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
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7-1
Life is Cellular
A. Cells – basic units of
structure and function in
living things
** Cell discovery only
occurred after the
microscope was invented
B. Early scientists that led to the
cell theory
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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
Schleiden
Schwann
Virchow
C. Cell Theory
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All living things are composed of cells.
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Cells are the basic units of structure and
function in living things.
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All cells come from preexisting cells.
D. Exploring the Cell: Microscopes
LM
1,000
×
SEM
2,000 ×
TEM
2,800 ×
* Lenses used to magnify image by focusing beams of light OR
electrons
• Magnification = image size
* Resolution = clarity of
detail
The electron microscope (EM):
The light microscope (LM):
• Allows greater magnification and
• Enables us to shape and
reveals cellular details
structure of a cell
• Magnify cells up to 2 mill X
• Magnify cells up to 1,000X
• Limits: no living specimens
Figure 4.1B
Figure 4.1C
Scanning EM:
(SEM)
surface
structures
Figure 4.1D
Transmission EM:
(TEM)
inside details
E. 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 Structures
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
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Function:
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Information center of the
cell
Contains DNA (chromatin
vs. chromosomes)
Directs cell activities
2 categories of
organisms
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Prokaryotes – organisms
whose cells lack nuclei (i.e.
bacteria)
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Eukaryotes – organism
whose cells contain nuclei
Nucleus
Structure:
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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
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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, flagella, centrioles
❚ Function:
❙ Framework
❙ Provide cell with support, structure and shape
❙ Movement (cilia, flagella)
❘ Microfilaments - allow movement of cytoplasm within the
cell (cytoplasmic streaming)
❘ Microtubules - Maintain cell shape, make up cilia, flagella
and centrioles
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
❚ 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
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Only in plants, algae, and some bacteria
Lies outside the cell membrane
Function
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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
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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
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Structure:
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Phospholipid bilayer
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hydrophilic heads, hydrophobic tails
Contains lipids (bilayer), proteins (channels),
and carbohydrate chains (identification cards)
Function:
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Regulates what enters and leaves the cell
Semi-permeable membrane
Protection and support
Cell/Plasma Membrane
CELLULAR BOUNDRIES:
CYTOPLASM
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Material between the cell membrane
and the nucleus
Contains the organelles of the cell
QUESTIONS:
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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
Plant vs. Animal Cell
Animal Cell
Plant Cell