Physiology of Marine Organisms - Chapter 6 Notes

History of Cell Structure

• Robert Hooke

  • Used a light microscope to view thin slices of cork.

  • Observed tiny, repeated units.

• Marcello Malpighi & Nehemiah Grew

  • Described and drew plant tissue.

• Antony van Leeuwenhoek

  • Drew and detailed animal cells.

• Matthias Schleiden & Theodor Schwann

  • Proposed the cell theory.

  • "All living things are composed of cells, the smallest structural unit of an organism."

• Ernst Ruska

  • Developed the first electron microscope in 1931.

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Microscopes

• Light Microscopes

  • Maximum magnification: ~1500x.

  • Use a light source (bulb or mirror) to shine through a specimen, focusing with glass lenses.

• Electron Microscopes

  • Maximum magnification: >200,000x.

  • Send a beam of electrons.

• Comparison

  • Light Microscope:

    • Lower Resolution (Max 200nm)

    • Lower Magnification

    • Cheaper to Purchase and Run

    • Portable

    • Staining is less harsh

    • Living specimens can (sometimes) be used

    • Colours are visible

    • Less skill is required

  • Electron Microscope:

    • Higher Resolution (Max 0.2nm)

    • Higher Magnification

    • More Expensive to Purchase and Run

    • Large (Often takes up a room)

    • Harsh treatment of specimens causes Damage

    • Living species cannot be used

    • No colour is visible

    • Only skilled operators can use

Resolution and Magnification

• Magnification: Enlarging.

  • Total magnification is calculated by multiplying all the lens magnifications together.

  • Staining: Binds to structures to help see them more clearly.

    • Methylene blue: For animal cell nuclei.

    • Iodine: Makes starch structures black.

• Resolution (Resolving Power): Level of Detail.

  • The distance between objects that can be seen clearly in the field of view.

  • Depends on the wavelength of light used.

  • $Resolution = wavelength / 2$

  • The best a light microscope can achieve is ~200nm.

Cell Organelles

• Cell membrane

• Nucleus

• Rough & Smooth ER

• Ribosomes

• Golgi body

• Mitochondria

• Chloroplasts

• Cell Wall

• Vacuole

Cell Membrane

• Found in cells themselves, nuclei, and organelles (Golgi, ER, etc.).

• Selectively permeable: Controls the movement of substances.

• Receives instructions from other cells (e.g., hormone binding).

• Other specializations/structures (e.g., microvilli for absorbing substances).

• Structure of the Cell Surface Membrane/ Fluid-mosaic Model

  • Phospholipids

  • Proteins

  • Cholesterol

  • Proteins are "fluid" in the bilayer, can diffuse through, and are not static.

Phospholipids

• Phospholipid Bilayer

• Made up of a glycerol backbone attached to:

  • 2 fatty acids (Non-polar/hydrophobic).

  • Phosphate (Polar/Hydrophilic).

• When phospholipids are mixed in water, tails move together and exclude water, creating a Micelle.

Proteins

• Embedded in the bilayer like tiles (or icebergs).

• Intrinsic Proteins: Extend through the bilayer.

  • Used in transporting substances in/out.

  • Channel/Carrier Proteins:

    • Allow hydrophilic substances to pass through the hydrophobic membrane.

    • Typically for specific molecules (i.e., selective).

• Extrinsic Proteins: Bound to the surface of the membrane.

  • Receptors for hormones to bind to, carrying a message to the cell.

  • Molecules to bind to other cells for recognition.

  • EX: Glycoproteins- proteins with carbohydrates connected

Cholesterol

• Small lipid molecule found between tails of phospholipids.

• Maintains fluidity:

  • Low Temps- keeps membrane fluid

  • High Temps- prevents from getting TOO fluid

Nucleus

• Large organelle, usually visible with both light & electron microscope

• Present in animal and plant cells

• Contains Chromatin: nucleic acids (DNA/RNA) and proteins bound together

  • Dark- Heterochromatin:

  • Light- Euchromatin: where genes are active

• Nucleolus: where ribosomes are synthesized

• Nuclear envelope is also a double membrane

Endoplasmic Reticulum (ER)

• The cytoplasm is filled with this network interconnecting membranes

• Rough ER (rER)

  • The majority

  • Many flat membranes called cisternae

  • “Rough” due to ribosomes on its surface (Which synthesize proteins)

  • Proteins packed up, passed through rER until “Budded off” as vesicle, and moves to the Golgi

    • All proteins that are secreted/released by the cell are made this way

• Smooth ER (sER)

  • Less abundant (in most cells) and no ribosomes

  • Does not synthesize proteins

  • Main function is synthesizing steroid hormones (EX: oestrogen & testosterone)

    • Testis & Ovary cells have much more sER

Ribosomes

• Small organelles found in all cells, made of protein and RNA

  • Bacterial ribosomes are slightly smaller

• Main function: PROTEIN SYNTHESIS

• Found free in the Cytoplasm and attached to rER

• Cells that need to produce lots of Protein need lots of Ribosomes (and in turn lots of rER)

Golgi Body/Golgi Apparatus

• Also made up of stacks of cisternae

• Involved in chemical modification of protein

  • The proteins have other chemical groups add (such as Carbohydrates)

• All secreted & membrane proteins pass through

• Receives vesicles from rER on Cis Face

• Vesicles of modified proteins leave the Trans Face

• Move to membrane, fuse and release the proteins

• Produces cell wall substances

• Produce Lysosomes (small organelles that contain digestive enzymes)

Mitochondria- “The Powerhouse of the Cell”

• Main function: production of ATP via aerobic respiration in both animals and plants

• Cells with high energy needs (EX: Muscles cells) tend to have high amounts

• Double membrane

  • Inner membrane folded into a cristae structure, surrounded by a fluid enzyme matrix

  • Matrix contains ribosomes and chromosomes (Suggesting that they were once their own organisms living symbiotically inside other bacteria)

Chloroplasts

• Only found in plant cells and carry out photosynthesis

• Large organelles, easily visible with light microscopes

• Double membrane, Enclosing an inner liquid stroma, containing enzymes and sugars

  • Thylakoid membranes in the stroma, stacked in structures called grana with large surface areas

  • Grana contain pigments, like chlorophyll, that trap light energy for photosynthesis

  • Starch grains found in stroma

• Chloroplasts contain DNA and ribosomes (sound familiar??)

Cell Wall

• Not in Animal cells (But can be in plant, fungi, bacteria)

• AICE Marine will only consider the cellulose cell wall of plants

• Provide strength and structure, stopping cells from bursting from excess water

• The main component is; Cellulose- is a polysaccharide polymer of sugar called β-glucose

  • Long, straight, linear molecule that can form hydrogen bonds with other Cellulose strands

  • Cellulose molecules bond to form Microfibrils, microfibrils bond to form fibrils, the number of cellulose molecules in fibrils make them strong.

Cell Wall- Layers

• Outer layer of Cell Wall, Middle Lamella

  • composed of calcium pectate (the glue that binds neighboring cells together)

  • This also helps jams to set

• Primary Cell Wall- First layer produced

  • All fibers align in one direction

  • Mixed with calcium pectate and hemicelluloses to make firm

• Secondary Cell Wall- Produced after plant cells have finished growing

  • Organized in different directions from primary, for extra support

  • In some species can contain Lignin (wood) or Suberin (Cork)

(Large Permanent) Vacuole

• Vacuoles are fluid filled sacs of membranes

• Only plants have a Large Permanent Vacuole

  • Surrounded by a Tonoplast Membrane

• Storage of Sap

  • Salts and Sugars

  • Low water potential ($H_2O$ encouraged to enter plant cell) maintains pressure, helps in support

• Storage of Pigments, Waste, or Toxins

  • Pigments give flowers color, often stored with waste products

  • Some plants separate chemicals in cytoplasm from chemical in the vacuoles

  • EX: Onions-

    • Enzyme Allinase in vacuole

    • Allinin in cytoplasm

    • React to form Allicin, an eye irritant, when the cells are broken

Drawing rules - For cells (~same as those for organisms)

• Only draw what you see

• Use a sharp pencil

• Draw Guidelines with ruler

• Use unbroken, firm lines

• Do not shade or sketch

• Include scale bars and magnification if appropriate

• Print all labels

• Give diagram a title

• Do not draw diagram that is too small

Calculating Magnification

• You can calculate the magnification of photomicrographs and electromicrographs

• You can use to determine the size of a cell or structure

• Calculating from a Diagram:

  • Measure the length of the image with a ruler

  • Ensure same units for actual and image length

  • Use formula to calculate

• Example Calculation-

  • The elodea cell X has an actual length of 81.8 µm

  • The image length of the photomicrograph is 90mm
    *Answer: Magnification= x1100

Calculating Actual Length

• Calculating from a Diagram with Magnification:

  • Measure the length of the image with a ruler (mm)

  • Rearrange the magnification formula to calculate the actual length

  • Change units into micrometers (µm)

• Example Calculation-

  • The mitochondria has an image length of 60mm

  • The magnification of the mitochondria is x40,000

• Calculating from a Diagram with a scale bar:

  • Calculate the magnification

    • Measure the length of the scale bar with a ruler

    • Divide the image length by the scale length (over the scale bar) to get the magnification

  • Measure the length of the image

  • Use the rearranged Magnification formula to calculate actual length

• Example Calculation-

  • Diatom scale bar has an image length of 20mm

  • The actual length of the scale bar is 25µm (as shown)

  • The image length of the diatom is 85mm
    *Answer: (Mag.= x800)=> Actual length= 106.25µm
    *Answer: Actual Length 1.5µm

Interpreting diagrams- Using the structures to tell you about the function

• Lots of mitochondria- suggests it needs lots of energy, maybe a muscle cell

• Lots of Golgi- produces/secretes proteins

• Microville (for surface area) & Mitochondria (to convert energy)- small intestines

Movement of substances- (across membranes)

• Diffusion

• Facilitated Diffusion

• Active Transport

• Osmosis

Diffusion

• Molecules are constantly moving randomly due to kinetic energy

• Diffusion is a PASSIVE PROCESS (no energy) moving based on the concentration gradient

  • High => Low

  • Higher chance of high moving

  • Lower chance of low moving

  • Never “Stops” but becomes equal

• Factors impacting:

  • Temp

  • Concentration Gradient

  • Distance

  • Surface area of exchange

Facilitated Diffusion

• Charged/hydrophilic particles cannot pass through the phospholipids nonpolar tails. (So passive diffusion of these particles cannot happen)

• They can still move across the membrane with the help of special proteins

  • Channel- intrinsic, inner pore where water soluble molecules can pass through, they are selective (EX: Sodium ion channel- will only allow Sodium)

  • Carrier- intrinsic, molecules bind on one side of the membrane, protein changes shape, molecule is transported across the membrane

• Still a PASSIVE process, molecules still only move down the concentration gradient

• The amount of proteins in the membrane is a factor that impacts the rate

Active Transport

• Pumping substances across the membrane using energy, key word ACTIVE

• Against the concentration gradient

• Carried out by carrier proteins, often called “pumps”

  • Molecule binds to one side,

  • ATP binds and is broken down into ADP, releasing energy,

  • changes shape of the protein and moving the substance across the membrane,

  • the protein then returns to original shape

• Can only happen in living, respiring cells

• Cells who do lots of active transport, need lots of mitochondria

Osmosis

• Specific type of diffusion, for Water molecules across a membrane

• Cell membranes poses aquaporins, special proteins for water

• Based on water potential, the potential energy of water in a solution compared to pure water

  • still moves High => Low

  • Pure water has the highest water potential (0 kPa)

  • Dissolving a solute into it will decrease it

• Osmometer- A tool that can model osmosis. A bag consisting of Visking tubing (a selectively permeable membrane for water)

  • Gets placed into tubes of different salinities

Solutions Vs. Cells

• Therms are used to describe solutions water potential compared the cells or tissues of organisms.

• Hypertonic- solution has lower water potential than the cells

  • water pulled out of cells

• Isotonic- solution has the same water potential as the cells

  • no net movement of water

• Hypotonic- solution has a higher water potential than cells

  • passes into cells

Organisms and Osmosis

• As salinities change, living organisms can gain or lose water from their tissues. Causing extensive damage

• Animal Cells:

  • No Cell Wall

  • To much water being drawn in can cause their membranes to burst

  • Losing too much water can cause the cell to die due to chemical reaction stopping

• Plant Cells

  • Cell Wall

  • Cannot burst if too much water gained

  • Turgor pressure gives plants support

  • Losing water pulls membrane away from wall

  • Loss of turgor pressure results in wilting

Gas Exchange

• Organisms need Oxygen for respiration and release Carbon Dioxide as waste

• This is a Diffusive process

• Factors affecting gas exchange

  • Temp

  • Concentration gradient

  • Diffusion Distance

  • Surface Area

• Refers to the exchange of gases across the membranes of gills (And similar structures)

Gas exchange in Marine Organisms

• Gas exchange in water is more challenging than in air

• Oxygen concentration in water is ~40x lower than in air

• In water Oxygen concentration is more variable

  • Higher Temps./Salinities= Less Oxygen

  • Lower Temps./Salinities= More Oxygen

• Water is more dense and more viscous than air.

  • So? =>

• Gills have two openings, an Inlet & Outlet apature

  • Lungs use the same aperture for both.

Size & Shape of Organisms Vs. Gas Exchange

• In order to efficiently exchange gases, large surface area (SA) is needed

• As the size of organisms increase the SA and volume(V) also increase, BUT NOT proportionally

  • Higher SA= higher rate of diffusion

  • Higher V= lower rate of diffusion

• Larger organisms have more cells

  • So?

• Small organisms: No special adaptations

• Larger organisms: Gills, lungs, protrusions, etc.

• Round= Lower SA/V Ratio

• Flat/Folded= Higher SA/V Ratio

Size & Shape of Organisms Vs. Gas Exchange

• In order to efficiently exchange gases, large surface area (SA) is needed

• As the size of organisms increase the SA and volume(V) also increase, BUT NOT proportionally

  • Higher SA= higher rate of diffusion

  • Higher V= lower rate of diffusion

• Larger organisms have more cells: So?

  • Higher demand for Oxygen

  • Higher distance between air and center cells

    • Distance for Oxygen to diffuse becomes too great

• Small organisms: No special adaptations

• Larger organisms: Gills, lungs, protrusions, etc.

• Round= Lower SA/V Ratio

• Flat/Folded= Higher SA/V Ratio

Circulatory System

• The method for delivering/transporting gases around an organism's body

• Red blood cells (haemoglobin)- bind reversibly with oxygen to form oxyhaemoglobin

• Route through Fish-

  • Blood passes through muscles and other tissues in capillaries, the smallest blood vessels. Release oxygen and gains carbon dioxide

  • Blood returns to the heart in Veins

  • Blood is pumped out of the heart in arteries towards the gills

  • Blood passes through capillaries on the gills. Releases its Carbon dioxide and gains Oxygen

  • Blood leaves the gills in the arteries and travels to muscles to deliver oxygen (In Tissues)

Fick’s Law and Gas Exchange Organs

$Diffusion Rate = (Surface Area * Concentration Gradient) / Diffusion Distance$

• Organs follow this rule

• means proportional to

• Ficks Law is used to predict the following common features of gas exchange surfaces

  • Large surface area

  • Steep concentration gradient of Oxygen/Carbon DIoxide

  • Short diffusion Distances

Gas Exchange Example- Coral

• No special Structures, exchanges across body wal

• Simple diffusion only

• SA/V ratio effective enough due to tentacles and increased surface area structures

• Some move tentacles to help move/bring in more oxygenated water

• Some polyps pass oxygenated fluid between themselves, evening distribution

Gas Exchange Example- Grouper/Tuna (Fish Gills)

• Fish take in water through their mouths and pass it over their gills, and forcing it out through their gill opening

• Operculum- a bony gill cover, that can open and close

• Gills are made up of filaments, containing folds (SA) called lamellae full of capillaries

• Lamellae are organized at 90° angles to the filaments

• Fish have different oxygen needs

  • Fast, active swimmers have high demands, high SA, and high respiration rate

    • Tuna, Mackerel, Swordfish (Pelagic, constantly moving)

  • Less active fish have lower needs, lower SA, and often use anaerobic respiration

    • Sole, Plaice, Flounder (Stationary, quick burst predators)

Concurrent VS. Countercurrent Exchange

• Concurrent Exchange:

  • Equilibrium is reached, diffusion stops

• Countercurrent Exchange:

  • Equilibrium not reached, diffusion is constantly taking place

Ventilation Movements

• In order to respire water needs to be passed over the gills

• Methods Used in Fish:

  • Ram Vent.-

    • Fish swim with an open mouth, forcing water over gills, out through opercular opening

    • No Muscle contractions (Force only from forward momentum)

    • No extra energy used/needed

    • Drawback => Fish must keep moving/swimming constantly

    • Sharks, Fast Swimming fish

    • ** Some fish can switch between, EX: Tuna, Ram Vent. at high speeds (high flow over gills) but can switch to Pumped Vent. at lower speeds

  • Pumped Vent.-

    • Use muscles in the buccal cavity (mouth space), to move water over the gills

    • Requires energy, can be very costly

    • Can still respire while not moving, allowing to remain in place

      • Benefits?

    • Adjustable ventilation rates: Faster swimming requires more respiration, meaning more Pumped Vent.

    • Grouper, Goldfish, Majority of fish

-Process of Pumped Ventillaion - Inflow of Water

• Mouth opens

• Volume of buccal cavity increased by muscle contractions and relaxation

  • Lowers the pressure inside the cavity, below external pressure

• Operculum closes as water tries to flow back across gills

Outflow of Water

• Mouth closes

• Volume of the buccal cavity is reduced by muscle contractions and relaxation

  • Pressure inside the cavity rises above external pressure

• Water flows over the gills and the operculum is forces open, allowing outflow of water

-Remember-

• Water always flows from HIGH => LOW pressure

• As V increases, Pressure decreases (And vice versa)

Osmoregulation

• For organisms that live in the ocean, what is their environments water potential?

• Many marine organisms are isotonic to the surrounding water, BUT if salinities change they can still be stressed by water loss/gain

• Stenohaline- organisms that only survive in a narrow range of salinities

• Euryhaline- organisms able to tolerate a wide range of salinities

Osmoconformers-

• Organisms isotonic with the environments salinity

• Do not regulate their internal body salinity, just match the water around them

• Most are stenohaline invertebrates

  • Not tolerant of salinity changes, an stress/die if things change around them

• Mussels are euryhaline osmoconformers (often live in estuaries)

  • When salinity changes, mussels can close their shells tight, seperating body tissues from the water

  • Increase/Decrease the solute concentrations of cells as the external salinity changes

  • Most still have a specific salinity they are restricted to, but have some control over osmoregulation happening

Osmoregulators

• Maintain (using energy) a consistent internal salinity

• Most Bony fish are Stenohaline osmoregulators *In Freshwater Fish

  • Drinks little water

  • Passively absorbs water and loses salt through skin

  • Actively uptakes ions through gills (along with water)

  • Excretes dilute urine
    *In Marine Fish

  • Passively loses water and absorbs salt through skin

  • Drinks ample water

  • Actively excretes ions through gills (along with water)

  • Excretes concentrated urine

Marine Fish

• Water constantly enters through the gills and skin through osmosis

• In order to prevent excess water:

  • Drink small amounts of water

  • Gills pump sodium and chloride ions into the blood fluids, Uses ATP to run pumps

  • Produce lots of dilute urine

Freshwater Fish

• Water is drawn out of the body and salt diffuses into the body

• Constant loss of water can lead to dehydration

• In order to prevent excess water loss:

  • Constantly drink seawater, to replace water loss

  • Sodium & Chloride ions are actively secreted by gills, pumps use ATP

  • Magnesium and Sulfate ions are actively secreted into the urine by kidneys

  • Reabsorption of water by kidneys, produce very concentrated urine

• Low salinity water ● Hypotonic

• High salinity water ● Hypertonic

Euryhaline Fish

• Salmon and Eels are osmoregulators that can tolerate large ranges of salinities

• They change the direction of their ion pumps depending on the salinity of the water around them

• When in salt water:

  • Water is hypertonic

  • Salts pumped out of gills

• When in freshwater:

  • Water is hypotonic

  • Salts pumped into gills