oxygen and metabolism Flashcards
aerobic Cellular respiration
Process that converts food energy (glucose) into cellular energy adenosine triphosphate (ATP)
ATP generated from AEROBIC respiration: - Glycolysis 2 ATPs,
- Krebs cycle 2 ATPs,
- Oxidative phosphorylation via electron transport chain (34 ATPs)
Anaerobic Cellular respiration
, Glycolysis converts glucose to pyruvate which is then converted to Lactate
stored as potential energy for when O2 conditions improve, but can create O2 debt to process with ATP (So, energetically expensive,…
High Lactate concentrations can cause glycolysis to stop completely
Goldfish (cypriniformes), can convert lactate to alcohol for more energy, which helps them tolerate low O2 environments
Water as respiratory medium
H2O has a much lower concentration of O2 than in air
•The concentration/percent saturation of O2 in H2O ,decreases with increasing temperature which is related to gas solubility (i.e., PV=nRT)
• O2 also decreases with increasing solutes in H2O (e.g., freshwater 25% more O2 than salt water)
• So, harder for fish to breath in warm salty than in cold fresh, H2O
oxygen in water dephs
O2 concentration in most natural waters are not homogenous, tends to be higher near the surface
low O2, fish smove to surface areas and use “aquatic surface respiration” (ASR), as an adaptive response
High viscosity of water relative to air means greater proportion of O2 used to power breathing in water (10%) than in air (1- 2%). So, breathing water is less efficient)
Cutaneous respiration
Gas exchange across the surface of the skin,
Can make up to 84 % of gas exchange occurring in Chinook salmon larvae and fry
As fish increase in size, efficiency of this strategy decreases because ratio of surface area to vol ratio decreases so its harder to absorb oxygen through skin as only way
Fick’s law of diffusion:
it’s to maximize diffusion
r (rate of diffusion) = diffusion constant x surface area x pressure gradient /diffusion distance
How to maximize rate of difusion (ficks law)
to maximize rate of diffusion you want either high SA and pressure gradient or low diffusion distance
GILLS
Specialised structures for efficient extraction of O2 from water • Large surface area with thin epithelium for gas exchange
maximize respiration by large surface area, small diffusion distance(very thin so minimized) (ficks law)
GILL STRUCTURE
Gill arches (typically 3-7 pairs) bony structure supporting the gills filaments (lamellae)
• Each Gill arch typically has spiky gillrakers used for food retention during feeding
• Opposite side to the gillrakers, has thin gill filaments (primary lamellae) perfused with small blood vessels necessary for gas exchange
longer gill filaments means..
more oxygen intake
Gill blood vessels
Large blood vessels pass through the gill arches, while thinner ones pass through and along the primary lamellae (filaments)
• Each filament has ridges called secondary lamellae with even thinner capillaries passing blood in OPPOSITE direction to the water flow
Why would tuna have smaller diffusion distance than a bony fish?
have smaller diffusion distance because they’re always moving so use a lot more oxygen
Countercurrent gas exchange
Water passing over gills has high dissolved O2 relative to blood and will naturally diffuse down its concentration gradient into the blood
• Secondary lamellae thinness and blood direction relative to water maintains lower O2 diffusion gradient in blood through the trajectory making process highly efficient
if they were going in the same direction there’d be less diffusion happening because the gradient would be less. soo good its oppposite
GILL IRRIGATION
•pump water by expansion-contraction of buccal cavity (before gills) and opercular chamber (past the gills)
• Muscles contract to drop branchiostegal rays generating negative pressure in buccal cavity
• Mouth opens and opercular valves shut to draw water in
• Mouth shuts, opercular valves open creating low pressure in opercular chamber
• Water rushes over gills in counter-current direction
RAM ventilation
type of gill irrigation
swimming with mouth and opercula valves open to pass water over gills
• Forward movement of fish keeps water moving in proper counter-current directions over gills
• More efficient way to ventilate gills because the work is done by swimming muscles already in use
• Most efficient in strong swimmers, but used by many species in combination with pumping
Air breathing in fish
65 independent evolutionary
Facultative air-breathers – breathe air only to supplement gills(e.g., Gouramis and bowfins)
Obligate air breathers – must breathe air or suffocate (e.g., lungfishes)
Air breathing structures in fish
3 main features
- The gut (stomach, swimbladder, and true lungs)
- Head structures (pharynx, gills, and opercula)
- Skin
Gas transport
O2 dissolves in the blood plasma and travels the body, but most of it is bound to Hemoglobin
Protein with 2-⍺ and 2-𝛽 AA chains and 4 prosthetic Fe2+ groups a high but dynamic affinity for O2
• Exhibits cooperative binding
Hemoglobin (Hb)
impacted by chemical environment
•Has high affinity for O2 at high pH (7+), but affinity lowered
when pH decreases (1-5)
• A right shift in Hb saturation curve(s) due to the lowering of pH is called the Bohr effect
•Very low pH conditions (1-2) can change Hb configuration and decrease the ability of the molecule to reach saturation, which is called the Root effect
(on saturation curve, right shift is bohr effect, down shift is root effect, happen together)
Hemoglobin and temperature
Hb affinity and saturation rate is also affected by ambient temperature
• Hb affinity for O2 also differs among species
high temp there’s less oxygen and hemoglobin doesn’t work as efficiently
Metabolic rate
Metabolism is sum total of biochemical processes taking place in organism and impacted by various factors
Rather than take all into account – assess standard metabolic rate (SMR)
USE Routine metabolic rate (RMR) – metabolic rate under fish’s routine conditions better metric
Maximum metabolic rate (MMR)
uses O2 as rapidly as it can take it up
MMR – SMR (or RMR) = metabolic scope predicts metabolic limits of species at given temperature
Factors raising the SMR / RMR without changing MMR decreases metabolic scope, which decreases species resilience and adaptability
Expanding metabolic scope can be achieved by acclimatisation (adjustment)– but not always possible
What are some adaptations to reduce metabolic costs of swimming:
(Assessing O2 consumption during maximum swimming velocity used as proxy for MMR)
body shape, size, flexion
