Oxygen and glucose diffuse across the cell membrane via passive transport.

Looking at the diagram:

We are shown a cell membrane with different molecules moving in and out. The labels point to specific parts or processes.

Let’s identify each label based on what’s happening:

- Label a: Points to the yellow structures embedded in the membrane — these are proteins that help glucose move into the cell. Since glucose is going from high concentration (outside) to low concentration (inside), and it needs a protein helper, this is facilitated diffusion.

- Label b: Points to small green pairs outside the cell. These are labeled “oxygen” inside the cell, so they’re oxygen molecules. Oxygen moves directly through the membrane without help — that’s simple diffusion.

- Label c: Points to the red-and-red-tail structures making up the main part of the membrane — those are phospholipids, forming the lipid bilayer.

- Label d: Points to purple hexagons outside the cell — these are glucose molecules. Glucose enters via facilitated diffusion using the channel proteins (labeled a).

Now, let’s match them correctly as per standard biology diagrams:

Typically in such diagrams:
- a = transport protein (for facilitated diffusion)
- b = oxygen molecule (diffusing freely)
- c = phospholipid bilayer
- d = glucose molecule

But since the question doesn’t ask us to name them — wait, actually, looking again… the user didn’t specify what the task is! But given the image has arrows and labels, and common homework questions about this diagram usually ask:

> What process is shown for oxygen? For glucose?

Or sometimes:

> Label A, B, C, D represent which components/processes?

Since no explicit question was asked, but the image includes movement of oxygen and glucose, and typical tasks involve identifying the type of transport...

Let me assume the most common question associated with this image:

“What type of transport is used for oxygen and glucose?”

Step-by-step:

1. Oxygen (green pairs): It moves straight through the membrane from outside (high concentration) to inside (low concentration). No protein needed → Simple Diffusion

2. Glucose (purple hexagons): Also moves from high to low concentration, BUT it uses a yellow protein channel → Facilitated Diffusion

Both are passive transport (no energy required), just differ in whether they need help crossing.

Final Answer should reflect this if that’s the implied question.

But wait — maybe the task is to label a, b, c, d?

In many textbooks, this exact diagram asks:

a = carrier protein / channel protein
b = oxygen molecule
c = phospholipid
d = glucose molecule

That fits perfectly.

So:

a → protein (used for glucose transport)
b → oxygen molecule
c → phospholipid (part of the bilayer)
d → glucose molecule

This is straightforward identification.

No math, no complex logic — just matching visual elements to biological terms.

I’ll go with labeling a, b, c, d as their correct biological identities.

Final Answer:
a = transport protein, b = oxygen molecule, c = phospholipid, d = glucose molecule