Chapter 6- Exchange Flashcards
How do organisms transfer materials between two environments
- transfer occurs at exchange surfaces
- always involves crossing cell plasma membranes
What are the two ways exchange can take place
- passively- no energy required by diffusion and osmosis
- actively- energy required by active transport
Features of specialised exchange surfaces
- large SA
- very thin so that the diffusion distance is short
- selectively permeable to allow selected materials across
- a transport system to ensure the movement of the internal medium to maintain a diffusion gradient
What’s the internal network of tubes in an insect for gas exchange called
tracheae which then divide into dead-end tubes called tracheoles
In insects what are the three ways gases move in and out of the tracheal system
- along a diffusion gradient
- mass transport- contraction of muscles can squeeze trache allowing air to be pushed along
- ends of tracheoles are filled with water- can carry out anaerobic respiration
Describe the spiracles on the tracheae
- tiny pores on the body surface
- the spiracles can be opened and closed by a valve
What are some limitations of the tracheal system
- relies mostly on diffusion to exchange gases
- insects have to be small to make sure the diffusion pathway is short
Describe the structure of the gills
- made of gill filaments stacked up in a pile
- gill lamellae at right angles to the filaments which increase the SA of the gills
- they face in opposite direction to the water ( countercurrent flow) to increase amount of water flowing over them
Describe the countercurrent exchange principle
- oxygenated blood meets water, diffusion of oxygen from the water to the blood takes place
- deoxygenated blood meets water, diffusion of oxygen from water to blood takes place
How is gas exchanged in the leaf of a plant
- photosynthesis- plant takes in CO2 and produces O2
- most of the CO2 is obtained from the external air and oxygen produced diffuses out of the plant
- at night oxygen diffuses into the leaf and CO2 diffuses out
Describe the structure of a plant leaf and gas exchange
- no living cell is far from the external air meaning there is a short, quick diffusion pathway
- diffusion takes place in the gas phase of diffusion so its more rapid than in water
Adaptions a plant has for efficient gas exchange
- many small pores called stomata to make a small diffusion pathway
- many interconnecting air spaces that occur throughout the mesophyll
- large SA of mesophyll cells for rapid diffusion
Describe the stomata
- minute pores on the underside of leaves
- each stoma is surrounded by a pair of specialised cells called guard cells which can open and close the stomatal pore
- they are able to close the stoma to reduce water loss as terrestrial organisms lose water by evaporation
How do insects limit water loss
evolved adaptions including:
- small SA to Vol ratio
- waterproof coverings
- spiracles
How do plants limit water loss
- thick waxy cuticle
- rolling up of leaves
- hairy leaves
- stomata in pits or grooves
- a reduced SA to Vol ratio
Why do aerobic organisms need a constant supply of oxygen
in order to release energy in the form of ATP in respiration
What are the lungs
- site of gas exchange in mammals
- they are protected by the ribcage
- they are ventilated by a constant supply of air
Name some parts of the human gas exchange system
- lungs
- trachea
- bronchi
- bronchioles
- alveoli
What is:
1. inspiration
2. expiration
- when the air passage of the atmosphere is greater than the air pressure inside of the lungs, air is forced into the lungs
- when the air pressure in the lungs is greater than that of the atmosphere, air is forced out of the lungs
What 3 muscles help with breathing
- diaphragm- sheet of muscle that separates the thorax from the abdomen
- internal intercostal muscles- contraction leads to expiration
- external intercostal muscles- contraction leads to inspiration
What is the structure of the human digestive system
its made up of long muscular tubes and its associated glands
-the glands produce enzymes to hydrolyse large molecules into smaller ones ready for absorption
Name 3 major parts of the digestive system
- oesophagus
- stomach
-ileum - large intestine
- rectum
-salivary glands - pancreas
*look on pages 151/152 for explanations
What are the two stages of digestion
- physical breakdown- structures such as teeth break down food into smaller parts to create a larger SA for chemical digestion
- chemical digestion- hydrolyses large insoluble molecules into smaller, soluble ones
What are the three digestive enzymes
- carbohydrase- hydrolyses carbohydrates to monosaccharides
- lipases- hydrolyses lipids to glycerol and fatty acids
- proteases- hydrolyses proteins to AA’s
What is emulsification
where lipids are split into tiny droplets called micelles by bile salts
What are the three different types of peptidases
- endopeptidases- hydrolyse the peptide bonds between AA’s in the central region
- exopeptidases- hydrolyse peptide bonds on the terminal AA’s
- dipeptidases- hydrolyse the bond between the two amino acids of a dipeptide
Structure of the ileum
- wall of ileum has villi which increase the SA therefore increasing rate of absorption
Properties of villi which increase efficiency of absorption
- they increase SA for diffusion
- very thin walls to decrease diffusion distance
- contain muscle so can maintain a diffusion gradient
- well supplied with blood vessels which can absorb molecules
- villi have microvilli which increase SA further
