Transcript CELL STRUCTURE AND FUNCTION

CELL STRUCTURE AND
FUNCTION
LIFE IS CELLULAR
LIFE IS CELLULAR
• Prokaryotes and Eukaryotes
– Cells come in many sizes and shapes.
• Typical size 5 to 50 micrometers
• Tiniest mycoplasma bacteria is 0.2 micrometers across
• Giant amoeba Chaos chaos is 1000 micrometers (µm) in
diameter.
– All cells have two things in common.
• They are surrounded by a barrier called a cell
membrane.
• They contain the molecule that carries biological
information-DNA.
MYCOPLASMA BACTERIA
CHAOS CHAOS AMOEBA
LIFE IS CELLULAR
– Cells are one of two categories, depending on
whether they contain a nucleus or not.
• The nucleus (plural is nuclei) is a large membraneenclosed structure that contains the cell’s genetic
material in the form of DNA.
– The membrane is a thin layer of material that serves as a
covering or lining.
• The nucleus controls many of the cells activities.
• Eukaryotes are cells that contain nuclei.
• Prokaryotes are cells that do not contain nuclei.
LIFE IS CELLULAR
– Prokaryotes
• These cells are usually smaller.
• They have genetic material that is not contained in a
nucleus.
• Despite being simpler cells, they carry out every activity
associated with living things.
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They grow
They reproduce
They respond to the environment
They move by gliding along a surface or swim through liquids
Bacteria are prokaryotes
PROKARYOTES
PROKARYOTES
LIFE IS CELLULAR
– Eukaryotes
• These cells are larger and more complex.
• They contain many structures and membranes, and are
highly specialized.
• They contain a nucleus in which their genetic material
is separated from the rest of the cell.
• Some are single celled and other are multicellular.
• Plants, animals, fungi are eukaryotes.
EUKARYOTES
EUKARYOTES
EUKARYOTES
EUKARYOTIC CELL STRUCTURE
• Comparing the Cell to a Factory
– The cellular structure of a eukaryotic cell seems,
at first glance, to be very complex.
– However, after looking at the cell under a
microscope, patterns begin to emerge.
– Organelles are within the eukaryotic cell and act
like specialized organs, or organelles, “little
organs.”
EUKARYOTIC PLANT CELL
EUKARYOTIC PLANT CELL
EUKARYOTIC PLANT CELL
EUKARYOTIC ANIMAL CELL
EUKARYOTIC ANIMAL CELL
EUKARYOTIC ANIMAL CELL
EUKARYOTIC CELL STRUCTURE
– The cell is divided into two parts
• The nucleus
• The cytoplasm
– The cytoplasm is the portion of the cell outside the nucleus.
• Nucleus
– The nucleus is the control center of the cell.
– The nucleus contains nearly all the cell’s DNA and
with it the coded instructions for making
proteins and other important molecules.
CELL NUCLEUS
CELL NUCLEUS
CELL NUCLEUS
EUKARYOTIC CELL STRUCTURE
– The nucleus is surrounded by the nuclear envelope.
• This is composed of 2 membranes.
• This has thousands of pores allowing material to move in
and out of the nucleus.
– Allows RNA, proteins, and other molecules to move through the
pores.
– The granular material in the nucleus is the chromatin.
• This consists of DNA bound to protein.
• When cells divide, the chromatin condenses to form
chromosomes.
– Contain the genetic information passed from one cell to next.
EUKARYOTIC CELL STRUCTURE
– The nucleolus is in the nucleus and is where the
assembly of ribosomes takes place.
• Ribosomes
– Proteins are assembled on ribosomes.
– Ribosomes are small particles of RNA and protein
found in the cytoplasm.
• This turns out proteins on instructions that come from
the nucleus.
EUKARYOTIC CELL STRUCTURE
• Endoplasmic Reticulum
– This is an internal membrane system where lipid
components of the cell membrane is assembled,
along with proteins and other materials that are
exported from the cell.
– The rough ER is where proteins are produced.
• Ribosomes are found on its surface.
– No ribosomes are found on the smooth
endoplasmic reticulum.
ENDOPLASMIC RETICULUM
ENDOPLASMIC RETICULUM
ENDOPLASMIC RETICULUM
EUKARYOTIC CELL STRUCTURE
• This contains enzymes that synthesize membrane lipids
and detoxify drugs.
– Liver cells contain a lot of smooth ER since this is where most
of the drugs are detoxified.
• Golgi Apparatus
– Proteins produced in the rough ER move into an
organelle called the Golgi apparatus.
– The function of the Golgi apparatus is to modify,
sort, and package proteins and other materials
from the endoplasmic reticulum for storage in
the cell or secretion outside the cell.
GOLGI APPARATUS
GOLGI APPARATUS
EUKARYOTIC CELL STRUCTURE
• The Golgi apparatus is where the finishing touches are
put on the proteins before they leave the production
area.
• Lysosomes
– These are the cleanup crew.
– These are small organelles filled with enzymes
that digest, breakdown, lipids, carbohydrates, and
proteins into small molecules that can be used by
the rest of the cell.
EUKARYOTIC CELL STRUCTURE
– Lysosomes also breakdown organelles that have
outlived their usefulness.
– They remove “junk.”
– Tay-Sachs disease can be traced to the failure of
the lysosomes.
• Vacuoles
– This is the storage area.
– These are sac-like structures that store water,
salts, proteins, and carbohydrates.
LYSOSOMES
VACUOLES
VACUOLES
EUKARYOTIC CELL STRUCTURE
• These also can pump water in and out of the cell to
maintain homeostasis which controls the internal
environment.
• Mitochondria and Chloroplasts
– Mitochondria
• Mitochondria are organelles that convert the chemical
energy stored in food into compounds that are more
convenient for the cell to use.
• These have an inner and outer membrane.
• These are inherited, in humans, from the ovum or egg.
EUKARYOTIC CELL STRUCTURE
– Chloroplasts
• Chloroplasts are organelles that capture the energy
from sunlight and convert it into chemical energy in a
process called photosynthesis.
• Chlorophyll is contained here.
– Organelle DNA
• Chloroplasts and mitochondria contain their own
genetic information in the form of small DNA
molecules.
MITOCHONDRIA
MITOCHONDRIA
MITOCHONDRIA
CHLOROPLASTS
CHOROPLASTS
EUKARYOTIC CELL STRUCTURE
• Cytoskeleton
– The supporting structure of the cell is the
cytoskeleton.
– The cytoskeleton is a network of protein
filaments that helps the cell to maintain its
shape. The cytoskeleton is also involved in
movement.
• Made up of protein filaments
– Microfilaments
– Microtubules
EUKARYOTIC CELL STRUCTURE
• Microfilaments support the cell and allow cells such as
amoebas to move.
• Microtubules help to maintain cell shape
– Also help in cell division with structures known as centrioles.
– Help to build cilia and flagella that enable the cell to swim
rapidly in liquids.
CYTOSKELETON
CYTOSKELETON
CELL BOUNDARIES
• Diffusion
– In solutions, particles move constantly.
– Particles collide with one another and spread out
randomly.
– Particles move from areas where they are more
concentrated to areas where they are less
concentrated, also known as diffusion.
– They do this until the concentration of particles is
the same throughout the system, known as
equilibrium.
CELL BOUNDARIES
– Because diffusion depends upon random particle
movements, substances diffuse across
membranes without requiring the cell to use
energy.
– After equilibrium is reached, there is still
movement of particles across the cell membrane
but the movement is equal in both directions.
DIFFUSION
DIFFUSION
DIFFUSION
CELL BOUNDARIES
• Osmosis
– Some substances might be too large or too
charged to cross the cell membrane (lipid bilayer).
– Membranes that are permeable indicates that
substances can diffuse across it.
– Impermeable membranes are those that
substances cannot diffuse across.
– Most biological membranes are selectively
permeable.
CELL BOUNDARIES
– Water passes through quite easily while some
solutions cannot.
– Osmosis is the diffusion of water through a
selectively permeable membrane.
– How Osmosis Works
• Take the example of a beaker with a permeable
membrane in the middle. On one side is a low
concentration of sugar water, on the other is a high
concentration of sugar water. Water will move from
the higher concentration (water) to the lower
concentration (water + sugar) across the membrane.
CELL BOUNDARIES
• The membrane is permeable to water but not to sugar.
• This movement of water will occur until there is an
equilibrium, or an equal amount on both sides of the
membrane of water and sugar.
• When this happens, the two solutions are said to be
isotonic (same strength).
• The more concentrated solution is hypertonic (above
strength) and the less concentrated solution is
hypotonic (below strength).
OSMOSIS
LEVELS OF CELL ORGANIZATION
LEVELS OF CELL ORGANIZATION
• The levels of organization in a multicellular
organism are individual cells, tissues, organs,
and organ system.
• Tissues
– In multicellular organisms, cells are the first level
of organization.
– Similar cells are grouped into units called tissues.
– A tissue is a group of similar cells that perform a
particular function.
LEVELS OF CELL ORGANIZATION
LEVELS OF CELL ORGANIZATION
LEVELS OF CELL ORGANIZATION
LEVELS OF CELL ORGANIZATION
– Most animals have four main types of tissue
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Muscle
Epithelial
Nervous
Connective tissue
• Organs
– Many types of tissues work together as an organ.
• The tasks of the body are too complex for just one type of
tissue to perform the task.
• Each type of tissue performs an essential task to help the
organ function.
LEVELS OF CELL ORGANIZATION
• Organ Systems
– A group of organs that work together to perform a
specific function is called an organ system.
– Specialized cells such as nerve and muscle cells
are able to function precisely because other cells
are specialized to obtain the food and oxygen
needed by those cells.
– This overall specialization and interdependence is
one of the remarkable attributes of living things.