gas exchange Flashcards
Adaptation for gas exchange across the body surface of a single-celled organism
Thin, flat shape
→ Giving it a large SA:V ratio
→ Short diffusion pathway, as all parts of cell are a small distance away from exchange surfaces
→ For rapid diffusion e.g. oxygen / carbon dioxide
How do insects respire? [5]
- Air moves through spiracles (pores) on the surface of the insect
- Muscles contract, moving air through trachea
- Gas exchange at tracheoles directly to and from cells
- Oxygen diffuses down conc. gradient to respiring cell
- Carbon dioxide diffuses down conc. gradient from respiring cells
Give 2 Adaptations for gas exchange in the tracheal system of an insect
Lots of thin, branching tracheoles
→ short diffusion pathway and large SA:V ratio
→ rapid diffusion
Rhythmic abdominal movements
→ increasing the amount of oxygen entering
→ maintains greater concentration gradient for diffusion
→ increase the efficiency of gas exchange
Give 4 adaptations for gas exchange across the gills of fish
Counter current flow
Vast network of capillaries on lamellae
→ moves oxygen away from exchange surface to maintain a concentration gradient
→ Maximising diffusion of oxygen
Each gill is made of lots of gill filaments (thin plates) which are covered in many lamellae
→ gill filaments provide a large surface area
→ lamellae increase surface area even more
→ increased rate of diffusion
Thin/flattened epithelium
→ shorter diffusion pathway between water and blood
→ increased rate of diffusion
Counter current flow [4]
→ Blood flows through lamellae and water flows over lamellae in opposite directions
→ Always a higher concentration of oxygen in water than in the blood it is near
→ A concentration gradient of oxygen between the water and blood is maintained along the whole length of lamellae
→ Maximising diffusion of oxygen
Describe the process of gas exchange in leaves [4]
- Stomata opened by guard cells
- Carbon dioxide / oxygen diffuses through the stomata
- down concentration gradient
- diffuses into air spaces of mesophyll layer
- diffuses directly into mesophyll layer where photosynthesis takes place
Give 4 adaptations for gas exchange by the leaves of plants
Lots of stomata
- Large surface area for gas exchange
- unimpaired movement of gases as gases do not have to pass through cells to reach mesophyll
Interconnecting air space in mesophyll layers (exchange surface)
- Gases come into direct contact with mesophyll cells
Mesophyll cells have a large surface area
- Rapid diffusion of gases
Thin
- Short diffusion pathways
Describe the structure of the lungs [4]
- Trachea
- Splits into two bronchi
- Each bronchus branches into smaller tubes called bronchioles
- bronchioles end in air sacs called alveoli
How does gas exchange occur at the alveoli? [6]
- Oxygen diffuses from alveoli
- Down its concentration gradient
- Across the alveolar epithelium
- Across the capillary endothelium
- Into the haemoglobin in the blood
(reverse for carbon dioxide)
Why is ventilation needed in the lungs?
maintains an oxygen concentration gradient by removing air with a lower concentration of oxygen and replacing it with air with a higher concentration
Give 5 essential features of the alveoli and gas exchange
- Epithelium one cell thick > short diffusion distance
- Alveoli folded > Large surface area for rapid diffusion
- Good blood supply from network of capillaries > maintaining concentration gradient
- Elastic tissue allows lungs to expand and recoil > taking in a large volume of air
- Location, centre of body warmest > increased kinetic energy of particles, rapid diffusion
Inspiration (breathing in) [7]
- active process, using energy
- external intercostal muscles contract, while internal relax
- diaphragm contracts, flattening
- ribs pulled upwards and outwards
- increased volume of thorax
- atmospheric pressure greater than pulmonary pressure
- air forced into lungs
Expiration (breathing out) [7]
- passive process, doesn’t require energy
- internal intercostal muscles contract, while external relax
- diaphragm relaxes, moving upwards
- ribs move downwards and inwards
- decreased volume of thorax
- atmospheric pressure less than pulmonary pressure
- air forced out of lungs
Give 2 examples of lung diseases
Fibrosis
Athsma
How might Fibrosis effect gas exchange? [2]
Scar tissue in lungs
- scar tissue thicker increasing diffusion distance
- scar tissue less elastic so lungs can’t hold as much air
