Facilitated Diffusion and Membrane Proteins

The video explains diffusion, a process where particles move from high to low concentration. Simple diffusion occurs directly across the phospholipid bilayer for small, non-polar molecules like oxygen. However, larger or polar molecules like sugar cannot pass through due to the cell membrane's selective permeability. This is based on size and polarity. To solve this, facilitated diffusion uses proteins as channels to transport these molecules across the membrane without energy. Facilitated diffusion is passive, specific to substances, and moves down the concentration gradient.

What is the process called when particles move from an area of high concentration to an area of low concentration?

• Endocytosis

• Active Transport

• Osmosis

• Diffusion

Which type of diffusion occurs directly across the phospholipid bilayer?

• Facilitated Diffusion

• Simple Diffusion

• Osmosis

• Active Transport

What does it mean when a cell membrane is described as selectively permeable?

• It allows all substances to pass through

• It blocks all substances from passing through

• It allows only certain substances to pass through

• It allows substances to pass through only during certain times

Which of the following factors primarily determine whether a substance can pass through the cell membrane?

• Temperature and pH

• Size and polarity

• Shape and color

• Density and volume

Why can't sugar molecules pass through the phospholipid bilayer?

• They are too large and non-polar

• They are too small and polar

• They are too large and polar

• They are too small and non-polar

What is the role of proteins in facilitated diffusion?

• They act as channels to help substances pass through the membrane

• They block substances from passing through the membrane

• They provide energy for diffusion

• They change the shape of the membrane

In facilitated diffusion, substances move from:

• Inside to outside the cell only

• Low to high concentration

• High to low concentration

• Outside to inside the cell only

Does facilitated diffusion require energy from the cell?

• Yes, it requires ATP

• No, it is a passive process

• Yes, it requires glucose

• No, it requires no molecules

Are proteins involved in facilitated diffusion specific to particular substances?

• Yes, each protein is specific to a particular substance

• No, they are non-specific

• No, any protein can transport any substance

• Yes, but only for small molecules

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