Download Cell Structure and Function

Cell Structure and Function
Cells and their Functions
Organelle Functions
Levels of Organization
• Cells can be grouped together into tissues, a
group of cells that are similar and work
together.
– Epithelial cells  epidermis
Neurons  nerve
• Tissues can be grouped together into organs,
a group of different tissues that work together
to perform a specific function.
– Epidermis, dermis, subcutaneous tissue  skin
Levels of Organization
• Organs can be grouped together into
organ systems, a group of organs that
work together to perform specific
connected tasks.
– Stomach, Intestines, Liver, etc.  Digestive
system
• Cells  Tissues  Organs  Organ
systems
Major functions of cells
• Break down food into nutrients
– Polymers into monomers
• Transport materials
– O2 to cells; CO2 away from cells
• Produce chemicals
– Hormones – a chemical signal used to control
body functions
• Work together to build tissues
organ systems
organs
organism
Cell Theory
• All living things are made of cells. All cells
have some structures in common, such as
DNA.
• Cells are the basic units of structure and
function in living things.
• Cells only come from already present cells
(pre-existing).
Cell Types
• Prokaryotes – a cell
with only one outside
membrane and no
nucleus or other
internal structures
• Simple cells
• Grow quickly
– Binary fission, cell
divides into identical
daughter cells
• Ex. - bacteria
• Eukaryotes – a cell
with several internal
structures, including
the nucleus, that are
surrounded by
membranes
• Complex cells
• Ex. – plant cells,
animal cells, fungi
cells
Cell Structure and Function
• Maintain homeostasis, the ability of organisms to
maintain their internal conditions
• Diffusion – the movement of molecules from an
area of high concentration to an area of low
concentration
• Osmosis – the movement of water through a cell
membrane
• Selectively permeable membrane – a membrane
that allows some molecules to pass but blocks
other molecules from coming through (semipermeable)
Selectively permeable membranes
Concentration Gradient
• A difference in the concentration of a substance
across a distance is the concentration gradient.
• Hypotonic – a solution whose solute
concentration is lower than the solute
concentration of another solution
• Hypertonic – a solution whose solute
concentration is higher than the solute
concentration of another solution
• Isotonic – a solution whose solute concentration
is equal to the solute concentration of another
solution
Concentration Gradients
Concentration Gradients
Eukaryotic Cells
• Contain a membrane-bound nucleus
– Controls the activities of the cell
• Contain membrane-bound organelles
– Transports materials
– Produces chemicals and substances
• Complex in structure
– Can reproduce in several different ways;
asexual and sexual reproduction
Cell Membrane
• Composed of a lipid bilayer.
• Hydrophilic outside, hydrophobic inside
• Proteins help transport large molecules
across the membrane
• Glycoproteins help cells “communicate”
with each other
Cell Membrane
Cell Membrane Function
• Regulates which materials enter and leave
the cell
• Protects the cell from outside environment
• Passive transport – the movement of
molecules across a membrane when the
movement requires no energy
– Ex. Diffusion and osmosis
• Facilitated diffusion – passive transport
that involves membrane proteins
Cell Membrane Function
• Active Transport – the movement of
molecules across a membrane when the
movement requires energy
• Endocytosis – a process in which a cell
membrane surrounds and encloses a
substance to bring the substance into the
cell
• Exocytosis – a process in which a
substance is released from a cell through
a pouch that transports the substance to
the cell surface.
Nucleus
• Controls information in the cell
• Surrounded by the nuclear envelope;
bilayer contains pores to let substances
enter and leave
• Contains the DNA, which is folded with
proteins making up the chromosomes
• Nucleolus – a ball of fibers in the nucleus
that makes ribosomes
Nucleus
Ribosomes
• Make proteins from directions found in DNA
• Made from a combination of RNA and other
proteins
• Found throughout the cell
• Found on the rough endoplasmic reticulum
Mitochondria
• Converts energy from bonds in glucose
into ATP through respiration, process in
which cells break down food to release
energy
Chloroplast
• Harvests energy from the sun through
photosynthesis
• Found in plants, some bacteria and protists
Endoplasmic Reticulum (ER)
• Makes different molecules
• Rough ER packages and sends off proteins
• Smooth ER makes lipids and carbohydrates
Golgi Apparatus
• Responsible for synthesizing, modifying,
and packaging proteins for export
Vacuoles and Lysosomes
• Vacuoles - transports and stores molecules
• Lysosomes – contain special enzymes to
break down large molecules
• Found throughout the cell
Cytoskeleton
• A group of fibers running throughout the inside
of a cell that supports the cell and helps the cell
move
• Microfilament – a long fiber used to move the
cell
– Made of a ball-shaped protein called actin
• Intermediate filament – a rod-like fiber used to
strengthen the cells shape and hold organelles
in place
• Microtubule – a fiber used by organelles to move
around.
– Made of a ball-shaped protein called tubulin
Cytoskeleton
Plant Cells
• Plant cells contain chloroplast used in
photosynthesis
• Cell wall – rigid layer of cellulose outside
the cell membrane
• Plasmodesmata – openings in the cell wall
used for communication and transport of
molecules
• Central vacuole – a large sac in the center
of the plant cell used for water storage.
Plant Cells