Catalyst (12/3)
1. Write 3 things you already know about cells.1. Blood cells (red and white)*2. Eukaryotes prokaryotes3. Plants have cell wall4. Cells make up every living things5. Prokaryotes split6. Mitosis/meiosis*7. Organelles
2. Write 2 things you want to know about cells1. What’s the function of different cells?2. How are cells affected when damaged?3. What a good way to remember difference between meiosis and
mitosis?*
A TOUR OF THE CELL(CELL STRUCTURE &
FUNCTION)
AP Biology-Chapter 6
Cell Function All known living things are
made of cells Structural and functional unit Produced by division of existing
cells Contain hereditary information
that is passed from cell to cell—DNA
Smallest units that perform vital physiological functions
Each cell maintains homeostasis at the cellular level
Homeostasis at higher levels reflects combined coordinated action of many cells.
Regulates itself!
Common Features of All Cells
Plasma membraneCytoplasmDNANucleoid region/NucleusRibosomes
=prokaryotes
=eukaryotes
Prokaryotes
No membrane bound nucleus“naked” circular DNANo internal membrane-bound organelles
“naked” circular DNASmall; <1.0-3.0 μm in diameterSimple structureComprised of Domain Bacteria and Archaea
Kary=seedNO membrane
bound organelles!
Prokaryotes older than eukaryotes
Eukaryotes
Have a membrane bound nucleus—linear DNA
Internal membrane-bound organellesLarge; 10-100 μm in diameterComplex structureComprised of Algae, Protozoa, Fungi,
Animals, and Plants (Domain Eukarya)
Prokaryotic Structures and Functions
External Structures Glycocalyces—capsule or slime layer Flagella Pili Fimbriae
Glycocalyces
Gelatinous, sticky substance surrounding outside of cell Composed mainly of polysaccharides
Some species make polypeptides Two types:
Capsule Slime layer
Capsule Composed of organized repeating units of organic
molecules Firmly attached to cell surface Protects cells from drying out May prevent bacteria from being recognized and
destroyed by host
Like “skin”
Flagella
Responsible for movement Long and whiplike Composed of filament, hook, and basal body Flagellin protein forms filament Base of filament inserts into hook Basal body anchors filament and hook to cell wall Capable of rotating 360°.
(cell wall)Basal Body
Eukaryotic flagella just move back and
forth
Pili
Long hollow tubules Typically only 1 or 2 per cell Join two bacterial cells to transfer DNA from one
to the other (conjugation) Also called:
Sex pili Conjugation pili
“reproduction”
Fimbriae
Nonmotile extensions Sticky and proteinaceous Used to adhere to other bacteria, hosts, and other
surfaces May be hundreds per cell Shorter than flagella
“not moving”
“stick”
“made from proteins”
Cell Wall
Provides structure and shape Protects cell from osmotic pressure Assists in attaching cells to other cells and
surfaces Made of peptidoglycan Target bacterial cell wall with antibiotics because
animal cells do not have them
Penicillan inhibits bacteria’s ability to repair and make
cell walls.
Catalyst (12/4)
1. What does the word “prokaryote” mean?Pro=before kary=seed (before the nucleus)
2. Who evolved first, eukaryotes or prokaryotes?Prokaryotes (less complex—endosymbiotic theory)
3. How does not having membrane bound organelles affect prokaryotes?
Naked DNA—more exposed to damage?Don’t go through mitosis/meiosisCan’t have sex—pili (conjunction)Make ATP not in mitochondria instead on plasma membrane(the two not crossed out are better answers)
Glycocalyces
Formed from glycolipids and glycoproteins
Never as organized as prokaryotic capsules
Helps anchor animal cells to each otherStrengthens cell surfaceProtects against drying outFunction in cell-to-cell recognition and
communication
Glycolipid=lipid & carbGlycoprotein=protein & carb
protein
Carbohydrate side chain
Flagella
Shaft composed of tubulin“9+2” arrangement of microtubulesanchored to cell by basal body; no hookbasal body has “9+0” arrangement of microtubules
single or multiple; generally found at one pole of cell
do not rotate, but undulate rhythmically
CilliaCan see 9+2 arrangement
Can see 9+0 arrangement
Cilia
Shorter and more numerous than flagella
Composed of tubulin in “9+2” arrangement
Coordinated beating propels cells through their environmentAlso used to move substances past
the surface of the cell
Cilia found in….Nasal cavityTrachea (throat)EarsFallopian Tubes
Microvilli
Small (0.08 um in diameter, 1 um long) Plasma membrane covered extensions with microfilaments
Actin cross links that allow limited motion Increase the surface area by approx. 600 fold (humans)
Several thousand microvilli present on apical surface of a single cell in human small intestinal cells
Found in absorptive and secretory epithelial cells Kidney cells Intestinal cells
Also occur in sensory cells Inner ear Taste buds Olfactory receptor cells
Also occur on sperm and egg. Clustering of microvilli around the sperm holds it close and tight, enhancing
fusion.
(small intestine)More microvilli in….KidneyIntestineEarTongue (taste buds)Nose (olfactory)
FUNCTION: absorption, secretion, cellular adhesion, and mechanotransduction (mechanical stimulus to chemical—sense touch, balance, hearing)
Cell Walls
Fungi, algae, and plants have cell walls but no glycocalyx
Composed of various polysaccharidesPlants—celluloseFungi—cellulose and chitinAlgae—cellulose and other
polysaccharides
(not in animals!)Rigid
!
*chitin makes fungi more closely related to animals than plants
Plasma Membrane
Fluid mosaic of phospholipids and proteins
Contains cholesterolControls movement into and out of cell
(picture on back)
Nonmembranous Organelles
Ribosomes Cytoskeleton Centrioles and centrosome
Ribosomes
Ribosomes Larger than prokaryotic ribosomes Site of protein synthesis Assembled in the nucleolus Made of RNA and protein Exported into the cytoplasm Free—unbound in the fluid cytoplasm
Produce proteins for use in the cell Bound—attached to the endoplasmic reticulum
(ER) Produce proteins for export, or for plasma membraneRough
ER
Cytoskeleton
Extensive Functions
Anchor organelles Cytoplasmic streaming and movement of organelles Critical in mitosis and meiosis Cell contraction Movement during endocytosis and amoeboid action Provides basic shape
Composed of Tubulin microtubules
Cylindrical tubes• In cilia and flagella• “superhighway” for organelles
Actin microfilaments Fine, thread-like protein fibers Work with myosin in muscle contraction
Intermediate filaments Provide tensile strength
“cell”
STRUCTURE & MOTION
Cytosol=liquidCytoskeleton-proteins that make structural part
thinnest
thickest
Centrioles
Barrel shaped microtubule structure Found in animal cells and algae; rarely in plants Organize the mitotic spindle
During mitosis
Nucleus
Largest organelle in the cell Consists of
Nucleolus—site of ribosomal RNA synthesis Chromatin—uncoiled DNA Nuclear Envelope—separates nucleus from cytoplasm
Two main functions Stores hereditary material Coordinates cell’s activity
CONTINUOUS!
Chromatin
Fibrous material consisting of DNA and proteins DNA is never found “naked” Always associated with histones—proteins Also associated with RNA and other molecules (hormones
and vitamins) During mitosis chromatin condenses to become
chromosomes
Chromatinchromosomes (condensed)
Catalyst (12/5)
What do you already know about the endomembrane system (Endoplasmic Reticulum, Golgi apparatus, microbodies, lysosomes)?
TEST CORRECTIONS DUE TODAY!! TURN IN IN UPPER LEFT HAND CORNER OF DESK!
Nuclear Envelope
Double membrane with a space in between called the perinuclear space
Outer membrane is continuous with rough ER
Nuclear pores regulate passage of material
Selectively permeable
Endomembrane System
Series of continuous membrane enclosed vesicles, or Discontinuous vesicles that communicate with one
another through vesicles that are formed at one surface and move to another where they are incorporated
Endoplasmic reticulum Rough ER Smooth ER
Golgi apparatus Vesicle—transport and storage Microbody
Peroxisome in animal cells Glyoxyomes in plant cells
Lysosomes
Flow of materials
“inside” “things that work together”
Type of vessicle
Rough Endoplasmic Reticulum
Netlike arrangement of hollow tubules Continuous with nuclear envelope Transport network
Molecules that are targeted for certain modifications and/or Specific final destinations
Produces and processes proteins for export or secretion Produces transmembrane proteins—embedded in the
membrane Adds carbohydrates to some Transports proteins to the golgi apparatus via vesicles Transports proteins directly to nucleus due to close
association of the ER lumen and the nucleus
(RER)—ribosomes attached
(glycoproteins)
Insulin, nonsteroid hormones
Na+/K+ pump, proteins in membrane
More RER in….ThyroidPancreasLiverAdrenal
Medulla
Smooth ER
Lipid production (fats)Detoxification of drugs and poisonsStores calcium
(SER)—no ribosomes
(Skin, ovaries, testes)(liver)
(bones, sarcoplasmic
reticulum) Specialized SER in
muscle cells
Golgi Apparatus
Series of cup-shaped, membrane-covered sacs called cisternae
Animal cells—10 to 20 stacks per cell Usually located near the nucleus Modifies proteins and lipids build in the ER
Molecules are added or removed off the ends Identification and destination tags are added
Produces some polysaccharides (e.g. pectin) Product is extruded from the GA vesicle
Secreted outside the cell Incorporated into plasma membrane Returned to rough ER Vesicle may mature into a lysosome
(GA)
“post office” of the cell—packages and sends proteins
Closer to ER
Secretory Vesicle
Transport cell secretions from the GA to the plasma membrane for release Hormones Neurotransmitters Vesicle=small,
membrane bound, holds something
Catalyst (12/6)
If you were absent yesterdayWhat do you already know about the endomembrane system (Endoplasmic Reticulum, Golgi apparatus, microbodies, lysosomes)?
If you were here yesterdaywhere in the body is there more RER? Why?
TEST CORRECTIONS WERE DUE YESTERDAY (BUT SOME OF YOU WERE’NT HERE)!! TURN IN IN UPPER LEFT HAND CORNER OF DESK!
Peroxisome
Roughly spherical and bound by a single membrane
Contain variety of enzymes Primary function to destroy toxic substances
In particular, hydrogen peroxide (by product of cellular metabolism)
In liver cells—detoxify alcohol and other harmful compounds
Self-replicate No DNA Import the proteins they need to perform fission
Lots of peroxisomes in liver cells—detox!
Break in 2
Lysosomes
Roughly circular membranous sacs Contain approx. 40 hydrolytic enzymes Digest cellular materials that have exceeded their lifetime
Cellular waste products Fats Carbohydrates Proteins Worn out organelles (e.g. mitochondria)
Safety net Internal environment has pH 4.8 If lysosome ruptures the hydrolytic enzymes would denature in the
neutral cytosol environment Maintains low internal pH with the help of H+ ion pumps located in
the membrane Avoids self-digestion by glycosylation of membrane proteins.
Many lysosomal disorders!
Perform hydrolysis
(breakdown)
Enzymes won’t break down the
cell!!
acidic
(the enzymes optimal pH is 4.8 but the cell’s pH is
7 denature)
Mitochondria
Relatively large, oblong, double membrane bound organelles
Occur in numbers directly correlated to the cell’s level of metabolic activity
Convert oxygen and nutrients into ATP Aerobic respiration
Elaborate structure very important to function Aerobic respiration is a complex
multi-step process Reproduce independently—
contain circular DNA
CELLULAR RESPIRATION
(exergonic/catabolic) Lots of mitochondria in muscles!!
Mitochondria DNA is maternally inherited(you got it from your
momma!)
Chloroplast
Relatively large, oblong, double membrane bound organelles
Occur in all green parts of plants Majority in leaves—one-half million
per square millimeter Convert solar energy and carbon
dioxide into glucose photosynthesis
Elaborate structure very important to function Photosynthesis is a multi-step
complex process Reproduce independently—
contain circular DNA
PHOTOSYNTHESIS (endergonic/anabolic)
Central Vacuole
Large, single membrane bound vacuole (can take up to 80% of cell)
Structural supportStorageWaste disposalProtectionGrowth
Vacuoles (in animals) small and used for temporary storage or material transport
(Plants only!)
(aka vesicle)
(turgor pressure) (salts,
nutrients, pigments) (can release molecules that are poisonous, odiferous, or unpalatable
to predators)
(endocytosis, exocytosis)
Groups of cells are organized into…
TissuesOrgansOrgan systems
More organized
These neighboring cells must be able to
AdhereInteractCommunicate
“stick to each other”
Cell to Cell Junctions
Plasmodesmata—plants only Cytosol passes through interacting with neighboring
cells Water and small solutes pass through
Sugars Amino acids Proteins and RNA
Larger molecules pass with aid of actin filaments
There are three types for animal cells
Occluding Junctions—Tight JunctionsAdhesive Junctions—Adherens Junctions and
DesmosomesCommunicating Junctions—Gap JunctionsAll three common in epithelial tissue
“stop or obstruct”
Tight Junctions
Hold cells togetherSeparate apical membranes and
basolateral membranesPrevents the movement of solute and water
between cells
Adherens Junctions
Proteins called cadherins and cateninsActin filaments connected to cateninsPerform signaling functions
Desmosomes
Fasten cells in strong sheets Still permit materials to move in intercellular space
Reinforced with intermediate filaments and connecting fibers
Also called anchoring junctions
Gap Junctions
Also called communicating junctions Cytoplasmic channels between neighboring cells
Special membrane proteins layer each channel Connected by hexagonal tubes called connexons Connexons can open and close
Pore wide enough for passage of: Salt ions Sugars Amino acids Other small molecules Electric current
Catalyst (12/7)
Explain how the different types of cell junctions help organize cells into tissues.
--Cell junctions are tight, adherens, gap.--tight help cells hold together, prevent movement of
fluids--communicate with the signaling of adherens jxns and
electric current passing allowed by gap jxns--gap junctions and plasmodesmata exchange cytosol,
sugars, amino acids, salts/ions allows them to interact or work together
“What is Health?”journal response due by MIDNIGHT TONIGHT!!
Evolution of Eukaryotic Cells
Endosymbiotic Theory Theory of the process of organelle incorporation
into a cell Larger anaerobic eukaryotes engulfed aerobic
prokaryotes Became endosymbionts that enables host cell to become
aerobic Symbiotic relationship became crucial over time
Developed by Lynn Margulis in 1966
“requiring air”
Close relationship between the individuals of 2 or more species
Endosymbiotic Theory
What would later become
plants
What would later become
animals
Evidence supporting Endosymbiotic Theory
Physical similarities exist between mitochondria, chloroplasts, and prokaryotes Similar size
Molecular data indicates mitochondria and chloroplasts are prokaryotic in origin Mitochondria and chloroplasts carry their own DNA, RNA, and unique 70S
ribosome Some mitochondrial DNA sequences similar to Rickettsia, bacterial
obligate intracellular parasite Lateral gene transfer occurred between mitochondria and the
host cell nucleus Mitochondria and chloroplast have double membrane
Possibly retaining their original membrane inside the membrane produced by the host cell
Mitochondria evolved from proteobacteria Chloroplasts evolved from cyanobacteria.
* this…evidence is always important
Process of swapping genetic material between neighboring bacteria (not necessarily of the same species)
Lateral (or Horizontal) Gene transfer
Catalyst (12/10)
Why are cells small but not infinitely small? compartmentalization, bigger to store
machinery (organelles), smaller= higher surface are to volume ratio (can more materials in and out and more rxns on cell membrane)
How does having smaller cells affect metabolic rate (rate at which the cell can perform all of its reactions)? Metabolic rate increases
Catalyst 12/11
Prokaryotes are much smaller than eukaryotic cells, what does this mean about their surface area to volume ratio? Explain how this affects their metabolic rate, growth rate, and generation time as compared to eukaryotes? Prokaryotes have a larger surface area to volume ratio Higher metabolic rate Grow faster Shorter generation time