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.

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………

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

ROUGHENDOPLASMIC

RETICULUM

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

Ribosome

Protein 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 of

Golgi complex

Vesicle

from ER

New

vesicle

forming

Transport vesicle

from 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

Centrioles visibleNo visible centrioles

Have small vacuolesHave large vacuoles

Do not have chloroplastsHave chloroplasts

Do not have a cell wallHave a cell wall

Animal cellsPlant Cells

IMPORTANT SLIDE!!!