AP BIO Unit 2 Review - Cell Structure and Function

Eukaryotic vs Prokaryotic Cells

P

Bacteria and Archaea

Lack nuclei and other membrane-enclosed organelles

E

Internal membranes

Compartmentalized

allows for concentration gradients
cell components have own function in own space
prevents molecules from roaming freely in the (selective)

Plant and animal cells have most of the same organelles: a nucleus, endoplasmic reticulum, Golgi apparatus, and mitochondria. Some organelles are found only in plant or in animal cells. Chloroplasts are present only in cells of photosynthetic eukaryotes

Both

Ribosomes

Genetic Material

Cytoplasms: inside of a cell where reactions take place

Cytocol: the liquid in a cell

Plasma Membranes

Cellular Components

Chloroplast

Photosynthetic
Membranes contain chlorophyll pigments and e- transport proteins
Plants, algae
Own DNA + evolves independently -> endosymbiotic theory
Double outer membrane
* Intermembrane space
Stroma
  * Fluid
  * outside thylakoid
  * Within the inner membrane
  * Site of Calvin-Benson cycle
    * Carbon fixation reactions of photosynthesis
  * Contains ribosomes + DNA
  * Helps synthesize organic materials from CO2 and H2O
Thylakoid
* Flattened membranous sac
* Light in -> chemical energy
Granum
* Stack of thylakoids
* Function in light reaction of photosynthesis
Plastid
* Family including chloroplasts, chromoplasts, amyloplasts
* In cells of photosynthetic eukaryotes

Endoplasmic Reticulum

Mechanical support, protein synthesis, intracellular transport

Plasma membrane

Bounds all cells
hydrophilic heads and hydrophobic tails
* charged p groups + hydrophobic fatty acid
* Amino acids with charged side groups are hydrophilic. These hydrophilic amino acids associate with the hydrophilic phosphate region of the cell membrane
Bilayer of phospholipids
fluidity
  * cholesterol
    * When temperatures are low, the fluidity of the cell membrane may decrease to a point that makes it nonfunctional. Cholesterol prevents this by packing between the phospholipids in the membrane. This increases the spacing between phospholipids, which increases the fluidity of the membrane
    *
The surface area must be large enough to adequately exchange materials
  * Metabolic requirements set upper limits
  * Surface area increases by n^2, volume increases by n^3
  * Small cells have a greater surface area to volume ratio
  * Increase in volume ->
    * Surface area decreases
    * Demand for internal resources increases
Surface area increases

Plant Cell Walls

Cellulose fibers embedded in other polysaccharides and proteins

Extracellular matrix

Support, adhesion, movement, regulation

RIbosomes

Comprise ribosomal RNA (rRNA) and protein
Synthesize proteins according to mRNA sequence
All forms of life
Free ribosomes in the mitochondrial matrix

Endoplasmic Reticulum

Rough
  * Membrane-bound ribosomes
  * Compartmentalizes
  * Phospholipid factory for the plasma membrane and organelles (endomembrane system)
Smooth
  * Detoxification
  * Lipid synthesis
  * Liver cells

Golgi apparatus

Membrane-bound
Flattened membranous sacs
Modifies and packages proteins
Cis side receives, trans face ships

Mitochondria

ATP synthesis
Mitochondrial matrix
  * Pyruvate oxidation
  * Krebs cycle (citric acid cycle)
  * Enclosed by the inner membrane
  * Contains ribosomes, enzymes, and mitochondrial DNA
    * Own DNA + evolves independently -> endosymbiotic theory
Double membrane
  * Provides compartments for different metabolic reactions
  * Outer smooth
  * inner highly convoluted and folded
    * increases surface area allows for more ATP to be synthesized
    * E- transportation and ATP synthesis occur here
crista
* Infolding of the inner membrane

Lysosomes

Recycle cell's organic materials
Membrane enclosed sacs
Hydrolytic enzymes
* Intracellular digestion

Vacuole

Membrane-bound sac
Food
* Formed by phagocytosis (endocytosis)
COntractile
* Freshwater protists, pump out excess water
Central
* Mature plant cells, hold organic compounds and water
* Fills with water -> pressure to cell wall -> maintain cell shape

Cytoskeleton

Cytoskeleton

Struct support
Motility
Signal transmission
Motor proteins “walk” on

Microtubules

Shape cell
Hollow
Tubulin polymer
Guide organelle movement
Separate chromosomes in dividing cells
Cilia
  * Hair
  * Flutters
  * Brings up mucus
  * The large number on the cell surface
Flagella
* One or few

Microfilaments

Thin rod
2 acetone intertwined
  * Actin interacts with myosin
  * Contract muscle cells
  * Amoeboid (crawling) movement
  * Cytoplasmic streaming (circular flow of cytoplasm within cells)
Muscle contraction, amoeboid movement, cytoplasmic streaming, support microvilli

Intermediate filaments

Diameter between microtubules and microfilaments
coiled
Support cell shape, fix organelles in place

Communication, Transport, and Diffusion

[[Cell junctions[[

Plasmodesmata
  * Perforates cell walls
  * Connects cytoplasm of adj plant cells
  * Lets in water, small solutes, and larger molecules
tight junctions
  * neighboring cells tightly pressed and bound by proteins
  * Continuous seal
  * The barrier prevents EC leaks
Desmosomes
  * Cells -> sheets
  * Anchored by int. Fil. (keratin)
  * Attach muscle cells
Gap/communicating junctions
* Cytoplasmic channel in adj cells
* Membrane proteins surround the pore

^^Most efficient^^

sphere - equal distance all sides
smaller cells - higher surface area to volume ratio

[[Active vs passive transport[[

Active transport requires direct energy because it is against concentration gradients

^^Osmosis^^

Water travels from low solute to high solute density

solute travels from high to low solute density

Hypotonic SOlution: The solution has a lower solute density which causes the cell to gain water

Hypertonic SOlution: The solution has a higher solute density which causes the cell to lose water

Isotonic SOlution: No net movement of water

[[Membrne Proteins[[

Endosymbiont Theory

Membrane-bound organelles evolved from
previously free-living prokaryotic cells
via endosymbiosis.