Prentice Hall – Science Explorer – Cells and Heredity Chapter 1 – Cell Structure and Function Section 1 – Discovering Cells

Questions and Comments Main Ideas; Visuals; Examples Key Terms/Connections An Overview of Cells

Cells are the basic units of structure and function in living things. Cells= what forms the parts of an organism and carries out all of its processes.

Cells

Cells and Structures The variety of ways cells are put together determine the structures of organisms.e.g. A tree’s cells arrange to form a trunk and leafy branches. A red newt’s cells form a body with a head and four legs.Cells and Function Cells are involved in an organism’s functions that are the processes that allow it to stay alive and reproduce. e.g. cells in your digestive system absorb food. The food provides your body with energy and materials needed for growth.Many and Small Most cells are too small to see with your eyes alone. - Until the late 1600s nobody knew cells

existed because there was no way to see them.

e.g. one meter squared of your skin’s surface contains more that 100,000 cells.

Connection: Like atoms, they were discovered later in history because they are too small to see with the eyes alone.

Who invented the first microscope and how did it contrast to the ones used today?

First Observations of Cells The invention of microscopes around 1590 allowed people to discover and learn about cells. Microscope= instrument that makes small objects look larger…microscope?

Microscope

What were the boxes within the cell that Hook observed?

Robert Hooke He was an English scientist who was one of the first to observe cells. In 1663 he used the compound microscope he made to observe the structure of a thin cork slice. - Cork is made up of dead cells, and to

Hooke these empty paces looked like small rectangles. Thus, he called them

cells (small rooms). - He described the cells contained many

boxes within and calculated that in a cubic inch there were about 1,200 million cells.

What are examples of single-celled organisms?

Was he the first to observe these single-celled organisms?

Anton van Leeuwenhoek At about the same time as Hooke, Leeuwenhoek, a Dutch businessmen who built simple microscopes in his free time began to observe tiny objects like drops of lake water, scraping from teeth and gums, and water from rain gutters. - In these he found many one-celled-

organisms that whirled, hopped or shot through water.

- He called these animalcules (little animals).

Development of the Cell Theory Many other scientists began to use microscopes to learn more about cells. Schleiden, Schwann, and VirchowThese were three German scientists. In 1838 based on his and other’s research Schleiden concluded all plants are made of cells. The next year, Schwann concluded all animals are made of cells—thus, he stated all living things are made of cells. In 1855, Virchow stopped the theory that organisms sprung from nonliving matter by proposing new cells formed from cells that already exist. What the Cell Theory SaysCell theory= widely accepted explanation of the relationship between cells and organisms. The cell theory states: - All living things are composed of

cells.- Cells are the basic units of

structures and function in living things.

- All cells are produced from other cells.

Since cells are common in all organisms they provide information about the functions of organisms.

Cell theory

Since cells come from other cells one can study cells to learn about growth and reproduction. Light and Electron Microscopes A useful microscope must have good magnification and resolution.

Connection: I learned about resolution in Digital Photography.

Magnification and Lenses Lenses in light microscopes magnify (enlarge) an object by bending the light that passes through it. - The lens is a convex lens (curved—

thinner on the edges, thicker in the center)

- The light passes through the sides and bends inwards, when the lights hits the eye the object appears larger.

Is the quality of images produced by compound microscope magnification worsened due to more magnification? Doesn’t the image begin to blur?

Compound Microscope Magnification Uses more than one lens and can magnify an object more. - Light passes through a specimen and

the first lens magnifies the object. Then the second lens further magnifies the magnified image.

e.g. First lens magnification= x10. Second lens magnification= x40Total microscope magnification=10x40=400. Resolution Resolution is the sharpness of an image. A good microscope helps you clearly distinguish the individual parts of an object. e.g. An image is made up of many small dots. If you look at it under a microscope the

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magnification and resolutions should allow you to see the dots.

How can you get a beam of electrons?

What is it between an electron beam and light that makes electron microscopes better?

Electron Microscopes Since the 1930s scientists developed electron microscopes.Electron microscopes use a beam of electrons instead of light to produce a magnified image. Electron microscopes can let you to see smaller objects and have a better resolution than light microscopes.

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Prentice Hall – Science Explorer – Cells and Heredity Chapter 1 – Cell Structure and Function Section 2 – Looking Inside Cells

Questions and Comments Main Ideas; Visuals; Examples Key Terms/Connection

sOrganelles= tiny cell structures that carry out specific functions in the cell.

Organelles

Enter the CellTo get within the cell you have to pass through the cell wall and cell membrane.

What other organisms other than plants have cell walls?

Cell Wall Cell wall= hard layer of nonliving material, mostly cellulose, that surrounds the cells of plants and some organisms. A plant’s cell wall helps protect and support the cell. Although the cell wall is strong, many materials, including water and oxygen, can easily pass through.

What is the cell membrane made of?

Cell Membrane Cell membrane= cell structure, which is like another barrier that controls which substance can enter or exit the cell. All cells have cell membranes.

- In cell with cell walls it’s located just within it. - In others it forms the outside boundary separating the cell from its environment.

The cell membrane controls what substances enter/exit the cell. For the cell to survive the cell membrane allows everything it needs to enter (food, oxygen); harmful waste products to exit and prevents harmful materials from entering.

Connection, the cell wall and call membrane are much like a wall surrounding a property and the gate.

Sail on to the NucleusNucleus= a large, oval structure located further within the cell. The nucleus is like the cell’s control center, directing all of its activities.

Nucleus

Connection: The nucleus is like the brain of a body.

Nuclear Envelope Nuclear envelope is the membrane surrounding the nucleus that protects it.

- Material pass in and out of the nucleus through pores in the nuclear envelope.

Is this your DNA? Do all cells contain the same chromatin, or are they selective to the cell’s job?

Chromatin Chromatins are floating strands within the nucleus that contain genetic material, the instructions for directing the cell’s functions.

Nucleolus The nucleolus is a small floating structure seen at the end of the nucleus where ribosomes are made.

Organelles in the CytoplasmCytoplasm= region of clear, thick, gel-like fluid that is in constant motion, between the cell membrane and nucleus.

- Many organelles are found here.

Cytoplasm

Mitochondria Mitochondria= rod shaped structures that convert energy in food molecules to energy the cell can use to carry out its functions.

Mitochondria

Connection: Mitochondria provide the cell with energy just like powerhouses provide a city with energy.

Does the endoplasmic reticulum just provide a passageway for materials to travel through, or does it direct their path too?

Endoplasmic Reticulum Endoplasmic Reticulum= maze of passageways where proteins and other materials are carried from one part of the cell to another.

Endoplasmic Reticulum

Connection: Like the school hallways.

Ribosomes Ribosomes= small, grain like structures attached to some surfaces of the endoplasmic reticulum or float in the cytoplasm. Ribosomes produce the very important proteins.

Ribosomes

Connection: Ribosomes are like factories.

Isn’t the membrane in charge of releasing things outside of the cell?

Golgi Bodies Golgi bodies= look like flattened sacs and tubes seen leaving the endoplasmic reticulum. They receive proteins and other newly formed materials from the endoplasmic reticulum, package them, and distribute them to other parts of the cell.

- They also release materials outside the cell.

Golgi Bodies

Connection: These organelles are like the mail room in a city by packaging and distributing things.

Chloroplasts Chloroplasts= large green structures floating in cytoplasm.

Chloroplasts

Connection:

They are only in plant cells and cells of other organisms that capture energy from sunlight and use it to produce food.

- They also make leaves green.

Chloroplasts are like solar cells.

How do animals that don’t have vacuoles store needed materials?

Which animals have vacuoles and which don’t?

Vacuoles Vacuole= large, water-filled sac floating in the cytoplasm. They are the storage areas for food and other materials needed as well as waste products. - Most plant cells have one large vacuole. - Some animal cells don’t have vacuoles,

some do.

Vacuole

Connection: Vacuoles are like a storage room.

What is the average life expectancy for most cells?

LysosomesLysosomes= small, round structures that contain chemicals to break down certain materials in the cell. e.g. some break down large food particles into smaller ones or old cell parts to release substances to be reused.

Lysosomes

Connection: Lysosomes are like the clean up crew

Specialized CellsPlants and animals are many-celled organisms with different cells specialized to perform specific functions. e.g. nerve cells are specialized to transmit information from one part of the body to another while red blood cells are specialized to carry oxygen throughout your body. In many-celled organisms cells are often organized into tissues, organs and organ system. - A tissue is a group of similar cells that

collaborate to perform a specific function. - An organ is a group of tissues that function

together. - An organ system is a group of organs that

collaborate to perform a major function. e.g. The brain is made of nervous tissues, which consist of nerve cells. Your brain is also part of the nervous system that directs body activities and processes.

How does a bacterial cell carry out all the functions animal and plant cells carry out with the several other organelles they contain?

Bacterial CellsBacterial cells are much smaller that plant or animal cells. e.g. a skin cell is about ten times larger than an average bacterial cell. A bacterial cell has a cell wall and cell

Do bacterial cells contain other organelles plant and animal cells don’t?

membrane, but no nucleus. Its genetic material is a thick, tangled sting found in the cytoplasm.

- The only organelle that a plant and animal cell have that they contain is ribosomes.

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Prentice Hall – Science Explorer – Cells and Heredity Chapter 1 – Cell Structure and Function Section 3 – Chemical Compounds in Cells

Questions and Comments Main Idea; Visuals; Examples Key Terms/ConnectionsElements and Compounds

Air is a mixture of gases including both elements and compounds. e.g. 3 gasses in the air are oxygen, nitrogen and carbon dioxide. ElementsElement= Any substance that can’t be broken down into simpler substances. The smallest unit of an element is an atom. - An element is made up of only one

type of atom. e.g. elements found in organisms include hydrogen, oxygen, nitrogen, phosphors and sulfur.

Element

Compounds Compound= two our more elements chemically combined. Smallest unit of many compounds are molecules - Most elements in organisms are

compounds. e.g. Each water molecule is made up of 2 hydrogen atoms and one oxygen atom.

Compound

What is the main difference between organic and inorganic compounds regarding their function, structure, properties…etc?

Organic and Inorganic CompoundsMost compounds that contain carbon are organic compounds.

- Most compounds in organisms are organic.

Some important groups of organic compounds in organisms are carbohydrates, lipids, proteins and nucleic acids. - Many of these are found in the foods

you eat, which come from other organisms.

Compounds that don’t contain the element carbon are inorganic.- Organisms contain many inorganic

compounds. e.g. water and sodium chloride.

CarbohydratesCarbohydrate= energy-rich organic compound made of the element carbon, hydrogen and oxygen. e.g. sugar and starches. Sugars are produced during photosynthesis. - Fruits and some vegetable contain a lot

of sugar. Sugar molecules can combine and form large molecules called starches—complex carbohydrates.e.g. plant based foods like pasta, potatoes, rice and bread contain starch. When you eat these, your body breaks down the starch into glucose, a sugar your cells can use to produce energy. Carbohydrates are important components of some cell parts. e.g. cellulose in cell walls is a type of carbohydrate. Cell membrane also has carbohydrates.

Carbohydrates

LipidsLipids= energy-rich organic compounds, such as fats, oils or waxes, that are made of carbon, hydrogen and oxygen. - Lipids contain even more energy than

carbohydrates. Cells store energy in lipids. e.g. During the winter, a bear live on the energy stored in fat cells. Cell membranes are also made mainly of lipids.

Lipids

What compounds do proteins make up?

ProteinsProtein= large organic molecule made of carbon, hydrogen, oxygen, nitrogen and sometime sulfur. e.g. foods containing protein are meat, eggs, nuts, beans.

Proteins

Structure of ProteinsAmino acids= smaller molecules that are chemically linked to other amino acids to form protein molecules. There are 20 common amino acids that cells can combine in different ways to from 1000s of different proteins. - The kinds of amino acids and the order

Amino acids

Connection: 20 amino acids are like the 26 letters in the alphabet. They can form thousands of words. The letters you use and

they are linked determine the type of protein.

the order they are used in determines the word. Even a change in one latter creates a new word.

What organelles are made up of proteins?

Functions of Proteins Proteins form parts of the cell membrane and make up main organelles. Enzyme= type of protein that speeds up chemical reactions that take place in cells.

-Without them crucial chemical reactions would either take too long or not occur.

e.g. enzymes in your saliva speed up digestion by breaking down starches into sugars in your mouth.

Enzyme

Where else is DNA found? Nucleic Acids Nucleic acids= very long organic molecules made of carbon, oxygen, hydrogen, nitrogen and phosphorus that contain instructions cells need to carry out all functions. There are 2 kinds of nucleic acids: - Deoxyribonucleic (DNA) is genetic

material that carries information about an organism, which directs all cells’ functions and is hereditary. It is mostly found in the nucleus’ chromatin.

- Ribonucleic acid (RNA) plays an important role in protein production and is found in the cytoplasm and nucleus.

Nucleic acids

Water and Living Things Water makes up 2/3 of your body and plays many important roles in cells. Most chemical reactions in cells couldn’t take place without water. Water also helps cells keep their size and shape. e.g. a cell without water is like a balloon with no air. Water helps keep the temperature of cells from changing rapidly because it changes slowly.

Prentice Hall – Science Explorer – Cells and Heredity Chapter 1 – Cell Structure and Function Section 4 – The Cell in Its Environment

Questions and Comments

Main Idea; Visuals; Examples Key Terms/Connections

Are cell walls in plants and other organisms also selectively permeable.

Selectively permeable= property of cell membrane that lets some substance pass through and not others.

- Cell membranes must let things needed, like food and oxygen, enter, while let waste products exit.

Selectively permeable

DiffusionDiffusion is the main method small molecules move across the cell membrane.Diffusion= process where molecules move from an area of higher concentration to lower concentration. - Concentration of a

substance is the amount of that substance for a given volume.

Diffusion

So cells do not control weather they need a material or not. If there is a lower concentration outside and the cell membrane is preamble to it, it diffuses in?

What Causes Diffusion As molecules move, they bump into each other and spread apart. - The more molecules in

an area, the more collisions, which will cause them to push further apart overtime until eventually, they’ll be spread evenly throughout the area.

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Diffusion of Oxygen One-celled organisms in ponds obtain oxygen from the water.

- The oxygen molecules diffuse from the area of higher concentration (pond) through the cell membrane to the area of lower concentration (inside cell).

Connection: I previously learned the cell membrane is permeable to oxygen molecules, which is why this can occur.

OsmosisOsmosis= diffusion of water molecules through a selectively preamble membrane. Since cells can’t function properly without adequate water, many cellular processes depend on osmosis.

Osmosis

Connection: I previously learned that the cell membrane is also preamble to water molecules, making osmosis possible too.

Osmosis and Diffusion In osmosis, water molecules move by diffusion from an area where they are highly concentrated through the cell membrane to an area where they are less concentrated.

When does an imbalance in water molecules between inside the cell and outside of the cell occur and how can you prevent it?

What are the consequences of a cell shrinking or swelling?

Effects of Osmosis Osmosis can have important consequences on cells. - When the concentration

of water in the cell is the same as outside the shape is normal.

- When the cell is floating in water that contains a lot of salt the concentration of water molecules outside the cell is lower than inside. Thus, water moves out of the cell by osmosis and the cell shrinks.

- When the cell is floating in water that contains a very small amount of salt the water inside the

cell contains more salt. Thus, the concentration of water outside the cell is higher than inside so the water moves into the cell causing it to swell.

Active TransportMoving materials through the cell membrane by diffusion or osmosis doesn’t require the cell to use its own energy. Passive transport= movement of dissolved material through a cell membrane without using cellular energy. If the cell needs a substance that is present in higher concentration inside than out it needs to use its own energy to move the molecules in the opposite direction they normally would. Active transport= movement of materials through a cells membrane using cellular energy. Active transport requires the cell to use its own energy, passive transport doesn’t.

Passive transport

Active transport

Connection: Passive transport is like riding your bike down the hill while active transport is like riding it up the hill. Going downhill, no energy needs to be exerted, but going up hill can pose as a physical demanding task.

Transport Proteins One method of active transport is for transport proteins in the cell membrane to pick up molecules outside and carry them in/take out substances

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using energy. e.g. calcium, potassium and sodium are carried in and out of the cell in this way.

How can the cell membrane engulf a particle when it is already surrounding and holding a cell together?

How does wrapping around a particle form a vacuole within the cell?

How does this bring in or take out a substance into/from the cell?

Transport by Engulfing Another method is for the cell membrane to surround and engulf a particle. - Then, the cell

membrane wraps around the particle and forms a vacuole within the cell.

- It uses its energy throughout the entire process.

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Why Cells Are Small Once a molecule enters the cell, if it were bigger, the stream of moving cytoplasm that carries it to its destination would have to travel farther to bring it to all parts of the cell, making it more time consuming. - It would also take longer

to remove wastes. A big cell couldn’t function well enough to survive.

Connection: The way the stream of moving cytoplasm moves molecules around the cell is like the currents of an ocean move a raft.