The Outer Organelle (Plasma Membrane)

What organelle surrounds, protects, and supports the cell?

The plasma membrane.

What is the plasma membrane?

An organelle that surrounds, protects, and supports the cell, acting as a barrier between the environment and the rest of the cell.

What does the plasma membrane act as?

A selectively permeable barrier.

What does “selectively permeable” mean?

It allows some substances to cross while denying others.

What determines if objects can fit through the plasma membrane?

Their size.

Can larger objects fit through the plasma membrane?

No, larger objects cannot fit through it.

Can smaller objects fit through the plasma membrane? How?

Yes, smaller objects can pass through its small openings.

What is the plasma membrane made of?

It is made of several components that together form the fluid mosaic model.

Why is the plasma membrane called a fluid mosaic model?

Because at room temperature it has the same viscosity as vegetable oil and contains many different components.

What are the main structural molecules in the plasma membrane?

Phospholipids.

What are phospholipids?

Lipids that have a hydrophilic head and a hydrophobic tail.

What are phospholipids exceptional at doing?

Letting water across the membrane.

What kinds of bonds do phospholipids have?

They have saturated and unsaturated bonds.

Why do phospholipids have saturated and unsaturated bonds?

To prevent them from packing too tightly, allowing movement of small molecules through small gaps in the membrane.

What else is found within the plasma membrane besides phospholipids?

Proteins with various responsibilities.

What are the functions of proteins in the plasma membrane?

They help with transport and recognition.

What is the last major component of the plasma membrane?

Cholesterol.

What is the role of cholesterol in the plasma membrane?

It stabilizes the membrane at high and low temperatures.

How does cholesterol affect the plasma membrane at high temperatures?

It makes the membrane less viscous.

How does cholesterol affect the plasma membrane at low temperatures?

It makes the membrane less rigid.