Unit 2: Cell Structure & Function Flashcards
What are the 2 types of cells?
Prokaryotes & Eukaryotes
Prokaryotes
Bacteria & Archaea
Eukaryotes
Protists, fungi, plants, animals, (everything else)
Prokaryote Characteristics
“before” “kernel” protype (pro) before nucleus - karyote (kernel)
Super fragile. NO nucleus
DNA stored in nucleoid (rough collection of nucleus but does not have own memberane)
Prokaryote Characteristics
DNA could be next to anything
Loose pile of jelly has everything everywhere (Cytosol)
No organelles other than
ribosomes
CANNOT Compartmentalize:
disorganized
Small size & ancient
(ex: mostly Bacteria & Archaea)
Eukaryote Characteristics
“true” “kernel”
Has nucleus & nuclear envelope
Cytosol (fluid in cell membrane)
Membrane-bound organelles
w/ Specialized
Structure/Function
Much larger in size
More complex/organized + CAN COMPARTMENTALIZE (hold chemicals in diff places)
(ex: plant/animal cell)
Nuclear Envelope
regulated membrane barrier that separates the nucleus from the cytoplasm ; composed of an outer and an inner phospholipid bilayer
What is the difference between nuclear envelope & cell membrane?
cell membrane encloses the cytoplasm & organelles is a lipid bilayer
Nuclear membrane encloses the nucleus & made up of double lipid bilayer
Surface Area
WANT LARGE SA
Cells must be HAVE LARGE SA to maintain a LARGE Surface Area to Volume RATIO
Why is it important to have high SA to Volume ratio?
Large S.A. allows ↑ rates of chemical exchange between cell and environment, HIGHER RATES of Diffusion of oxygen/materials in & waste out
Example of Surface Area
Crushed ice = melts rly quickly bc HIGH SA, dries more quickly & loses temp fast (absorbs heat faster)
big ice = melts slower but water = not as cold
How does SA increase ?
we chop off all cells & stick them back together to increase SA for necessary elements/chemicals to enter body (ex: oxygen)
Calculate SA
H * W * Sides of boxes * # boxes
Calculate Volume
L * W * H * # boxes
Calculate SA to Volume Ratio
SA / Volume
SA example in Animal - Small Intestine
highly folded surface to increase
absorption of nutrients
Villi
finger-like projections on Small Intestine wall
Microvilli
projections on each cell (fingers of fingers) super tiny
Order of small -> large SA examples
microvilli, villi, folds
SA example Plant
Root hairs - extensions of root epidermal cells;
increase SA for absorbing water & minerals
Nucleus
Control Center of cell
Contains DNA (& mRNA) + instructions
Surrounded by Double membrane (nuclear envelope)
Continuous with the rough ER (connected by nuclear envelope)
Nuclear pores
control what enters/leaves nucleus (holes)
Chromatin
complex of DNA + proteins; makes up
chromosomes (loose pile of DNA)
Nucleolus
region where ribosomal subunits (rRNA + proteins)
are formed
Ribosomes
Makes proteins ( protein synthesis)
Composed of rRNA + protein
Large subunit + small subunit
Free Ribosomes
float in cytosol, produce proteins used
within cell
Bound ribosomes
attached to ROUGH ER, make proteins for
export from cell
Endomembrane System
(Inside) Regulates protein traffic & performs metabolic functions
all membranes/organelles
Endoplasmic Reticulum (ER)
Network of membranes and sacs
Rough & Smooth
Rough ER
Ribosomes on SURFACE (covered in ribosomes = rough)
Packages proteins for secretion(export), send
transport vesicles to Golgi, make replacement membrane
Smooth ER
No ribosomes on surface = smooth
Synthesizes lipids, metabolize carbs,
detox drugs & poisons, store Ca2+ (calcium ion)
Golgi Apparatus
Packaging, Modifying, Synthesis of materials (small molecules) for transport in vesicles
Series of flattened membrane sacs (cisternae)
Produces lysosomes
Cis & Trans Face
Cis Face
RECEIVES Vesicles from ROUGH ER golgi side
Trans Face
ships vesicles
golgi side
Lysosomes
Lys = breaks apart
Function: Intracellular Digestion; Recycle cell’s materials
Contains hydrolytic enzymes
Apoptosis
programmed cell death
Vacuoles
Storage for materials (food, water, minerals, pigments,
poisons)
Membrane-bound vesicles
Ex: food vacuoles, contractile vacuoles
Plants: large central vacuole: stores water, ions
Mitochondria
Site of Cellular Respiration
Double membrane: Inner & Outer membrane
Cristae & Matrix
Technically bacteria ate a bacteria
Makes ALL of energy for cells
Mitochondria Cristae
folds of inner membrane; contains enzymes for ATP
production; increased SA to ↑ ATP made
Mitochondria Matrix
fluid-filled inner compartment, created by cristae
Chloroplasts (similar to Mitochondria BUT only in PLANTS)
Site of photosynthesis
Double membrane
Thylakoid disks in stacks (grana); stroma (fluid encircling grana)
GRANA contains CHLOROPHYLLS (pigments) for capturing sunlight
energy
has protein that absorbs everything but green
Endosymbiont theory
Mitochondria & chloroplasts share similar origin
Ancestor Eukaryotic cells ate (engulfed) & evolved /arose from free-living prokaryote cells
Endosymbiont theory EVIDENCE (might be FRQ)
Double-membrane structure
Have own ribosomes
Have own DNA
Reproduce independently w/ in cell
Peroxisomes
Breaks down fatty acids; detox alcohol
Involves production of hydrogen peroxide (H2O2)
Cytoskeleton
Network of Protein Fibers
Support, Motility(cell movement), Regulate biochemical
activities
Support & Structure for cells
Centrosomes
microtubule (part of skeleton) organizing center. where microtubules grow
Animal cells contain centrioles
Centrioles
an organelle inside animal cells that are made of microtubules & are involved in cilia, flagella & cell division; helps organize microtubules for skeleton structure
Microtubules (cytoskeleton)
(Tubulin Polymers) Hollow tubes
Maintains cell shape, cell-movement in cell division, organelle movements
Microfilaments (cytoskeleton)
(Actin Filaments) 2 intertwined strands of Actin
Maintains cell shape, changes in cell shape, muscle contraction, cytoplasmic streaming (plant cells), cell motility, cell division (animals cells)
Intermediate Filaments
Fibrous proteins coiled into cables
Maintains cell shape, anchorage of nucleus, creates nuclear lamina
Flagella
long hairlike structures + few; propel through water from cell membrane (tail ex: sperm) used to move entire cell
Cilia
small hairlike structure on outside of Eukaryote cells
Short & Many; locomotion or move fluids
Have “9+2 pattern” of microtubules, moves faster than flagella
Plant cells
Have Cell wall, Cellulose, Plasmodesmata:
Cell wall
Protect plant,
Maintain shape
Composed of cellulose
Plasmodesmata
channels
between cells to allow passage
of molecules from cell to cell
Extracellular Matrix
Outside plasma membrane of Animal cells
Composed of glycoproteins (ex. collagen)
Strengthens tissues & transmits external signals to cell
Intracellular Junctions (Animal cells)
Tight junctions, Desmosomes, Gap junctions
Tight Junctions
2 cells are fused to form watertight seal
Desmosomes
“rivets” that fasten adjacent cells into strong sheets
Gap junctions
channels thru which ions, sugar, small molecules can pass
Plant cells Only
Central Vacuoles, chloroplasts, cell wall, plasmodesmata
Animal Cells Only
Lysosomes, Centrioles, Flagella, Cilia
Desmosomes, tight & gap
junctions, Extracellular matrix (ECM)
Cell Membrane
Plasma membrane is Selectively Permeable
Allows some substances to cross more easily than others
Mostly Phospholipids - hydrophilic heads & hydrophobic tails
Fluid Mosaic Model
Phospholipid Bilayer
Fluid: membrane held together by weak interactions
Mosaic: phospholipids, proteins, carbs
ALLOWS SMALL NONPOLAR molecules to easily move thru out body - CO2 exit, O2 enter
Early Membrane Model
(1935) Davson/Danielli –
Sandwich model
Assumed Phospholipid bilayer between 2 Protein layers (sandwich)
Problems: varying chemical
composition of membrane,
hydrophobic protein parts
Freeze-Fracture method:
Revealed structure of membrane’s interior
Phospholipids
Bilayer
AMPHIPATHIC = hydrophilic head,
hydrophobic tail
Hydrophobic barrier:
keeps Hydrophilic
molecules out (toe to toe not head to toe) - WONT let water in/let water leak out but maintain mostly water
Membrane Fluidity (hands moving)
The phospholipid bilayer provides Selective permeability and Fluidity to the membrane, allowing certain nonpolar molecules to pass thru
Cholesterol helpers
Adaptations
Low Temps
Low temps of Membrane Fluidity
phospholipids
w/unsaturated tails (kinks prevent
close packing)
Adaptations for membrane fluidity
bacteria in hot springs (unusual lipids); winter wheat (unsaturated phospholipids)
How does Cholesterol affect Membrane Fluidity?
(Stabilizes membrane) Resists Changes by:
LIMIT fluidity at HIGH temps (molecules move fast)
HINDER close packing at LOW
temps (not getting too lose/tight)
Ex: moving hands, but even if slowly moving & packed, molecules can somehow get thru but less often
Membrane Proteins
Integral & Peripheral
Integral Proteins
Embedded in membrane
Determined by Freeze Fracture
Transmembrane w/ hydrophilic heads & hydrophobic tails
Peripheral Proteins
Extracellular/Cytoplasmic Sides of membrane
NOT embedded
Held in place by the Cytoskeleton or ECM
Provides stronger framework
Transmembrane Protein Structure
Hydrophilic ends, Hydrophobic interior
Functions of Membrane Proteins
Transport, Enzymatic Activity, Signal Transduction, Cell-Cell Recognition, Intercellular joining, Attachment to cytoskeleton & Cellular Matrix
Carbohydrates
Cell-cell recognition; Develops organisms
Glycolipids, Glycoproteins
Selective Permeability
Small molecules (Polar or Nonpolar) cross easily (hydrocarbons,
hydrophobic molecules, CO2, O2)
*Nonpolar Small = EASY to get in
Hydrophobic core PREVENTS passage of ions, LARGE POLAR molecules
Passive Transport
NO ENERGY (ATP) needed!
Diffusion down concentration gradient (high → low
concentration)
Molecules move to diff sides of membrane until reach Equilibrium
Ex: hydrocarbons, CO2, O2, H2O
Osmosis
Diffusion of Water
From HIGH concentration to LOW concentration
Water able to fight off gravity to push itself to area w/ HIGH concentration of SOLUTE to reach Equilibrium
External Environments can be… to internal environments of cell
Hypotonic, Isotonic or
Hypertonic
Hypotonic solution like Hippo
Too much water
Animal cell - Lysed ( bursts open too watery)
Plant cell - Turgid (normal)
Isotonic Solution
Normal
Animal Cell - Normal (Equilibrium of water moving IN & OUT at same time)
Plant Cell - Flaccid (floppy plant)
Hypertonic
Not Enough water
Animal cell - shriveled
Plant cell - Plasmolyzed (water sucked out)
Water Potential Equation
H2O moves from high ψ →low ψ potential
Water potential equation:
ψ = ψS + ψP
Water potential (ψ)
free energy of water
Solute potential (ψS)
solute concentration (osmotic potential)
Pressure potential (ψP)
physical pressure on solution; turgor pressure (plants) - always given
Pure water: ψP = 0 MPa
Plant cells: ψP = 1 MPa
Calculating Solute Potential (ψS)
ψS = - NEGATIVE iCRT
i = Ionization constant (# particles made in water)
C = Molar concentration (given) - more salt = more concentrated & negative
R = Pressure constant (0.0831 liter bars/mole-K)
T = temperature in K (273 + 0C)
Adding Solute to concentration does what?
The addition of Solute to water LOWERS the Solute Potential (MORE NEGATIVE) & DECREASES the Water Potential.
Ex: add salt (solute) to water = less water & more negative
Where will WATER move?
From an area of: higher ψ → lower ψ (more negative ψ)
Low solute concentration (more water) → High solute concentration (less water)
High pressure → Low pressure
Calculate the solute potential of a 0.1M NaCl solution at 25°C.
ψS = - iCRT
NA CL = 2 ions
= -2 (0.1) (0.0831) (25+273)
=-4.953
If the concentration of NaCl inside the plant cell is 0.15M, which way will the water diffuse if the cell is placed in the 0.1M NaCl solution?
Water Diffuses from the outside (0.1M less negative) to the inside (0.15 bc it is more negative)
Facilitated Diffusion
Uncontrolled & Passive
Transport proteins (channel or carrier proteins) Help Hydrophilic substances cross
Either: Provide hydrophilic channel OR Loosely bind/carry molecule across)
Ex: ions, polar molecules (H20,
glucose)
Aquaporin
channel protein that allows
passage of H2O
Glucose Transport Protein
Carrier Protein
Need glucose in cell but its BIG & POLAR so cant get in on own
Transport protein = big enough hole that seals itself
Active Transport
Requires ENERGY (ATP)
Proteins transport substances AGAINST Concentration Gradient (low -> high)
Ex: Na+/K+ pump, proton pump
Electrogenic Pumps:
Generate voltage across membrane
Na+/k+ pumps, proton pumps
Na+/K+ Pump
Pump Na+ OUT, K+ INTO cell which becomes more Negative (More NA solution intracellularly & more K extracellulary)
Nerve transmission, pumps ions AGAINST concentration gradients NEED ATP
spark/voltage across membrane (important for osmotic equilibrium)
Proton Pump
Push protons (H+) across
membrane
Ex: mitochondria (ATP
production)
Cotransport - club reference
Membrane Protein allows “downhill” diffusion of one solute to drive “uphill” transport of other
Ex: H+ (super tiny) has to bring in 2 sugars (sucrose) w/ them to get back into cell to reach equilibrium
Passive Transport
Little or NO Energy
High -> Low concentrations
DOWN the concentration
gradient
Ex: Diffusion, osmosis,
Facilitated Diffusion
(w/transport protein)
Active Transport
Requires Energy (ATP)
Low -> High
concentrations
AGAINST the
concentration gradient
ex: pumps, exo/endocytosis
Osmoregulation
Control Solute & Water Balance
Contractile vacuole
If constantly in fresh water, osmosis = constantly try to make water enter, but pump forces out fresh water so keeps enough salt in body & has backup flusher (if not, = hypotonic & cell explodes
Contract Vacuole
“bilge pump” forces out fresh water as it enters by osmosis (ex: freshwater protist)
If constantly in fresh water, osmosis = constantly try to make water enter, but pump forces out fresh water so keeps enough salt in body & has backup flusher (if not, = hypotonic & cell explodes) LOTS OF ATP/ACTIVE TRANSPORT!
What if the freshwater protist is put into saltwater? What would happen to contract vacuole?
Would NOT have to work as hard/ use as MUCH ATP bc not as much water to pump out as in fresh water
Bulk Transport
Transport of proteins, polysaccharides, large molecules
Endocytosis & Exocytosis
Why is Bulk Transport important?
Bc LARGE cells CANNOT js go thru cell membrane bc they would break it/make a hole NEEDS HELP
Endocytosis
Takes in macromolecules, Form new
vesicles, (EATING/CONSUMING) + lysosome help (has digestive enzymes which eat vesicles)
Active Transport
TYPES: Phagocytosis, Pinocytosis, Recepter Mediated Endocytosis
Phagocytosis
“cellular eating” - solids
Pinocytosis
“cellular drinking” fluids
Receptor Mediated Endocytosis
Ligands (like hormones) or target molecules bind to specific receptors on cell surface to get into cell/mediates endocytosis
Exocytosis
Vesicles fuse w/ cell membrane, THROWS OUT/EXPEL contents (EXPORTING/PUKING)
Vesicles
filled w/ fluid they inherit from parent organelle (ex: Golgi) & are formed by pinching off other organelles when materials need to be transported OUT of the cell or between organelles W/ IN cell
Tugor Pressure
Pressure from fluid in a cell which presses cell membrane against the cell wall
HIGH = stiffer, Firm plant
LOW = (loss of water) Wilted plant
Plasmalyzed
water sucked out
What is on the x axis of a graph?
What is on the y axis?
x = Independent variable
y = dependent
When graphing an experiment should u use percent of total _ or total?
PERCENT
If the Solute potential is rly low/negative, what does that mean?
Water is dried out = hypertonic
