse across the cell membrane? (3 marks) Answer should include any 3 of the following: = surface area greater surface are = faster diffusion = temperature higher temperature = faster diffusion = concentration gradient greater gradient (the greater the difference between the higher and lower concentration areas) = faster diffusion = size of diffusing particle smaller particle = faster diffusion = diffusion medium solid=slower, liquid = faster, gas = fastest 6 Why does winter road salt cause damage to plants on the roadside? (1 mark) = the excess salt mixes with water in the environment and essentially places the plant in a hypertonic solution that then causes water to exit the plant cell thereby damaging the plant 7 Salting fish was a common practice How did this practice prevent the fish from rotting? (1 mark) = the excess salt mixes with water in the environment and essentially places any potential bacteria that could lead the fish to rot in a hypertonic solution that draws the water from the bacteria causing it to die 8 Compare and contrast endocytosis, including both phagocytosis and pinocytosis, and exocytosis Include an example of the use of each process in the body (4 marks) 13
= endocytosis and exocytosis both active transport processes that use ATP and vesicles to transport substances = endocytosis specifically refers to the use of vesicles to actively move substances into the cell and includes phagocytosis or "cell eating" whereby larger particles are brought into the cell and pinocytosis or "cell drinking" whereby fluids and smaller particles are brought into the cell; also includes receptor-mediated endocytosis which only occurs in response to a ligand of some sort specifically binding to a receptor to initiate the process of endocytosis = exocytosis specifically refers to the use of vesicles to actively move substances out of the cell and includes constitutive exocytosis or secretion whereby a substances is continually secreted from the cell and receptormediated or regulated exocytosis whereby a substance is only moved out of the cell in response to some sort of ligand specifically binding to a receptor to initiate the process of exocytosis = phagocytosis uptake of bacteria pathogens for destruction within the cell = pinocytosis uptake of nutrients by cells in the small intestine = receptor-mediated endocytosis iron and cholesterol uptake = constitutive exocytosis collagen and plasma membrane lipids = regulated exocytosis 14