Topic 3 Flashcards
Surface area to volume ratio
The surface area of an organism divided by its volume
the larger the organism, the smaller the ratio
Factors affecting gas exchange
diffusion distance
surface area
concentration gradient
temperature
Ventilation
Inhaling and exhaling in humans
controlled by diaphragm and antagonistic interaction of internal and external intercostal muscles
Inspiration
External intercostal muscles contract and internal relax
Pushing ribs up and out
Diaphragm contracts and flattens
Air pressure in lungs drops below atmospheric pressure as lung volume increases
Air moves in down pressure gradient
Expiration
External intercostal muscles relax and internal contract
Pulling ribs down and in
Diaphragm relaxes and domes
Air pressure in lungs increases above atmospheric pressure as lung volume decreases
Air forced out down pressure gradient
Passage of gas exchange
Mouth / nose -> trachea -> bronchi -> bronchioles -> alveoli
crosses alveolar epithelium into capillary endothelium
Alveoli structure
Tiny air sacs
highly abundant in each lung - 300 million
surrounded by the capillary network
epithelium 1 cell thick
Why large organisms need specialised exchange surface
They have a small surface area to volume ratio
higher metabolic rate - demands efficient gas exchange
specialised organs e.g. lungs / gills designed for exchange
Fish gill anatomy
Fish gills are stacks of gill filaments
Each filament is covered with gill lamellae at right angles
How fish gas exchange surface provides large surface area
Many gill filaments covered in many gill lamellae are positioned at right angles creates a large surface area for efficient diffusion
Countercurrent flow
When water flows over gills in opposite direction to flow of blood in capillaries
equilibrium not reached
diffusion gradient maintained across entire length of gill lamellae
Name three structures in tracheal system
Involves trachea, tracheoles, spiracles
How tracheal system provides large surface area
Highly branched tracheoles
large number of tracheoles
filled in ends of tracheoles moves into tissues during high metabolic activity
so larger surface area for gas exchange
Fluid-filled tracheole ends
Adaptation to increase movement of gases
When insect flies and muscles respire anaerobically - lactate produced
Water potential of cells lowered, so water moves from tracheoles to cells by osmosis
Gases diffuse faster in air
How do insects limit water loss(4)
Small surface area to volume ratio
Waterproof exoskeleton
Spiracles can open and close to reduce water loss
Thick waxy cuticle - increases diffusion distance so less evaporation
Dicotyledonous plants leaf tissues
Key structures involved are
mesophyll layers with many interconnecting air spaces
Palisade and spongy mesophyll - lots of air spaces and chlorophyll.
Stomata created by guard cells
Gas exchange in plants
Palisade mesophyll is site of photosynthesis
Oxygen produced and carbon dioxide used creates a concentration gradient
Oxygen diffuses through air space in spongy mesophyll and diffuse out stomata
Role of guard cells
Swell - open stomata
Shrink - closed stomata
At night they shrink, reducing water loss by evaporation
Xerophytic plants
Plants adapted to survive in dry environments with limited water (e.g. marram grass/cacti)
Structural features for efficient gas exchange but limiting water loss like:
Stomata in sunken pits and small hairs reduce conc extraction gradient as water vapour is trapped
Thick waxy cuticle
Leaves modified to spines which reduces surface area
Roots seep deep down to reach water
Rolling up of leaves as majority of stomata in lower epidermis this traps layer of still air reducing concentration gradient
Adaptations of xerophyte
Adaptations to trap moisture to increase humidity -> lowers water potential inside plant so less water lost via osmosis
-sunken stomata
-curled leaves
-hairs
Thick cuticle reduces loss by evaporation
longer root network
Digestion
Process where large insoluble biological molecules are hydrolysed into smaller soluble molecules
So they can be absorbed across cell membranes
Locations of carbohydrate
digestion
Mouth -> duodenum -> ileum
Locations of protein digestion
Stomach -> duodenum -> ileum
Endopeptidases
Break peptide bonds between amino acids in the middle of the chain
Creates more ends for exopeptidases for efficient hydrolysis