Download Cells - Avon Community School Corporation

Cell: Basic unit of life
 Adult human contains ~75 trillion cells
 Cells are very diverse in size, shape,
function

› Ex: Neuron – long thin axons coupled with
cell body – serve to move electric signals
throughout body
› Ex: Red Blood Cell – doughnut-shaped, small,
carry oxygen to organs

Two types:
› 1) Prokaryotic
› 2) Eukakryotic

Prokaryotic cell:
› Do NOT contain nucleus
› DNA found in cytoplasm
› Do NOT contain membrane-bound
organelles
› Simpler
› Smaller (usually unicellular)

Eukaryotic cell:
› DOES contain nucleus
› DNA found in nucleus
› DOES contain membrane-bound organelles
 Ex: mitochondria, ER, golgi, lysosomes, vacuole
› More complex
› Larger size (usually a part of a multicellular
organism)

ALL cell contain:
› Cell/plasma membrane
 a membrane which encloses to cell
 Serves to protect cell from pathogens and
permit molecules to pass into cell
› Cytoplasm
 Houses the cells organelles and genetic
material
› Ribosomes
 Protein synthesis takes place here
› DNA/RNA
 Genetic material
Also called plasma membrane
 Boundary that separates cell’s contents
from the external environment
 Actively functioning component of cell

› Regulates the movement of substances in
and out of the cell
› Helps cells to adhere to other cells
(important in forming tissues)

Characteristics:
› 1) Thin, flexible
› 2) Outpockets and infoldings (increase
surface area)
› 3) Selectively permeable (only allows some
molecules in/out)

Structure:
› 1) Lipid bilayer
 Two layers of phospholipids
 Tails face inward (fat-like; hydrophobic – water hating)
 Heads face out (phosphate; hydrophilic – water loving)
› 2) Cholesterol
 Keeps membrane fluid in cold weather
› 3) Proteins
 Structure and cell communication
› 4) Carbohydrates
 Cell communication

Membrane proteins:
› Transmembrane/integral:
 Help to transport ions and other molecules
 Structure
› Peripheral/Extensions:
 Connection of organelles to membrane
 Structure
 Cell communication
› CAM
 Cellular adhesion molecule
 Guides a cell’s interactions with other cells
 Ex: CAMs help white blood cells move to injury
Contains organelles
 Contains cytoskeleton

› Network of protein fibers that form a support
system
Usually slightly neutral pH
 Serves to help cells communicate signals



Called ER
Two types:
› Smooth:
 No ribosomes found on
surface (appears
smooth)
 Contains enzymes
important in lipid
synthesis, absorption of
fat, metabolism of drugs
› Rough
 Contains ribosomes
 Site of protein synthesis –
sends items to smooth
ER and Golgi for further
processing
Site of protein synthesis
 Two types:

› 1) Attached (to rough ER)
› 2) Free (found floating in cytoplasm)

Parts:
› Protein
› RNA molecule (rRNA – ribosomal RNA)
Stacks of membranebound sacs
 Takes in proteins

› Then, refines, packages
›
›
›
›
and delivers final
proteins
Arrive to Golgi enclosed
in vesicles
Vesicles fuse with Golgi
As move through Golgi,
the proteins are
modified chemically
When reach outermost
layer, packaged again
in vesicles and shipped
Major sites of cellular respiration
(breakdown food to form energy - ATP)
 Can reproduce
 Contain own DNA
 Contains outer and inner membrane

› Inner membrane folds inward to form cristae
(fingers)


Matrix: inner space
Many mitochondria found in muscle
cells (which require a LARGE amount of
energy)

Lysosomes:
› Tiny sacs containing
enzymes that break down
nutrient molecules, foreign
particles, broken
organelles

Peroxisomes:
› Tiny sacs containing
enzymes that catalyze the
synthesis of bile acids,
detox hydrogen peroxide,
breakdown lipids, detox
alcohol
› Abundant in liver and
kidney

Cilia:
› Tiny hairs
› Assist in movement
› Move fluids (like mucus)
over tissues

Flagella:
› Tail-like extensions
› Assist in movement
› Usually cells contain
single flagella
› Ex: sperm
Membrane-bound sacs formed by cell
membrane folding inward
 Used for storage of macromolecules,
water, toxins, pigments

Thin, thread-like strands within cytoplasm
 Integral part of cytoskeleton


Microfilaments:
› Actin proteins
› Provide cell
movement
(contraction,
cilia/flagella)

Microtubules:
› Tubulin protein
› Thicker

Functions:
› House genetic material
› Direct all cell activities

Enclosed by nuclear membrane (lipid
bilayer)
› Contain pores which allow molecules to exit

Found within nucleus:
› Nucleolus: small, dense organelle made of RNA
and protein, forms ribosomes
› Chromatin: loosely coiled fibers of DNA and
proteins (chromosomes)
Cell membrane is semi-permeable
 Rely upon concentration gradients to move

› Def: difference in concentration between two areas
› Continually work to reach a state of equilibrium
(uniform concentration)

Two types of cellular movement:
› 1) Passive transport:
 No energy required
 Ex: diffusion, osmosis, facilitated diffusion, filtration
› 2) Active transport
 Energy required
 Ex: exocytosis, endocytosis, proton pumps
Passive transport (no energy use)
 Molecules/Ions spread from regions where
they are more concentrated to less
concentrated
 Can occur if:

› Membrane allows it
› Concentration gradient exists
Ex: oxygen and carbon dioxide moving
in/out of blood
 Animation

Passive transport (no energy use)
 Molecules/Ions spread from regions where
they are more concentrated to less
concentrated
 Can occur if:

› Membrane allows it
› Concentration gradient exists
› Membrane proteins assist(change shape when
molecule attaches)
Ex: movement of glucose and amino acids
 Animation

Passive transport (no energy use)
 WATER molecules spread from regions
where they are more concentrated to less
concentrated
 Can occur if:

› Membrane allows water (but usually not other
molecules) to pass through
› Concentration gradient exists
 Solution
can be:
› Hypertonic:
 Higher osmotic pressure inside
 More water –less solutes - on
inside of the cell
 Result: water rushes OUT, cell
shrinks
› Hypotonic:
 Lower osmotic pressure inside
 Less water – more solutes – on
inside of the cell
 Result: water goes IN, cell
expands
 Solution
can be:
› Isotonic:
 Same osmotic pressure on body sides
 Molecules CONTINUE TO MOVE
 Net concentration of water and solutes does not
change!
Animation





Passive transport (no energy use)
Molecules are FORCED from regions where
they are more concentrated to less
concentrated
Usually used to separate solids from water
Relies upon hydrostatic pressure (created
by weight of water due to gravity) to force
molecules
Teacher Demo (applesauce and water)


Requires use of energy (ATP molecules)
Also requires the use of special membranebound proteins to assist molecule movement
› Carrier proteins (change shape when molecule
attaches)



Moves particles AGAINST concentration
gradient (low to high)
May use up to 40% of cell’s energy
Ex: Proton pump, Na/K pump, movement of
nutrients into cells that line intestines




Requires use of energy (ATP molecules)
Molecules too large to enter cell through
passive transport
Molecules are packaged inside vesicles (using
infolding of cell membrane)
Molecule moves INWARD

Three forms:
› Phagocytosis:
 Cell “eating”
 Take in solid particles (bacteria, debris)
› Pinocytosis:
 Cell “drinking”
 Take in liquid particles (water w/ dissolved items)
› Receptor-mediated:
 Moves specific kinds of particles into cell
 Proteins extend to outer surface where they form
receptors
 Bind to ligands




Requires use of energy (ATP molecules)
Molecules too large to leave cell through
passive transport
Molecules are packaged inside vesicles and
SECRETED OUT
Molecule moves OUTWARD


Series of changes cell undergoes from its
formation to its division
Rate of cell cycle depends upon checkpoints
and stimulation
› Ex: restriction checkpoint
 Determines cell’s fate (division, resting, death)
› Cancer: inability of cell to respond to checkpoints,
cells divide uncontrollably
› Stimulation: cells will divide spontaneously when
hormone or growth factor triggers it
 Ex: development of milk during pregnancy
 Includes:
› Interphase: preparatory phase
 Grows, makes copies of organelles,
obtains nutrients replicates DNA
 Three stages: G1, S, G2
 Includes:
› Mitosis: Nuclear division
 Phases: Prophase, Metaphase, Anaphase,
Telophase
 Prophase: chromosomes condense (become visible),
centrioles migrate to opposite ends, nuclear envelope
disappears
 Metaphase: chromosomes line-up in middle, spindle
fibers attach to centromeres
 Anaphase: chromosomes separate, cell elongates
 Telophase: final stage, chromosomes unwind (go back to
chromatin), nuclear envelope reforms (prophase in
reverse!)
 Includes:
› Cytokinesis:
Cytoplasmic division
 Animals:
 Cell membrane begins
to constrict, pinch
inward
 Creates cleavage furrow
 Uses microfilaments to
contract and pinch
› Animation

Differentiation:
› Def: Process of cell specialization
› Cell gains function/structure

Stem cells:
› Def: cells who have NOT gained
specialization, divide frequently
› Divides through mitosis
continually (two options)
 1) Forms 2 daughter cells
 2) One daughter cell and one
progenitor cell
 Progenitor cell: partially
specialized cell

Apoptosis:
› Cell that does not divide or
specialize
› Cell death
› Normal part of development
 Ex: fetus – rids hands of
webbing
› Could also be due to injury or
disease
 Ex: sunburn (peeling skin)