Spreading of molecules from a region of high concentration to low concentration

When water molecules diffuse across a selectively permeable membrane.

Many molecules crammed in a small volume

Few molecules spread out in a larger volume (dilute)

When molecules are distributed equally throughout a region

Semi-permeable membrane

A membrane that allows some molecules to pass through but not others

When a cell uses energy to pump a substance across a membrane.

Facilitated diffusion

When a substance diffuses through a special protein channel across a membrane.

Molecules that CAN pass through membrane

Small uncharged molecules like O2, CO2, H20

Molecules that CAN'T pass through membrane

Large molecules like sugar or charged ions like sodium+ or chlorine-

Sodium/Potassium pump

This protein that pushes Na+ or K+ across a cell membrane. This uses ATP energy because it is against the flow of diffusion.

When the cell membrane pinches in a bubble of materials to bring into the cell. This happens when white blood cells engulf bacteria. or a virus enters a cell.

When a bubble of materials fuses with the cell membrane and is released out of the cell. This happens when a cell releases a hormone or expels waste.

What happens when you put salt on a leech? Why?

The leech shrivels up. Water moves out of the leech by osmosis, out towards the salt where there is less. The salt can't diffuse past the skin.

What happens when you put baking soda on a bee sting? Why?

The swelling goes down and the venom gets pulled out into the baking soda by osmosis. Fluid moves out of the sting since baking soda can't diffuse in.

What happens to the smell of a fart in a room with no fans? Why?

It gradually spreads evenly around the room. The gas particles are in constant random motion and diffuse from the area of high concentration towards lower concentration.

How do viruses like covid get into a cell?

They enter by endocytosis. The virus capsule has proteins that fit receptors on the cell membrane like a key in a lock. This triggers the cell to make a bubble of membrane that brings the virus in.

Why does an electric shock make muscles contract?

The shock forces membrane channels to open in our nerves. This allows + charged sodium ions to rush in. This flow of + ions travels down the nerve like dominoes and ultimately signals the muscle to contract.

How do neuron signals work?

Neurons use pumps to push + sodium ions outside the membrane, like water behind a dam. When a neuron is stimulated, membrane channels open allowing the + ions to rush in. This is electrical flow travels down the neuron to trigger the next neuron.

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Cell Membrane Vocab

Question	Answer
Diffusion	Spreading of molecules from a region of high concentration to low concentration
Osmosis	When water molecules diffuse across a selectively permeable membrane.
High concentration	Many molecules crammed in a small volume
Low concentration	Few molecules spread out in a larger volume (dilute)
Equilibrium	When molecules are distributed equally throughout a region
Semi-permeable membrane	A membrane that allows some molecules to pass through but not others
Units of concentration	% or grams/Liter or grams/mL
Active transport	When a cell uses energy to pump a substance across a membrane.
Facilitated diffusion	When a substance diffuses through a special protein channel across a membrane.
Molecules that CAN pass through membrane	Small uncharged molecules like O2, CO2, H20
Molecules that CAN'T pass through membrane	Large molecules like sugar or charged ions like sodium+ or chlorine-
Sodium/Potassium pump	This protein that pushes Na+ or K+ across a cell membrane. This uses ATP energy because it is against the flow of diffusion.
Endocytosis	When the cell membrane pinches in a bubble of materials to bring into the cell. This happens when white blood cells engulf bacteria. or a virus enters a cell.
Exocytosis	When a bubble of materials fuses with the cell membrane and is released out of the cell. This happens when a cell releases a hormone or expels waste.
What happens when you put salt on a leech? Why?	The leech shrivels up. Water moves out of the leech by osmosis, out towards the salt where there is less. The salt can't diffuse past the skin.
What happens when you put baking soda on a bee sting? Why?	The swelling goes down and the venom gets pulled out into the baking soda by osmosis. Fluid moves out of the sting since baking soda can't diffuse in.
What happens to the smell of a fart in a room with no fans? Why?	It gradually spreads evenly around the room. The gas particles are in constant random motion and diffuse from the area of high concentration towards lower concentration.
How do viruses like covid get into a cell?	They enter by endocytosis. The virus capsule has proteins that fit receptors on the cell membrane like a key in a lock. This triggers the cell to make a bubble of membrane that brings the virus in.
Why does an electric shock make muscles contract?	The shock forces membrane channels to open in our nerves. This allows + charged sodium ions to rush in. This flow of + ions travels down the nerve like dominoes and ultimately signals the muscle to contract.
How do neuron signals work?	Neurons use pumps to push + sodium ions outside the membrane, like water behind a dam. When a neuron is stimulated, membrane channels open allowing the + ions to rush in. This is electrical flow travels down the neuron to trigger the next neuron.

Created by: buchwalder

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