Presentation is loading. Please wait.

Presentation is loading. Please wait.

Regents Biology 2006-2007 Cell Membranes & Movement Across Them.

Similar presentations


Presentation on theme: "Regents Biology 2006-2007 Cell Membranes & Movement Across Them."— Presentation transcript:

1

2 Regents Biology 2006-2007 Cell Membranes & Movement Across Them

3 Regents Biology Cell (plasma) membrane  separate cell from its environment  cell membrane is the boundary IN food sugars proteins fats salts O 2 H 2 O OUT waste ammonia salts CO 2 H 2 O products cell needs materials in & products or waste out

4 Regents Biology

5

6

7 Building a membrane  How do you build a barrier that keeps the watery contents of the cell separate from the watery environment? What substance do you know that doesn’t mix with water?  FATS   LIPIDS  oil & water don’t mix!!

8 Regents Biology Lipids of cell membrane  Membrane is made of phospholipids  phospholipid bilayer “attracted to water” “repelled by water” inside cell outside cell phosphate lipid

9 Regents Biology Semi-permeable membrane  Need to allow passage through the membrane  But need to control what gets in or out  membrane needs to be semi-permeable So how do you build a semi-permeable membrane? aa H2OH2O sugarlipidsalt NH 3 So what needs to get across the membrane?

10 Regents Biology Phospholipid bilayer  What molecules can get through directly? *small molecules inside cell outside cell fats & other lipids can slip directly through the phospholipid cell membrane, but… what about other stuff? lipid salt aa H2OH2O sugar waste

11 Regents Biology Permeable cell membrane  Need to allow more material through  membrane needs to be permeable to…  all materials a cell needs to bring in  all waste a cell needs excrete out  all products a cell needs to export out inside cell outside cell lipidsugaraa H2OH2O salt “holes”, or channels, in cell membrane allow material in & out waste

12 Regents Biology outside cell Semi-permeable cell membrane  But the cell still needs control  membrane needs to be semi-permeable  specific channels allow specific material in & out inside cell sugaraa H2OH2O salt waste

13 Regents Biology How do you build a semi-permeable cell membrane?  channels are made of proteins  proteins both “like” water & “like” lipids bi-lipid membrane protein channels in bi-lipid membrane

14 Regents Biology Protein channels  Proteins act as doors in the membrane  channels to move specific molecules through cell membrane

15 Regents Biology Most cell membranes are composed principally of 1. DNA and ATP 2. proteins and lipids 3. chitin and starch 4. nucleotides and amino acids

16 Regents Biology Most cell membranes are composed principally of 1. DNA and ATP 2. proteins and lipids 3. chitin and starch 4. nucleotides and amino acids

17 Regents Biology Movement through the channel  Why do molecules move through membrane if you give them a channel? ? ?

18 Regents Biology Molecules move from high to low  Diffusion  move from HIGH to LOW concentration

19 Regents Biology Diffusion  Move from HIGH to LOW concentration  “passive transport”  no energy needed

20 Regents Biology

21 Simple Diffusion  Move from HIGH to LOW inside cell outside cell Which way will fat move? low high  fat

22 Regents Biology

23 Diffusion through a channel  Move from HIGH to LOW inside cell outside cell sugar Which way will sugar move? low high  sugar

24 Regents Biology Diffusion  Move from HIGH to LOW concentration  through membrane  simple diffusion  no energy needed  through a protein channel  facilitated diffusion (with help)  no energy needed high low

25 Regents Biology

26 Active transport  Cells may need molecules to move against concentration difference  need to pump “uphill”  from LOW to HIGH using ATP  protein pump  requires energy  ATP ATP

27 Regents Biology

28

29 Transport summary diffusion facilitated diffusion active transport ATP

30 Regents Biology 2006-2007 Osmosis Movement of Water Across Cell Membrane

31 Regents Biology Osmosis  Osmosis  diffusion of water from HIGH concentration of water to LOW concentration of water  across a semi-permeable membrane

32 Regents Biology  Normally, in the process of osmosis, the net flow of water molecules into or out of the cell depends upon differences in the 1. concentration of water molecules inside and outside the cell 2. concentration of enzymes on either side of the cell membrane 3. rate of molecular motion on either side of the cell membrane 4. rate of movement of insoluble molecules inside the cell

33 Regents Biology Keeping water balance  Cell survival depends on balancing water uptake & water loss freshwaterbalancedsaltwater

34 Regents Biology Managing water balance  Balanced conditions  no difference between cell & environment  example: blood  problem: none  water flows across membrane equally, in both directions  volume of cell doesn’t change balanced

35 Regents Biology Managing water balance  Freshwater  a cell in fresh water  example: Paramecium  problem: gains water, swells & can burst  water continually enters Paramecium cell  solution: contractile vacuole  pumps water out of cell freshwater

36 Regents Biology Controlling water  Contractile vacuole in Paramecium

37 Regents Biology Managing water balance  Saltwater  a cell in salt water  example: shellfish  problem: lose water  plasmolysis in plants  shrinking cell  solution: take up water saltwater

38 Regents Biology


Download ppt "Regents Biology 2006-2007 Cell Membranes & Movement Across Them."

Similar presentations


Ads by Google