topic 7 - respiration & gas exchange systems

Aerobic respiration

The cellular process in which cells break down glucose and other organic compounds in the presence of oxygen to produce a large amount of usable energy in the form of ATP, carbon dioxide, and water

Anaerobic respiration

Metabolic process where cells generate energy (ATP) in the absence of oxygen, using an electron acceptor other than oxygen, such as sulfate or nitrate, or by producing fermentation by byproducts like lactic acid or ethanol

Benefits of aerobic respiration

Releases more ATP molecules than anaerobic respiration (28-32 ATP vs 2 ATP)

May have allowed for the evolution of multicellularity and larger organism size

Benefits of anaerobic respiration

Quickly releases energy, and can occur in low oxygen environments

Fick’s law

Describe the net movement of particles from regions of high concentration to low concentration through a process called diffusion

Diffusion

Can occur across the cell membrane or cell wall in unicellular organisms, or across the body wall (like fungi)

To maximise diffusion rate, gas exchange surfaces need to be…

• High surface to volume ratio

• Thin and partially permeable

• Pressure gradient

• Diffusion coefficient which is influence by the molecules weight and solubility of different gas molecules

Structural differences in stomata and guard cells in plants aid in regulating gas exchange

Essential for regulating gas exchange by controlling the size of the pore. The guard cells’ unique shape and internal features, such as differential wall thickness and specialised chloroplasts and tonoplasts, allow them to change volume and turf or pressure.

Change in turgor causes the cells to bend and twist, opening or closing the stomatal pore to balance the need for CO2 uptake

Photosynthesis parenchyma tissue has two types:

• Upper palisade

• Spongey mesophyll cells

Upper palisade

1-3 layers thick, elongated cells where most of photosynthesis occurs

Spongey mesophyll cell

Irregularly shaped cells arranged in such a way that there is plenty of airspace in this lower region of the leaf

Vascular tissue form a highly branched network to supply the rest of the leaf with water and nutrients

Difference between mycelium and and roots

Mycelium is the root-like, vegetative structure of a fungus, composed of microscopic filaments called hyphae

Roots are the specialised organs of a plant for anchoring, absorbing water, and storing energy.

Mycelium (root of fungi)

• Made of thin filaments called hyphae

• Composed of chitin

• Decomposes matter, absorbs nutrients, forms symbiotic relationships

• Grows outward like a web to colonise and decompose

• Heterotrophs - gets energy from organic matter

• Helps form spores for reproduction

Roots

• Made of multicellular tissues

• Composed of cellulose

• Anchors the plant, absorbs water/nutrients

• Grows from the plant‘s root system

• Autotrophic - supports photosynthesis via the rest of the plant

• Does not directly reproduce

Adaptations that allow some small animals to have direct gas exchange across external surfaces

• Having long and thin bodies, by-opting other structures with large surface areas to aid in gas exchange

• Ventilation where gasses are moved across the gas exchange surface, either via body movements or movement of the respiratory structure itself; ensures that the pressure gradient for diffusion is optimised and increases the rate of diffusion across the gas exchange surface

• Circulation where gas is moved to and from the gas exchange surface and the body tissues, this can occur via dissolution into a circulatory fluid like blood or directly via a network of branching tubes

Respiration (process common to all vertebrates)

Glycolysis

• Occurs in the cytoplasm of cells

• Breaks down glucose into pyruvate

• Produces a small amount of ATP and NADH

• Anaerobic (does not require oxygen)

Krebs cycle (citric acid cycle)

• Takes place in the mitochondrial matrix

• Processes pyruvate into CO2, NADH, FADH2, and a little ATP

• Requires oxygen indirectly (as part of aerobic respiration)

Electron Transport Chain (ETC) & Oxidative Phosphorylation

• Happens across the inner mitochondrial membrane

• Uses NADH and FADH2 to pump protons and generate a proton gradient

• Oxygen acts as the final electron acceptor, forming water

• Produces the majority of ATP

Respiratory systems of terrestrial vertebrates

• Have lungs, vast surface areas for gas exchange

• Kept moist by surfactants

• Surfactants reduce surface tension of the lung to aid in the diffusion of gasses

Respiratory system of birds

• Must be capable of high rates of gas exchange, cause they fly

• Lungs do not move

• Ventilated by air sacs

• Pumps air to and from the lungs in specific orders

• Fresh air passes over the gas exchange surfaces during both inhalation and exhalation resulting in a constant supply of fresh air, enabling the bird to experience a near continuous state of gas exchange into the lungs

Respiratory system of fish

• Gills (evolved because water contains much less oxygen than air and is denser and more viscous, making it harder to move across respiratory surfaces)

• Filaments covered in lamellae to increase the surface area for gas exchange

• As water flows over the gill surface, oxygen diffuses form the water into the blood within the gill capillaries

• Carbon dioxide diffuses from the body into the water to be expelled

• Internal gills of fish are particularly efficiently because they employ a countercurrent exchange mechanism where water and blood flow in opposite directions, maintaining a concentration gradient that maximises oxygen uptake and carbon dioxide removal