Topic 5 - Respiratory system (respiratory pigments) [Part 1]

What are the four respiratory pigments

  • hemoglobin (red)

  • chlorocruorin (green)

  • hemerythrin (violet)

  • hemocyanin (blue)

which animals use it as part of their circulatory system

  • hemoglobin (red)

    • humans

    • most vertebrates

    • some invertebrates

  • chlorocruorin (green)

    • segmented worms - earthworms + leeches

    • marine worms (bristleworms)

  • hemerythrin (violet)

    • certain marine invertebrates - bottom dwelling worms

    • brachiopods

  • hemocyanin (blue)

    • many mollusks - chitons, many gastropods (snails + slugs)

    • cephalopods (octopus + squid)

    • arthropods (crustaceans - lobster, shrimp)

    • arachnids (spiders + scorpions)

    • horseshoe crab

determine if each pigment uses iron or copper when binding with oxygen

  • hemoglobin (red) → iron

  • chlorocruorin (green) → iron

  • hemerythrin (violet) → iron

  • hemocyanin (blue) → copper

determine colour of pigment when oxygenated

  • hemoglobin (red) → bright red

  • chlorocruorin (green) → darker green

  • hemerythrin (violet) → violet-pink

  • hemocyanin (blue) → blue

determine colour of pigment when deoxygenated

  • hemoglobin (red) → dark red

  • chlorocruorin (green) → light green

  • hemerythrin (violet) → colourless

  • hemocyanin (blue) → colourless

define porphyrin

  • a heterocyclic ring that holds an iron ion - part of the heme group → polypeptide subunit

list the six coordination bonds that help anchor iron in heme of one subunit

  • 4 bonds total - from nitrogen atoms of porphyrin

  • 1 bond total - from nitrogen atom associated with histidine amino0acid residue of hemoglobin

  • 1 bond total - from oxygen when hemoglobin is oxygenated

differentiate between T-state and R-state hemoglobin

T-state (tense)

  • interactions between globulin subunits are stronger (compared to R-state)

  • oxygen affinity is lower in this state (is bonded less tightly - easier to release)

  • is deoxy-Hb

  • polypeptide subunits wrap tightly around the heme group - making it difficult for oxygem to gain access to iron → results in oxygen bind to be weaker

R-state (relaxed)

  • oxygen affinity is higher

  • oxy-Hb

  • polypeptide subunits are wrapped loosely around the heme group → easier for oxygen to gain access to iron (Fe2+)

Draw out a typical oxygen-adult hemoglobin equilibrium curve

Cooperative Binding (Positive Cooperativity): Hemoglobin is a tetramer, consisting of four subunits, each containing a heme group that can bind one oxygen molecule.

  • Initial Low Affinity (T-State): Initially, hemoglobin is in a "tense" (T) state with low affinity for oxygen.

  • Conformational Shift (R-State): Once the first oxygen binds, the iron atom moves into the plane of the porphyrin ring, initiating a structural shift in the entire protein to a "relaxed" (R) state.

  • Increased Affinity: This transition increases the affinity of the remaining heme groups, making it easier for the second, third, and fourth oxygen molecules to bind

*make sure to label the axis correctly when recreating the graph

  • represents how a small change in partial pressure of oxygen can result in a large change in deliver of oxygen

identify the scientific name of the shape of curve and explain why this curve has this particular shape

  • sigmoidal shape

  • due to co-operative binding of oxygen to hemoglobin

Explain what a left Bohr shift means in terms of oxygen binding capacity with hemoglobin

Bohr shift - a physiological phenomena in which factors can affect the loading or unloading of oxygen by hemoglobin

Bohr shifts to left → oxygen binds strongly to hemoglobin

Bohr shifts to right → oxygen is released readily by hemoglobin

Determine what causes a left Bohr shift in relation to pH, blood CO2 levels, temperature and 2,3-bisphosphoglycerate levels

  • increase in pH

  • decrease in blood CO2 levels

  • decrease in temperatures

  • decrease in 2,3-bisphophoglycerate levels

Draw out a typical oxygen-fetal hemoglobin equilibrium curve

Differentiate between the structure of fetal and adult hemoglobin

fetal hemoglobin - 2 alpha chain + 2 gamma chains

adult hemoglobin - 2 alpha chain + 2 beta chains

Explain why fetal hemoglobin has a higher oxygen binding affinity compared to adult

hemoglobin

  • has 2 gamma chains that binds less strongly (compared to the beta chains) to 2,3-bisphosphoglycerate (2,3-BPG), a molecule that reduces oxygen affinity

Draw out a typical oxygen-myoglobin equilibrium curve

Be able to correctly identify the scientific name of the shape of curve, and why this curve has this particular shape

  • shape of myoglobin curve - hyperbolic

  • oxygen-myoglobin equilibrium is on the left - affinity of oxygen bound to myoglobin is greater than hemoglobin

Differentiate between the structure of myoglobin and adult hemoglobin

  • myoglobin

    • heme-containing respiratory pigment

    • monomeric protein

    • binds to oxygen more tightly than hemoglobin does

State the location of myoglobin

  • founded in striated muscle tissues (skeletal and cardiac)

  • plays a part in storing oxygen at high concentration inside muscle cells - needed for movement

Describe which types of animals has myoglobin (especially why diving animals

require higher levels of myoglobin

  • vertebrates

    • reptiles

    • amphibians

    • mammals

    • fish

  • higher concentrations of myoglobin allow organisms to hold their breath for a longer period of time

    • diving mammals (ie. whale + seals) have muscles with particularly high abundance of myoglobin

Describe how carbon monoxide affects binding of oxygen to adult hemoglobin

  • Carbon monoxide binds to hemoglobin with affinity that is about 240 times greater than that of oxygen

  • binds similarly to oxygen at the same site of hemoglobin - small quantities of CO effectively displace oxygen and stabilize the R-state

  • carbon monoxide binds at lower capacities of hemoglobin - by filling active sites

  • shifts equilibrium towards R-state → Bohr shift to left

  • oxygen carried by Hemoglobin is less likely to be released at the tissues - reduces the toxic effects of carbon monoxide

  • carbon monoxide (CO) drastically reduces oxygen binding to hemoglobin by binding to the sites with 240 times greater affinity - > decreases oxygen carrying capacity

  • when carbon monoxide binds to the hemoglobin → makes the remaining oxygen attached to the hemoglobin have higher affinity → harder to release

Oxygen-Haemoglobin Dissociation Curve • LITFL • CCC Ventilation