Think about… 3.1 Cell me mbrane 3.2 Movement of substances across membranes

Think about… 3.1 Cell membrane 3.2 Movement of substances across membranes Recall ‘Think about…’ Summary concept map

Easy dish decorations Let me show you how to make it! spring onion flower

Easy dish decorations 1 Cut several vertical slits at one end.

Easy dish decorations Place it in water for 1 minute. 2

Easy dish decorations 3 Cut tips curl outwards like a flower!

Why do the cut tips of spring onion curl outwards after placing in water 1

The cut tips will curl inwards if the spring onion is put in sucrose solution. 2 Why

3.1 Cell membrane cell membrane

3.1 Cell membrane outside cell cell membrane inside cell • separates the cell contents from the outside environment

3.1 Cell membrane  outside cell inside cell • control the movement of substances into and out of cells

3.1 Cell membrane What is the structure of the cell membrane?

3.1 Cell membrane 3D Model fluid mosaic model(流動鑲嵌模型) Structure of cell membrane • explained by

3.1 Cell membrane Fluid mosaic model protein molecules phospholipid bilayer(磷脂雙層)

3.1 Cell membrane Phospholipids lipid molecule= 1glycerol molecule + 3fatty acid molecules

3.1 Cell membrane Phospholipids phospholipid molecule: 1 fatty acid molecule replaced by phosphate group

3.1 Cell membrane Phospholipids water-loving ‘head’

3.1 Cell membrane Phospholipids water-repelling ‘tail’

3.1 Cell membrane Phospholipids outside cell phospholipid bilayer inside cell

3.1 Cell membrane Phospholipids outside cell phospholipid molecules arrangedtail-to-tail inside cell

3.1 Cell membrane Phospholipids outside cell water-loving ‘heads’ face water-based environment inside cell

3.1 Cell membrane Fluid mosaic model protein molecules phospholipid bilayer(磷脂雙層)

3.1 Cell membrane Proteins • protein arrangement: embed half-way through bilayer penetrate through bilayer

3.1 Cell membrane Proteins What are their functions?

3.1 Cell membrane Proteins i) Act as channels water soluble substances ions water soluble substances ions

3.1 Cell membrane Proteins ii) Act as carriers active transport energy

3.1 Cell membrane Proteins iii) Act as chemical receptors hormones turn on cell activities

3.1 Cell membrane Proteins iv) Act as enzymes enzymes speed up reactions

3.1 Cell membrane Proteins v) For recognition (識別) carbohydrate molecule glycoprotein (糖蛋白) different among cells

3.1 Cell membrane Cell membrane Fluid mosaic model Why called fluid mosaic model?

3.1 Cell membrane Cell membrane Fluid mosaic model some protein molecules phospholipid bilayer can move laterally

3.1 Cell membrane Fluid mosaic model protein molecules interspersed in a mosaic pattern

3.1 Cell membrane Fluid mosaic model • cell membrane - differentially permeable - flexible - supports the cell contents How can the model explain these properties and function?

3.1 Cell membrane 1 Differential permeability • lipid-soluble substances, simple and small molecules: outside cell inside phospholipid bilayer: water-repelling / fat-loving through bilayer inside cell

3.1 Cell membrane 1 Differential permeability • water molecules, certain ions, water-soluble substances: outside cell phospholipid bilayer: impermeable to them through channel proteins or carrier proteins inside cell

3.1 Cell membrane 1 Differential permeability • large molecules:  outside cell  cannot pass through inside cell

3.1 Cell membrane 2 Flexibility fluid nature of phospholipid bilayer membrane can change shape or seal itself

3.1 Cell membrane 2 Flexibility cell division fluid nature of phospholipid bilayer membrane can change shape or seal itself

3.1 Cell membrane 3 Supporting role • interspersed protein molecules give strength

3.1 Cell membrane 3 Supporting role • interspersed protein molecules give strength support cell contents

3.1 Cell membrane What is the membrane structure according to the fluid mosaic model? How is it related to its properties and functions?

3.1 Cell membrane Phospholipid differentially permeable Proteins

3.1 Cell membrane interspersed support

3.1 Cell membrane Fluid flexible

diffusion diffusion osmosis active transport phagocytosis 1 1 2 3 4 3.2 Movement of substances across membrane

3.2 Movement of substances across membrane 3D Animation Diffusion (擴散) • all substances are made up of particles cannot move from one place to another can move more freely solid liquid gas

3.2 Movement of substances across membrane In liquid or gas Diffusion (擴散) no difference in concentration • no concentration gradient • particles move randomly in all directions

3.2 Movement of substances across membrane In liquid or gas Diffusion (擴散) higher concentration lower concentration • concentration gradient exists

3.2 Movement of substances across membrane In liquid or gas Diffusion (擴散) until evenly distributed net movement • net movement of particles from higher to lower concentration

3.2 Movement of substances across membrane In liquid or gas Diffusion (擴散) until evenly distributed net movement • no energy is required • passive process

Think about… 3.1 Cell me mbrane 3.2 Movement of substances across membranes