The Cell
A
cell is the smallest unit of
living matter.
 Don’t confuse this with: atom,
element, proton, etc.
Cell Size
Three Main Parts
Plasma membrane
 Nucleus
 Cytoplasm

These are ALL CELLS!
Cell Theory
“Theory” is not a casual term in science.
 Tested innumerable times with consistent
results.
 Universally accepted
 One of the most basic, fundamental
concepts in the foundation of biology.

Cell Theory
–1800s; several scientists working
independently had similar results.
1. All organisms are made of cells.
2. A cell is the structural & function unit
of organs.
3. All cells come from pre-existing cells.
4. Cells are capable of selfreproduction.
There are two types of
cells:
1.
2.
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Prokaryotic- cells that DO NOT have a
nucleus or other cell ORGANELLES
Eukaryotic- cells with a NUCLEUS &
cell ORGANELLES
Which is more complicated?
REMEMBER YOU ARE EUKARYOTIC!
Prokaryotic
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vs
Pro = before
Karyote=kernel(nucleus)
DNA is NOT contained
within a nucleus
Most have a cell wall
outside the plasma
membrane
May have type of flagella
or pilus
Archaea and Bacteria
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Eukaryotic
Eu= true
Karyote=nucleus
DNA contained in double
membraned nucleus
Only plant cells have cell
wall
Contains membrane
bound organelles
Plants, animals, protists,
fungi
Types of Organisms

Unicellular organisms
– Bacteria, Protists, etc.

Multicellular organisms
– Plants
– Animals
 Muscles, skin, nerves, liver, digestive, bones,
blood, immune system, lungs, etc.
Why cells aren’t bigger

If cells get too large in volume compared to
their surface area then it’s difficult to distribute
nutrients throughout the cell and too hard to
get rid of build up of wastes.
The Cell Membrane
A phospholipid bilayer
With proteins embedded in it
Hydrophillic heads and Hydrophobic
tails

The phospholipid consists of hydrophilic heads,
which point towards the outside environment
and the cytoplasm. The hydrophobic tails repel
the water and point in. Thus, the
phospholipids form a bilayer that acts like
a barrier between the cell and the
environment. The phospholipid bilayer also
contains cholesterol, which makes the bilayer
stronger, more flexible and more permeable.
There are a number of important proteins in the
plasma membrane
Fluid Mosaic Model of the Cell
Membrane
The purpose of the membrane is to control what
goes in and out of the cell.
 Semi-permeable means certain molecules can
be transported across the membrane while
others are kept out.
 Proteins that are found in the bilayer are
receptor proteins, which deal with
communication, recognition proteins and
transport proteins that regulate the
movement of water and soluble molecules
through the membrane.

Transport of molecules across the
membrane
 Transport is either active or passive.
 Active transport is moving molecules against
the concentration gradient and energy is
required in the form of ATP.
 Passive transport is moving molecules down
the concentration gradient and no energy is
required.
– diffusion, which moves from high concentration
to low concentration
– osmosis, which is the diffusion of water
molecules
Cell membrane interactive
cell membrane interactive
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The Organelles
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..\Desktop\tdc02_vid_organelles.zip
The Nucleus- DNA container
Nucleus
 cellular
control center
– Controls cellular activity
 contains
hereditary material (DNA in
chromosomes)
 self duplicating structure -divides when
the cell divides
Structure of Nucleus

Nuclear Envelope (membrane):
– Double lipid bilayer: keeps DNA separated
from the rest of the cell
– Continuous with Endoplasmic Reticulum
Nucleolus: assembly of ribosomes for
protein synthesis
 Nuclear pores: holes that allow stuff in
and out

Endoplasmic Reticulum
Rough Endoplasmic Reticulum

“HIGHWAY” for cell transport
consists of a network of interconnected, flattened
sacs whose walls are formed of a single membrane.
The outer surface is "rough" because it is studded
with small particles called ribosomes.
 The ribosomes synthesize proteins and discharge
them into the sacs where they are packaged in
membranes which travel through the cytoplasm to
other organelles…….
 (GOLGI BODIES) where they are further processed.

Golgi Bodies
Add carbohydrates component to
the protein and package the
finished product before it leaves
the cell.
 Form the plasma membrane and
membranes of lysosomes

Lysomes
produced by the Golgi apparatus
 contain powerful protein digesting enzymes
 responsible for the breakdown and absorption
of materials taken in by the cell.
 Often, a cell engulfs a foreign substance
through ENDOCYTOSIS, another form of
active transport. During endocytosis, the cell
membrane puckers up, forms a pouch around
materials outside the cell, and pinches off to
become a vesicle. If the contents need to be
destroyed, lysosomes combine with the vesicle
and release their enzymes.
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vacuoles
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fluid-filled, membrane-surrounded cavities inside
a cell. The vacuole fills with food being digested
and waste material that is on its way out of the
cell.
removing unwanted structural debris
surrounding the cell
sequestering materials that might be toxic to the
cell
containment of waste products
maintaining internal hydrostatic pressure or
turgor within the cell (especially plant cells)
storing small molecules
exporting unwanted substances from the cell.
vacuoles
Mitochondria
Mitochondria are the cells' power sources.
 They are distinct organelles with two
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membranes.
Usually they are rod-shaped, however they can
be round.
 The outer membrane limits the organelle.
 The inner membrane is thrown into folds or
shelves that project inward. These are called
"cristae mitochondriales
 Contain their own DNA which can be passed on

Endosymbiosis
It is theorized that mitochondria and
chloroplasts were once free living bacteria
that got caught in evolution
 Both are double membraned, contain their
own DNA and can self replicate

Quick check
What is meant by the phrase "the cell is the
functional unit of life"?
 How are the organelles in a cell like the organs
in a human body?
 Why do you think cells that produce large
numbers of proteins have more rough
endoplasmic reticulum (ER) than cells that
produce fewer proteins?
 In which kinds of human cells would you expect
to find the most mitochondria? The most
lysosomes? The most ribosomes? Explain your
answers.

centrioles
Centrioles

Found only in animal cells, these paired
organelles are typically located together near the
nucleus,
 centrioles are positioned so that they are at right
angles to each other, Each centriole is made of
nine bundles of microtubules (three per
bundle) arranged in a ring.
 Centrioles play a notable role in cell division.
cytoskeleton
ELEMENTS OF THE CYTOSKELETON
All of the microfilaments and microtubules
combine to form the cytoskeleton of the cell.
 The cytoskeleton is different from cytoplasm. The
cytoskeleton provides structure. Cytoplasm is just a
fluid.
 The cytoskeleton connects to every organelle and
every part of the membrane. Think about an amoeba.
All of the pieces work together so that the foot might
reach out towards the food. Then the lysosomes and
peroxisomes are sent to begin digestion. The
movement of the organelles and cytoplasm is all
related to the tubules.
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Plant Cell
Plant cell wall
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rigidity of the cell wall renders plants sedentary
Made of Cellulose
animals lack of wall allows their cells more
flexibility, which is necessary for locomotion.
protects the intracellular contents
provides a porous medium for the circulation
and distribution of water, minerals, and other
nutrients, and
houses specialized molecules that regulate
growth and protect the plant from disease.
Cell wall

The main chemical components of the
primary plant cell wall include cellulose
(in the form of organized microfibrils; a
complex carbohydrate made up of several
thousand glucose molecules linked end to
end.
Plant cell wall
Chloroplasts
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Chloroplasts are specialized organelles found in
all higher plant cells. These organelles contain
the plant cell's chlorophyll, hence provide the
green color. They have a double outer
membrane. Within the stroma are other
membrane structures - the thylakoids and grana
(singular = granum) where photosynthesis
takes place.
Chloroplasts
DIFFERENCES BTW PLANT AND
ANIMAL CELLS
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PLANT CELL
Fixed structure.
Has a cellulose cell
wall and a cell
membrane
Chlorophyll in
chloroplasts
large vacuoles
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ANIMAL CELL
Can change shape.
No Cellulose cell wall
No Chlorophyll or
chloroplasts
Small or no vacuoles
Has centrioles