Section 6

GENERAL CELL STRUCTURE

• Adaptation vs. Cellular Level: Marine organisms must adapt to changes in ocean conditions, beginning at the cellular level.
• Light Microscopes:
  • Specimen is placed on a slide.
  • Magnification is determined by the objective lens and eyepiece.
  • Dyes (e.g., methylene for animals, iodine for plants) are used.
  • Resolution: Smallest distinguishable distance between points, determined by light wavelength; maximum resolution for light microscopes is 200 nm.

ELECTRON MICROSCOPES

• Utilize electron beams with high resolving power (< 1 nm; up to 200,000x magnification).
• Lenses are electromagnets and images are displayed on screens.
• Specimens are in vacuums to prevent electron scattering; heavy metals are used for staining.

LIGHT VS ELECTRONS

PLANT CELLS VS ANIMAL CELLS

• Animal Cell Components:
  • Cell Membrane, Mitochondrion, Centriole, Ribosomes, Endoplasmic Reticulum, Nucleus, Nucleolus, Chromosome, Vacuole, Golgi Apparatus, Cytoplasm, Flagellum (in some).
• Plant Cell Components:
  • Cell Wall, Chloroplast

ORGANELLES OF A CELL

• Components include:
  • Cell Surface Membrane
  • Nucleus
  • Rough & Smooth Endoplasmic Reticulum
  • Ribosomes
  • Golgi Body
  • Mitochondria
  • Chloroplast
  • Cell Wall
  • Large Vacuole

CELL SURFACE MEMBRANE

• Structure: Semi-permeable outer membrane controlling movement and responding to hormones.
• Composition:
  • Phospholipids: Glycerol phosphate (hydrophilic head) with two fatty acids (hydrophobic tails).
  • Proteins: Carrier and channel proteins facilitating transport; cholesterol regulates fluidity (low temp - maintains fluidity, high temp - prevents excess fluidity).

PHOSPHOLIPID BILAYER

• Components:
  • Glycoproteins, Glycolipids, Integral and Peripheral Proteins.
• Fluid Mosaic Model: Proteins embedded within the phospholipid bilayer, facilitating molecular movement.

NUCLEUS

• The primary organelle housing DNA (chromatin made of DNA and proteins), encompassing the nucleolus responsible for ribosomal RNA production.

ENDOPLASMIC RETICULUM (ER)

• Rough ER: Ribosomes situated here, involved in protein production.
• Smooth ER: Lacks ribosomes; responsible for synthesizing steroid hormones (e.g., testosterone).

RIBOSOMES

• Composed of RNA and proteins, essential for protein synthesis. Found free in cytoplasm or on rough ER.

GOLGI BODY

• A stack of membranes (cisternae) modifies proteins received from rough ER before sending them to the cell membrane in vesicles for secretion.

MITOCHONDRIA

• Known as the powerhouse of the cell, it produces ATP through aerobic respiration; has a double membrane with inner folds (cristae) and contains ribosomes and DNA.

CHLOROPLAST

• Unique to plant cells, involved in photosynthesis; contains stroma (liquid) and thylakoids (light-dependent reactions).

CELL WALL

• Present in plants (and some fungi/bacteria), made of cellulose, provides structural support, and prevents lysis due to turgor pressure.

LARGE VACUOLE

• Found predominantly in plant cells; storage of cell sap and maintenance of turgor pressure.

MAGNIFICATION FORMULA

• M = rac{I}{A} where M = magnification, I = image length, A = actual length.
• Example: A cell's actual length is $81.8 ext{ μm}$, with an image measurement of $90 ext{ mm}$ (or $90,000 ext{ μm}$); magnification can be calculated as M = rac{90,000}{81.8}
  ightarrow M ext{ approximately } 1100.

ACTIVE AND PASSIVE TRANSPORT

• Active Transport: Requires energy ( ATP) as it moves substances against a concentration gradient.
• Passive Transport: Does not require energy, occurs along the concentration gradient.

DIFFUSION

• Diffusion: Movement from high to low concentration (passive).
• Facilitated Diffusion: Movement of polar substances through protein channels.
• Osmosis: Movement of water from higher to lower water potential across a membrane.

OSMOSIS TERMINOLOGY

• Hypertonic: Higher solute concentration.
• Hypotonic: Lower solute concentration.
• Isotonic: Equal solute concentration.

SURFACE AREA TO VOLUME RATIO

• Higher surface area to volume ratio enhances diffusion rates. Thinner and larger surface area leads to better gas exchange.

GASEOUS EXCHANGE IN MARINE ORGANISMS

• Facilitated by the interaction of temperature, pressure, and salinity.
• Diffusion affected by concentration gradients and distance.

CIRCULATORY SYSTEM IN FISH

• Blood delivers O2 and removes CO2, pumped through gills to exchange gases.

RAM VENTILATION

• Water flows through gills while the fish swims, utilizing no energy for muscle contraction.

PUMPED VENTILATION

• Water is actively pumped over gills, requires energy; adjustments can be made based on water O2 levels.

OSMOREGULATION

• Marine organisms regulate internal salinity; stenohaline (narrow tolerance) vs. euryhaline (wide tolerance).

OSMOREGULATORS & OSMOCONFORMERS

• Osmoregulators: Maintain constant internal osmotic pressure (ex: bony fish).
• Osmoconformers: Internal salinity matches external environment (ex: mussels).

SALMON AND EELS

• Salmon: Euryhaline, alternating between freshwater and saltwater, adjusting ion pumps as necessary.