Welcome to Science Grade 8s

Unit 1- Understanding Life Systems: Cells

• What the curriculum says:“Cells are the smallest unit of life, and each cell is a system nested within a system. In Grade 8,students will continue to develop their knowledge of organisms by focusing on the structure and function of cells in plants and animals. Our knowledge of cells has increased enormously since the middle of the twentieth century, and students will examine the implications of this knowledge for individuals, society, and the environment.”

What this means:We will be learning about the structure of cells and how they work in plants and animals

Cells come in many shapes and forms

Can anyone guess what type of cells these are?

Technology in this unit

• During this unit, we may have the opportunity to do some experiments, build some models, and use some scientific technology. How much hands-on stuff we do depends on how much I can trust you to follow the safety expectations we go over, so, when the time comes, pay attention and be mature

Vocabulary in this unit

• By the end of this unit, you should be familiar with (and using) the following terminology to discuss cells:

• organelle, diffusion, osmosis, cell theory, selective permeability, membrane, stage, eyepiece

Before we can build and explore…..

• You need some background knowledge• To start, please flip to page 67 of your student workbooks• Read pages 67-72 and complete the activities on pages 72

to 74 ON LINED PAPER IN YOUR SCIENCE BINDER (do not write in the workbooks)

• Right now, we have 34 students in this class. You will be paired up with one person to share a workbook that you will be assigned.

• Together you are responsible for keeping your workbook as new as possible

From last time….

• Last class, we looked at the difference between living and non-living things

• Living things:• Grow, repair themselves, and reproduce• Need energy• React to changes in their environment• Have a lifespan• Create waste• Are made up of at least one cell

The Cell Theory

• The Cell Theory helps explain the basics of cells and how they work

• ***You will be expected to know all 3 parts of the cell theory, so it might be best to write this stuff down

1. All living things are made up of at least one cell2. Cells are the most basic units of life3. Every cell comes from cells that already exist

The Cell Theory

• 1. All living things are made up of at least one cell• -some life forms are unicellular (made up of one cell)• -other living things have many, many, many more• Any guesses about how many cells humans have?

Lesson 2- The Cell Theory

• 2. Cells are the most basic parts of life• Cells give all living things structure

The Cell Theory

• 3. Every cell comes from cells that already exist• New cells are “born” through the division of old cells

At the bottom of your “Cell Theory” note…

• Please complete worksheet 4.2-1, questions 1-3• **remember the date and title please• **either write the question down or include part of the

question in your response• Example: “The microscope helped scientists form the cell

theory by…..”

Lesson 3- Parts of a Cell

• As we discussed earlier, we are going to be learning about plant cells and animal cells

• The basic structures of each type of cell have some common features and other features that help us separate plant cells and animal cells

Common Features

• All cells have small parts/structures that are called organelles

• Think of organelles as the organs of the cell• Just like our bodies need our organs to perform specific

functions (lungs, heart, liver, etc.), the organelles of cells have very specific jobs to do within the cell

-All organelles float around in the cytoplasm (watery fluid) of a cell. Cytoplasm is NOT an organelle

**think about cytoplasm is the stuff that holds the parts of the cell in place (like Jell-o in a jellied salad)

Common Features

• 3 organelles exist in both plant and animal cells• cell membrane• Nucleus• vacuoles

Cell Membrane

• The cell membrane is like the jacket, skin, or cover of the cell• It surrounds the cell• Food enters the cell through the cell membrane• Waste exits the cell through the cell membrane

Nucleus/Nuclei

• The nucleus is the “control centre” of the cell• Our bodies also have a control centre- what is it?• The nucleus controls most of what happens inside the cell• A nuclear membrane covers the nucleus (like an inner jacket)• The nucleus is where the cell’s chromosomes are• Chromosomes carry information that the cell needs to function • A location on a chromosome with a specific set of information

about a living things characteristics (eye colour, hair colour, etc.) is called a gene

Inside the nucleus

Vacuoles

• Vacuoles are like the gas tanks of cells• They are used to store water, sugar, and other energy

sources• Vacuoles also store waste until it can be expelled• *plant cells have much larger vacuoles than animal cells

The difference between plant cells and animal cells

• Plant cells have a few extra parts that animal parts do no have

• Use the information found on pages 87-88 to complete your chart

• At the bottom of your chart, please complete questions 1 and 2 (from page 89)

Activity 1- building cell models

• Last week, your homework was to fill out your cell model organizer to create a proposal for your project.

• Please hand it to Mr. T. so he can review it• If you get a thumbs up- you can start building• If you get a thumbs down- you will need to review parts of

your proposal before moving forward• If you don’t have it done- I cannot help. Get it handed in

ASAP

Activity 1- building cell models

• Next week, you will be given class time to build. So please bring your materials next Wednesday.

• If you are building at home, you may treat this period as time to catch up on your other school work or to read. Please come with an alternative activity, or I will find something for you to do.

Lesson 4- Cells in their environment: the cell membrane

• Last class, we learned that the cell membrane is like the skin or jacket of the cell

• This is the outer layer of the cell separates the interior of the cell from its outside environment; it protects the cell

• This layer controls what passes into and out of the cell.• The cell membrane is selectively permeable because

only certain particles are able to pass through it

What the heck does ‘permeable’ mean??

• Things that are permeable let allow other objects to pass through them• Think of a tunnel as permeable

• Things that are impermeable do not allow other objects to pass through them• Think of a wall as impermeable

• Selectively permeable is in the middle; some things can pass, other things cannot• Think of a strainer or a security guard

What are cell membranes made of?

• Cell membranes are made of a phospholipid bilayer (two layers of fat)

• Proteins are built into these fat layers and serve as channels (doorways)

• These proteins open and close to let things pass into and out of the cell (when they are supposed to)

• Cells have different sized protein channels so that different sized particles can pass through• Water, oxygen, carbon dioxide particles

pass through easily• Larger particles (fats, sugars) do not

pass through as easily

For your Study Notes

• Please read the information on page 97, then complete the questions on page 98, the fill-in-the-blank activity on 99 and create your own sketch of the parts of the cell membrane.

Lesson 5- Cells in their environment- Movement

• Time to stand up!!!!• Everyone to the center of the room as tightly as possible

What do you notice?

Time to separate

• By walking, spread yourselves out as much as possible; use every corner of the classroom

NOW, what do you notice?

Back to your seats please

• What does this have to do with cells?!?

Diffusion

• This is how particles move within cells• Particles more from highly concentrated areas (your

circle) to less concentrated areas (free space)• Think of a freshly baked apple pie. • Originally you would only smell it if was really close, but

as it sits out the smell travels• Same with less desirable smells (those closest will notice

it most and strongest)

Concentration Gradient

• When there is unequal concentrations of a particle, it creates a concentration gradient

• Diffusion can only happen with a concentration gradient exists• For example, if there is a higher concentration of water particles

outside the cell than inside, the cell membrane allows for a transfer of those particles (through the protein channels) into the cell until the concentration is the same inside and out

Confused?!?

• Time to get up again!!• We need 5 traffic cops• Everyone else, wait for further instruction

Why is diffusion important to cells?

• Diffusion helps cells “bring in” essential materials and “send out” wastes

• Example: blood cells• Blood brings oxygen to your cells for them to be able to

function (from highly concentrated areas to areas of lower concentration)

• Blood also removes carbon dioxide from your cells (from highly concentrated areas to areas of lower concentration)

For your study notes

• Please read over pages 100 and 101• Please complete the questions on pages 102 and 103

Lesson 6- An Important type of Diffusion

• As I hope you all know, all living things need water to survive

• Cells are no different; diffusion provides cells with the water they need to function• Let’s test what you learned from your cell model

assignment: what part of the cell allows water to pass into the cell?

Osmosis

• Osmosis is a special type of diffusion.

• During osmosis, water travels across the cell membrane from an area of higher water concentration to one of lower concentration

• This will only happen when there is a concentration gradient

Osmosis

• Take a look at the picture here.

• The diagram on the left represents a situation where we have a higher concentration of sugar inside the cell

• Outside the cell the sugar/water solution is diluted

Osmosis

• On the diagram on the right, osmosis is occurring

• Water moves through the cell membrane (the line in the middle) from an area of high water concentration to one of low concentration. As a result, there is more water inside the cell.

Water Concentration

• Thinking back to Grade 7 Science…..• A solution is made up of two parts: a solute and solvent• The solute is what is dissolved (the sugar)• The solvent is what is doing the dissolving (the water)• The more sugar we have dissolved in the water, the

higher the level of concentration.

Concentrated- high level of solute

Diluted- low levels of solute

Osmosis in Cells

• Sugars, salts, and proteins are common solutes in cells• Water is almost always the solvent in cells• When water moves into or out of the cell through the cell

membrane, the concentration of the solution inside the cell changes.

Concentration in cells

• There are three pictures above: Each one represents a different state that cells can be in.

• Can you guess what the concentration is like in each case?

• If so, should water be coming into or out of the cell?

Hypotonic

• Water moves from where it is more concentrated.

• If there is a lower concentration of water inside the cell than outside, water moves into the cell, causing the cell to swell

Hypertonic

• If there is a higher concentration of water inside the cell than outside, water moves out of the cell, causing the cell to shrivel

Isotonic

• When the concentration of water is the same inside the cell and outside, things are said to be “normal”

• Water still moves into and out of the cell but it does so at the same rate

What causes cells to change shape?

• Especially in plant cells, vacuoles take up most of the space

• Vacuoles are storage units, and often store water• When extra water needs to come into the cell, the

vacuoles push outward and swells• This is called turgor pressure• When there is not enough water in the cell, the

vacuole shrinks and there is less turgor pressure• This causes plants to wilt

For your notes….

• Read pages 104-106 from the text book• Questions on pages 107 and 108

Lesson 6 Demonstration- The Egg experiment

• Did you know that eggs are considered by some to be the largest single-cells on earth?

• Well, we are going to roll with this to see what happens to eggs when we change the environment around them

Demonstration- Day 1

• Mr. T. came to your room yesterday and gave your classroom a bowl of eggs submerged in vinegar. • What were your observations?• What changed about the eggs? Why?

Demonstration- Day 2 AM

• This morning, Mr. T. came to your room and took eggs out of the vinegar that (hopefully) looked like this:• How did the eggs feel? Why?• How did the eggs look? Why?

Demonstration- Day 2 PM

• After making our observations about our “egg cells”, we are now going to put our eggs in different solutions to see how they respond

• Our 3 solutions are: • a) corn syrup (high sugar concentration)• b) salt water (high salt concentration)• c) distilled water

Predictions

• What do you predict will happen to each egg after being placed in each solution?• What makes you think this will happen?

Observations

• Each group will be responsible for watching an egg. Your goal is to record your observations as detailed as possible. You will be charged with presenting your findings to the rest of the class.• Things to consider watching for/writing down?• Any changes in appearance?• Smell?• Did the process happen right away? (a timer might be a good

tool)

Time to share……

Remember, sharing is as much about listening to others as it is about sharing your ideas

Questions………

What happens next??

• What if we put the corn syrup and/or salt water eggs into the distilled water?

• What do you think will happen? Why?

Lesson 7- Endocytosis and Exocytosis

Larger particles need to travel too

• The past few lessons (and labs) have shown us how small particles pass into and out of the cell (diffusion) and how water can travel through the cell’s membrane (osmosis)

• There are some particles that are too large to travel through these processes

• Cells use the processes of endocytosis and exocytosis to take in and get rid of larger particles

Endocytosis

• Endocytosis allows large materials to pass into the cytoplasm than cannot pas through the cell membrane

• There are different types of endocytosis (phagocytosis, pinocytosis, endocytosis), but they all essentially involve the cell surrounding or “attacking” the molecules• Kind of looks like pac-man

Phagocytosis

• One specific type of endocytosis is called phagocytosis, which can be translated to mean “cell eating”

There are 4 general steps:1. The cell extends to make

finger- or jaw-like shapes called pseudopods

2. Like chopsticks, these grasp the material outside the cell

3. The pseudopods come together and form a vacuole around the material

4. The cell “digests” or breaks down the particles into smaller parts so they can be converted into energy/food

The opposite of Endocytosis

• The process that cells use to expel particles too large to move through diffusion or osmosis is called exocytosis (think: exo looks like exit)

• During this process, the cell pushes wastes from its cytoplasm into the outside environment

Exocytosis steps

1. A cell vacuole moves toward the cell membrane and eventually attaches 2. The vacuole pushes through the cell membrane and releases the contents into the outside environment3. The vacuole joins the cell membrane

Cells are good sharers

• Although waste is the most common thing that passes out of a cell through exocytosis, the process can also be used to expel other materials

• Cells often share materials so one cell might use exocytosis to send material out that a neighbouring cell may need (example: proteins)

For your notes

• Please use the materials from pages 109 and 110 of your workbook to take any notes you might find helpful

• Use this info. to answer the questions and complete the activities found on pages 111 and 112 (on the worksheet provided)

Lesson 8- genetically modified organisms

The Debate

• Now that we have learned what cells are made up of and how they work, it’s time to think about how our understanding of cells creates some debates today.

• If you had the ability to use science to grow “superfoods” (that could change the size, amount, appearance and taste of natural foods) would you?

• If you had the ability to pre-screen your baby to check for diseases and even CHANGE their genetics to protect from diseases or change they way they look, would you?