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Cells: The Basic Unit Of Life

Chapter 2

A Joke

•  Why did the chicken cross the playground?

To get to the other slide!!

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Can you name the world’s largest cell????

•  It’s the “yolk” of the ostrich egg. It’s the size of a softball!

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Think about it…. •  Can you feel the flurry of activity within your cells

that keep you alive? (yes? Or no?)

NO!!!! •  WELL, HOW DO YOU KNOW YOUR CELLS ARE

WORKING? •  BECAUSE YOU CAN BREATHE, DIGEST YOUR

FOOD, AND MOVE, SILLY!!! •  PLANTS AND ANIMALS ARE ONLY ABLE TO DO THESE

THINGS SIMPLY BECAUSE OF ITS CELLS.

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Target Objectives:

•  I Can: -- describe the

difference between unicellular organisms and multicellular organisms,

--describe the difference between prokaryotic cells and eukaryotic cells.

Chapter 2

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Cell Theory

• Confirmed discoveries that all scientists believe to be true about cells:

1.  All living things are made of cells 2. Cells are basic units of life 3. All cells are made from other cells

Why Cells are Important •  What happens inside cells causes us to be

who we are. (Genes) •  All growth and life starts from a single cell. •  All diseases start at the level of the cell.

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It’s a Small World

•  A cell is the smallest unit that is capable of performing “life functions”. It is the basic unit of all living things. If it’s living, it is made of cells!

•  Cells come in many shapes and sizes •  Most are too small to be seen without a

microscope *electron microscope is best •  Cells are US!! •  Believe it or not, YOU also began as just one

cell !

Not All Cells Are Created Equal •  We have about 200 different cells in our body,

and about 100 trillion in all. •  Each type is specialized to do a particular job. •  The size & shape of a cell relates to its function.

(Examples include: (Bone cells, blood cells, skin cells, muscle cells)

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white blood cell

red blood cell

cheek cells sperm

nerve cell

muscle cell

Amoeba

Paramecium

Other examples of cells include:

Organisms and Their Environment •  Any living thing is known as an organism…

including bacteria. •  Organisms can be grouped as either: •  Unicellular- one cell •  Multicellular- more than one cell

– “Most” cells cannot live on their own…They must be in a group to survive.

EX: If you scrape your knee on the sidewalk, the cells that are left on the sidewalk won’t survive on their own!!

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Cells are either Prokaryotic or Eukaryotic

(each type has is own characteristics)

The Discovery of Cells

before nucleus

true nucleus

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1. Prokaryotic Cells (proh KARY ah tick)

•  Small, Simple, “primitive” cells

•  All are unicellular •  Lack a nucleus: circular

genetic material floats free in cell

•  Lack membrane-bound organelles (“little organs”)

•  Example: Bacteria

2. Eukaryotic Cells (yew KARY ah tick)

•  Unicellular or multicellular •  DO HAVE:

–  nucleus (with DNA) –  membrane-bound organelles

•  Complex internal structure –  “Compartments” allow many

different chemical reactions to take place simultaneously

– Ex: protists, fungi, plant &

animal cells.

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Eukaryotic Cells - Contain 3 basic cell structures:

1) Nucleus

2) Cell Membrane 3) Cytoplasm with organelles

*add this to your notes

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CAN’T STRESS IT ENOUGH… • Cells are the basic units of of all living organisms • Most cells can only be observed under a microscope Basic types of cells:

Animal Cell Plant Cell Bacterial Cell

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Inside All Cells

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All Cells have : •  No matter what type of cell it may be (prokaryotic,

eukaryotic), ALL cells have the following:

•  CELL MEMBRANE •  RIBOSOMES

•  CYTOPLASM & ORGANELLES •  DNA (Heredity Material)

Add this to your notes!!!

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All Cells Have a Cell Membrane (also called “plasma” membrane)

•  It is the thin protective layer around cells that is made up of phospholipids & proteins.

• Acts as a “barrier” between the inside of the cell and the cell’s external environment

•  Controls the passage of materials into and out of the cell. That’s why it is known as “selectively permeable” Ex: Water & oxygen molecules, food molecules, and waste products

– Found just inside the outer cell wall in plant cells

Plasma/Cell Membrane Cell membrane

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All Cells Also Contain Cytoplasm, Organelles & DNA

•  ORGANelles- contain all the chemicals and structures that enable cells to live, grow, and reproduce

*just like your organs!! * They are located in the cell’s constantly moving cytoplasm –  All cells have organelles, but not necessarily the same kind

(bacteria, plant cells and animal cells differ) –  Some organelles are surrounded by a membrane, and some

are not. Ex: ribosomes •  All cells have DNA – contains instructions for the cell’s

activities.

•  Cytoplasm- the gel-like sea of fluid that all of the cell’s organelles “float” in. *constantly moving

Lesson 2-2 The Organelles of the Cell

Animal cell

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Organelles: •  Are very small, specialized

structures in cells which operate like organs by carrying out specific tasks

•  Can only be observed under a microscope

* Have specific function (job)

* Found floating throughout the cytoplasm

The Need for Protein •  Protein is a very important substance in the cell

because it takes part in nearly every cell activity – Needed for chemical reactions that take place in the

cytoplasm – Also part of cell membrane

•  • Ribosomes are also important because they produce these proteins

- are not covered by a membrane, so they can also be found in prokaryotic cells as well as animal cells - some float freely in the cytoplasm of animal cells, and some are attached to the endoplasmic reticulum… - ribosomes are produced in the nucleolus

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Endoplasmic Reticulum (ER) - Extends from the nucleus to the cell membrane

- Breaks down drugs and certain other chemicals that could damage the cell

-  it’s known as the “Internal delivery system”….Meaning that Substances can move from one place to another (thru tunnels)

- Looks like a “cloth folded back and forth” *folds make tunnels

- - 2 types: rough and smooth

Rough and Smooth

•  Rough ER- “has ribosomes” attached to it (The Proteins made by the ribosomes pass into the ER and are later released to be used elsewhere in the cell)

•  Smooth ER- lacks ribosomes, but acts as a storage organelle

•  Makes lipids and other materials for use inside and outside of the cell

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Golgi Complex/Bodies

•  Looks like ER, but it is located closer to the cell membrane

•  It is made up of “Stacks of flattened sacs”

•  Have a shipping side & a receiving side mainly for “packaging”

•  Primary job: to receive, modify and ship lipids & proteins made by ER!!

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Golgi Complex/Bodies

•  The Golgi complex moves materials to other parts of the cell by way of “transport vesicles”.

How?? •  Part of the membrane

“pinches off” to form a small compartment This small compartment transports its contents (such as cellular substances) to be delivered to other parts of the cell .

Transport vesicle

*It also carries cellular substances to the cell membrane where they are released to the outside of the cell

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Lysosomes •  Contain digestive enzymes

that help break down food molecules, cell wastes, and worn-out cell parts

•  Lysosomes are known as the “clean up crew”

Interesting Fact…

•  Did you know that before you were born, lysosomes caused the destruction of cells that formed the webbing between your fingers? Yep!

•  They say they also contribute to the aging process in us L

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Rod shaped with a folded membrane inside - Site of Cellular

respiration

Mitochondria “Powerhouse of the Cell”

Mitochondria

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Active cells like muscles have more mitochondria

In Animal Cells: Mitochondria

• This is where food is broken down into carbon dioxide and water to produce energy In other words… Burn sugars to produce energy (ATP) Adenosine Triphosphate

What is Cellular Respiration?

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Mitochondria

•  Most of the ATP (energy used by the cell) is made in the inner membrane

•  Can work only if they have oxygen

•  The reason you breathe air •  Lots found in active cells, such as

muscles, the heart, and liver because they need more energy!

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-  Usually the Largest organelle -  Directs all cell activities -  Contains instructions for everything the cell does -  These instructions are found on hereditary material called DNA

Nucleus “Control Center”

Nucleus

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NUCLEAR MEMBRANE •  Nucleus is surrounded by the nuclear membrane •  Nuclear membrane separates

nucleus from cytoplasm •  This membrane controls

movement of materials in & out of nucleus

NUCLEOLUS

•  AKA “little nucleus” •  Found Inside nucleus •  Disappears when cell

divides •  Ribosomes that

make the proteins are produced here

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So, let’s recap the function of each organelle - -

Target Objectives:

•  I Can: -- describe the functions

of each organelle in a plant and animal cell.

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Target Objectives:

•  I Can: -- describe the

difference between a plant and animal cell.

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Two Main Types of Eukaryotic Cells

Plant Cell Animal Cell

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- Dead layer - Gives structure and

shape to plant and bacterial cells

Cell wall

Cell Wall

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Plant Cell

Made of cellulose which forms very thin fibers

It’s strong and rigid

Cell wall

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Function is to: a) Protect and support

the cell b) Resist entry of

excess water into the cell

c) Gives shape to the cell

Cell wall

Plant Cell

How is Cell Wall is important to the Cell Membrane?

-  The cell wall provides strength and support to the cell membrane (by keeping it from tearing).

-  Cell Membrane- keeps the cytoplasm inside and allows nutrients in and waste products out

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Contain the green pigment chlorophyll

Traps sunlight to help make sugars (food)

Process called photosynthesis

Plant Cell Organelles Chloroplast

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-  Have a large central vacuole -  Stores sugars, proteins,

minerals, wastes, & pigments

-  Because of this Plant cells DO NOT HAVE LYSOSOMES!

-  Contains cell sap -  Juice in fruits are here

Plant Cell Organelles Vacuole

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-  REMEMBER: -  Plant cells have a large

central vacuole -  Stores sugars, proteins,

minerals, wastes, & pigments

BREAKING NEWS!!!

-  Because of this Plant cells DO NOT HAVE LYSOSOMES!

Did you know???? The vacuoles in grapes hold so much juice…. •  That they must dry in

the sun for several weeks before they become raisins. A grape loses about ¾ of its original weight in the process.

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Different kinds of plant cells

Onion Epidermal Cells

Root Hair Cell

root hair Guard Cells

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mitochondrion

nucleus

glycogen granule

cell membrane

cytoplasm Animal cell

-  Unlike plant cells, animal cells have no cell wall or chloroplasts

vacuole

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Animal Cell Organelles

•  Centrioles are located near the nucleus of a cell.

•  Comes in paired structures • Help cell divide

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Different kinds of animal cells

white blood cell

red blood cell

cheek cells sperm

nerve cell

muscle cell

Amoeba

Paramecium

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Similarities between plant cells and animal cells

Both have a cell membrane surrounding the cytoplasm

Both have a nucleus

Both contain mitochondria

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Differences between plant cells and animal cells

Animal cells Plant cells

Relatively smaller in size Irregular shape

No cell wall

Relatively larger in size Regular shape

Cell wall present

No Chloroplasts Chloroplasts

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Animal cells Plant cells

Vacuole small or absent

Nucleus at the center

Large central vacuole

Nucleus near cell wall

Differences between Plant Cells and Animal Cells

WHAT ARE THE “LONGEST” CELLS IN YOUR BODY?

The LONGEST cell in your body…..

•  Are nerve cells in your brain called “Neurons”. They can be more than 1m long (~ 3 ft.)

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Target Objectives:

•  I Can: -- describe the

difference between cells, tissues, organs, and organ systems.

Organization of Life The Building Blocks of Life!!!!! •  Life is Organized on

Several Levels "   Cells – life starts here "   Tissues "   Organs "   Organ Systems "   Organism "   Populations "   Communities "   Ecosystems

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Levels of organization •  Cells are grouped together and work as a whole to perform special functions

Tissues

•  A tissue is a group of cells that perform a particular function.

•  Also includes the material between and around your cells

•  (Fat cells, blood cells, and muscle cells)

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What are some ways you use your muscles?

•  It’s not just by riding your bike, walking, riding, swimming, or even throwing or kicking a ball.

•  You are using your muscles (tissue) even when you: •  Swallow your food (tongue) •  Digest your food (stomach) •  Blink your eyes (eyelid) and even so much as breathe!!!

(diaphragm)

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Did you know….

•  An elephant’s trunk is constructed of 300lbs of hair, skin, connective tissue, nerves, and muscles. Its muscle tissue is composed of 150,000 subunits that allow the elephant to drink, breathe, grab and greet friends.

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Organs

•  Organs consist of at least 2 different types of tissue functioning together for a common purpose.

•  Examples: stomach, intestines, heart, lungs, skin, liver, kidneys

Organs Depend On Each Other

•  The organs in an organ system depend on each other

•  If one fails, other organs are affected •  Failure of one organ system can affect

other organ systems •  If your digestive system stopped

converting food to energy, then none of the other systems would have energy to function

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What is the largest organ of the human body?

•  Your skin is the largest organ of the human body.

•  In your life time, you will shed about 40lbs of dead skin cells.

•  The Bad news: You’ll spend a lot of time washing the ring from around the tub! Ha! Ha!

•  The good news! Cells are constantly being formed and replacing dead cells. 67

More about your skin…

Hair and fingernails… •  Are composed of

specialized “skin cells”. •  Why doesn’t it hurt when you

cut them??? •  Even though they grow

continuously, both are composed of dead cells along with a protein called keratin. If they were alive and contained nerves: haircuts and manicures would be quite painful.

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Organ Systems

•  Are composed of two or more different organs that work together to provide a common function

•  Examples: Digestive, nervous, circulatory, respiratory

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System •  Several organs and tissues work together

to carry out a particular set of functions in a co-ordinated way – Human : digestive, respiratory, excretory, circulatory and reproductive systems

–  Plant : root and shoot systems

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Human Body Systems Examples of systems : ´ Digestive System ´ Respiratory System ´ Circulatory System ´ Nervous System

Digestive System

•  Job: Breakdown and absorb nutrients that are necessary for growth and maintenance

•  Major Organs: Mouth, esophagus, stomach, small and large intestines.

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Nervous

•  Job: •  sends electrical impulses throughout the

body; directs behavior of all other body activities

•  Major Organs: Brain, spinal cord and

nerves

Circulatory

•  Job: transport nutrients, gases (such as oxygen and CO2), hormones and wastes through the body

•  Major Organs: Heart, blood vessels blood, and spleen

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Respiratory

•  Job: provide gas exchange between the blood and the environment

•  Major Organs: Nose, trachea and lungs, mouth, diaphragm

“The Human Body” (according to Amoeba Sisters)

•  The 11 Systems of the Human Body

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Small Size •  Remember: •  Almost all cells are too small to be seen

without a microscope. •  It would take 50 of your cells to cover up

this period. •  An electron microscope is used when

things are too small to be viewed with other microscopes.