What is meant by the following statements?

Hey there,

Hopefully @CoolCavy will be able to help you out, she's really good at Biology!

omg i feel pressured xD thanks a*** <33
we have just done this and i have a revision guide next to me so i'll help you out in a sec
i'll edit in my answer i just really need the toilet first
xx

omg i feel pressured xD thanks a*** <33
we have just done this and i have a revision guide next to me so i'll help you out in a sec
i'll edit in my answer i just really need the toilet first
xx

Hey there,

Hopefully @CoolCavy will be able to help you out, she's really good at Biology!

Quote the OP with your reply.

1.) ATP is used in active transport to directly move molecules
2.) ATP is used in active transport to individually move molecules using a concentration gradient which has already been setup by (direct) active transport . This is known as Co-transport.

Does the 2nd statement basically mean that e.g. Sodium ions are (direct active transport) moved out of the epithelial cells and into the lumen and this is done in order to setup a concentration gradient for e.g. glucose molecules to diffuse into the cell via Sodium's transport protein? And effectively glucose molecules are also using active transport (as they're are also moving against the conc gradient but with the help of Sodium ions)?

you sound like you know about co-transport and active transport already so i don't want to patronize you but just in case you don't in terms of ATP

1)active transport:
ATP used to change the shape of the carrier protein so that it can transport the molecule across the cell membrane
2)co transport:
1)Sodiumions actively transported out of the epithelial cell using activetransport (a sodium-potassium pump). This reduces the concentrationof sodium in the cell as it is exchanged for potassium. Theconcentration of sodium outside of the cell is now much greater thanthe concentration of sodium inside the cell.
2)Thesodium ions on the outside of the cell now move down theirconcentration gradient through a different protein carrier. They arecoupled with glucose molecules and as such glucose is drawn into the epithelial cell
3)Theglucose then passes into the blood plasma via facilitated diffusion,the sodium ions are exchanged for potassium ions and the cycle beginsagain.
Co-transportis an indirect form of active transport as it is the sodium ionstransporting the glucose rather than ATP directly.

so yes i think your statement at the bottom is correct although the glucose molecules are moving by facilitated diffusion but this can only happen as a result of the active transport of sodium ions hope this helps
also @Changing Skies and @z33 are also excellent at biology so they might be able to help as well x

Thank you!

you sound like you know about co-transport and active transport already so i don't want to patronize you but just in case you don't in terms of ATP

1)active transport:
ATP used to change the shape of the carrier protein so that it can transport the molecule across the cell membrane
2)co transport:
1)Sodiumions actively transported out of the epithelial cell using activetransport (a sodium-potassium pump). This reduces the concentrationof sodium in the cell as it is exchanged for potassium. Theconcentration of sodium outside of the cell is now much greater thanthe concentration of sodium inside the cell.
2)Thesodium ions on the outside of the cell now move down theirconcentration gradient through a different protein carrier. They arecoupled with glucose molecules and as such glucose is drawn into the epithelial cell
3)Theglucose then passes into the blood plasma via facilitated diffusion,the sodium ions are exchanged for potassium ions and the cycle beginsagain.
Co-transportis an indirect form of active transport as it is the sodium ionstransporting the glucose rather than ATP directly.

so yes i think your statement at the bottom is correct although the glucose molecules are moving by facilitated diffusion but this can only happen as a result of the active transport of sodium ions hope this helps
also @Changing Skies and @z33 are also excellent at biology so they might be able to help as well x

no problem xx

Sorry for bothering you again
Do you know why glucose molecules are unable to enter the epithelial cell by simple diffusion?

hey no worries buddy
yes, it is because inside the cell there is a high concentration already so more won't diffuse from the outside into the cell by simple diffusion as it would be going against the concentration gradient
xx

Sorry, I don't think I phrased my question correctly.
Do glucose molecules not have their own transport proteins, why do they have to diffuse across the membrane via Sodium's transport protein?
And if this is possible, then surely glucose can be actively transported too but via its own transport protein?

hey no worries buddy
yes, it is because inside the cell there is a high concentration already so more won't diffuse from the outside into the cell by simple diffusion as it would be going against the concentration gradient
xx

Also, regarding you point, surely there wouldn't be a high concentration of glucose molecules in the epithelial cell as the glucose molecules diffuse out of the cell into the capillary?

yeah it does but not all at the same time so there would still be a lot more glucose in the cell than outside it

Ah I see. I think its to do with the relative concentrations.
Also, are the concentrations of sodium and glucose lower in the blood stream (Capillary) than in the epithelial cells?

yes they would be i think as the blood in the capillary is constantly moving

And does glucose diffuse out of the cell and into the blood, via Sodium's transport protein again?