3 Flashcards
How does an organisms surface area to volume ratio effect it’s metabolic rate?
in smaller organisms with a higher SA:V:
- rate of heat loss increases
- higher metabolic rate and respiration
- to generate enough heat to maintain a constant body temperature
Why can’t insects use their bodies as an exchange surface?
They have a small SA:V ratio in order to conserve water
What are the function of spiracles in an insect?
holes on the surface of the body which open and close for gas exchange and to control water loss
What are the function of trachea in an insect?
Tubes which penetrate inside the body carrying air to every tissue
Describe water’s movement in tracheoles of insects during gas exchange
During flight:
- the muscles respire anaerobically
- the water diffuses from the tracheoles into the cell by osmosis
- volume in the tracheoles decreases and air is drawn in
What are the function of the lamellae in fish
- give increased surface area
- blood and water flow across them in opposite directions (countercurrent exchange system)
What are the adaptations of gills?
- each gill is made of many gill filaments which are covered in many lamellae providing a large surface area
- vast network of capillaries on lamellae (remove o2 to maintain a conc gradient)
- thin epithelium so shorter diffusion pathway between water and blood
How do fish maintain flow of water over gills (6m)
- open mouth, operculum shuts
- floor of mouth lowered
- water enters due to lower pressure
- mouth closes, operculum opens
- floor of mouth raised increases pressure
- higher pressure forces water over gills
Why is the countercurrent exchange system in fish efficient?
- water and blood flow over lamellae in opposite directions
- always higher conc of o2 in water than blood
- conc gradient of o2 is maintained along whole length of lamellae so equilibrium is not met
Why is the parallel flow exchange system in fish less efficient?
- Only has a steep diffusion gradient INITIALLY
- equilibrium would be met
What are the two ways fish can ventilate?
Passively and actively (more efficient)
Describe alveoli
- lined with epithelium cells
- walks only 1 cell thick so short diffusion pathway
- network of capillaries
Describe inspiration (breathing in)
- external intercostal muscles contract
- internal intercostal muscles relax
- ribs move up and out
- diaphragm contracts and flattens
- volume of thorax increases
- pressure in thorax decreases
- air pressure outside the lungs is greater so air moves in
(Air moves down a pressure gradient)
What is tidal volume?
The volume of air in each breath
What is breathing rate
Number of breaths we take per minute
How do you calculate pulmonary ventilation rate?
Tidal volume x breathing rate
(Can be measured using a spirometer)
What’s the function of the pleural space
Filled with pleural liquid which prevents lungs rubbing with ribcage
Why is oxygen uptake a measure of metabolic rate in organisms
Oxygen is used in respiration which provides energy
What is digestion
The hydrolysis of large insoluble molecules into small soluble molecules
Where are lipids digested
Small intenstine
Where is amylase found and what is it’s function?
In the mouth
- turns starch into maltose and glucose
by hydrolysing the glycosidic bonds
What are the adaptations of villi?
- many capillaries and lymph vessels = rich blood supply
- microvilli = large surface area
- lacteal connects to the lymph system
How are polysaccharides and disaccharides digested into monosaccharides?
By hydrolysis of the glycosidic bonds
What are the 3 disaccharide enzymes
Maltase, sucrase, lactase
What’s the role of bile salts?
To emulsify lipids and large droplets into small micelles which have a large surface area for lipase action
What’s the role of HCL in the stomach
- destroys bacteria
- ensures optimum pH 2 for mucus acts enzymes
What is the second section of the small intestine called?
Ileum —> digestion finishes and the products are absorbed
What happens in the duodenum (small intestine)?
Pancreatic juice, bile and Maltase is secreted
Where is bile produced and stored?
Produced in liver, stored in gall bladder
What’s the role of bile?
- neutralises HCL so enzymes in small intestine don’t stop working
- emulsifies fats into micelles
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels (5m)
- Micelles contain bile salts and fatty acids
- release fatty acids to lining of the ileum
- Fatty acids absorbed by diffusion
- Triglycerides reformed in cells
- Vesicles move to cell membrane
Describe the role of enzymes in the digestion of proteins in a mammal
- hydrolysis of peptide bonds
- endopeptidase produces shorter polypeptides
- exopeptidase produces amino acids
- dipeptidase produces amino acids
What are the advantages to lipid droplet and micelle formation?
- droplets increase surface area for lipase action
- so faster hydrolysis of lipids
- micelles carry fatty acids and glycerol through membrane
Explain how cells lining the ileum of mammals absorb glucose by co transport with sodium ions
- maintains diffusion gradient for sodium ions to go from ileum cell to blood
- sodium moving in by facilitated diffusion brings glucose with it
How are the chambers in the heart adapted (atria & ventricles)?
Atria: thin walled and elastic so they can stretch when filled with blood
Ventricles: thick muscular walls pump blood under high pressure
In the heart why is the left ventricle thicker than the right
Because it has to pump blood all the way around the body
How are arteries adapted?
- thick walls to withstand high pressure.
- Muscular and elastic to control blood flow
How are veins adapted?
- thin walls due to lower pressure
- have valves to prevent back flow of blood.
- have less muscular and elastic tissue bc they don’t control blood flow
In the heart why are two pumps needed (left and right)
- to maintain blood pressure around the whole body
- when blood passes through narrow capillaries of lungs the pressure drops so would not be flowing strongly enough around the whole body
- so it is returned to the heart to increase pressure
Describe atrial systole (1)
- atria contracts which decreases volume and increases pressure inside atria
- pressure in atria > pressure in ventricles
- AV valves open
- blood is pushed into ventricles
- semilunar valves stay closed
Describe ventricular systole (2)
- ventricles contract from the bottom up which decreases volume and increases pressure inside ventricles
- AV valves close and Semi lunar valves forced open
- pressure in ventricles > Atria
- blood is pushed out of heart through arteries
Describe diastole (3)
- atria and ventricles relax which increases volume and decreases pressure inside chambers
- blood from veins fill atria and flows to ventricles
- AV valves open
- pressure inside atria > ventricles
- SL valves shut
What are the nodes involved in heart contraction and where are they
- Sinoatrial node (SAN) = wall of right atrium
- atrioventricular node (AVN) = in between the two atria
What does myogenic mean
The hearts contraction is initiated from within the muscle itself rather than by nerve impulses
Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs
- Renal vein
- Vena cava to right atrium
- Right ventricle to pulmonary artery
Explain how an arteriole can reduce the blood flow into capillaries
- muscle contracts
- narrows lumen
What blood vessel carries blood at the lowest pressure ?
Vena cava
Explain why different enzymes are required in digestion
- substrates all have different shapes
- enzymes have a specific primary structure giving a specific tertiary structure
- therefore an active site with a specific shape
- only substrates that are complementary can bind to the active site
- to form an enzyme substrate complex
Explain the role of the heart in the formation of tissue fluid
- contraction of ventricles produces high blood pressure
- this forces water out of blood capillaries
Explain the advantage of the Bohr effect during exercise
- increases dissociation of oxygen
- for aerobic respiration at the cells
Explain the effect of increasing CO2 concentration on the dissociation of oxyHb
- decreases Hbs affinity for O2
- by decreasing blood pH
- increases rate of O2 unloading
- curve shifts right
How does binding of 1 molecule of o2 to Hb make it easier for the second to bind
-binding of first oxygen changes tertiary structure of Hb
- which creates another binding site
Explain how a reduced tidal volume affects the exchange of CO2 between blood and alveoli
- less CO2 exhaled
- so reduced concentration gradient
- more CO2 stays in blood
Describe the pathway taken by an O2 molecule from an alveolus to the blood
alveolar epithelium to epithelium of capillary
Describe the structure of the human gas exchange system and how we breathe in and out
- trachea, bronchi, bronchioles, alveoli
- breathing in: diaphragm & external IC muscles contract
- volume increase and pressure decrease in thorax
- breathing out: diaphragm relaxes & internal IC muscles contract
Give 3 ways an insects tracheal system is adapted for gas exchange
- tracheoles have thin walls so short diffusion pathway
- highly branched/ large number of tracheoles so short diffusion pathway & large surface area
- trachae provide tubes full of air so fast diffusion
Explain how water from tissue fluid is returned to the circulatory system 4m
- plasma proteins remain
- reduces water potential of blood
- water moves to blood by osmosis
- returns to blood by lymphatic system
What’s the function of micelles? 5m
- they include bile salts and fatty acids
- they make the fatty acids more soluble in water
- they release fatty acids to the lining of the ileum
- they maintain high conc gradient of fatty acids to lining
- fatty acids are absorbed by diffusion
Describe the mechanism for the absorption of amino acids in the ileum (5m)
- Facilitated diffusion of amino acid
- co-transport
- sodium ions actively transported from cell to blood
- creating sodium ion conc
- facilitated diffusion of amino acids into blood.
Describe the transport of carbohydrates in plants 5m
- sucrose is actively transported into phloem
- by companion cells
- lowers WP in phloem and water enters by osmosis
- producing higher hydrostatic pressure
- mass flow to respiring cells
Compare fish vs mammal circulation
Fish) - heart contains deoxygenated blood
- single circulation
Mammal) - heart contains deoxygenated and oxygenated blood
- double circulation system
Describe the complete digestion of starch by a mammal
- hydrolysis of glycosidic bonds
- starch to maltose by amylase
- maltose to glucose by Maltase
- membrane bound
How do larger organisms exchange
- need a specialised surface for gas exchange eg lungs
- because they have a smaller SA:V ratio and a long diffusion pathway
- and they have a higher demand for oxygen
What are the adaptations of xerophytic plants
- stomata in pits/grooves which trap water vapour so less evaporation of water
- thick waxy cuticle which increases diffusion distance so less evaporation
- rolled leaves which trap water so less evaporation
- hairs which trap water so less evaporation
- longer root network to reach more water
How does gas exchange occur in the alveoli?
- o2 diffuses from alveoli down it’s conc gradient
- across the alveolar epithelium
- across the capillary endothelium and into the blood
How would lung disease effect someone
. Scar tissue in lungs: - thicker tissue and less elastic so diffusion distance is increased
. Faster ventilation rate to get enough oxygen into lungs
. Lungs can expand and recoil less so can’t hold as much air so reduced tidal volume and forced vital capacity
How can asthma effect someone
Asthma attack can cause constriction of airways so narrow diameter so airflow in/out of lungs is reduced (FEV reduced)
Less o2 enters the blood so less gas exchange
What is FEV
Max volume of air that can be breathed out in 1 second
Describe the role of endopeptidases
- hydrolyse peptide bonds within a protein
- breaking it into 2 or more smaller peptides
Describe the role of exopeptidases
- hydrolyse peptide bonds at the ends of protein molecules
- removing a single amino acid
Describe role of dipeptidases (type of exopeptidases)
- hydrolyse peptide bonds between to amino acids
so that they can cross the cell membrane
Explain why the combined actions of endo and exopeptidases are more efficient than exopeptidases on their own
- endopeptidases hydrolyse internal peptide bonds
- increasing surface area for exopeptidases to act on
What’s the function of atrioventricular valves
Prevent back flow of blood from ventricles to atria
What’s the function of semilunar valves
Prevent backflow of blood from arteries to ventricles
Describe the formation of tissue fluid
- higher hydrostatic pressure at end of capillaries than tissue fluid
- which forces water out of capillaries
- large plasma proteins remain in the capillaries because they’re too large to leave
How can high blood pressure lead to an accumulation of tissue fluid
- high hydrostatic pressure
- which increases outward pressure from arterial end of capillary
- so more tissue fluid is formed and the lymph system is not able to drain tissues fast enough
Describe the cohesion tension theory of water transport in the xylem
- water evaporates from leaves during transpiration. Where water evaporates from mesophyll cells into air spaces
- water vapour diffuses through the stomata
- reducing wP in the mesophyll cells and increasing wP gradient
- water drawn out of xylem down a wP gradient creating tension
- hydrogen bonds result in cohesive forces between water molecules so water gets pulled up as an unbroken column
- water adheres to walls of the xylem
How does light effect the rate of transpiration
- faster transpiration
- stomata open in light to let CO2 in for photosynthesis so water can evaporate faster
How does temperature effect the rate of transpiration
- faster transpiration
- water molecules gain more kinetic energy so move faster
How does humidity effect the rate of transpiration
The higher the humidity the slower the rate of transpiration
- as humidity increases more water is in the air so has a higher water potential
- decreasing the water potential gradient from leaf to air
- so water evaporates slower
How does wind effect the rate of transpiration
- wind blows away water molecules from around the stomata
- which decreases the water potential of air around the stomata
- which increases the water potential gradient
- so water evaporates faster
How is the xylem adapted for its function
- cells joined with no end walls, forming a long continuous tube. Water can flow as a continuous column
- cells contain no cytoplasm/nucleus so no obstructions and easier water flow
- thick cell walls with lignin -> provides support and can withstand tension
- pits in side walls - allow lateral water movement
What two types of cells does phloem tissue have
- Sieve tube elements
- no nucleus - easier flow of organic substances
- sieve plate - Companion cells
- many mitochondria so high rate of respiration to make ATP for active transport of solutes
What’s the order of AV and SL valves opening and closing in the heart
1 - AV valves close
2 - SL valves open
3 - SL valves close
4 - AV valves open
What happens when the oxyHb curve shifts left
- haemoglobin has higher affinity for O2
- O2 associates more readily and dissociates less readily
What happens when the oxyHb curve shifts right
- haemoglobin has a lower affinity for O2
- O2 dissociates more readily and associates less readily
As partial pressure of oxygen increases what happens to saturation of haemoglobin with oxygen
Saturation increases because number of oxygen molecules binded to iron increases
What is the Bohr effect
How changing carbon dioxide concentration effects % saturation of oxygen on a oxyhaemoglobin curve
When does haemoglobin have a higher affinity for oxygen
- at low CO2 concentrations
- in blood passing away from the lungs
- at higher pH
Describe mass flow of sucrose down a phloem (5m)
- sucrose moves down into the sieve tube element (STE) causing the wP to decrease
- water moves from the xylem into the STE element by osmosis
- causing the hydrostatic pressure in the STE to to increase
- at the sink cell the hydrostatic pressure decreases bc of water moving out of the STE
- sucrose moves down the hydrostatic pressure gradient and into the sink cell
Describe the complete role of micelles in lipid digestion
- lipids are digested into monoglycerides, fatty acids and glycerol by lipase and bile salts. these form micelles
- micelles deliver these things to the epithelial cells of the ileum for absorption by diffusion
- once in the cell these will be modified back into triglycerides inside the Golgi body and endoplasmic reticulum
Briefly outline lipid digestion
- bile salts (in micelles) emulsifies lipids and large droplets into fatty acids. they increase surface area for lipase action
- lipase hydrolyses lipids into glycerol and fatty acids
- micelles are then what deliver the products to the ileum for absorption by diffusion
Why do endo and exopeptidases act at different places on a molecule
- active sites are different shapes
- so different ESCs are formed
What are insects adaptations to prevent water loss
- small SA:V ratio
- waterproof exoskeleton
- spiracles which can close to limit water loss
- spiracles have hair around them that prevent water loss
