Currently unavailable: for new students
Degree: Atmospheric and Environmental Sciences (Doctorate) - Edinburgh University
I'm a GeoSciences PhD student at the University of Edinburgh. I changed my undergraduate subject from English Literature to Biology and Plant Sciences. I'm happy to help with science questions, since I am fascinated by the natural world. I am fascinated by human nature too, so any English Literature queries are also welcome.
At the moment, I help out on undergraduate courses in ecology. I've been a support worker in the past as well.
I understand that as a student, you might be juggling a lot of different ideas in your head and trying to make sense of things under pressure. I am very patient and will explain in lots of ways until we find the way that works for you.
These days, exams seem to take over your life and replace enjoying learning. I hope that you will find something exciting in your subject and my job is to help you get over the first hurdle of understanding. We've all been there and found something hard, perhaps because we've been put off by a poor explanation or because there doesn't seem to be enough time.
Remember that our tutorial is not an exam and the pressure is off! So you're free to actually think about what their questions are asking. Examiners aren't always so great at making sense themselves!
How to get in touch:
Just send a 'WebMail' with your question or even just a general topic that is the problem. Please include your exam board so I'll know the syllabus you have.
I look forward to talking things over with you!
|Biology||A Level||£24 /hr|
|Geography||A Level||£24 /hr|
|English Literature||GCSE||£22 /hr|
|Environmental Forestry||Masters Degree||Distinction|
|Plant Sciences||Bachelors Degree||1st|
|Before 12pm||12pm - 5pm||After 5pm|
Please get in touch for more detailed availability
Stomata can be thought of as gates. This is why the size of the guard cells is so important. How the guard cells change in size is a simple matter of how much fluid they can hold - their turgor. Osmosis is the movement of water through a semi-permeable membrane (a membrane that allows small molecules like H2O through it, but not larger molecules) from higher to lower water potential. When guard cells have low water potential then water enters the cell and makes it a turgid cell. Due to their inner cell wall being thicker and more rigid, the guard cells bend away from each other when they fill with water and this opens a pore - the gates open.
So how does water potential change in guard cells? The guard cells use ATP driven proton (H+) pumps to efflux (eject) positively charged protons and hyperpolarise the plasma membrane. This activates inward potassium (K+) channels and so K+ ions enter the cell and decrease the water potential. Water moves by osmosis and causes the cell to expand.
To reverse this, anions such as chloride (Cl-) are released through channels in order to depolarise the plasma membrane. This deactivates the inward K+ channels and activates the outward channels so K+ ions are effluxed. The release of both anions and K+ increases water potential and leads to loss of turgor. The guard cells change from being turgid to being flaccid and stop bending away from each other - closing the gates.see more