Ch. 7
1. Introduction to Cells
Cell theory
Cell size
Cell shape
Cell features
CELL THEORY
• All living things are made up of one or more
cells (living = cells)
• Cells are the basic unit of structure & function
in organisms (smallest living part = cells)
• All cells rise from existing cells (cells come
from cells)
CELL SIZE
** 200 types of cells** **100 trillion cells = human body**
• Cell size limited by surface
area-to-volume ratio
• Surface area (cell membrane)
= big = a lot of places for
substances to go in & out
Volume (total space cell
takes up) = small = a little
bit of space to have to travel
So. . . A large
surface area to
volume ratio =
can exchange
substances
more efficiently
Ex: 6:1
C E L L
S H A P E
• A cell’s shape reflects its
function
• Nerve cells = much longer
than they are thick
• Shape may increase
surface area for exchange
• Skin cells = broad & flat
• Grow in some ways &
remain small in other
• Makes surface area to
volume larger
C E L L
F E A T U R E S
ALL CELLS HAVE…
• 1. Cell membrane ~ outer boundary
• 2. Cytoplasm ~ fluid inside cell (cytosol) & all
structures suspended
C E L L
F E A T U R E S
ALL CELLS HAVE…
• 3. Ribosomes ~ proteins are made here!
• 4. DNA ~ instructions, regulates activities, enables
reproduction
Features of Prokaryotic Cells (single celled)
• DNA = a single loop near center
• Ribosomes & enzymes = in
cytoplasm
• Cell wall surrounds membrane
– Structure & support
– Capsule allows cling to surfaces
• Very small
• Live in wide range of habitats
Features of a Eukaryotic Cell
• Single celled or multi
cellular
• Complex organization =
more specialized
functions
• Contains compartments
separated by
membranes = organelles
(some are connected by
channels)
• DNA in a nucleus
2. INSIDE the cell: Framework
Cytoskeleton
Helps cell move, keep its shape, & organize parts
Microfilament ~ long, thin, actin, contract to pull in
& expand to push out
Microtubules ~ thick, hollow, tubulin, info. mol.
pass thru
Intermediate fibers ~ mod. thick, anchors organelles
& enzymes
Cytoskeleton
INSIDE the cell: Directing activity
Nucleus “The Brain”
Double membrane (nuclear
envelope) which
protects & houses DNA
Pores to allow passage of
RNA
& ribosome parts
Contains nucleolus, which
makes ribosome parts
INSIDE the cell: Directing activity
Ribosomes
Made of protein & RNA
“Free”
~makes proteins that
remain in cell
“Bound”
~makes proteins that
leave cell
~attached to organelle
INSIDE the cell: protein processing
Endoplasmic reticulum (ER)
System of internal
membranes which move stuff
Rough
w/ ribosomes
modify proteins for export
Smooth
w/o ribosomes
makes lipids, breaks down
toxic substances
INSIDE the cell: protein processing
Golgi apparatus/body
Set of flattened sacs
Modifies proteins when they
come in by vesicle from the
ER
Modifies, sorts, & packages
proteins for export
**VESICLES move these substances in & out
of ER & golgi**
INSIDE the cell: energy production
Mitochondrion
“Power house”
Makes ATP (cellular energy) in
inner membrane
Smooth outer membrane &
folded inner membrane
INSIDE the cell: energy production
Chloroplast
Found in plant cells &
some
protist
Uses light energy to make
sugar from carbon
dioxide & water ~ photosynthesis
Double membrane w/sacs
INSIDE the cell: storage & maintenance
• Lysosome ~ contains enzymes that break down
large molecules. Ex: food, old, damaged cell parts
• Central vacuole ~ large compartment of plant cells.
Stores water, ions, nutrients & waste. If full, plants
stand upright (turgur pressure). If lose water, plants wilt.
• Other vacuoles ~ food & contractile
3. Diversity in ________.
Vary in . . .
• shape
• way obtain & use energy
• make up of cell walls
• Movement
flagella  long, threadlike
pili  short, thick, attachment
Diversity
in
________.
Animal cells
Plant cells
Central vacuole
 Chloroplasts
 Cell wall
Vary in organelles
 Specialized function
 Ex: muscle cells=many
mitochondria