Exchange and transport systems 3 Flashcards
Factors affecting rate of exchange
Surface area to volume ratio
Length of diffusion pathway
Concentration gradient
Gas exchange in insects?
Oxygen diffuses in through SPIRACLES
Gas then enters large tubes called tracheae, and then through to the tracheoles
Tracheoles allow oxygen to diffuse directly to cells.
Carbon dioxide diffuses out the opposite way
What are some adaptations that are applicable pretty much anywhere for gas exchange?
- Tracheoles have thin walls so short diffusion pathway.
- IF THEY HAVE IT, a good blood supply to maintain concentration gradient.
- Tracheoles are often branched so has a large surface area.
- Large SA:VOL ratio for maximum absorption
Adaptations of spiracles in insects
- spiracles have valves that can periodically close to minimise water loss
- spiracles have hairs that further reduce water vapour loss
Describe gas exchange within fish
- water passes through the fish’s mouth and out through the gills.
- each gill has lots of plates called gill filaments (giving a large surface area).
- gill filaments are covered in lots of tiny structures called lamellae.
- lamellae have lots of blood capillaries and a thin surface layer of cells.
some fish gills use a COUNTERCURRENT FLOW. What does this involve?
- the direction of blood and water flow opposite ways.
- this makes it so blood is always passing water with a higher oxygen concentration
- this means a concentration gradient of oxygen is maintained the whole lamellae
- so more oxygen enters the blood, and so more aerobic respiration to release energy for swimming
Some fish use CONCURRENT FLOW. What does this involve?
- blood and water flow in the same direction
What is the structure of the thoracic cavity?
- epiglottis and larynx
- trachea
- bronchi and bronchioles
- ribs and intercostal muscles
- pleural membrane and pleural cavity
- diaphragm
What occurs during inspiration?
- air containing oxygen is sucked in through mouth
- air moves into lungs
- volume of chest cavity increases
- diaphragm contracts and pushes digestive organs down
- pressure in chest cavity decreases below atmospheric pressure
- external intercostal muscles contract and ribs rise
What occurs during expiration?
- external intercostal muscles relax and ribs fall
- pressure in chest cavity rises above atmospheric pressure
- diaphragm relaxes and is pushed up by digestive organs
- volume in chest cavity decreases
- air moves out of lungs
- air is forced out through mouth, removing carbon dioxide
Adaptations of alveoli?
- large surface area
- thin walls for small diffusion path
- surrounded with many blood capillaries than make it so a concentration gradient is maintained
- RBCs are flattened against the capillary walls
- alveoli are covered in a substance called pulmonary sufactant
- pulmonary sufactant has a low surface tension, and stops the water lining the alveoli from sticking together.
How are carbohydrates digested
- salivary glands secrete carbohydrases (AMYLASE) which break polysaccharides into disaccharides
- these enzymes denature in the stomach
- the pancreas releases pancreatic AMYLASE to digest any polysacchrides that weren’t broken down
- MEMBRANE BOUND disaccharidases hydrolyse disaccharides into monosaccharides, which are small and soluble for digestion
Definition of digestion
The hydrolysis of large, insoluble molecules into smaller, soluble molecules for absorption
What happens in lipid digestion and absorption?
Lipase hydrolyses the ester bonds between the monoglycerides and fatty acids
Bile salts emulsify these and form micelles
Micelles transport the monoglycerides and fatty acids to the lining of the ileum, where they diffue over the membrane passively (they are non-polar)
Monoglycerides and fatty acids are repackaged by the golgi apparatus and sometimes proteins are added
The newly synthesised molecules with proteins are called chylomicrons and these exit the cell into the lymphatic system
What is the structure of haemoglobin?
- four polypeptide chains chemically bonded together
- each with a haem group packed in the middle.
What is affinity?
the degree to which a substance tends to combine with another (chemical attraction)
What is cooperative binding?
- binding of one molecule affects the binding affinity of subsequent molecules
What affects the oxygen dissociation curve position?
- The organism’s environment (oxygen availability)
- How active/metabolically active the organism is
When is haemoglobin associated with oxygen?
When it exists as oxyhaemoglobin (HbO8)
When is haemoglobin dissociated with oxygen?
When they both exists separately (Hb and 4O2)
Some xerophytic plants have sunken stomata. Explain the advantage of this adaptation.
- prevents water loss
- due to a shallower water potential gradient
Describe how water is moved through a plant according to the cohesion-tension hypothesis.
- water transpires from leaves
- reduces water potential gradient across cells
- water is pulled out the xylem
- creates tension, and cohesive forces between water pull water up in a column up the xylem
Describe the mass flow hypothesis for the mechanism of translocation in plants. (PHLOEM)
- the source of sugar in leaves are actively transported into the phloem
- via the companion cells
- this lowers the water potential in the phloem’s sieve cells
- so water enters via osmosis from the xylem down the water potential gradient
- this causes an increase in pressure in the phloem, and causes mass movement (towards sink)
- sugars converted in root for storage for respiration.
What is the structure of myoglobin?
- 1 polypeptide chain, 1 haem group, 1 Fe ion
When is myoglobin used?
- when pO2 drops so low, only then will it dissociate
- as it has a high affinity for O2
What is the Bohr effect?
O2 dissociation curve position will change in favour of releasing O2 in different ways.
e.g., in low O2 environments, the haemoglobin’s O2 affinity will be higher and so the curve position will shift to the left
What does the Bohr effect mean for haemoglobin?
- increased [CO2] REDUCES haemoglobin’s affinity for O2
- so haemoglobin is more likely to dissociate from O2
- this adaptation enables organisms to meet metabolic demand
Outline the features and their purpose of an artery
Muscular tissue - able to withstand high blood pressure
Elastic tissue - able to stretch and recoil to maintain high blood pressure
Smooth endothelial wall - reduces friction between artery and blood
Outline the features and the purpose of a vein
Wide lumen - maximises blood flow
Valves - prevents back flow of blood
Little elastic and muscular tissue
Outline the features and their purpose of a capillary
One cell thick - a short diffusion path for substances to be exchanged quickly
Outline the features and their purpose of a venule
smaller than veins, larger than capillaries
Outline the features and their purpose of a arteriole
Muscular tissue - able to contract and relax to vasoconstrict/vasodialate
Thin endothelial lining - reduces friction between blood and arteriole wall
Elastic tissue - able to recoil and stretch, maintaining blood pressure
What is tidal volume
the volume of air we breathe in and out at each breath at rest
What is breath rate
the number of breaths per minute, can be calculated from the spirometer
trace by counting the number of peaks or troughs in a minute
What are the benefits of the Bohr effect when exercising
Increase the dissociation of O2
For aerobic respiration at respiring tissues (muscles)
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels.
Lipase is released from the pancreas which hydrolyses lipids into monoglycerides and fatty acids, and bile salts from the liver emulsify these and form micelles
The micelles move to the epithelial layer of the ileum and release the monoglycerides and fatty acids. These thendiffuse via passive diffusion across the membrane into the epithelial cells
The monoglycerides and fatty acids are then repackaged and modified inthe golgi apparatus, where carbohydrates are added onto them, forming chylomicrons.
There chylomicrons exit the cell and into the surrounding lymph vessels by using a golgi vesicle, where releases them via exocytosis
what are the adaptations of the xylem and explain them
long cells end to end with no end walls -> allows continuous columns of water
cellulose walls are lined with lignin -> able to withstand tension that is caused when water gets pulled through
no cytoplasm or organelles -> nothing to obstruct the flow of water
outline the cohesion tension theory
water transpires from stomata at the leaves as it evaporates due to the atmosphere having a lower water potential than inside the leaves
so water potential is now low in the leaves
water moves by osmosis through the xylem to replace the lost water
water molecules get pulled up the xylem due to the cohesive property
so water flows in continuous columns up the xylem
adhesion of the water molecules causes the walls of the xylem to be pulled in, creating tension
environmental factors affecting the rate of transpiration
light intensity
temperature
air movement
humidity
suggest some precautions that a student should take when setting up a potometer in order to gain reliable results
seal all joints
cut the shoot underwater
dry the leaves
ensure that zero bubbles are present
note down where the bubble starts
insert the plant into the apparatus under water
a student has to cut a plant with a sharp scalpel to cut it. describe how she should ensure she handled the scalpel safely during this procedure
cut away from her body
cut on a hard surface
scientists who investigate disease may look at risk factors. what is a risk factor
something that increases chances or increases the probability of getting that disease
explain the role of the diaphragm in breathing out
the diaphragm relaxes and moves up
it reduces the volume in the thoracic cavity and increases pressure in the thoracic cavity
so the pressure in the cavity rises higher than atmospheric pressure, so air is forced out
what happens to the oxygen binding sites as more oxygen binds to it
they become more exposed, meaning oxygen is able to bind easier
is oxygen complementary to the haem groups
NO
the haem group is a flat surface that the oxygen binds to
what is partial pressure
the pressure exerted by an individual gas in a mixture of gases
what is pO2
the partial pressure exerted in a mixture of gases by O2
what is oxygen loading
when haemoglobin associates with oxygen
(at the lungs)
what is oxygen unloading
haemoglobin dissociating with oxygen (at the respiring tissues)
what is the shape of the curve of a oxyhaemoglobin dissociation curve
sigmoidal
what is the effect of CO2 on the oxyhaemoglobin curve called
the bohr effect
explain what causes the Bohr effect to arise
respiring tissues release CO2 as a waste product
this accumulates in the blood
CO2 decreases the blood pH by making it more acidic
the change in blood pH changes the tertiary structure of the haemoglobin, making it so that the affinity for O2 is lowered
so oxygen is unloaded more easily
an animal lives in a high relief climate, so a low pO2 climate. where does their pO2 saturation of a oxyhaemoglobin dissociation curve lie
it lies lower that normal and to the right
an animal lives in a low relief climate, so a high PO2 climate. where does their PO2 saturation of a oxyhaemoglobin dissociation curve lie
lies a bit higher and to the left
describe and explain the relationship between surface area to volume ratio of an organism and metabolic rate
as surface to volume ratio increases, so does the metabolic rate of the organism
a large SA:VOL will lose more heat
the higher metabolic rate releases the heat
how does abdominal pumping in an insect help with gas exchange
body can be moved by muscles to pump the air, so maintains a concentration gradient for oxygen and carbon dioxide
rules for drawing a diagram in an exam
dont use shading
use single lines
add labels
dont cross label lines
add a magnification scale
draw out the layers of a lead cross section
waxy cuticle
upper epidermis
palisade mesophyll
mesophyll cells
lower epidermis
guard cells and stomata
adaptations of the leaf for efficient gas exchange
many stomata so all cells are within a short distance for diffusion
many large interconnected air spaces in the spongy mesophyll that increase the surface area of contact between air and cells
leaf in thin to keep diffusion pathways short
