Here’s what a “cell” is!

Cell - the smallest unit of an organism
that carries on the functions of life

A cell can perform all the processes
of life.
•Many Sizes:
•nerve cells - up to a meter long
•human egg cell - dot of an i
•bacteria - 80,000 could fit in the dot
of an i
•Different shapes:
•Related to their function (job)
•Cell types:
•Prokaryotic cell - very simple; no
membrane-bound structures
(ex: bacteria)
•Eukaryotic cell - more advanced; has
membrane-bound structures
(ex: animal cells, plant cells)
Early Cell Scientists
Robert Hooke (1665)
• An English scientist who looked at slices of
cork under a crude compound microscope
and saw “a great many little boxes” that he
called “cells.” First person to see cells.
• “Cell” comes from the Latin word for
“little room.”
Early Cell Scientists
Anton van Leeuwenhoek (1673)
• A Dutch shopkeeper who looked
at pond water using a simple
microscope and saw what he
called “animalcules.”
• Today, we call them singlecelled organisms.
An Early Simple Microscope
Early Cell Scientists
Matthias Schleiden (1838)
• A German botanist who discovered
that all plants are made up of similar
units, or cells.
Early Cell Scientists
Theodor Schwann
(around 1830)
• A German scientist who stated that all
plants and animals are made up of building
blocks, or cells.
• He also observed that there are
similarities and differences between plant
and animal cells.
Early Cell Scientists
Rudolph Virchow (1858)
• This German physician also reported
that every living thing is made of up
vital units, known as cells. He also
predicted that cells come from other
cells.
Cell Theory
1. All living things are made up of one or
more cells.
2. Cells are the basic unit of structure
and function in living things.
3. All cells come only from other living
cells.
Cell Structure
Animal Cell
Plant Cell
Cell Structure
• A cell is like a small town:
Different parts have different and
specialized jobs.
• Plant cells and animal cells have many
similar structures, but have several
important differences.
Cell Membrane
Structure:
•Outer boundary of the
cell
•Double lipid membrane
•Selectively permeable
Cell Membrane
Function (job):
•Protects inside
•Supports/gives shape
•Controls what
enters/leaves “gatekeeper”
•Helps maintain homeostasis
(ability to keep a stable
environment)
Analogy:
Townline
Cell Wall
Structure:
•ONLY IN PLANTS
•Made of cellulose
•Strong & rigid
•Dead layer
Cell Wall
Function (job):
•Protects/support
•Gives shape
Analogy:
Castle Wall
Cytoplasm
Structure:
•Jelly-like substance
•80% water
Cytoplasm
Function (job):
•Organelles float in
cytoplasm
•Materials for growth
are found in cytoplasm
•Expels waste through
cell membrane
Analogy:
•Town property
Nucleus
Structure:
•Surrounded by nuclear
membrane
•Usually round/oval
•Near center
Nucleus
Function (job):
•Control center of cell
•Controls cell activities
•Contains chromosomes
Analogy:
Mayor and city council
Mitochondria
Structure:
•Has an outer
membrane and an inner
folded membrane
•Rod shaped
Mitochondria
Function (job):
•Cellular respiration
•Turns food into useable
energy (ATP)
Analogy:
Power house (powerplant)
Ribosomes
Structure:
•Tiny, round, dark
•Can be free floating or
attached to
endoplasmic reticulum
Ribosomes
Function (job):
•Protein factories
•Assembles proteins
used in growth, repair
and control
Analogy:
Factory
Endoplasmic Reticulum
Structure:
•Network of tubes and
canals
•Smooth ER - no
ribosomes attached
•Rough ER - ribosomes
are attached
Endoplasmic Reticulum
Function (job):
•Transports materials
“intracellular highway”
Analogy:
Roads and highways
Golgi Bodies
Structure:
•Series of flattened
sacs
Golgi Bodies
Function (job):
•Processes, packages and
secretes material
•Materials that are
transported by the ER
usually stop first at the
Golgi bodies where they are
stored or altered before
moving to other parts of the
cell
Analogy:
Center for Manufacturing
and shipping (UPS)
Lysosomes
Structure:
•ONLY IN ANIMALS
•Contains powerful
digestive chemicals
Lysosomes
Function (job):
•Contains digestive
enzymes (chemicals),
breaks things down
•“suicide sac”
Analogy:
Garbage collectors
Vacuoles
Structure:
•Fluid-filled sacs that
float in the cytoplasm
Vacuoles
Function (job):
•Stores water and food
materials
•Stores waste and helps
the cell get rid of
waste
•Plant cells contain a
large central vacuole filled with water - helps
give shape
Analogy:
Storage warehouse
Chloroplast
Structure:
•ONLY IN PLANT
CELLS
•Green, oval-shaped
•Contains green pigment
chlorophyll
Chloroplast
Function (job):
•Site of photosynthesis
•Traps the sun’s energy
to make glucose
Analogy:
Greenhouse or solar cell
How are plant and animal
cells different?
PLANT CELLS:
Have cell walls,
chloroplasts,
large vacuoles
How are plant and animal
cells different?
ANIMAL CELLS:
Have lysosomes
How are different cells
adapted to their functions?
Plant Cells: Rigid cell
walls allow plants to grow
upright.
Muscle Cells: Have
large quantities of
mitochondria for
energy.
How are different cells
adapted to their functions?
Red Blood Cells: Thin,
flexible discs allow them
to squeeze through tiny
blood vessels.
Nerve Cells: Have long
projections through which
messages are sent throughout the
body.
Vocabulary
Permeable
Diffusion
Osmosis
Mitosis
Chromosome
Centriole
Centromere
Organization of Living
Things
Five main levels of organization
1. Cell
2. Tissue
3. Organ
4. Organ System
5. Organism
Tissue
• Example: Muscle
• Tissues are made of specialized
cells.
Organ
• Examples: Heart, Lung, Brain
• Found in both plants and animals.
• Composed of tissue that is
organized into groups that work
together to perform special
functions.
Organ System
• Example: Circulatory System
• A group of organs that work
together.
10 Organ Systems in complex
organisms
(humans, dogs, birds, etc.)
1. Circulatory
2. Digestive
3. Nervous
4. Respiratory
5. Skin
6. Skeletal
7. Muscular
8. Reproductive
9. Excretory
10.Endocrine
ORGANISMS
• Different organ systems work
together to keep the organism
alive.
QUESTION:
• Classify the following as a tissue, organ, or
organ system.
a. Brain, spinal cord, and nerves
b. Heart
c. Group of muscle cells
QUESTION:
• Can a single-celled organism
contain tissue? Explain.
QUESTION:
• Give one example of each:
a. Cell
c. Tissue
b. Organ
d. Organism
Cell Processes
• Think of the cell membrane as being
like a gatekeeper at an ancient castle.
• It was the gatekeeper’s job to decide
when to open the gate and allow
people to pass into and out of the
castle.
• The gatekeeper controlled the
permeability of the castle walls.
Permeable
• If the gatekeeper allowed friendly
folk to enter, he or she was allowing
the castle walls to be permeable.
• Permeable means that in cells certain
substances can move
freely through the membrane.
Impermeable
• If the gatekeeper prevented enemies
from entering, he or she was allowing
the castle walls to be impermeable.
• Impermeable means that in cells
substances cannot pass freely
through the membrane.
Selectively Permeable
• Because the gatekeeper can select those
that can enter the castle, he or she was
allowing the castle walls to be selectively
permeable.
• Because the cell membrane allows some
materials to pass through and is
impervious to others it is
selectively permeable.
Substances that move into or
out of a cell do so by one of
three methods:
Diffusion
• This is the main way by which substances
move into and out of cells.
• The process by which molecules tend to
move from an area of higher
concentration to an area of lower
concentration.
• Eventually there is an equal concentration
of molecules inside and outside of the
cell.
Osmosis
……is the diffusion of water molecules
through a permeable membrane.
Osmosis is important to cells
because cells cannot function
properly without adequate
water.
Osmosis
• In osmosis, water molecules move by
diffusion from an area where they
are highly concentrated…through the
cell membrane…to an area where they
are less concentrated.
*The cell doesn’t need to use energy to
move materials across the membrane.
Active Transport
•Requires the cell to
use energy to let things
pass through the
membrane.
•Large proteins in the
cell membrane are
involved in active
transport.
Cell Division
• The cells in your body are constantly
changing. Most new cells replace
damaged or dead cells. These new
cells are made during a process called
cell division.
• When cell division takes place
two identical cells are produced.
Cell Division
• In single celled organisms, cell
division results in the formation of
two new organisms.
Dividing
Paramecium
Cell Division
• In many celled organisms, cell division
increases the number of cells making
up the organism.
• As the cells increase in number, the
organism grows.
Feeling Fine
Cell Cycle
The cell
divides.
The cell
grows and
develops.
The cell prepares for
division.
This cycle may take a few hours or a few
days!
Mitosis:
Cell Division
1 hour
Preparation for
Division
2 hours
DNA Replication
10 hours
Growth
9 hours
This process by which a cell’s
nucleus divides into two identical
nuclei is called
Mitosis
• Mitosis occurs in several phases.
• Most of a cell’s life is spent in
the growth and development
phase, called ‘interphase.’
Interphase
•The cell is making enough
protein, mitochondria, and
other substances for two cells.
•In the nucleus, each
chromosome is forming an
exact copy of itself.
•In animal cells, two pairs of
centrioles are forming in the
cytoplasm.
Prophase
•The nuclear membrane
dissolves.
•The centrioles migrate to
opposite sides of the cell.
•Spindle fibers form between
the centrioles.
•Chromatid pairs are pulled to
the center of the cell by the
spindles.
Metaphase
•The chromosomes align
across the center of the
cell.
•Each chromosome
attaches to a spindle fiber
at its centromere.
Anaphase
•The centromeres split and the
chromatids become two
identical chromosomes.
•The spindle fibers shrink,
pulling the chromosomes to
opposite sides of the cell.
•The cell stretches out to
prepare for division.
Telophase
•The chromosomes reach
opposite ends of the cell.
•The spindles disintegrate.
•A nuclear membrane forms
around each set of chromosomes,
forming two new nuclei.
•A furrow forms in the cell
membrane, deepens, and divides
the cell completely.
Mitosis in Plants
....is different!
• Plants do not have centrioles. But
they do have spindle fibers.
• The rigid cell wall can’t form a furrow
in the middle, so a cell plate forms
across the middle.
Mitosis in Plants
....is different!
• After the cell divides into two new
cells, each forms its own cell wall.
QUESTION:
During what phase of mitosis does
a cell divide into two new cells?
Answer:
During telophase!
QUESTION:
How does mitosis differ in plants
and animals?
Answer:
Plants do not have
centrioles. Plants form a
cell plate before dividing.