Download A View of the Cell

A View of the Cell
Chapter 7
The Discovery of Cells
The Plasma Membrane
Eukaryotic Cell Structure
Web links to study guides
Cell Theory

All living things are made up of 1 or more cells.

A cell is the smallest unit that can carry on all of the
processes of life

Before the 17th century, no one knew that cells
existed.

One of the 1st microscopes was made by the
Dutch drapery store owner Anton von
Leewenhoek.

1st person to observe & describe microscopic
organisms & living cells
Animalcules
Robert Hooke

1665 – Robert Hooke used a
microscope to examine a thin slice of
cork & described what he saw as “a
great many little boxes”.

He thought the boxes looked like small
rooms in which monks lived, so he called
them “Cells”
Hooke’s microscope
Micrographia
Cell Theory



1838 – German botanist Matthies Schleiden
concluded all plants are composed of cells.
1839 – German zoologist Theodor Schwann
concluded that animals are made up of
cells.
1855 – German physician Rudolf Virchow
concluded that plant cells come only from a
plant and animal cells arise only from an
animal

Cells only come from other cells!
Cell Theory – three main parts



All living organisms are composed of
one or more cells.
Cells are the basic unit of structure &
function in an organism.
Cells come only from reproduction of
existing cells.

This means that all cells came from ONE
original.
Light
Microscopes

Light microscopes
can magnify up to
1,500X and resolve
objects as small as
200 nanometers
(2x10-7)
Electron Microscopes

1st built by Ernst Ruska (1986 Nobel Prize)
in 1933.



He used accelerated electrons & magnetic coils
to make an image.
EMS can resolve objects that are 103 time
smaller than the light microscope.
Transmission EMS can magnify a sample
up to 50,000x and provide a resolution of
0.1 x 10-9 m.
Prokaryote - Eukaryote
Stuff Cells are made of
Intro Clip
Plasma Membrane

Like a
“smart”
security
blanket for
the cell.

Lets some
molecules in
and keeps
others out
Plasma Membrane

Lipid bilayers have 2 important characteristics


1. Polar molecules can stick together like magnets, but are
not PERMANENTLY stuck like in a chemical bond.
2. Lipid bilayers are fluid.
(imagine life preservers floating on a pool with strings
hanging down into the water)
What is a mosaic?

The patterns that
the proteins make
on the membrane
make the surface
look like a mosaic.
Phospholipid membrane

Basic Building
Block of the cell
membrane is the
phospholipid.

Double layer of
lipids forms a
flexible lipid
bilayer. (bi = 2)
Try this!
Passage Ways



Proteins in the cell membrane serve
many purposes.
Channels – Proteins act as passage
ways through which only certain
molecules can pass.
Receptors – Proteins transfer
information into the cell by reacting to
certain other molecules
Passage Ways

Markers – Proteins are the “name tags” of
cells giving them identity.
Cellular Boundaries

The plasma membrane



Acts as a selectively permeable
membrane
Is flexible
The cell wall



Plants, fungi, most bacteria and some
protists
Fairly rigid
Gives additional support and protection
Plant Cell Wall

Made up of carbohydrate



Cellulose
Forms a thick mesh
Functions to protect the cell and give it
support ONLY


Very porous – allows molecules to pass
through
DOES NOT select what materials can enter
the cell – that is the cell membrane’s job
Control in the cell
Start with the Nucleus
1.
Nucleus – leader of the eukaryotic cell.

Contains the directions to make proteins in
chromatin – strands of DNA




Remember, the types of proteins a cell produces are
what makes it unique
Proteins are necessary for ALL functions of the cell
We call this DNA chromosomes when it is all coiled
up before the cell reproduces itself
THIS is where all heredity information is
stored
Cell Nucleus
Nucleus cont.
2. Nucleolus - inside the nucleus
Assembles ribosomes that will move outside the
nucleus into the cytoplasm
(more on ribosomes later, but they are the factories that
make proteins from amino acids)

3. Nuclear Envelope – pair of membranes that
surround DNA & nucleolus
4. Nuclear Pores – allows material to pass through
nuclear envelope
5. Cytoplasm – fluid region between cell
membrane and nucleus
Cytoplasm
5. Cytoplasm surrounds the nucleus, suspends
the organelles
 Has two main components – Cytosol &
organelles


Cytosol – consists mostly of water along with
proteins, carbohydrates, salts, minerals, &
organic molecules.
Organelles (Endoplasmic reticulum,
mitochondria etc.) carry out specific functions in
the cell
Ribosomes
6. Ribosomes - manufacturing centers
A. This is where proteins are made.
B. Free ribosomes – scattered throughout
the cytoplasm. Produces proteins used
in the cell.
C. Fixed ribosomes – produce proteins used
outside the cell
Endoplasmic Reticulum
the chemical reaction center
7. Endoplasmic Reticulum – a large
workspace within the cell
 Complex system of membranes that
forms a transport system between the
nucleus and the cytoplasm


May have ribosomes attached – Rough ER.
No ribosomes – Smooth ER
Smooth Endoplasmic
Reticulum
7a. Smooth ER
A. Builds lipids for cell membrane
B. neutralizes poisons (will break down
morphine & amphetamines)
Rough Endoplasmic Reticulum
7b. Rough ER
A. Ribosomes attached
B. sites for proteins that are exported
Golgi Bodies
8. Molecular mail of
the cell
A. saclike pieces of
membrane pinched
off that are full of
chemicals
Ex – found in cells that
produce large
number of
chemicals – saliva
& digestion aids
Mitochondria
9. Power house
A. Releases energy from the nutrients taken in
B. Ex – Found in greater numbers in liver cells &
heart cells
Lysosome
10. Lysosome recycling centers of
the cell
A.
Contain strong
destructive enzymes
that break down food
& foreign objects
Ex – Found in white
blood cells
Stuff for Lysosomes to
destroy…
Cytoskeleton
11. Maintain the shape of
cell & hold organelles in
place


Microtubules- hollow
tubes like plumbing
pipes
Microfilaments- have a
structure that resembles
rope and can contract
causing movement.
Muscle cells have many
microfilaments
Centrioles
12. Centrioles
organize the
microtubules of the
cytoskeleton during
cell division in
animal cells
Plant cells don’t have
centrioles
Cilia & Flagella
13. Cilia & Flagella - Hairlike organelles that
extend from the surface of the cell, where
they assist in movement


Cilia- short hairlike projections
Flagella- long whiplike projections
In humans beating cilia line parts of the
respiratory system, moving dust particles &
bacteria away from the lungs
Vacuoles
14. Vacuoles are membrane-bound spaces in the
cell used for storage of materials.


Examples of things the vacuole may store are food,
enzymes and waste.
Vacuoles are difficult to see in animal cells, since they are
so small.
Plant vs. Animal Cells
1. Both have the same organelles.
2. Both are Eukaryotic cells.
Plants have
1. Large vacuoles – may take up to 90%
of the volume of a cell
A. gives support to the cell
B. stores food or waste material

Animal cell Usually smaller in
size Cell wall is absent. Cellulose
in any form is absent Cytoplasm is
denser, more granular and
occupies most of the space in the
cell . Vacuoles absent. If present,
they are small, temporary and
concerned with excretion or
secretion Vacuoles are large and
prominent. May be one or
more Plastids are absent Plastids
are usually present Centrosome is
present Centrosome is absent.
Instead two small clear areas
called polar caps are
present Prominent and highly
complex Golgi bodies present
near nucleus Contain several sub
units of Golgi apparatus called
dictyosomes

Plant cell Usually larger in
size Cell wall made up of cellulose
is present Cytoplasm is pushed to
the periphery and forms a thin
lining against the cell wallThe
central space in the cell may be
occupied by a large, single
vacuole
Plant Cells
2.
Chloroplasts –
contains chlorophyll
(gives the plant
leaves their green
color)
A. site of photosynthesis
Plant Cells
3. Chromoplasts – color
pigments found in flower
petals (red, orange, and
yellow)
A. no known chemical function
in the cell
B. attracts animals & insects to
the flower
Plant Cells
4. Leucoplasts – colorless vacuoles
A. storage for starch and fat molecules
5. Cell Wall – thick outer layer that
protects & supports the cell.
A. made of cellulose