The Cell
Chapter 15
The Cell Theory

The theory has three
main parts summarized
as:



All living things are
made up of one or more
cells
The cell is the functional
unit of life
All living cells come
from pre-existing cells
The cell as a factory:

The parts of a cell can be compared to the
workers and jobs in a factory


Each department in a factory has specific jobs that
need to be done or else the factory becomes less
efficient and eventually shut down.
The same idea is true for the cell, if one of its
components stops working efficiently then the cell
or the organism could die.
Cell Membrane:


The “gate keeper” or “bouncer” of the cell
Decides which materials enter, which ones
stay and which ones leave a cell.




Keeps the good ones in and bad ones out.
Every cell has a cellular membrane
(including both animal and plant cells).
It is a thin flexible covering surrounding all
cells.
Made up of primarily proteins and fats
Nucleus




The “Boss”
With few exceptions all
plant and animal cells
possess a nucleus (plural
form is nuclei).
Dark mass usually seen in
the middle of the cell
contain the DNA or genes
for the cell which are the
instructions for all the
activities of the cell
Nuclear Envelope



The membrane that
encloses the contents of
the nucleus.
“the Boss’ office”
It has pores in it for
larger materials to pass
in and out.
Nucleolus

A visible darker staining
region inside the nucleus.
nucleolus

It is where RNA and
ribosomes are made.
Cytoplasm


The rest of the cell
material that is inside
the cell membrane but
outside the nucleus
Organelles and vacuoles
are considered part of
the cytoplasm
Cell Organelles



Like your body which has organs to
perform the necessary functions for life,
similarly cells have organelles which
perform the necessary function of
particular cells.
Many organelles are bound by their own
membrane
The proportion of the different organelles
inside a particular cell depends on the
function of the cell.

For example a cell that produces a lot of
hormones will have a large amount of golgi
apparatus which is the organelle responsible
for packaging the products of a cell.
Ribosomes




The “workers” that put together the products
of the cell.
The location of protein synthesis
Made from RNA from the nucleolus
Some are free in the cytoplasm and others are
embedded in the endoplasmic reticulum (ER).

The proteins produced by free ribosomes in
cytoplasm are generally used within the cell
Endoplasmic Reticulum



The “assembly line” for
the products of the cell
It consists of
membranous channels
that wind through the
cytoplasm
There are two types of
endoplasmic reticulum:
1) Rough endoplasmic reticulum
2) Smooth endoplasmic reticulum
Rough Endoplasmic Reticulum:




AKA “rough ER”
The ER that has
ribosomes embedded in
it.
Manufactures proteins
for other cells and also
phospholipids for the
cell membrane
Assists in the movement
of molecules towards
the cell membrane
Smooth Endoplasmic Reticulum




Aka : Smooth ER
Lack ribosomes
Manufactures steroids
Example: testicle cells which produce
testosterone have abundant amounts of
smooth ER.
Golgi Apparatus
May looks similar to smooth ER, but
it is a set of about 7 or 8 flattened
saccules between ER and the cell
membrane
 “Packages, processes and labels”
the products from the ER
 Makes concentrated packages of
proteins
 Puts carbohydrate chains (labels)
on the packages of proteins so that
specific cells recognize them once
they are released in the blood.
Vesicle



“storage containers”
Double membrane
bound sacs carrying
different products and
substances from one
part of the cell to
another.
Also carry food, waste
products, digestive
enzymes.
Lysosomes


“Janitors or quality control”
Vesicle-like structures that
contain enzymes used for
digestion of molecules in the
cells.


Example: to digest unwanted cells
(dying cells) and cell parts that are
defective
Think of them as the quality control
or health board, that can shut
down the cell at any time.
Mitochondrion




Plural form “mitochondria”
“The Generator” or “power
house” of the cell
Give the cell the energy it needs
by a series of chemical reactions
called cellular respiration
Fluid filled, with a complex
internal membrane


The inner fluid is called the matrix
The inner membrane which folded
in the matrix is called the cristae.
Vacuole




“Storage Containers”
Vacuoles serve a variety of
functions, including storing
nutrients, wastes and water.
Irregular shape
They are usually much
larger in plant cells than in
animal cells.

Example: in the plant cell they
take up almost the entire cell.
Centriol


“Traffic Cop”
Organizes organelles
and chromosomes
during cell reproduction
Plant cells vs Animal cells

There are some structures
that plant cells possess that
animal cells do not.
Including:




Cell wall
Chloroplasts
Also, plant cells have larger
vacuoles (that sometimes
appear to take up the entire
cell).
Plant cell do not have a
centriol!
Cell Wall


The cell wall provides
and maintains the shape
of these cells and serves
as a protective barrier.
Has large pores that
allow many molecules
to enter.
Chloroplasts




Chloroplasts are specialized
organelles found in all higher plant
cells.
These organelles contain the plant
cell's chlorophyll, hence provide the
green color.
The place where photosynthesis
takes place.
They have a double outer
membrane. Within the stroma are
other membrane structures

- including the thylakoids and grana
where photosynthesis takes place.
Vacuoles in Plant cells




Help the cell wall keep its shape
Stand up, close eyes
Pretend you are a plant that has not been
watered for a week…what would you look like
Now your mother waters the plant…what does
it look like now.
Cell membrane
Lysosome
Nucleus
Nucleolus
Centriol
Cytoplasm
Rough ER
Smooth ER
Nuclear
Envelope
Ribosomes
Vacuole
Golgi Apparatus
Mitochondrion
Cell Wall
Cell membrane
Cytoplasm
Lysosome
Vacuole
Nucleus
Rough ER
Nucleolus
Smooth ER
Nuclear
Envelope
Chloroplast
Mitochondrion
Ribosomes
Golgi Apparatus