Transcript The Cell cp 13

The Cell
Ch. 7
Cell History
• Hooke - is the scientist who 1st coined the
term “cell” – in the 1660’s he observed cork
from a tree stem (they reminded him of the
rooms monks lived in)
Schleiden looked at plant cells & Schwann
looked at animal cells. They both observed
that
cells make up all parts of an organism. Along
with Virchow they formulated the Cell Theory.
• Schleiden, Schwann,
Virchow
The Cell Theory
• It has 3 components.
1. All living things are made of cells.
• 2. Cells are the basic units of structure &
function.
• 3. All cells come from pre-existing cells.
Variety in Cells
• Cells come in a great variety of shapes & sizes. The
smallest cells are mycoplasmas & the largest cells are
ostrich eggs. The size & shape of the nerve cell are
related to its function.
• Sketch of a skin cell:
• Sketch of a nerve cell:
Cell Size
• The surface area of the cell does not
increase at the same rate as the
volume. Because of this, cells typically stay
small & will divide rather than getting
larger.
Differences in Cells
•
1. Prokaryotes - have no true nucleus –
DNA is not arranged into chromosomes –
ex. = bacteria – they have no membranebound organelles.
• 2. Eukaryotes - have a nucleus - & cellular
organelles.
Parts of the Cell
• 1. Nucleus - control center of the cell – controls most
of the activities of the cell ; also transmits hereditary
information & contains DNA. The nucleus holds
chromosomes (threadlike) that are seen only when
the cell is dividing & chromatin (granular) when the
cell isn’t dividing.
• 2. Nucleoli - these are found in the nucleus –
where the assembly of ribosomes begins.
• 3. Nuclear envelope - double membrane - this
surrounds the nucleus & acts as a boundary
between the nucleus & the cytoplasm – it
contains pores that allow substances to pass
• 4. Cell membrane this acts as the outer
boundary of the cell &
contains
phospholipids &
proteins - it is very
important because it
regulates what enters
& leaves the cell
• 5. Cell wall - this is found in plants, algae,
fungi, & bacteria- it protects & supports the
cell – it lies outside of the cell membrane &
allows water & gases to pass through –
plant cell walls are made of cellulose
• 6. Cytoplasm - is the
jellylike layer of the
cell – it contains the
organelles & moves
materials throughout
the cell in a process
called cytoplasmic
streaming
• 7. Endoplasmic reticulum - this is a series
of canals or channels that winds through
the cytoplasm – it acts as the cell’s internal
transport & connects with the nuclear
envelope; there are 2 types – (1) smooth
ER- this builds lipids for the plasma
membrane, (2) Rough ER - has ribosomes
attached - Protein synthesis
• 8. Ribosomes- the sites of protein
synthesis; 2 types (1) Free - makes protein
to be used in the cell, (2) Bound - make
protein to be transported out of the cell
• 9. Golgi Bodies - these pinch off from the
ER – they are stacks of membranes that
look like tiny flattened balloons – they are
areas for storage & packaging of chemicals
– enzymes in this apparatus attach
carbohydrates & lipids to proteins
• 10. Mitochondria - the
cell’s powerhouse –
they produce the
energy for the cell –
they have many folds
on the inside called
cristae that increase
surface area for more
energy
• 11. Plastids - are found
only in plants – some
store food, others have
pigments – 3 types:
(1) Leucoplasts colorless – store starches
in roots & stems
(2) Chromoplasts they are orange & yellow
– beta carotene
(3) Chloroplasts these are green & the
sites for photosynthesis
• 12. Vacuoles bubblelike
storage
structures that
store water,
liquids, wastes,
& foods – these
hold plants erect
& firm
• 13. Lysosomes - these are membrane-bound
organelles that are formed in Golgi bodies – they
are loaded with enzymes that digest large
particles found in the cell – also break down old
organelles
• 14. Microtubules - hollow cylinders of
protein that support & shape the cell –
found in the cytoskeleton, spindle fibers,
centrioles, basal bodies , cilia, & flagella
• 15. Spindle fibers - appear during cell
division & move chromosomes through the
cytoplasm
• 16. Centrioles - small dark
bodies located outside
the nucleus – they are
active during cell division
• 17. Cilia - short,
threadlike structures
used for movement –
they are numerous &
hairlike
• 18. Flagella - long,
whiplike structures
used for movement –
usually only 1 per cell
• 19. Cytoskeleton - network of
protein filaments that helps
the cell to maintain its shape
– also involved in cell
movement - these are made
of:
a) microtubules - hollow
tubes of protein – maintain
cell shape & serve as “tracks”
along which organelles are
moved (used to make cilia &
flagella)
b) microfilaments - long, thin
fibers that function in the
movement & support of the
cell – tough, flexible
framework that supports the
cell
THE CELL – PART 2
• CELL TRANSPORT
Cells must get nutrients in & wastes out of the cell in
order to stay alive. They have several methods of
doing this. Some methods expend energy. Some do
not. The cell membrane regulates what enters &
leaves the cell & also provides protection &
support. The cell membrane is a double-layered
sheet called a phospholipid bilayer. The cell
membrane is like a fluid-mosaic.
PASSIVE MECHANISMS
• – no cellular energy is required
1. Diffusion - molecules or ions spread from higher
concentrations to lower concentrations – this continues until
equilibrium is reached
• 2. Facilitated
diffusion - glucose
combines with a
special protein
carrier that helps
pass it across the
membrane (still
from higher
concentration to
lower
concentration)
• 3. Osmosis - water
molecules diffuse
from a higher to a
lower concentration
(water tends to diffuse
toward the area of
higher osmotic
pressure)
Tonicity
• Drawing 1:
• Drawing 2:
• Drawing 3:
Cell is _______________ Cell is _________________ Cell is
________
Solution is _______________ Solution is
________________ Solution is _____
Cell will _________________ Cell will
__________________ Cell will ______
• 4. Filtration molecules are forced
through membranes
by the hydrostatic
pressure that is
greater on one side of
the membrane than
on the other (this
usually happens with
blood vessels)
ACTIVE MECHANISMS – cellular energy is
required
• 1. Active transport - using carrier proteins to move
substances from lower concentrations to higher
concentrations (sugars, a.a.’s, ions)
• 2. Endocytosis molecules that are too
large to enter a cell by
diffusion enter by the
formation of a
vesicle - 2 Types:
a) phagocytosis “cellular eating” –
takes in solids
(common in white
blood cells)
b) pinocytosis “cellular drinking ” –
takes in liquids (water)
• 3. Exocytosis - sends
materials out of the
cell
• Organisms with only
one cell are called
unicellular while
organisms with many
cells are called
multicellular.
LEVELS OF ORGANIZATION
•
1. Cells - basic functional unit of life
2. Tissues - group of similar cells that perform
a particular function
3. Organs - groups of tissues working
together
4. Systems - group of organs working together
(11 in the body)