Bell work

Sandworms are annelid worms that live on theseafloor. They absorb oxygen and excrete wastesthrough their skin. Which characteristic will besthelp the worm carry out these functions?A. large number of heartsB. large diameter blood vesselsC. large mouth compared to body volume D. large surface area compared to body volume

Science Fact of the Day:The human heart has enough pressure to squirt

blood up to 30 feet away.

CO:

LO:

All cells are surrounded by a thin, flexible barrier known as a cell membrane.

What is the cell membrane’s function (job)?

(2 things)

The two main functions of the cell membrane are:

1) to regulate what enters and leaves the cell and

2) to provide protection and support.

What is the cell membrane made (composed) of?

(3 types of molecules)

The composition of cell membranes is a double-layered sheet called a lipid bilayer.

DRAW THIS!

Lipid

Phosphate

carbohydrate

Bi- means 2

Also called the phospholipid bilayer

Proteins are embedded in the lipid bilayer. Proteins form channels or pumps that help

move large materials across the cell membrane.

Carbohydrates are attached to many

proteins embedded on the outside of the

bilayer.

The carbohydrates allow individual cells

to identify one another.

How do substances move into/out of the cell membrane?

(4 ways)

Why does food coloring spread out in water?

Every living thing lives in a liquid environment that it needs to survive.

In a solution, particles are constantly

moving.

They collide with one

another and tend to spread out randomly.

Particles move from an area of high concentration to an area of low

concentration.This process is known as diffusion.

The concentration is the amount of a

substance dissolved into water.

(Kool-aid demo)

A concentration gradient is a difference between two concentrations.Diffusion is the movement of particles down the concentration gradient.

High Concentration

Low Concentration

When the concentration of a solute is the same

throughout a system, the system

has reached equilibrium.

When equilibrium is reached, particles

do continue to move across the

membrane.

Substances that diffuse across a membrane do not require the cell to use energy.

If a substance is able to diffuse across a membrane, the

membrane is said to be permeable to it.

If a substance cannot diffuse across a membrane, the

membrane is said to be impermeable to it.

Selectively permeable means that some substances can pass across while others cannot.

Biological membranes are selectively permeable.

Diffusion of water through a selectively permeable membrane is called osmosis.

Remember: SALT SUCKS

Isotonic means “same strength”. Hypertonic means “above strength”. Hypotonic means “below strength”.

Draw This

Label: IsotonicWater: SameSolute: Same

Label: HypertonicWater: Low (outside cell)Solute: High

Label: HypotonicWater: High (outside cell)Solute: Low