Exchange Of Substances Flashcards
What is peristalsis (oesophagus, intestines etc)
Squeezing motion (autonomic nervous system)
Stomach
Muscular sac
Stores and digests food
Inner layer produces enzymes like pepsin
Ileum
Long muscular tube at the end of small intestine where most digestion occurs
Produces enzymes from epithelial cells that line walls and glands pour their secretions into it
Large intestine
(Around the outside)
Absorbs water
Rectum
Stores faeces to be ejected from the anus
Salivary glands
Secretes saliva which contains salivary amylase that hydrolyses some starch into maltose but mainly breaks down into small pieces
Pancreas
Under stomach
Secretes pancreatic juice
Contains pancreatic amylase, protease,carbohydrate,lipase and nucleases
Bile from liver is stored in
The gallbladder
Digestion is
The physical and chemical breakdown of food
Physical break down
No bonds are broken
Large pieces are broken down by teeth (mastication) and churned by stomach muscles
Purpose of physical breakdown
Makes injection possible
Larger surface area for efficient chemical digestion
Chemical digestion
Hydrolyses large, insoluble molecules into small, soluble ones
Uses a H20 molecules
Carbohydrate digestion process
In mouth, physical digestion by mastication and chemical digestion by salivary amylase, which hydrolyses some starch into maltose but mainly, into smaller chunks for ingestion. Mineral salts in saliva maintain a neutral pH.
Peristalsis pushes food through oesophagus into stomach, where (pH around 2) a highly acidic environment denatures amylase enzyme and no hydrolysis of starch occurs. The churning of the walls breaks food, including undigested starch into smaller pieces (physical digestion)
Then food moves through peristalsis into the duodenum, where pancreatic juice and bile are secreted through the same duct. Pancreatic amylase hydrolyses the remaining starch, into the disaccharide maltose.
Alkaline salts keep the pH neutral (from intestinal wall).
Peristalsis pushes food from duodenum into ileum, where epithelial cells that line the walls, produce the membrane- bound disaacharidase maltase.(not released into the lumen)
This hydrolyses maltose into alpha glucose, which can then be absorbed via co-transport.
Sucrose (found mainly in fruits) is hydrolyses by —— into —— and ——
Sucrase
Glucose
Fructose
Lactose (found mainly in dairy) is hydrolysed by —— into —— and ——
Lactase
Glucose
Galactose
What is chyme
Name of Food moving from stomach to ileum
Alkaline salts in ileum purpose
Keep pH neutral
Lipid digestion procedure
In small intestine
Lipases (produced by pancreas) hydrolyse the ester bond in triglycerides to produce a monoglyceride and two fatty acids
These then undergoes emulsification, where they are split into micelles (tiny droplets) by bile salts and increases the surface area of lipids to speed up enzyme action
Emulsification is —— process
Physical
A Michelle structure describe
Lipid has bile salts attached to it which are hydrophobic on inside (touching lipid) and hydrophilic on the outside
Protein digestion
Endopeptidases hydrolyse peptide bonds between amino acids in the central region of the protein molecule to form series of peptide molecules
Exopeptidases hydrolyse the peptide bonds on the terminal amino acid, from the peptide molecules formed after Endopeptidases work, releasing dipeptide and amino acids.
Dipeptidases hydrolyse the peptide bonds between dipeptide
They are membrane bound to epithelial cells of the ileum.
Why is it more efficient to digest proteins using Endopeptidases rather than exopeptidases?
Because Endopeptidases work on the central region, they split up the protein into smaller chunks, which have a larger surface area for exopeptidases to work upon, (more terminal regions to work upon), hence increases efficiency and rate of digestion.
Adaptations of the ileum for absorption
Villi/microvilli - large SA
Thin walls so small diffusion distance and capillaries
Muscle moves, which mixes contents so, maintains a diffusion gradient
Blood circulates maintaining diffusion gradient
Absorption of triglycerides process
Micelles (4-7nm) come into contact with the epithelial cell lining of ileum, due to movement within lumen, where they break down, releasing monoglyceride and fatty acids - which are non-polar so diffuse across cell-surface membrane easily.
Once in cell they are transported to smooth ER, where they recombine to form triglycerides.
Then to golgi where the triglycerides associate with cholesterol and lipoproteins to form structures called chylomicrons - which are special particles adapted for the transport of lipids.
They move out the epithelial cell via exocytosis and enter lymphatic capillaries called lacteals at the centre of each villus.
Once in blood system, they are hydrolysed by an enzyme in the endothelial cells of the blood capillaries, from where they diffuse into cells.
Three organelles expected to be in abundance in epithelial cell that lines ileum
ER-recombination of triglycerides
Golgi- associate with cholesterol and lipoproteins to form chylomicrons
Vesicles - to exit cell via exocytosis
What is the purpose of chylomicrons travelling through the lymphatic system?
Means they bypass the liver, hence it isn’t overloaded.
What do chylomicrons look like and what are they made of and have —— heads and are suspended in ——, which is possible because they are ——
Iridescent droplets
Triglycerides associated with cholesterol and lipoproteins
Hydrophobic heads, hence are stable, and can be suspended in plasma.
Trachea
Flexible airway made of muscle, ciliated epithelial cells and goblet cells that are supported by rings of cartilage that prevent collapse due to air pressure, during inhalation - produces mucus as well.
Bronchioles
Series of branching sub division of bronchus; epithelial cell lining and a smooth muscle lining that allows constriction of flow of air.
Bronchi
Two division of trachea, each leading to one lung. Similar structure to trachea and produces mucus and has cillia. Larger bronchi are supported by a proportional amount of cartilage.
Ribcage
Bony box that supports and protects lungs - moved by muscles between them
Lungs
Loved structured series of highly branched tubules
Diaphragm
Sheet of muscle involved in ventilation
Separates the thorax from the abdomen
Alveoli
Minute air sacs, where gas exchange occurs
Elastic fibres between them allow stretching when inflated and recoil during expiration.
During inspiration
External intercostal muscles contract and elevates ribs
Internal intercostal muscles relaxes
Diaphragm contracts and flattens
Thorax volume increases
Pressure in thorax decreases
Direction of air movement is into the lungs
During expiration
External intercostal muscles relaxes and lowers ribs
Internal intercostal muscles contracts
Diaphragm relaxes and domes
Thorax volume decreases
Pressure in thorax increases
Direction of air movement is out of lungs
Why do mammals have evolved specialised surfaces for gas exchange
Aerobic organisms require a constant supply of oxygen to release energy in the form of ATP
Volume of of oxygen absorbed and volume of CO2 released is large
Large organisms with Lange number of cells
Maintain a high body temp which is related to metabolic and respiratory rates.
Endotherms
Mammals that maintain body temperature
When temp drops they generate more heat by increasing O2 consumption therefore metabolic rate increases.
Exotherms
Use the environments temperature hence metabolic rate and temp rate both increase and decrease together on graph.
Why are lungs inside the body
Air is not dense enough to support and protect delicate structures and the body as a whole would lose a lot of H2O and dry out.
Tidal stream
Ventilated lungs and constantly replenished air
Ficks law
Diffusion is directly proportional to SA and Conc difference and inversely to diffusion path length
Adaptations of flatworm for gas exahneb is
Flattened shape so no cell is too far away from the surface
Five features of specialised exchange surfaces
Larger SA to V ratio
Movement of medium or transport system to maintain conc gradient
Short diffusion pathway
Selectively permeable
Ventilation is
The continual movement of air in and out of lungs which also maintains the concentration gradient
Inspiration and expiration due to
The pressure differences between the atmosphere and the thoracic cavity
Internal and external intercostal muscles work —— and are located
Antagonistically
External outside ribs internal between inside of ribs
During inspiration there is a bigger volume in lungs hence
Lowers pressure in lungs so air moves in
The intercostal muscles sticks
Plucural membrane to the ribs
Normal breathing is due to
Natural relaxation of diaphragm and elastic recoil
Tidal volume is
Volume of air normally taken in at each breath
Pulmonary ventilation equation
Dm^3 per min = tidal vol (dm^3) x breathing rate (min)
Adaptations of gas exchange system humans
Alveolar epithelium - number and shape of small sacs means there is a large surface area to volume ratio
Large surface area of capillary network for efficient exchange also maintains conc gradient
Narrow diameter of capillary means RBC can just fit in, hence right up against the wall so small diffusion distance for gas(also one cell thick) Additionally narrow diameter means slow flow of blood provides time for diffusion process to occur.
Pulmonary surfactant allows the for the dissolving of gases in alveolar sacs.
How many phospholipid bilateral will an oxygen molecule pass through after entering alveoli
5
Inside membrane of alveoli, outside of alveoli, outer wall of capillary, inner wall of capillary and then one wall of rbc
How many phopsholipid bilayers will one CO2 molecule pass through after entering alveoli
4 because it’s carried in blood plasma
Chronic pulmonary obstructive diseases
Type of persistent bronchitis, where bronchioles become inflames and reduced diameter and elepastic lining becomes floppy and air sacs break down hence create less but larger sacs which is no ideal for gas exchange called emphysema.
Order of bronchioles and bronchi and trachea
Trachea, bronchi, bronchioles
Single cell organisms gas exchange three points
They are small so have a large surface area to volume ratio and Diffusion occurs across body surface for oxygen
Cell wall/no other barriers to pass through
Short diffusion distance as cell-surface membrane is very thin
Describe the process in which gas exchange occurs in an insect
Air enters through holes in the side of the body called spiracles, which can be open and closed like valves. Generally closed to prevent water loss.
Internal network of tubes called tracheae carry air to tissue and are held open/supported by rings of chitin.
Branched tubes are known as tracheoles, from where there is a short diffusion pathway to the body cells.
State the three ways of movement of gases (respiratory) in the tracheal system of an insect
Along the conc gradient
Mass transport
Tracheole ends filled with water
Explain “Along the conc gradient” - way of movement of respiratory gases in an insect.
O2 is used up during respiration so the concentration near the end of the trance oles is less. CO2 is more inside and less outside, hence diffuses out - diffusion in air rather than water means diffusion is more rapid and efficient.
Why are the spiracles of an insect generally closed?
To prevent water loss.
Explain “Mass Movement” - way of movement of respiratory gases in an insect.
The contraction of muscles squeezes the trachea, so speeds up exchange as mass movement of air is enabled.
Explain “Tracheole ends filled with water” - way of movement of respiratory gases in an insect.
During major activity, the insect respires anaerobically, which produces lactate, which is soluble so lowers (makes more negative) the water potential of the muscle cells. Water moves via osmosis from the tracheoles to cells. The water in the ends of the tracheoles decreases in volumes and draws in more air, so more rapid diffusion occurs. Greater rate of exchange occurs so there is also a greater evaporation of water.
Limitations of insect respiratory gas exchange system, although it is efficient
Relies mostly on diffusion, so for effectiveness the diffusion pathway must also be small, hence limits the size of the insect.
Where are gills located
Inside body
Behind head
Gill structure describe
Gill filaments In a pile and perpendicular to the filaments are gill lamellae, which is the site of gas exchange and increase SA.
What keeps water moving in fish? What is the Order of where the water passes?
A ventilation system
Water in through mouth, forced over gills, out through the opening on either side of the gills(operculum).
How is oxygen transported to the site of gas exchange in fish?
O2 is dissolved in water and absorbed in by the gills. The movements of mouth and operculum are co ordinated to produce a stream of water over the gills and out of the operculum.
Name the way of flow of gas exchange system in fish??
Counter - current gas exchange system
Describe the counter current gas exchange system and explain its advantages
Water and blood flow in opposite directions
So blood is always meeting water with a higher O2 conc
Which maintains the diffusion gradient across the whole length of the gill
Therefore diffusion of O2 from water into blood can occur along the whole length of the gill and maximum possible gas exchange is achieved.
Disadvantages of a parallel flow gas exchange system
Same direction
So equilibrium would be obtained half way across the gill, so diffusion of O2 into the blood stops.
Photosynthesis equation
6CO2 + 6H20 + light energy gives C6H12O6 + 6O2
Respiration equation
C6H12O6 + 6O2 gives 6CO2 + 6H20 + ATP
Photosynthesis and respiration are essentially
Inverse
Which is dominant; photosynthesis or respiration?
Photosynthesis - if light exists.
If the rate of photosynthesis = the rate of respiration, then
There is no net uptake of CO2 or O2
Structure of plants adapted for gas exchange which is similar to insect gas exchange adaptations
No cell si far from external air
Diffusion in the gas phase so quicker than if it were in water.
General/all structures of plants adapted for gas exchange
No cell is far from external air
Diffusion in gas phase so quicker than if it were in water
Spongy mesophyll layer has air spaces that contain gases that readily come in contact with mesophyll cells
Storage are small pores and are numerous so no cell is far away from it so short diffusion pathway (Fick’s law)
Large surface are of mesophyll layer
How stoma and guard cell works
Guard cells open pore for letting in gas but close to stop evotranspiration at night
Stoma is open when pore takes in water because of uneven cellulose cell wall
Xerophytes are
Plants adapted to physiologically dry habitats by means of mechanism to prevent water loss
Sand dunes Salt marshes have a low water potential Tundra Coniferous forest Acid bogs
Holly Leaves adaptations to limit water loss
Thick waxy cuticle provides an increased waterproof barrier that reduces water loss by evotranspiration
Marram grass adaptations to limit water loss
Found in sand dunes
Rolled up leaves which traps water vapour inside so no diffusion gradient forms between the inside and the outside of the leaf
Evergreen (Christmas needle) adaptations to limit water loss
Decrease surface area to volume ration so less surface to lose water via evotranspiration, hence slows the rate of diffusion but gas exchange is also reduced.
Cacti adaptations to limit water loss
Thick cuticle Rolled up leaves Hairy leaves Stomate in pits of grooves Swollen stem
Thick cuticle prevents water loss because
Provides and increased waterproof barrier tor deuce water loss by evotranspiration
Rolling up of leaves prevents water loss because
Traps H20 vapour inside so no diffusion gradient can form between the inside and outside of the leaf
Hairy leaves prevents water loss because
HEATHER
Especially on lower epidermis traps moist air next to the leaf surface, so diffusion gradient is low, so less water loss by evotranspiration
Stomate in pits or grooves prevents water loss because
Traps still air next to lead and reduces the diffusion gradient
Swollen stem prevents water loss because
For photosynthesis
Stores water
Helps survival during drought periods
Lambs Ear water loss adaptations
Hairy leaves
