Presentation on theme: "When you finish your quiz:"— Presentation transcript:
1 When you finish your quiz: Investigation 5.3When you finish your quiz:Turn it in to your HW binGet out your TextbookOpen to pagesRead procedure for inv 5.3
2 Lab Write-UpPurpose: To discover the relationship between cell size and diffusionData Table:CubeDimensionsSurface Area (cm2)Volume (cm3)Surface Area to Volume RatioDiffused Distance (cm)3x3x3 cm2x2x2 cm1x1x1 cm0.1x0.1x0.1 cm
3 Lab ProcedureWe will use “cells” of different sizes to test diffusion ratesCells are made of agarAgar comes from seaweed: it is the main substance in JelloHow will we test diffusion?Agar also contain phenolphthalein solutionWhat is phenolphthalein?It is an indicator for the presence of a baseChanges color in the presence of a baseWhat will we use as the diffusion substance?A base: Sodium Hydroxide (NaOH)
5 Lab Write-UpHypothesis: Which cube size will be the best at diffusing chemicals? Why?Cube size ____ will be best at diffusing chemicals because…Discussion:Questions 1,2,4,7,8 (pg. 121)Conclusion:Parts A-ESide note: You only get ONE CUBE of agar per group!Old Carpenter’s saying: Measure TWICE, cut ONCE
6 When you are done: Turn your quiz into the HW bins Switch lab books with your partnerGrade your partner’s Investigation 5.3 Write-UpMake sure both your names and the total points (out of 10) are on the topOpen textbooks to pg 119: Investigation 5.2and pre-read the procedure
7 Cell Size Limitations Hint for Note-taking: write only what is Why are cells so small?Hint for Note-taking:write only what isunderlined
8 Cell Size and Diffusion ALL cells had a diffusion distance of around 0.5 cmThis took about 10 minutesWould this work for an actual cell?
9 Most cells are between 2µm and 200µm A micrometer is 1 millionth of a meter!Too small to be seen with naked eyeWhy can’t organisms be one big giant cell?
10 Diffusion (passive transport) Particles (molecules and atoms) move from HIGH concentration to a LOWER concentration.This is random movement.The cell does not have to work or expend energy, so no ATP is used.Diffusion in Action
11 Limits to Cell Size Diffusion limits cell size Movement of food or wastes is from higher concentration to lower concentrationThe larger the distance, the slower the diffusion rateA cell 20 cm across would require months for nutrients to get to the center
12 Volume vs. Surface AreaAs an object like a cube gets bigger, volume increases more rapidly than surface area.When the cell size doubles (for example from 1 cm3 to 2 cm3), there will be 8x as much volume as before, but only 4x as much surface area as before.
13 Think of a mouse and an elephant Mice are always coldElephants are too hot
14 What is osmosis and how does it affect cell diffusion? Osmosis and DiffusionWhat is osmosis and how does it affect cell diffusion?
15 What is Osmosis? Osmosis: Diffusion of water across a membrane Different types of membranes will allow some, none, or all particles to move across themWhen water moves across, this is osmosis
16 Types of MembranesPermeable: Allows particles to pass through in either directionSemi-Permeable: Only allows some particles to pass throughImpermeable: Does not allow particles to pass throughDifferentially Permeable: Allows particles to pass through in only ONE direction based on osmotic differential
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