Slides/AP Videos 2.1-2.11

Cell Theory

Cell Theory

All living things are composed of one or more cells

the cell is the basic unit of life

all cells are related by their descent from an ancestral cell

Eukaryotic Cells

Cells with membrane-bound organelles, a nucleus serving as a site for DNA, and belonging to the __________ domain including plants, animals, fungi, and protists.

cytoplasm

the gelatinous liquid that fills the inside of a cell

eukaryotic - between plasma membrane and nucleus

prokaryotic - bound by the plasma membrane

Prokaryotic Cells

Cells lacking a nucleus and membrane-bound organelles, belonging to the archaea and bacteria domains, with ribosomes not membrane-enclosed.

may have a nucleoid

nucleoid

(prokaryotic) a region where DNA is stored but is not membrane-bound

nuclear envelope

a highly regulated membrane barrier that separates the nucleus from the cytoplasm in eukaryotic cells (nucleus is enclosed within)

nucleus

(eukaryotes) the structure in a cell that contains chromosomes

plasma membrane, cytosol, chromosomes (genome), ribosomes

all cells posses… (4 parts)

(reflects the common ancestry of all known life)

Plasma Membrane

Selective barrier allowing passage of substances, composed of a double layer of phospholipids, facilitating the movement of small, nonpolar molecules.

• allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell

• the nonpolar interior allows for small, nonpolar molecules to pass in/out of cell with relative ease

Chromosomes

DNA-containing structures that carry genes, with genes coding for proteins, and ribosomes responsible for protein synthesis based on mRNA sequences.

gene

a section of DNA that codes for a protein

ribosomes

small cellular parts responsible for protein synthesis, based on the sequence of a strand of messenger RNA (mRNA) - mRNA sequence originate from the genome of a cell

• composed of rRNA and proteins

• composed of small and large subunit

all cells posses ____ , indicating common ancestry of life

Endoplasmic Reticulum

a network of membrane tubes within the cytoplasm of eukaryotic cells (typically around the nuclear envelope)

Organelle providing mechanical support, intracellular transportation, and protein synthesis, existing in smooth and rough forms.

smooth ER (smooth endoplasmic reticulum)

(eukaryotic) the site of cellular detoxification and lipid synthesis; does not have ribosomes attached

rough ER (rough endoplasmic reticulum)

(eukaryotic) an organelle that has ribosomes fastened to its surface (attached to its membrane) and helps compartmentalize the cell

• associated with packaging the newly synthesized proteins made by attached ribosomes for possible export from the cell (either out or inside membrane)

functions: carries out protein synthesis on ribosomes that are bound to its membrane

Golgi Complex (golgi apparatus)

(eukaryotic) A series of flattened, membranous sacs modifying and packaging proteins for distribution within the cell or export, traveling through membranes for modification

• have incoming secretory vesical

  • travels thru membranes (from short to long) and endures modification

• involved in the correct folding and chemical modification of newly synthesized proteins and packaging proteins for trafficking

secretory vesicles

membrane containers that help move material from one part of the cell to the next

Mitochondria

Double-membrane organelles producing ATP energy for eukaryotic cell functions, with the inner membrane highly folded for efficiency.

• double membrane provides compartments for diff metabolic reactions

• outer membrane is smooth

• inner membrane is highly convoluted (folds called cristae)

• produce energy from macromolecules

cristae

folds in the inner membrane of a mitochondria

inner mitochondrial membrane

electron transport and ATP synthesis occur in the…

• folding increases SA, which allows for more ATP production

highly convoluted, and the increased surface area of the cristae allow for increased numbers of ETC proteins and ATP synthases, maximizing oxidative phosphorylation

matrix

the fluid inside the inner and outer membrane of the mitochondria

krebs cycle (citric acid cycle) reactions occur here

intermembrane space

the space between the inner and outer membrane of the mitochondria

Lysosomes

Membrane-enclosed sacs found in some eukaryotic cells that contain hydrolytic enzymes for intracellular digestion and apoptosis (programmed cell death)

• can be used to digest a variety of materials such as damaged cell parts or macromolecules

• hydrolytic enzymes, contribute to cell function:

  • intracellular digestion

  • recycling of organic materials

  • apoptosis

Vacuoles

Membrane-bound sacs mostly used for storage (of nutrients, waste, water), found in eukaryotic cells, aiding in water retention in plants (for turgor pressure) and various roles in waste release

turgor pressure

(eukaryotic - plants) an internal cellular force, usually caused by water pushing up against the plasma membrane and cell wall

vacuoles aid in water retention

Chloroplasts

Double-membrane organelles in photosynthetic eukaryotic cells (algae and plants), specialized for capturing sunlight energy and producing sugar (photosynthesis)

location of light-dependent reactions

• inner membranes contain chlorophyll pigments (comprised of the photosystems and electron transport proteins) that can be found between the photosystems, embedded in the thylakoid membrane

grana

stacks of membranous sacs (thylakoids) within chloroplasts

(stacks of thylakoids)

*increased surface area for Photosystems and ETC proteins in the thylakoid membranes, thereby increasing photophosphorylation and NADPH in the light reactions

thylakoids

(chloroplasts) highly folded membrane compartments that are organized in stacks

→ folding of internal membrane increases efficiency of reactions in chloroplasts

chlorophyll embedded in membrane

stroma

the fluid that fills chloroplasts

• between inner membrane and thylakoids

carbon fixation (Calvin-Benson Cycle) reactions occur here

Surface Area-to-Volume Ratio

Critical for efficient exchange of materials with the environment, influencing metabolic efficiency and heat exchange in cells and organisms.

ex: mitochondria and chloroplasts have double membranes, various root tissues, villi and microvilli on intestinal epithelial, taste receptors

as organisms/cells increase in size, metabolic efficiency decreases (including efficiency in heat loss to environment)

gas exchange

the process by which gaseous molecules from the environment are absorbed by a cell while waste gases from the cell are released into the environment

ex: stomata in plant cells

Cell Membrane

Composed of phospholipids and proteins, selectively permeable, with integral and peripheral proteins serving various functions.

• established a unique internal environment for a cell (regulating transport)

phospholipids

composed of a hydrophilic phosphate head and two hydrophobic fatty acid tails

• are amphipathic (polar head, nonpolar tail)

• spontaneously form bilayers in aqueous environments

peripheral proteins

(cell membrane) proteins on the membrane’s exterior/interior surface

• loosely bound to surface of membrane

• hydrophilic with charged and polar side groups

integral proteins

(cell membrane) proteins that penetrate the membrane

• span the membrane

• hydrophilic with charged and polar side groups

• hydrophobic with nonpolar side groups penetrate hydrophobic interior bilayer

• ex) transmembrane proteins

transmembrane proteins

(cell membrane) proteins that pass completely through the bilayer

cell membrane proteins

examples of functions: transport, cell-to-cell recognition, enzymatic activity, signal transduction, intercellular joining, attachment for extracellular matrix or cytoskeleton

fluid mosaic model

a moving phospholipid bilayer composed of varying types of molecules (proteins, steroids, carbohydrates)

• non-static structure

  • most lipids and some proteins can shift and flow along the surface of the membrane/across the bilayer

• held together primarily by hydrophobic interactions (which are weaker than covalent bonds)

cholesterol

a type of steroid that is randomly distributed and wedged between phospholipids in the cell membranes of eukaryotic cells

• regulates bilayer fluidity under different environmental conditions

  • larger quantity = greater fluidity

steroids can contribute to membrane fluidity

glycoproteins

(cell membrane) 1+ carbohydrates attached to a membrane protein

useful in cellular identification

→ (diversity and location of the (molecules) carbohydrates and lipids enable them to function as markers)

glycolipids

(cell membrane) lipid with 1+ carbohydrates attached

useful in cellular identification

→ (diversity and location of the (molecules) carbohydrates and lipids enable them to function as markers)

cytoskeleton

a network of protein filaments that extends throughout the cytoplasm

• while not part of the membrane itself, it interacts with both the exterior and interior of the cell

functions: supports plasma membrane, gives cell an overall shape, aids in correct positioning of organelles, provides transport paths, etc.

{helps cells maintain shape and internal organization while also providing mechanical support that enables the cell to carry out essential functions like division and movement}

cell wall

a rigid covering that surround plant/fungi/prokaryotic cells composed of complex carbohydrates

structural boundary - protects and maintains shape of cell, prevents against cellular rupture (when internal water pressure is high), helps plants stand up against gravity

permeable barrier - plasmolysis

***animal cells don’t have this***

ex: plants - cellulose (polysaccharide)

fungi - chitin (polysaccharide)

prokaryotes - peptidoglycan (polymer consisting of sugar and amino acids)

plasmodesmata

(cell wall) small holes between plant cells that allows the transfer of nutrients, wastes, and ions

selective permeability

the cell membrane’s ability to regulate the molecules/ions that are able to pass in and out of the intracellular environment

→ direct consequence of membrane structure

polar, large, charged

the hydrophobic interior of the lipid bilayer makes it very unlikely that ___/___/___ molecules can cross

___/___/___ (hydrophilic) substances require a transport protein to move through a cell membrane

small, nonpolar

___, ___ molecules cross the cell membrane with ease

ex) O2, CO2, N2

small, polar

___, ___ molecules can cross the cell membrane but very slowly (can pass through the membrane directly in minimal amounts)

ex) H2O

transport protein

proteins that move molecules across a membrane within a cell

has a specific shape and polarity to accommodate a specific polar/charged/large substance

concentration gradient

the difference in concentrations between two different areas (when a solute is more concentrated in one area than another - permeable membrane separates two diff concentrations of molecules)

flows from high to low concentration in attempt to create equilibrium

**a larger difference indicates a steeper ____ and a faster rate of diffusion

passive transport

the process by which molecules/ions diffuse across a membrane from high to low concentration

→ net movement of molecules from high to low concentration without metabolic energy (such as ATP)

plays a primary role in import of materials and export of wastes

no

when particles move WITH the concentration gradient, do they require energy?

diffusion

(passive transport) a natural phenomenon wherein particles spread out from high to low concentration

• movement of molecules from high concentration to low concentration

• small nonpolar molecules pass freely across cell membrane (N2, O2, CO2)

• small amounts of very small polar molecules, like water, can ____ across a cell membrane

a larger concentration difference indicates a steeper gradient and a faster rate of ____

Active Transport

Process moving molecules against their concentration gradient, requiring energy input such as ATP, and facilitated by carrier proteins like pumps.

pump

(active transport) a type of carrier protein that shuttles molecules through the membrane, against the concentration gradient

• requires metabolic energy (such as ATP) to

  • move molecules against gradient to prevent equilibrium

• establishes and maintains concentration gradients

adenosine triphosphate (ATP)

most common molecule that transfers energy, allowing cellular work to continue

Na+/K+ ATPase (aka sodium-potassium pump)

a useful active transport protein in maintaining ion gradients in animal cells

contributes to the maintenance of membrane potential

• 3 Na+ pumped out

• 2 K+ pumped in

membrane potential

the voltage difference across the membrane

→ voltage is created by differences in the distribution of positive and negative ions across a membrane

electrochemical gradient

a type of concentration gradient that relies on membrane potential - electrical potential difference (voltage) across a membrane

→ membranes may become polarized by the movement of ions across the membrane

Cotransport

Secondary active transport utilizing energy from an electrochemical gradient to move two different ions across the membrane through a protein

symport

(cotransport) two different ions are transported in the same direction

antiport

(cotransport) two different ions are transported in opposite directions

facilitated diffusion

movement of molecules from high concentration to low concentration through transport proteins

speeds diffusion of larger/polar/charged molecules by utilizing transport proteins

→ allows for hydrophilic molecules and ions to pass through membranes

• large and small polar molecules

• large quantities of water can pass through aquaporins

• charged ions, including Na+ and K+, require channel proteins

carrier protein

(facilitated diffusion) a protein that spans the membrane and changes shape to move a target molecule from one side of the membrane to the other

channel protein

(facilitated diffusion) a hydrophilic tunnel spanning the membrane that allow specific target molecules to pass through

aquaporins

(facilitated diffusion) transport proteins specialized for the movement of water

→ large quantities of water move this way

ion channels

(facilitated diffusion) a channel proteins that are specialized for the movement of particular ions

ex: Na+, Cl-

→ the movement of ions in one direction can create an electrochemical gradient across the cell membrane (creating membrane potential, polarizing the membrane)

Osmosis

The diffusion of water through a selectively permeable membrane driven by differences in solute concentrations.

*also defined as the passive transport of water from areas of high to low water concentration

→ water moves to area w higher solute concentration (water concentrations and solute concentrations are inversely related)

• water would diffuse out of a hypotonic environment to a hypertonic environment (solute is hypertonic to hypotonic)

osmolarity

the total solute concentration in a solution

solute

the substance being dissolved

solvent

a substance that dissolves a solute

(water has high solvency abilities)

solution

a uniform mixture of one or more solutes dissolved in a solvent

( solvent + solute = ___ )

Tonicity

Measurement of relative solute concentrations between two solutions affecting water movement into or out of a cell

→ internal cellular environments can be hypotonic, hypertonic, or isotonic to external environments

isotonic

(tonicity) a solution where solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

• equal concentrations of solute and solvent (dynamic equilibrium)

hypertonic

(tonicity) a solution that has a solute concentration greater than that inside the cell; cell loses water

more solute, less solvent

hypotonic

(tonicity) a solution that has a solute concentration less than that inside the cell; cell gains water

less solute, more solvent

lysed

animal cells in a hypotonic solution

→ inflated/popping

normal

animal cells in an isotonic solution

shriveled

animal cells in a hypertonic solution

→ small/deflated

turgid

plant cells in a hypotonic solution

→ normal and inflated

flaccid

plant cells in an isotonic solution

→ not fully inflated

plasmolyzed

plant cells in hypertonic solutions

→ walls caved in

osmoregulation

the ability of organisms to maintain water balance with their environment and control their internal solute concentration

contractile vacuole

an adaptation possessed by freshwater protists to osmoregulate and maintain homeostasis

plasmolysis

the process in which cells lose water when they are placed in a hypertonic solution

Water potential

Measure of water's tendency to move by osmosis, calculated from pressure potential and solute potential

→ the more negative the water potential, the more likely water will move into the area

the water potential of pure water in an open container is zero (no solute, no pressure)

solute potential

represented by Ѱ_s and is always negative in value

• determined by the ionization constant of the solute, the molar concentration of the solution, the temperature in Kelvin and the pressure constant, R

• Ѱ_s = -iCRT

  • ionization constant

    • sucrose = 1

    • NaCl (salt) = 2

  • molarity

    • moles of solute/volume of a solution

*the addition of solutes = more negative ___

pressure potential

represented by Ѱ_p and is 0 bars in an open container at STP (standard temp and press.)

unit of measure → bars

• in an open system, ___ ___ is zero, so water potential is equal to solute potential

Endocytosis

the process by which a cell can engulf extracellular material; the cell uses energy to take in macromolecules and particulate matter by forming new vesicles derived from the plasma membrane

phagocytosis

endocytosis of solid particles (cell takes in large particles)

pinocytosis

endocytosis of liquid matter (cell takes in extracellular fluid containing dissolved substances)

receptor-mediated endocytosis

(endocytosis) receptor proteins on the cell membrane are used to capture specific target molecules

exocytosis

endocytosis in reverse; removes large cellular waste or release cellular products

→ internal vesicles use energy to fuse with the plasma membrane and secrete large macromolecules out of the cell

ex: signaling proteins, hormones, waste

Compartmentalization

Membranes and organelles isolating cellular functions to increase efficiency and reduce competition for space/resources/energy to perform cellular functions

*prokaryotes isolate functions into cellular areas

allows for various metabolic processes and specific enzymatic reactions to occur simultaneously, ex: lysosomes

Endosymbiont theory

Explanation for the origins of mitochondria and chloroplasts through symbiosis, leading to mutualistic relationships and evolution

→ states that an ancestral eukaryotic cell engulfed an ancestral mitochondrion/chloroplast, establishing a mutualistic relationship, then survived and reproduced often

*chloroplast/mitochondria evolved from previously free-living prokaryotic cells via endosymbiosis

symbiosis

(endosymbiotic theory) describes a close, long-term, physical interaction between two different organisms

double membranes, circular DNA, ribosomes

proof/evidence for endosymbiotic theory

both chloroplasts and mitochondria have ___

(3 parts)

solute (potential relationships)

increasing the amount of ___ in water will cause:

• an increase in solute potential

• a decrease in water potential

water potential (potential relationships)

increasing ____ ____ will cause:

• an increase in pressure potential

pressure potential (potential relationships)

decreasing ___ ___ will cause:

• a decrease in water potential