Transcript The Cell - CoconinoHighSchool

The Cell
Overview
of cell
function
and
structure
The Cell: The Basic
Unit of Life
The Cell is a highly complex and well
organized structure which manages
hundreds of thousand of complex reactions
almost every second.
The term Cell was first evoked by a biologist
called Robert Hooke in the 17 century, who
on observing a section of cork through a
microscope, noted that the plant stem was
divided into series of units or cells.
Cork Cell as viewed from a
microscope
The four characteristics of cells.
All organisms -living thingsare made of
cells.
Cells
Cells do the
jobs that keep
organisms
alive.
Cells are the smallest
part of a living thing.
These cells are like
tiny building blocks.
Cell Basics: All Organisms
are Made of Cells
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The cell is the basic unit of structure & function
The cell is the smallest unit that can still carry on all
life processes
Both unicellular (one celled) and Multicellular
(many celled) organisms are composed of cells
Before the 17th century, no one knew cells existed
Most cells are too small to be seen with the
unaided eye
In the early 17th century microscopes were
invented & cells were seen for the 1st time
Cell Basics: Principles of
the Cell Theory
 All
living things are made of one or
more cells
 Cells are the basic unit of
structure & function in organisms
 Cells come only from the
reproduction of existing cells
Cell Basics: Cell Diversity
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Not all cells are alike
Cells differ in size, shape, and function
The female egg cell is the largest cell in
the body & can be seen without a
microscope
Bacterial cells are some of the smallest
cells & are only visible with a microscope
Cells are limited in size by the ratio
between their outer surface area & their
volume
Cells come in a variety of shapes, & the shape which
helps determine the function of the cell (e.g. Nerve
cells are long to transmit messages in the body, while
red blood cells are disk shaped to move through blood
vessels)
The Cell: Basic Unit of Life
The cell is the
smallest unit of life
capable of
independently
sustaining and
reproducing itself.
Cells can be divided
into two principal
types, prokaryotic
and Eukaryotic
cells that is, with
and without a
nucleus.
Cells are always building and breaking down
material. Cells release energy from foods, and
then use that energy to make needed cell parts.
A cells function is to make your body operate.
Prokaryotic vs. Eukaryotic
"Karyose" comes from a Greek word which
means "kernel," as in a kernel of grain. In
biology, we use this word root to refer to the
nucleus of a cell. "Pro" means "before," and
"eu" means "true," or "good." So
"Prokaryotic" means "before a nucleus," and
“Eukaryotic" means "possessing a true
nucleus." This is a big hint about one of the
differences between these two cell types.
Prokaryotic cells have no nuclei, while
Eukaryotic cells do have true nuclei.
nucleus
chloroplasts
cytoplasm
Cell wall
Cell membrane
Cell membrane
cytoplasm
Nucleus
Animal Cells
•Cell membrane
•Cytoplasm
•Vacuoles
•Nucleus
Plant Cells
•Cell wall
•Cell membrane
•Cytoplasm
•Vacuoles
•Chloroplasts
•Nucleus
Compare and Contrast plant
and animal cells.
Prokaryotic Cells
Prokaryotes were here first and for billions
of years were the only form of life on Earth.
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Prokaryotic cells are less complex
Unicellular (one celled)
Do not have a nucleus & no membranebound organelles
Most have a cell wall surrounding the cell
membrane & a single, looped chromosome
(genetic material) in the cytoplasm
Prokaryotic Cells
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Prokaryotic cells feature three major
shapes: rod shaped, spherical, and
spiral.
Prokaryotic cells include bacteria &
blue-green bacteria.
Prokaryotic cells are found only in the
kingdom Monera
Prokaryotic Cells
Prokaryotic Cells such as Bacteria perform many
important functions on earth. They serve as
decomposers, agents of fermentation, and play
an important role in our own digestive system.
Also, bacteria are involved in many nutrient
cycles such as the nitrogen cycle, which restores
nitrate into the soil for plants.
Eukaryotic cells
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Eukaryotic cells have a true
nucleus
Animals, plants, fungi, and
protists are eukaryotes
Eukaryotic cells also contain
membrane-bound organelles
such as mitochondria and
chloroplasts.
Eukaryotic
cells
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Nucleus
Chloroplast
Golgi
Mitochondria
Animal vs- Plant Cell
Animal Cell
Plant Cell
Animal cell
An animal cell is a form of eukaryotic
cell which make up many tissues in
animals. The animal cell is distinct
from other eukaryotes, most notably
plant cells, as they lack cell walls and
chloroplasts, and they have smaller
vacuoles. Due to the lack of a rigid cell
wall, animal cells can adopt a variety
of shapes. Human cells are biologically
categorized as animal cells.
Animal cell
Plant Cells
Plant cells are quite different from the cells of
the other eukaryotic organisms. Their
distinctive features are:
 A large central vacuole
 A cell wall made up of cellulose and protein
 They contain chlorophyll, the pigment that
gives plants their green color and allows
them to perform photosynthesis.
 Plant groups without flagella (including
conifers and flowering plants) also lack
centrioles that are present in animal cells.
Plant Cell
Fungi Cells
Fungal cells are most similar to animal
cells, with the following exceptions.
 A cell wall made of chitin.
 Only the most primitive fungi, chytrids,
have flagella.
 Primitive fungi have no such divisions,
and each organism is essentially a
giant supercell. These fungi are
described as coenocytic.
Fungi Cells
Cell structures we will cover
Vacuole
Chloroplast
Ribosomes Nucleus
Golgi Apparatus
Mitochondrion
Lysosome
Unit Membrane
Cell Membrane
Cell Wall
Chromatin-
Centriole
Endoplasmic Reticulum
Chromosomes
Unit Membrane
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Cell Membrane
Separates the cytoplasm of the cell from its
environment
Protects the cell & controls what enters
and leaves
Cell membranes are selectively permeable
only allowing certain materials to enter or
leave
The cell membrane is constantly breaking
down & being reformed inside living cells.
K. Certain small molecules such as CO2,
H2O, & O2 can easily pass through them
membrane
Cell Membrane
Structure - same as unit membrane.
Function - acts as a boundary layer to
contain the cytoplasm (fluid in cell)
- interlocking surfaces bind
cells together
- selectively permeable to
select chemicals that pass in and out of
cells
Cell Wall
Structure
- a non-living secretion of the cell
membrane, composed of cellulose
- cellulose fibrils deposited in
alternating layers for strength
- contains pits (openings) that make it
totally permeable
Function
- provides protection from physical
injury
- together with vacuole, provides
skeletal support
Nucleus
The nucleus (pl. nuclei; from Latin nucleus or
nuculeus, kernel) is a membrane-enclosed
organelle found in most eukaryotic cells.
 Contains most of the cell's genetic material, or
DNA
Main structural elements of the nucleus are:
 nuclear envelope
 Nucleolus
 Chromatin
 nucleoplasm
Nucleus
Nuclear Envelope
 Structure - two unit membranes
with a fluid-filled space
- nuclear pores present
- outer membrane may be
continuous with endoplasmic
reticulum
 Function - selectively permeable to
control movement in or out
- contains nuclear contents
Nucleus
Nucleus - Is surrounded by a double
membrane and contains the cell's DNA
and the nucleolus, the site of RNA and
ribosome production.
The nucleus regulates all cell activity. It
does this by controlling the enzymes
present.
Nucleolus
Structure - non-membranous
matrix of RNA (ribonucleic acid)
and protein
Function - instructions in DNA are
copied here
- works with ribosome's in the
synthesis of protein
Chromatin-Chromosomes
 Chromatin
is a mass of
uncoiled DNA and associated
proteins called histones.
 When cell division begins,
DNA coils around the proteins
forming visible structures
called chromosomes.
Chromatin
Structure -composed of long thin
strands of DNA
Function -contains instructions that
control cell metabolism and
heredity
Chromosome Structure
and Replication
A chromatid is a single DNA
molecule.
 Double-stranded chromosomes have
two chromatids; normally, each one is
identical to the other. The point where
the two chromatids are attached is
called the centromere.
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Endoplasmic Reticulum
Endoplasmic Reticulum (E.R.)
Extensive internal membrane system
throughout the cell which not only acts
as a transport and communications
system but also the principal site lipid
synthesis and plays a role in protein
synthesis.
Endoplasmic Reticulum
(ER)
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Endoplasmic Reticulum (ER) Structure sheets of unit membrane with ribosomes
on the outside
- forms a tubular network throughout
the cell
Function - transports chemicals between
cells and within cells
- provides a large surface area for the
organization of chemical reactions and
synthesis
Ribosome's
Ribosome Structure - nonmembraneous, spherical bodies
composed of
RNA (ribonucleic acid) and
protein enzymes
Function - site of protein synthesis
Golgi Body or Apparatus
Golgi Apparatus modifies,
packages, & helps secrete cell
products such as proteins and
hormones
 Consists of a stack of flattened sacs
called cisternae
 Receives products made by the ER
or endoplasmic reticulum
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Mitochondria
Mitochondrion Structure - composed
of modified double unit membrane
(protein, lipid)
- inner membrane infolded
to form cristae
Function - site of cellular respiration
i.e.. the release of chemical
energy from food
Glucose + Oxygen ------> Carbon
Dioxide + Water + Energy (ATP)
Lysosome
Lysosome Structure - membrane bound
bag containing hydrolytic enzymes
- hydrolytic enzyme = (water
split biological catalyst)
i.e. using water to split chemical
bonds
Function - break large molecules into small
molecules by inserting a molecule of
water into the chemical bond
Vacuoles
Vacuole Structure
- a single layer of unit membrane
enclosing fluid in a sack
Vacuole Function
- produces turgor pressure
against cell wall for support
- stores water and various
chemicals
- may store insoluble wastes
Vascular tissue transports food &
water
Chloroplast
Chloroplast Structure
- composed of a double layer of modified
membrane (protein,
chlorophyll, lipid)
- inner membrane invaginates to form layers
called "grana"
(sing., granum) where chlorophyll is
concentrated
Function - site of photosynthesis
Chlorophyll
Carbon Dioxide + Water --------> Glucose + Oxygen
radiant energy(light)
(food)
Centriole
Centriole Structure - nine triplets of
microtubules form one centriole
- two centrioles form one
centrosome
Function - forms spindle fibres to
separate chromosomes during cell
division
Cell Complexity