AS Christmas Revision

Aim to• Consolidate all the work from the advent term

• Get ready for some Mock Exams

NOTE: to open a hyperlink – either click on it when you are in fullscreen mode or right click and then “open hyperlink”

SECOND NOTE: this might not be exhaustive (ie have everything) so use this in conjuction with your syllabus! (also on intranet) to check you haven’t missed anything

Cells alive Scale Demo

• How Big Are Cells?

Have a look at how big cells are….

Remember: Actual Size = Image Size / Magnification

IMA triangle

© Pearson Education Ltd 2008This document may have been altered from the original

Week 1

Calculations of actual size from magnification given

© Pearson Education Ltd 2008This document may have been altered from the original

Week 1

Please note that magnification sizes are subject to variation on different screens

Try it then move this box to see if you’re right

100μm = 0.1 mm

Inner Workings of a Cell – soundtracked

Inner Workings Harvard – extended narrated version

First click on the first link then try and call out what organelles you are looking at aloud! (do this in a private place otherwise you will look like a nutcase)

Then click on the second one to see if you were right

Then try this link for professor MegaCell Game…

Organelles Game

Organelles Revision – use your powerpoints we made in class to revise.

Then…

Mitochondria:

Where respiration happens. Energy is generated in a chemical reaction between glucose and oxygenNucleus:

Contains DNA in big bundles called chromosomes. These carry your genes which control your characteristics

Ribosomes:

Your nucleus sends DNA messages to these instructing them what to build. They make proteins (including enzymes)

Animal Cell

Plant Cell

Prokaryotic Cell

Some specialised cells – use your ppts to revise

(a) Phospholipid molecule enlarged and (b) layer of phospholipids at the surface of water

© Pearson Education Ltd 2008This document may have been altered from the original

Week 3Membranes Revision

These will spontaneously form structures when mixed with water – a micelle, vesicle or a bilayer

This is so that hydrophobic bits are shielded from water and hydrophilic bits are next to the water..

Heres a simulation

A phospholipid bilayer

© Pearson Education Ltd 2008This document may have been altered from the original

Week 3

Great explanation of how phospholipids for bilayers

Explanation

The fluid mosaic model – can you remember what each bit does???

© Pearson Education Ltd 2008This document may have been altered from the original

Some Youtube vids and simulations…

Membrane transport overview

DiffusionDiffusionDiffusion is when something travels from an area of high concentration to an area of low concentration. For example, consider the scent from a hamburger.

The “scent particles” from this hamburger are in high

concentration here:

Eventually they will “diffuse” out into this

area of low concentration:

Oxygen passes into cells by diffusion

I took this slide from a GCSE powerpoint. For you at AS – remember only Small or Non-Polar (hydrophobic) molecules can pass through the phospholipid bilayer

Simple Diffusion

Osmosis

Osmosis

is the net movement of

water from an area of its

high concentration

to an area of its

low concentrationacross a partially-permeable membrane.

Shuffle these around to get the definition – I’ve done the first one for you

Remember: At AS level we talk about WATER POTENTIAL in terms of Ψ (psi)

Maximum Ψ = 0 (pure water)

Low Ψ = -500KPa (v. salty water)

Note negative values

Facilitated Diffusion – Channel Protein

animation

Facilitated Diffusion – Carrier Protein

animation

When a carrier or channel just isn’t big enough… BULK TRANSPORT

Active Vs Passive Transport

• Youtube summary of active vs passive transport

Now play this GAME –I must confess I only got 80% in 1;15 minutes

here the first time around (its tough!) – some of it is beyond AS level but have a go

(hint: extrinsic = peripheral / surface)

The Cell CycleMitosis is the division of a nucleus

The cell cycle describes the life cycle of a cell (duh)

Mitosis is the birth of a new cell (stricly speaking mitosis and cytokinesis)

After this the cell must grow (G1)

Then it decides whether to head towards division again (a checkpoint)

Then DNA is copied (S phase – part of interphase)

Then it grows again and the centriole is copied (G2) before it can do mitosis again

MitosisIn case your wondering – blue stuff is chromosomes (hoescht stain) and green stuff is GFP modified microtubules (spindle and cytoskeleton)

1.Interphase: DNA Copied

2. Prophase – chromosomes condensing

3. Metaphase – chromosomes line up on equator

4. Anaphase – chromosomes move to opposite poles

5. Telophase: chromosomes reach poles

5. Cytokinesis (not part of mitosis) = cell division

A cell – start here

AMAZING VIDS: Watch the chromosomes wiggle about

Synchronised mitosis in a maggot (urgh!)

More mitosis

• Great 3D animation inside a cell – watch this and try to figure out what stage you’re at

• And then be amzed at these people who did mitosis through synchronised swimming (spot the centrioles and their green spindle fibres)

Stem Cells and differentiation

How does an embryo go from all the same cell to about 210 cell types in an adult person??

Watch this zebrafish do it speeded up (you don’t need to know the annotations)

Finally, if you’ve got 20 mins then watch this excellent video about stem cells – it covers all the points.

http://www.eurostemcell.org/films/a-stem-cell-story/English