Respiration and Gas Exchange

Question 1

What is respiration?

Answer 1

process by whch an organism exchanges gasses between themselves and the environment

Answer 2

In order for gas exchange to occur, gases must first be dissolved in water before being able to diffuse across gas exchange surfaces, meaning they must be kept moist

Question 3

aerobic respiration summary

Answer 3

32-38 ATP molecules per cycle
allowed for the evolution of multicellularity
glygolysis, pyruvate oxidation, TCA/Krebs, Oxidative phosphorylation

Anaerobic
not a lot of oxygen
glycolysis and then a recycling of NAD+ etc.

Question 4

What is diffusion

Answer 4

movement of particles from areas of high concentration to low concentration. Across cell membranes or cell wall in unicellular organisms etc.

passive with no expenditure of cellular energy

Question 5

Body exchange surfaces/Gas exchange surfaces

Answer 5

surfaces that allow for diffusion

have species features to enhance diffusion such as
- high SA:V
- very thin
- partially permeable
- movement of external medium and internal medium (air/blood) to maintain diffusion gradient

Question 6

Ficks Law

Answer 6

R(diffusion)= (SAxPaxDiffusion coefficient)/Diffusion distance

volume scales in a cubic manner wiht body dimensions
surface area scaled with the square

Question 7

Dynamic equilibrium

Answer 7

when the rate in and out are the same

Question 8

Why are gas exchange systems in plants and fungi different?

Answer 8

plants and fungi are different because they lack a centralised ststem for transortation of gases around the body, therefore each region has some capacity for gas exchange and must rely in simple diffusion of gases to nearby tissues

Question 9

gas exchange in plants

Answer 9

stomata
- carbon dioxide diffuses in, and oxygen diffuses out
- guard cells change aperture of defree to whcih stomata open, therefore regulating gas exchange
- the stomatal complex is constrained to the lead base, with the pores being formed in rows adjacent to the leaf veins
- each cell is responsible for their own gaseous needs, therefore the stomata can be found anywhere
- leaves tend to have the highest amount of stomata since they are the most metabolically active cells, therefore leaves have the most GES qualities

Question 10

other features of plants that enable efficient gas exchange

Answer 10

most living cells have some part of their membrane exposed to air

cells are loosely packed, providing a system of airways. Since air diffuses 1000 times faster than water

Each cell is located near the surface, reducing travel distances

Question 11

What are lenticels

Answer 11

small pores that allow gases in and out and interact directly with living tissues

Question 12

what are rhizomes

Answer 12

underground stem modifications that grow undergrousn as well as sometimes on teh soil surface that helps plants that are growing in wetlands or underwater and therefore have less efficient gas diffusion

Question 13

How does gas exchange in fungi work?

Answer 13

very simple, can be both multicellular and unicellular (multicellular or basal)
rely on diffuson across their cell or body walls
some fungi can be slow growing or remain dormant and diffusion works well

yeast (unicellular/basal):
- switches between aerobic and anaerobic depending on gas availability

mycellium (multicellular)
- large branch network which posess microscopic hyphae that extend into small crevised in the soil or other substrates to interact with small air pockets
- majority of gas exchange occurs there
- large SA:V
- can form colonies which produce fruiting bodies that extend above substrate into the air, which can exchange gas via their thin body walls

Question 14

how is gas exchange different with animals compared to fungi and plants

Answer 14

generally more complex than plants and fungy as the organisms can move around

they vary based on the lifestyle and habitat of the animals

Question 15

Animals with thin tissues (annelids)

Answer 15

avoid the need for specialised gas exchange structures by relying on oxygen diffusion across their body wall
worms can do this
they can also coopt other structures iwth large surface areas to aid in gas exchange, such as projecting feet and feeding tentacles

Question 16

Larger animals require 2 main specialised processes to ensure sufficient GE

Answer 16

1. ventilation
   gases are moved across the GES, either via body movements or the movement of the respiratory structure itself. Where the pressure gradient is optimised for diffusion.
2. Circulation
   gas is moved to and from the GES and the body tissues. Occurs via dissolution into a circulatory fluid like blood, or directly via a netwrok of branching tubes

Question 17

GE in terrestrial environments (main points to consider)

Answer 17

oxygen availability is high but water loss is an issue, and since GES need to remain moist, this is an issue that is solved with internal GES

Question 18

small terrestrial animals GE

Answer 18

Network of tubes
direct oxygen delivery to cells throgh small openings called spiracles, along the sides of the thorax and abdomen.
Travels through the trachea into finer tubes called tracheoles, then into individual cells for gas exchange
Insects can close spiracles if needed to prevent water loss, adn can also contract their abdomen, a form of ventilation, that sucks more air inside their body

Question 19

Large terrestrial animals GE

Answer 19

Highly vascularised lungs
air enters through nose or mouth, travelling through trachea and branching into bronchi. Lung may be further divided into bronchioles which end in alveoli. Walls of the lungs are thin and divided into many small capillaries

Question 20

Pneumocyte cells

Answer 20

secrete special molecules wiht a hydrophilic and hydrophobic end to reduce surface tension of the lung to aid in diffusion of gases

Question 21

Bird specialised GES

Answer 21

birds need higher rates of oxygen, therefore they have unidirectional flow of air

lungs do not move but are ventilated by air sacs which pumpp air to and from lungs in specific orders, therefore fresh air pumps over GES in both inhilation and exhilation

parabronchi within the lungs increase teh SA and interact directly with capillary network to effectivelt exchange gases and transport them

Question 22

aquatic species

Answer 22

have gills- both internal and external ones exist
made up of many individual filaments, covered in lamellae to increase SA.

Water flows over them, oxygen diffuses from water into blood within the gills’ capillaries, and CO2 diffuses out into the water.

Internal gills are more efficient becuse they employ counter-current exchange mechanisms wehre water and blood flow in opposite directions, maintaining a concentration gradient that maximised oxygen uptake and CO2 removal