Download Cells

Chapter 7
Cell Structure and
Function
(Aligned with 7.1 Intro Sheet and 7.2 Cell Structure Chart)
IMPORTANT: My hope is that
you will use this on your computer
as a way to ensure that your
chart is filled in completely. If
you MUST print it out, please
make sure you print SIX SLIDES
PER PAGE!! Save a tree!!
7-1
Life is Cellular
A. Cells – basic units of
structure and function in
living things
B. Early scientists that led to the
cell theory









Anton van Leeuwenhoek (1600s) – given credit for
developing the 1st mini microscope, looked at pond water
and made detailed drawings
Robert Hooke – coined the term “cell” when he looked at
slices of cork and dead plant cells
Robert Brown (1833) – observed a dark structure near
the center of the cell (we now know this is the nucleus)
Matthias Schleiden (1838) – stated all plants are made
of cells
Theodore Schwann (1839) – stated all animals are made
from cells
Rudolph Virchow (1855) - stated all cells come from the
division of preexisting cells
Lorenz Oken – stated all new cells are the result of
division of preexisting cells…VIRCHOW STOLE HIS
THUNDER
C. Cell Theory
 All living things are composed of cells.
 Cells are the basic units of structure and
function in living things.
 All cells come from preexisting cells.
Exploring the Cell : Microscopes
* Lenses used to magnify image by focusing beams of light OR electrons
The electron microscope (EM):
• Allows greater magnification and
reveals cellular details
• Magnify cells up to 2 mill X
• Limits: no living specimens
LM
1,000

The light microscope (LM):
• Enables us to shape and
structure of a cell
• Magnify cells up to 1,000X
* Resolution = clarity of detail
TEM
2,800 
Magnification = image size
SEM
2,000 
•
Figure 4.1B
Figure 4.1C
Scanning EM:
(SEM)
surface structures
Figure 4.1D
Transmission EM:
(TEM)
inside details
Why are cells so small?
A small cell allows a sufficient surface area
to allow nutrients and wastes to cross per
it’s volume.
(in other words: it can’t get too big for it’s
own good)
volume= 27,000
volume= 27,000
Ratio: .6 to 1
Ratio: .2 to 1
need as high a surface area to volume ratio as possible
What is in a Cell?
ALL cells:
* contain cytoplasm, cell membrane, and DNA
* are either a prokaryotic or a eukaryotic
Prokaryote
Eukaryote
•The smallest cells in nature
•DNA not contained in a
nucleus, free in the cytoplasm
•Ribosomes are the ONLY cell
organelle
•Who are they? Bacteria
•Much larger and more
complex
•DNA is wrapped with a
nuclear membrane (nuclear
envelope)
•MANY more cell organelles
•Who are they? Protists,
Fungi, Plants, Animals
7-2
Cell Structure
A. Cellular Control Center
•
Nucleus, nucleolus, chromatin/chromosomes, nuclear membrane/pore
B. Organelles that Store, Clean Up and Support
•
Vacuoles, vesicles, lysosomes, cytoskeleton (microtubules,
microfilaments), centrioles
C. Organelles that Build Proteins
•
Ribosomes, endoplasmic reticulum (smooth and rough), golgi
apparatus
D. Organelles that Capture and Release Energy
•
Chloroplasts, mitochondria
E. Cellular Boundaries
•
Cell wall, cell membrane
F. Fluid Portion Outside of Nucleus (Sort of a boundary!)
•
cytoplasm
CELLULAR CONTROL CENTER:
NUCLEUS


Function:
 Information center of the
cell
 Contains DNA (chromatin
vs. chromosomes)
 Directs cell activities
2 categories of
organisms
 Prokaryotes – organisms
whose cells lack nuclei (i.e.
bacteria)
 Eukaryotes – organism
whose cells contain nuclei
Nucleus
Structure:
 NUCLEOLUS – a small, darkened region in the nucleus
that is made up of RNA and proteins, this is where
ribosomes are made
 CHROMOSOMES – large structures formed from
DNA that contain the genetic info
 CHROMATIN – uncondensed DNA found in non-dividing
cells
 NUCLEAR ENVELOPE – double membrane around the
nucleus that contains pores, allows molecules to move
in and out of the nucleus, and protects the nucleus
 NUCLEAR PORES – allows passage of materials into or
out of nucleus (RNA, ribosomes)
Nucleus
ORGANELLES THAT STORE,
CLEAN UP, SUPPORT: VACUOLE
Structure:
Large, central structure in plants
Many, small, circular structures in animal
cells
Filled with liquid
Function:
Storage of water, salts, proteins,
carbohydrates, waste products
Pressure system for plants, prevents wilting
Special case: contractile vacuole - prevents
excess water intake, leading to cell-bursting
ORGANELLES THAT STORE, CLEAN
UP, SUPPORT: VESICLE
 Store and move materials between cell organelles and
to/from cell surface
ORGANELLES THAT STORE, CLEAN
UP, SUPPORT: LYSOSOME
Structure:
Small, circular structures
Found only in animal cells
Contain digestive enzymes
Function:
Digestion of:
Worn out organelles
Debris
Large ingested particles
Lysosomes are responsible for your hands
not being webbed!!
Lysosome
ORGANELLES THAT
STORE, CLEAN UP,
SUPPORT:
CYTOSKELETON
Structure:
Hollow tubes of proteins
Examples: cilia (cells lining tracea), flagella (sperm
cells), centrioles
Function:
Framework
Provide cell with support, structure and shape
Movement (cilia, flagella)
Microfilaments – made of actin threads,allow movement
of cytoplasm within the cell (cytoplasmic streaming)
Microtubules – hollow structure made of tubulin, maintain
ORGANELLES THAT STORE, CLEAN
UP, SUPPORT: CENTRIOLES
Organize cell division
ORGANELLES THAT
STORE, CLEAN UP,
SUPPORT:
PLASTID
Structure:
Differ based on type of plastid (chloroplast is
one example)
Found only in plants
Function:
Store food/starch
Store pigments (give color to fruits & veggies)
ORGANELLES THAT BUILD PROTEINS:
RIBOSOMES
 Structure:
Small (25 nm) ball-like
structures
Found free-floating in cytoplasm
or attached to rough
endoplasmic reticulum
Composed of RNA and protein
Make peptide bonds between
amino acidsprotein
 Function:
Synthesis of proteins (where
proteins are made)
ORGANELLES THAT BUILD PROTEINS:
ENDOPLASMIC RETICULUM
 Structure:
Network of flattened sacs
Can be rough (w/
ribosomes) or smooth (w/o)
 Function:
Transport materials within
or out of cell
Synthesis of
macromolecules
Rough - proteins, lipids,
carbs
Smooth - lipids
ORGANELLES THAT BUILD PROTEINS:
GOLGI APPARATUS
Structure:
Flattened stacks of membranes
Vesicles attached to top and
bottom
Function:
Collection, modification, packaging
of proteins and other substances
Vesicles attach, deposit materials
GA modifies materials based on needs
Vesicles attach to membrane and
distribute modified substances
ORGANELLES THAT CAPTURE/RELEASE ENERGY:
CHLOROPLAST
Structure:
Double membrane
Elaborate structure inside
Function:
Another power station
Found in plant cells only
Conversion of light energy (sun) into chemical
energy (glucose)
ORGANELLES THAT CAPTURE/
RELEASE ENERGY:
MITOCHONDRIA
Structure:
Double membrane
Cristae - inner folds, increase
surface area
Outer membrane for protection
of cell
Function:
“Powerhouse” of the cell
Able to self-replicate ( # in
cells with high energy need)
Converts sugars into energy
for cells
CELLULAR BOUNDRIES:
CELL WALL



Only in plants, algae, and some bacteria
Lies outside the cell membrane
Function




Helps to protect and support the cell
Very porous (water, oxygen, carbon dioxide, etc. can pass
through easily)
Gives rectangular shape to plant cells
Layers



1st layer – contains pectin (gluey substance that helps
hold the cells together)
2nd layer – primary cell wall (made of cellulose)
3rd layer (in woody stems) – secondary cell wall
(composed of cellulose and lignin to make cellulose more
rigid)
CELLULAR BOUNDRIES:
CELL MEMBRANE – outer boundary
 Structure:
 Phospholipid bilayer
•
hydrophilic heads, hydrophobic tails
 Contains lipids (bilayer), proteins (channels),
and carbohydrate chains (identification cards)
 Function:
 Regulates what enters and leaves the cell
 Semi-permeable membrane
 Protection and support
Cell/Plasma Membrane
CELLULAR BOUNDRIES:
CYTOPLASM
 Material between the cell membrane
and the nucleus
 Contains the organelles of the cell
Plant vs. Animal Cell
Animal Cell
Plant Cell
QUESTIONS:
 Describe the steps involved in the synthesis, packaging,
and exporting of a protein from a cell.
 What are the two major parts of the cell?
 How do contractive vacuoles help maintain water
balance?
 What is the difference between rough and smooth ER?
 Why is the cell membrane sometimes referred to as a
fluid mosaic? What part of the cell membrane acts like
a fluid? And what makes it like a mosaic?
 How do the properties of lipids help explain the
structure of the cell membrane?
 Why do you think it’s important that cell membranes
are selectively permeable?
QUESTIONS:
 Describe the steps involved in the synthesis, packaging, and exporting of a protein
from a cell.
 Proteins assembled on ribosomes (if targeted for export to cm or to
specialized locations w/in cell, complete their assembly on RER protein in
vesicle  Golgi apparatus (further modifies proteins before sorting and
packaging them in membrane bound vesicles)  vesicle  final destination
 What are the two major parts of the cell?
 Cytoplasm with organelles, and nucleus
 How do contractive vacuoles help maintain water balance?
 Pump out excess water
 What is the difference between rough and smooth ER?
 Rough has ribosomes, smooth does not
 Why is the cell membrane sometimes referred to as a fluid mosaic? What part of
the cell membrane acts like a fluid? And what makes it like a mosaic?
 It is made of many parts (like a mosaic) that can float around in the fluid
phospholipid bilayer
 How do the properties of lipids help explain the structure of the cell membrane?
 Hydrophilic lipid heads are attracted to water, hydrophobic fatty acid tails
turn away from water. A bilayer forms when heads turn outward towards
water inside and outside a cell
 Why do you think it’s important that cell membranes are selectively permeable?
 Allows needed substances to enter and wastes to leave, while keeping
molecules that are not needed out