• Cytology- the study of cells

  • Cell Theory

    • All living things are made of cells

    • Cell is the basic unit of life

    • All cells come from pre-existing cells

• Cytology Techniques

  • Light Microscopy- up to 1000x magnification

  • Electron microscopy- up to 10,000,000x magnification

  • Cell fractionation0 isolate different components of cells for a detailed study

• Types of Cells

Prokaryotic- Simpler, smaller cells that are more abundant Unicellular Ex)	Eukaryotic- Lots of membrane-bound organelles BOTH multicellular and Unicellular Unicellular: protists, yeast Multicellular: plant, animal, mushrooms+
No nucleus No membrane-bound organelles Can have: Cell wall, plasma membrane, capsule, Nuceloid (circular DNA), ribosomes, cytoplasm, plasmid, pili, flagella	ALL: Plasma membrane, cytoplasm, nucelus, smooth/rough ER, ribosomes, cytoskeleton, golgi body, plasma membrane mitochondria, vesicles Plant ONLY: cell wall, vacuole, chloroplast Animal ONLY: centrioles, lysosomes, extracellular matrix (ECM), can have flagella

• The Utility of Membrane-Bound Organelles

Nucelus -Site of DNA storage and replication—relays info to ribosomes -Nuclear Envelope- Double membrane surrounds the nucelus with protein pore channels Nuceleolus -Region of the nucelus where ribosomal RNA genes are concentrated	Ribosomes -Site of protein synthesis using RNA transcript of a gene -Complex of RNA + proteins with 2 subunits (large + small) Types of Ribosomes: based on PROTEINS made Free- floating in the cytoplasm → make proteins that STAY in cytoplasm Bound- attached to the rough ER → make proteins that go into membranes + exported from cell	Endoplasmic Reticulum- netwoek of membrane channels attached to a nucelar membrane Rough ER: targeted protein synthesis, compartimentalizes the cell, structural support Bound with ribosomes, closest to nucelus Smooth ER: Synthesizes LIPIDS, detoxification, breaking down glucogen No ribosomes attached, farther from nucelus
Vesicles -Small compartment surrounded by membrane Many functions:	Golgi Apparatus -Modifies, sorts, + packages proteins & lipids for delivery “UPS of the cell” -Series of flattened, membrane-bound sacs	Plasma Membrane -Controls movement of materials in/out the cell + communication between cell/environment -Phospholipids bilayer with embedded proteins Membrane-protein functions: Transport Enzymatic activity Signal transduction- recieve chemical messages from environment and relay to cellCe Cell-cell recognition- glycoproteins serve as identification Attachment to cytoskeleton/extracellular matrix (ECM), intercellular joining
Mitochondria -Converts glucose to ATP energy through aerobic cellular respiration, in charge of apoptosis (programmed cell death) Structure: Double membrane w/ highly folded inner membrane (cristae) Matrix- fluid filled inner cavity contains DNA, free ribosomes, enzymes *Reproduce independently of the cell	Chloroplasts -Photosynthesis: building (anabolism) of sugar from ATP, CO2 and light with O2 byproduct -Structure: Double membrane Stroma: liquid inside inner membrane w/ DNA, robosomes, enzymes Thylakoid sacs: membrane sacs where ATP is made—stacked into grana	Lysosomes -Digestion of waste materials, damaged cell parts, large molecules, sometimes apoptosis -Sac full of digestive (hydrolytic) enzymes Lysosomal Storage diseases: -Lysosome picks up molecules but cnanot digest → grow larger until it disrupts cell/organ function -Often fatal
Peroxisomes -Digestive sac that breaks down fatty acids -Detoxifies poisons like alcohol -Produces peroxide (H2O2)		Vacuoles -Storage Food vacuoles- contain undigested food fused with lysosomes Central Vacuole- Found in plants for storage of water/pigments/defensive compounds , stockpiling proteins/inorganic ions, depositing metabolic byproducts Contractile vacuoles- Found in freshwater protists pump out excess water -Membraneous sac full of storage materials	Cytoskeleton Functions: Structural support/maintaining cell shape Anchorage of organelles Regulation of cell/organelle motlity Movement of chromosomes during cell division -Network of structural proteins extending throughout the cytoplasm assembled from protein subunits Microtubes- connected to vescicles Microfilaments- Intermediate Filaments- cell motility (movement) Cilia + Flagella: -Motility (movement) related extension of cytoskeletal proteins Centrosome: -Microtube-oganizing center ONLY in animal cells
Cell Wall -Provide structural support -Cross-linked netwoek of structural polysaccharides Cellulose-plant cells Chitlin- fungi Peptidoglycan- Bacteria	Extracellular Matrix (ECM) -Cell anchorage/cell communication ONLY in animal cells -Network of connective proteins and proteoglycan molecules outside the cell membrane	Intercellular Junctions* -Proteins that connect cells to other cells Open Junctions: ALLOW communication and exchange of materials Gap Junctions- channels between adjacent ANIMAL cells Plasmodesmata- channels connecting adjacent PLANT cells Closed Junctions: PREVENT movement of substances between cells Desmosomes: Cellular rivets that anchor cells to provide structural support in tissues Tight Junctions: Cell-cell connections that make a waterproof seal to prevent passage of materials

• The Endomembrane System- how eukaryotic cells send proteins from ribosomes → destinations

  • Organelles involved: Ribosomes, Endoplasmic reticulum, Nucelus, Golgi apparatus, Vesicle

• Ex. Pathway of processing/Packaging a secretory protein: Secretory vesicles → rough ER → Golgi body → Membrane

Endosymbiotic Theory- Explains the origins of eukaryotes

• Chloroplasts & Mitochondria arose from endosymbiosis

  • Membrane-bound organelles evolved from once free-living prokaryotes (aerobic bacteria and photosynthetic bacteria) engulfed by a host cell w(ancestor of eukaryotic cells)A

  • Evidence:

    • Both have their own DNA, DOUBLE membrane, ribosomes, enzymes

    • Both divide independently

  

Compartimentalization:

• Refers to way eukaryotic cells are divided into membrane-bound organelles with specialized functions

• Purpose: More efficient movement of nutrients/materials through cell through increasing surface area + increased metabolic efficiency

  • Cells are small to maintain a LARGER/HIGHER surface area : volume ratio

  • Compartimentalization helps bigger cells like eukaryotes to get nutrients to the center more efficiently

AP Classroom Videos

2.1 Subcellular Components

• ALL living cells contain a genomse and ribosomes—reflect the common ancestry of all life

  • Ribosomes synthesize protein acording to the mRNA sequence and the instructions are encoded in that mRNA sequence originate from the genome of the cell—free floating not membrane-bound

    • Consists of TWO subunits not membrane enclosed

    • Made of ribosomal RNA (rRNA) and proteins

      

  • Endoplastic Reticulum- network of membrane tubes withn the cytoplasm of eukaryotic cells

    • Rough ER

      • Ribosomes attached to membrane

      • Compartimentalizes cell b/c associated with packaging the newly synthesized proteins made by attached ribosomes for possible export from cell

    • Smooth ER

      • No ribosomes attached

      • Detoxification and lipid synthesis

  • Golgi Apparatus

    • Series of flattened membrane-bound sacs in eukaryotes

    • Correct folding + chemical modification of newly synthesized proteins and packaging for protein trafficking

  • Mitochondria

    • Double membrane—outer and inner

    • Outer is smooth—inner is highly convoluted forming folds called cristae

    • Functions in production of ATP energy

      

  • Lysosome

    • Membrane-enclosed sacs found in some eukaryotic cells with hydrolytic enzymes

    • Used to digest a variety of materials like damaged cells or macromolecules

  • Vacuoles

    • Membrane-bound sacs in eukaryotes

    • Variety of roles from storage to release of waste

  • Chloroplasts

    • In eukaryotic cells like plants/algae

    • Double outer membrane

    • Captures energy from the sun and producing sugar through photosynthesis

2.2 Cell Structure and Function

• Chloroplasts- photosynthesis

  • Thylakoid

    • Highly folded membrane compartments organized in stacks called grana

    • Contain chlorophyll pigments that comprise the photosystems and electron transport proteins found between the photosystems embedded in the thylakoid membrane

    • LIGHT-DEPENDENT reactions occur here

    • *Folding of membranes increases efficiency of reactiosn

  • Stroma

    • Fluid between inner chloroplast membrane and outer thylakoids

    • Carbon fixation (Calvin-Benson cycle) reactions occur here

• Mitochondria- metabolic reactions

  • Double membrane povides compartments for different metabolic reactions

  • Krebs Cycle reactions occur in the MATRIX of the mitochondria

  • Electron transport/ATP synthesis occur in the inner mitochondrial membrane

    • Folding of inner membrane increases surface area enabling more ATP production

    

• Vacuole

  • In plants vacuoles aid in retention of water for turgor pressure

    • Turgor Pressure- Internal cellular force caused by water pushing up against membrane and cell wall

• Lysosome

  • Intracellular digestion

  • Recylcng of organic material

  • Programmed cell death (apoptosis)

• Endoplasmic Reticulum

  • Mechanical support

  • Intracelular transport

  • Rough ER protein synthesis on the bound ribosomes

2.3 Cell Size

• Cells are typically small

  • Moving meterials in and out of cells gets more difficult the larger a cell is—smaller cells more efficient

  • Smaller cells have higher surface area to volume ratios thus more efficient with exchange of materials—needed for demands like exchanging oxygen, removing waste, taking in nutrients

  • As cells increase in volume relative SA decrease making it larger for larger cells to meet the demand for internal resources

• Complex structures used to increase efficiency

  • Folded membranes increase surface area

  • Root hairs on plant root surface increases surface area → more absorption of water and nutrients

  • Ex. Small Intestine

    • Membrane folding increases surface area

    • Outer lining is highly folded containing infger-like projections called villi

    • Surface of each villi has additional microscopic projections called microvilli further increase surface area

  • As organisms increase in size their SA:V ration decreases, affecting properties like rate of heat exchange with the evironment

    • Elephant having large flat ears to dissipate more thermal energy as blood flows closer to the surface

  • Organisms evolve highly efficient strategies to obtain nutrients and eliminate wastes

    • Stomatal openings of leaes obtain molecules from and release molecules into the environment

      • When stomata are open CO2 eneters and O2 and H2O can be released into the atmosphere

Topic 2.4 Plasma Membranes

• Cell embranes provide a boundary between the interior of the cell and outside environment

  • Control transport of materials in and out of cell

• Phospholipids are amphipathic—Hydrophilic head hodrophobic tail

  • Spontaneously form a bi-layer in an aqueous environment

    • Tails located inside the bilayer

    • Heads exposed to the aqueous envrionment outside

• Peripheral proteins

  • Losslely bound to the surface of the membrane

  • Hydrophilic with charged and polar side groups

• Intergral proteins

  • Span the membrane

  • Hydrophilic with charged and polar side groups

  • Hydrophobic with nonpolar side grousp that penetrate hydrophobic interior of bilayer

  • Ex. Transmembrane proteins

• Membrane protein functions:

  • Transport

  • Cell-Cell recognition

  • Enzymatic activity

  • Signal transduction

  • Intercellular joining

  • Attachment for extracellular matrix/cytoskeleton

• Structure—a mosaic of protein molecules in a fluid bilayer of phospholipids

• Held together primarily by hydrophobic interactions—weaker than covalent bonds

• Most lipids and some proteins can shift and flow along the surface of the membrane or across the bilayer

• Cholestrol (steroid) is randomly distributed/wedged between phospholipids in the membrane of eukaryotes

  • Regulates bilayer fluidity under different environmental conditions

• Carbohydrates- diversity and location of carbodydrates and lipids enable them to function as markers/identifiers

  • Glycoproteins- one or more carbohydrates attached to a membrane protein

  • Glycolipids- lipid with one or more carbohydrates attached

Topic 2.5 Membrane Permeability

• Selective permeability is a consequence of membrane structure

  • Smaller molecules pass freely

  • Hydrophilic substances such as large polar molecules and ions CANNOT freely move across the membrane

  • Hydrophilic substances move through transport proteins

    • Channel Proteins- a hydrophilic tunnel spanning the membrane that allows specific target molecules to pass through

    • Carrier Proteins- Spans the membrane and change shape to move a target molecule from one side to another

    • Small polar molecules like H2O can pass through directly in small amounts

• Cell Walls act as a structural boundary:

  • Protects and maintains the shape of the cell

  • Prevents against cellular rupture when internal water pressure is high

  • helps plants stand up against the force of gravity

• Cell Walls act as a permeable boundary

  • Plasmodesmata- small holes between plant cells allow the transfer of nutrients, waste, ions

• Cell Wall- comprised of complex carbohydrates

  • Plants- Cellulose (Polysaccharide)

  • Fungi- Chitlin (Polysaccharide)

  • Prokaryotes- peptidoglycan (polymer consisting of sugar and amino acids)

Topic 2.6 Membrane Transport

• Concentration gradient

  • When a solute is more concentrated in one area than another

  • Membrane separates two different concentrations of molecules

• Passive transport:

  • Net movement of molecules from high to low without metabolic energy like ATP needed

  • Primary role in import of materials and export of wastes

• Active Transport:

  • Direct input of energy to move molecules from low to high concentration

• Endoctosis requires ENERGY to take in molecules to the cell

• Exocytosis- internal vesicles use energy ot fuse with the plasma membrane and secrete large macromolecuels out of cell

  • Includes: Proteins like signaling proteins, hormones, waste

Topic 2.7 Facilitated Diffusion

• Facilitated Diffusion- movement of molecules from high → low concentration through transport proteins

  • Large and small polar molecules

  • Large quantities of water pass through aquaporins

  • Charged ions (NA+ and K+) require channel proteins

    

• Active Transport- moves molecules AGAINST concentration gradient (low → high)

  • Require carrier proteins called protein pumps

  • Require metabolic energy (ATP)

  • Establish and maintain concentration gradients

• Cotransport- secondary active transport uses energy fom electrochemical gradient to transport two DIFFERENT ions across the membrane through a protein

  • Symport- two different ions transported in the SAME direction

  • Antiport- two different ions transported in the OPPOSITE direction

• Cell membrane allows for formation of gradients

  • Electrochemical gradient

    • Type of concentration gradient

    • Membrane potential: electrical potential difference (voltage) across the membrane

  • Membranes may become POLARIZED by the movement of ions across

    

  • Ex. Sodium-Potassium (Na+/K+) Pump contributes to the maintenance of the membrane potential

    • 3 sodium ions pumped for every 2 potassium ions pumped to establish concentration gradient

Topic 2.8 Tonicity and Osmoregulation

• Osmosis- diffusion of free water across a selectively permeable membrane

  • Move larger quantities of water via aquaporins

• Osmolarity- total solute concentration in a solution

  • Water has high solvency

  • Solute- being dissolved

  • Solvent- dissolves a solute

  • Solution- uniformed mixture of one of more solutes dissolvd in a solvent

• Tonicity- measurement of the relative concentration of solute between two solutions (in and out of the cell)

  • Internal cellular environments can be hypotonic, hypertonic, or isotonic to external environments

  • Hypertonic- MORE solute, less solvent

  • Isotonic- equal concentrations

  • Hypotonic- less solute, more solvent

• Water moves by osmosis into area with higher solute concentration

  • Water concentration and solute concentrations are inversely related

  • Water would diffuse OUT of a hypotonic environment (less solutes) into a hypertonic one (more solutes) OR high water potential to low water potential

    • Solutes diffuse along their own concentration gradients from hypertonic environment to hypotonic

  • When a cell is in an isotonic environment a dynamic equilibrium exists with equal amounts of water oving in and out of the cell at equal rates—no net movement of water

• Osmoregulation

• In plant cells it maintain water balance and allows control of internal solute composition/water potential

  • Environmental hypertonicity- less cellular solute and more cellular water → Plasmolysis- water leaves the cell

  • Isotonic- Equal solute and water → Flaccid plant cell

  • Environmental hypotonicity- more cellular solute and less cellular water → Turgid

• Turgidity- The optimum state for plant cells

  • Cell wall helps maintain homeostasis for plant in environmental hypotonicity

    • Osmotic pressure high outside of the plant cell (hypotonicity)

    • Water flows into the plant vacuoles via osmosis → vacuoles expand and press against cell wall

    • Cell wall expands until it exerts pressure back on the cell → Turgor Pressure

• Osmoregulation in animal cells maintains water balance and allows control of internal solute composition/water potential

  • Environmental hypertonicity- Less cellular solute more cellular water → shriveled

  • Isotonic solution- equal solute and water → normal state

  • Environmental hypotonicity- more cellular solute less cellular water → lyse (bursting)

Graphing

• Characteristics:

  • Title- experiment details and what is measured

  • Labeled axes with units

  • Scaling—unifrom intervals; scale large enough to analyze data and scale numbers on grid lines

  • Identifiable lines/bars

  • Trend line- line of best fit shows overall direction/pattern of data

• Line graph

  • Reveals trends or progress over time for multiple groups/treatments

  • Tracks changes over time, concentrations, etc.

• Scatterplot (X Y Graph)

  • Determine relationships between two different things

  • Compare two variables that may/may not have linear relationship

• Histogram

  • How values in data are distributed across equal intervals

  • Explore relationships between two or more variables

• Bar graphs

  • Comparing multiple groups/treatments

• Box and Whisker

  • Shows variability in sample

  • Compare distributions in relation to the mean

• Dual Y*

  • Represent relationship between two dependent variables

Water Potential

• Water potential measures TENDENCY of water to move via osmosis

  • Calculated from Pressure Potential and Solute Potential

    • Water potential = pressure potential + solute potential (measured in bars)

      

• Moves from area of HIGH → LOW water potential areas

  • More negative/lower water potential = more likely water moves INTO the area

• Water potential of PURE water has a value of ZERO in an open container

• Osmoregulation and Water Potential

  • Increasing amount of solute = Decrease in solute potential / decrease in water potential

  • Increasing water potential = Increase in PRESSURE potential

    • Decreasing pressure potential = Decrease in water potential*

• In an open system, pressure potential is zero, so water potential is equal to the solute potential

• 

Topic 2.9 Mechanisms of Transport

• Diffusion- Movement of molecules from high → low concentration

  • Small nonpolar molecules pass freely (O2, CO2, N2)

  • Small amounts of very small polar molecules also diffuse

• Facilitated Diffusion- movement of molecules from high concentration to low concentration through transport proteins

  • Large and small polar molecules

  • Charged ions (Na+, K+) require channel proteins

• Large quantities of water move via aquaporins

  • Differences in relative solute concentrations facilitates osmosis

• Active transport- move molecules/ions against concentration gradient from low → high concentration

  • Protein pumps are carrier proteins in active transport

  • Require metabolic energy (ATP)

  • Establishes and maintains concentration gradients

• Endocytosis- Cell uses energy to TAKE IN macromolecules/particulate matter by forming new VESCICLES derived from the plasma membrane

  • Phagocytosis- Cell engulfs/eats large particles then fuses with lysosomes to produce digestive enzymes to break down materials; common in immune cells

  • Pinocytosis- drinking/uptake of extracellular fluid with dissolved substances

  • Receptor-mediated endocytosis- Selective—receptor proteins on the membrane capture specific target molecules

• Exocytosis- internal vescicles use energy to FUSE with plasma membrane and secrete macromolecules OUT of the cell

Topic 2.10 Compartimentalization

• Cells have a plasma membrane that allows them to establish and maintain internal environments different from external environments

• Eukaryotic cells have additional internal membranes/membrane-bound organelles that compartmentalize the cell

• Cellular compartments allow for various metabolic processes and specific enzymatic reactions ot occur simultaneously → increased cell efficiency

• Membrane minimizes competing interactions

  • Example:

  • Hydrolytic enzymes of lysosome function at an acidic environment

  • With this compartmentalization, inside of lysosome can maintain a more acidic pH and allow for efficient hydrolysis to occur while the rest of the cytoplasm can remain a more neutral environment

  • May lead to cell damage/death if membranes around lysosomes were to burst as it would lead to the release of hydrolytic enzymes released into the cytoplasm that would digest important cellular materials/molecules

• Mitochondria membrane folding maximizes surface area for metabolic reactions to occur

  • Electron transport and ATP synthesis occur in mitochondrial membrane

  • Folding of inner membrane increases surface area allowing MORE ATP to be made

• Chloroplasts membrane folding maximizes surface area for metabolic reactions to occur

  • Thylakoids highly folded membrane compartments that increase the efficiency of light dependent reactions in the chloroplast

Topic 2.11 Origins of Cell Compartmentalization

• Both eukaryotes and prokaryotes have a plasma membrane that separates their internal environment from their surroundings

• Prokaryotic cells have an internal nucleoid region containing its genetic material while eukaryotic cells store genetic material in a membrane-bound nucelus

  • Nucelus and other internal membranes (ER) theorize to have formed from the infoldings of the plasma membrane

  • Mitochondria evolved from previously free living prokaryotes via endosymbiosis

    • A free living aerobic prokaryote engulfed by anaerobic cell

    • The prokaryotic cell did not get digested but eventually formed a symbiotic arrangement

    • Over time engulfed cell lost some of its independent functionality and became the mitochondria

  • Chloroplast evolved similarly

    • Free-living photosynthesic prokaryote engulfed by another cell and formed a mutually beneficial arrangement then lost its independent functionality over time to become the chloroplast

• Similarities

  • Both have a double membrane-regulate passage of materials into and out of cell to maintain a stable internal environment

  • Both have their own circular DNA encoding genetic information and can reproduce similarly to prokaryotes

  • Both contain their own ribosomes that synthesize proteins