Glucose molecules do not easily pass across a cell membrane, even if there is a higher concentra

Glucose molecules do not easily pass across a cell membrane,...

Key Concepts

Passive Transport

Passive transport is the process by which substances move across a cell membrane down their concentration gradient without the need for energy. This mechanism relies on the inherent kinetic energy of particles to drive movement from areas of high concentration to areas of low concentration.

Facilitated Diffusion

Facilitated diffusion is a subtype of passive transport that uses specific protein channels or carriers embedded in the cell membrane to enable the transport of molecules that cannot easily cross the lipid bilayer on their own. It allows for the selective and efficient movement of molecules, like certain sugars, along their concentration gradient.

Membrane Permeability

Membrane permeability refers to the ability of a cell membrane to allow substances to pass through it. Since many large or polar molecules do not readily diffuse across the lipid bilayer, cells depend on protein channels and carriers to help control the movement of these molecules into and out of the cell.

Transcript

00:01 We're being asked to identify a passive transport across the membrane.

00:09 Let's break that down and see what that means.

00:12 Passive means that no energy is required.

00:18 And across a membrane, obviously it has to cross a membrane.

00:22 So here's a membrane, and it needs to go from one side of it to the other side of it.

00:27 Now, the purpose of a membrane is to separate.

00:32 The inside and the outside so things can't just cross freely as they please so there needs to be a protein that allows this substance in and because this protein has to allow the substance in without the use of energy it needs to be a channel protein channel proteins just basically provide a tunnel that are specific to a molecule to go across the membrane okay so let's look at our answer choices and see which one of these does not use energy and it is across a membrane.

01:08 So the first answer choice, the movement of h plus into the thylacoyd disc.

01:15 And real briefly, this is what that's talking about.

01:20 You have nadph, which gets created in the light reactions of photosynthesis, and the nadph gets split into nadp.

01:33 Plus and a hydrogen this hydrogen gets split into electrons and protons okay i'm gonna switch colors here now the electrons go through a series of membrane proteins which harness the energy of the electron they lower the energy of the electron and they use that energy of the electron to pump hydrogen into the thylacoid membrane then you have a surplus of hydrogens in the thylquite membrane and then eventually these hydrogens the gradient of these hydrogens is used to drive the atp synthetase which makes atp but the bottom line here is that to create this proton gradient inside the thylacoid membrane you are harnessing the energy of the electron so this process is not passive.

02:39 Let's look at our next choice.

02:42 The next choice is the uptake of glucose.

02:46 Now the way the glucose enters is through a protein called the simporter.

02:52 And sim because it brings things together.

02:58 So it brings in together glucose in together with sodium.

03:02 There is a concentration gradient of sodium outside of the cell that makes sodium want to come inside the cell.

03:13 And the simporter harnesses that gradient created by the sodium to bring glucose along with it...

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