The Building Blocks of Life: Cells

History of Cells

Until recently, the oldest fossils on earth were little more than 600 million years old.

The world is estimated to be 4.5 billion years old.

Within the last few years, the electron microscope has allowed scientists to discover that life may have possibly existed 3.5 billion years ago.

Fleas, whales, flowers and Douglas firs all come from the same single ancestral cell.

History of Cells

 Every human spent about half an hour as a single cell

 Every square inch of the human body has an average of 32 million bacteria on it.

The History of the Cell: Part II By the early 1800s improvements to the

microscope allowed scientists to investigate structures within a cell.

These improvements led to the development of the cell theory

Using an electron microscope, scientists can see things that are 0.0000001m in size.

Bacteria on the head of a pin.

Here is a fly…up close

The Cell Theory

Three Parts:

1. All living things are made up of one or more cells.

2. The cell is the functional unit of life.

3. All living cells come from pre-existing cells.

The Theory

Before the development of this theory people believed that living things could come from non-living things. (i.e. insects from a raindrop)

Seeing that the cell theory was uniform scientists could look for a general explanation of life processes as opposed to looking at the life processes of specific organisms.

A Cell

Think of a cell as self-contained city. The city imports certain materials to maintain

itself. It also exports certain materials that it

produces. There is a central control of the city

(Municipal Hall, Provincial Government) Specific parts of the city have specific

functions.

Common features of all cells They all have a cell membrane (this is what

encloses a cell) They all have a cytoplasm (the interior fluid of

all cells) They all have DNA in them

Cell Membrane

Cytoplasm

DNA

How DNA is held in a cell

• Some cells have their DNA free in the cytoplasm

• These kind of cells are the most primitive and simple

• Most cells have their DNA enclosed in a membrane.

• These are more advanced and complex cells.

DNA free in the cytoplasm DNA inside the nucleus

Cells are very small Cells are larger

Very few other structures Many other structures

Examples : Bacteria Examples : Plant and Animal cells

Primitive Cells Advanced Cells

Prokaryotic Cells Eukaryotic Cells

Science 9 Review (woo-hoo!)

Cells need nutrients to grow and repair Where do these nutrients come from?

DIGESTION!

What parts of the cell are you already familiar with? (hands up!) Can you recall their function?

The cell membrane

• A phospholipid bi-layer composed of 50% phospholipids and 50% embedded proteins.

Phospholipids…

Phospholipids are the main structural components of membranes

They each have a hydrophilic head and two hydrophobic tails

Draw one and label

Cell Membrane

In water, phospholipids form a stable bilayer The heads face outward and the tails face inward

DRAW IT!!

Three main functions of cell membranes

1. The cell membrane is the outer boundary of the cell.

2. The cell membrane is selectively permeable and controls what enters and leaves a cell.

3. Recognition markers on the outside of the cell membrane are for cell to cell identification.

The Brain: The nucleus

The largest organelle. Separated from the

cytoplasm by the nuclear membrane.

The nucleus is the ‘brain’ of the cell: it contains the DNA, and controls the cell activities.

The nucleus and the nuclear membrane

Chromatin and the nucleolus

Chromatin long strands of DNA

(genetic information) that float around within the nucleus.

The nucleolus a dark area within the

nucleus where ribosomes are made.

Chromatin

Nucleolus

Pore

NUCLEUS

Nuclear membrane

DRAW IT!!

More about Cells….The Cytoplasm

Cytoplasm:

All the contents of a cell, including the plasma membrane, but not including the nucleus.

“Soupy” mixture that contains a variety of cell structures called organelles.

continuous with the nuclear membrane

Rough Endoplasmic Reticulum (RER)

ribosomes attached at tiny holes (making it ‘rough’) The function of the Rough Endoplasmic

Reticulum is to synthesize and export proteins and glycoproteins.

Chromatin

Nucleolus

Pore

NUCLEUS

Nuclear membrane

ROUGHENDOPLASMICRETICULUM

Ribosomes

Smooth endoplasmic reticulum

connected to the RER (and nucleus), but has no attached ribosomes

smooth ER makes lipids (fat)

DRAW IT!!

Products leave the ER in vesicles:

1

Vesiclebuds off from ER

RibosomeProtein inside vesicle

ROUGH ERProtein created

DRAW IT!!DRAW IT!!

Vacuole

In plant cells, vacuoles are larger, act as storage areas, and help regulate water

When vacuoles fill with water, they get larger What happens to a plant cell when this takes

place? The vacuole pushes against the cell wall

The firmness makes veggies crisp and plants stand up!

In animal cells, vacuoles are called vesicles…

Vesicles Vesicles have a simple structure. Liquid filled sacs surrounded by a single

membrane. Package liquids containing a wide variety of

substances and carry these materials to other parts / outside of the cell.

Vesicles also form around material (liquid or solid) that are brought into the cell.

Vesicles are the shipping containers within cells.

Ribosomes

Where proteins are synthesized. May be free, or attached to the RER. Where the information that DNA contains is

transformed into protein.

Lysosomes

Contain digestive enzymes Digest worn out organelles, food particles,

viruses and bacteria Cell janitors – keep the cytoplasm clean

the Golgi complex is a stack of membranous sacs, like a stack of pancakes

these receive and modify products of the ER, then send them on to other organelles or to the cell membrane.

think of it like a distribution company, with a “shipping and receiving” function

The Golgi complex

The Golgi complex

“Receiving” side ofGolgi complex

Vesiclefrom ER

Newvesicleforming

Transport vesiclefrom the Golgi

Golgi apparatus

“Shipping”side of Golgicomplex

Mitochondria

The “power-house” of the cell. This is the structure where cellular respiration

occurs. (i.e. where food is converted into energy)

In everyday language: glucose (sugar) + oxygen carbon dioxide +

water + energy

The mitochondrion (mitochondria)

Note: Folds/Creases

Note: Double Membrane

Cell appendages

Cilia: thin, tail-like projections that beat in one direction or have sensory functions

Flagella: long, whip-like projection used for movement

Plant vs Animal Cells…Round 1 Animal cells have centrioles Centrioles are protein fibres that aid cell

division by helping to move chromosomes

Animal cells take round 1!

Plant vs Animal Cells…Round 2 Plant cells have a cell wall The cell wall protects that plant cell and helps

maintain the cell’s shape Made of cellulose Plant cells take round 2!

Round 3…the final blow

Chloroplasts are found in plant cells only They carry out photosynthesis, which

converts sun’s energy into nutrients Carbon dioxide + water + sunlight glucose

+ oxygen Without chloroplasts, we would have no

oxygen and no sugar

What makes plants green?

Ok, smarty pants… Why are plants green?

Chloroplasts contain chlorophyll, which absorbs sunlight

If chlorophyll is green, then what colors of light (ROYGBIV) do they absorb?

Common structures in plant and animal cells:

Organelles found in plant cells

Cell wall – made of cellulose, gives cell strength and protection

Larger vacuoles – store water and keep cell rigid

Chloroplasts – make sugar from CO2 and sunlight - photosynthesis

Organelles found in animal cells

Centrioles – attachment for the cytoskeleton, organise spindle fibres during cell division

Plant Cells Animal cells

Have a cell wall Do not have a cell wall

Have chloroplasts Do not have chloroplasts

Have large vacuoles Have small vacuoles

No visible centrioles Centrioles visible

IMPORTANT SLIDE!!!