Organisms Exchange Substances With Their Environment 3 Flashcards
Define digestion
The hydrolysis of large Insoluble food molecules into small soluble food molecules that can be absorbed and assimilated
What is the surface area to volume ratio like for smaller organisms and larger organisms
Smaller organisms have a large surface area to volume ratio
Larger organisms have a smaller surface area to volume ratio
What are the features of small organisms that allows them to simply exchange substances across their surface
Big surface area for susbyabce exchange
Short diffusion distance from the outside to the centre of the organisms
What features does large organisms have which means substances can’t diffuse across the surface
Smaller surface area to volume ratio and a larger distance from tbe outside to the centre of the organism
Larger organisms usually have a higher metabolic rate so it requires more efficient transport of waste out of cells and reactants into the cell(oxygen, carbon dioxide, nutrients, urea, amino acids)
What are some evolved features for efficient Gas exchange
-Flattened shape(No cell is far from the surface e.g. flatwork, leaf)
-Specialised exchange surface(Increase surface area to volume ratio e.g. lungs gills)
What are some key features of specialised exchange surfaces
-Large surface area to volume ratio
-Very thin membranes(short diffusion distance)
-Movement of environmental medium
-Transport system(movement of internal medium to maintain a diffusion system)
-Partially permeable so only specific molecules can pass through
Explain the process of digestion of carbohydrates/polysaccharides
Salivary glands and pancreas produce amylase which hydrolyses polysaccharides into disaccharides by hydrolysis glycosidic bonds
In the duodenum and iluem, membrane bound disacchardases are produced which hydrolysis disaccharides into monosaccharides
What are the two types of digestion and explain them
Mechanical: Hydrolysis of large food molecules into smaller forms to increase surface area
Chemical: Hydrolysis of large food moelcules into smaller soluble molecules with the action of enzymes
What does Maltase, sucrase and lactase do
Maltase hydrolyses Maltose into glucose
Sucrase hydrolyses sucrose into glucose and fructose
Lactase hydrolyses lactose unto glucose and galactose
What is the oesophagus
Peristalsis pushes food down into the stomach, what is peristalsis
A muscular tube that connects the mouth to the stomach
The contraction and relaxation of the walls of the oesophagus
What happens to carbohydrates in the stomach
Nothing because there’s no amylase, only churning of carbohydrates
How is the ileum adapted to absorption
Why is pancreatic juice alkali
Inner walls are folded into villi which are further folded into microvilli which increases surface area for absoption
To maintain a neutral pH as food from the stomach is acidic brcuqse it contains HCL
Starch is hydrolysed into — which is then hydrolysed into —-
Maltose
Glucose
What is absorption
Digested food molecules cross the walls of the intestine into the blood
How is the small intestine adapted to increase absorption rates
-Lots of microvilli(projections on the surface of intestines) which increases surface area
-Lots of mitochondria which releases ATP
What are cotransport proteins
Proteins that transport two or more moelcules across a membrane
What are peptidases
Enzymes involved in the hydrolysis of proteins by hydrolysing peptide bonds between amino acids
Explain how peptin,endopeptidases, exopeptidases and dipeptidases are involved in the digestion of proteins
PEPTIN: Hydrolyses proteins into peptides
ENDOPEPTIDASES: Hydrolyses peptide bonds between amino acids in the central region of the protein to form smaller peptide moelcules+increase surface area
EXOPEPTIDASES: Hydrolyses peptide bonds on the terminal amino acids of a peptide
DIPEPTIDASES: Hydrolyses peptide bonds between amino acids in a dipeptide
Where is carbohydrase, lipase and protease produced
CARBOHYDRASE: Pancreas, Small intestines, Salivary glands
LIPASE: Pancreas, Small intestines
PROTEASE: Pancreas, Small intestines, stomach
What is beneficial about the function of endopeptidases
They make more ends for exopeptidases to act on and also increase the surface area
What are lipids digested by
Lipase and bile salts
Explain the process of lipid digestion and absorption
-Lipase is produced in the pancreas which hydrolyses ester bonds in triglycerides to form monoglycerides and fatty acids
-Bile acid emulsifies large globules of fat into smaller droplets to increase surface area for faster hydrolysis by lipase
-Bile salts, monoglycerides and fatty acids combine to make micelles which makes fatty acids and monoglycerides more soluble in water
-Micelles carry fatty acids and monoglycerides to the epithelial cells through diffusion as they are non polar
-Fatty acids and monoglycerides join to form triglycerides
-Golgi apparatus packages triglycerides and proteins to form a chylomicron
-Excocytosis occurs which releases the chylomicron from the epithelial cells into the lacteal
-The lacteal takes the chylomicron to the blood capillaries
EXAM QUESTION: Describe the processes involved in the absorption and transport of digested lipid moelciles from the ileum to lymph vessels(5 marks)
- Micelles contain bile salts, fatty acids and monoglycerides
- Makes fattya cider and monoglycerides more soluble in water
- Fatty acids and monoglycerides absorbed by diffusion
- Triglycerides are formed
- Excocytosis
Insects have a thick exoskeleton
Describe the exoskeleton
It is made from a hard fibrous material for protection and a lipid layer to prevent water loss from evaporation of surfaces
Insects don’t have lungs, instead they have a …
Tracheal system
What are 3 insects adaptations to prevent water loss
-Insects gave a small surface area to volume ratio where water can evapourate from
-Insects have a waterproof exoskeleton
-Pair of valves over spiracles which can open and close to reduce water loss
Explain Spiracles
Explain Trachea
Explain Tracheoles
SPIRACLES: Holes in exoskeleton, Pair of valves over spriracles which can open and close, hairs around valve to reduce water loss
TRACHEA: Network of tubes with rings of chitin in it which strengthens the tubes and keeps them open
TRACHEOLES: Dead end tubes(made of dead cells), end at body cells (to deliver oxygen to all repairing cells), contains air sacs(gas is stored), (larger insects) filled with water
Explain how oxygen is transported in the tracheal system of an insect
During respiration, oxygen is used up so the oxygen cocnetrarion at tracheole ends decreases so there is now a cocnetrarion gradient for oxygen so oxygen diffuses down the cocnetrarion gradient from the atmosphere, along he trachea and tracheoles into the cell
Explain how carbon dioxide is transported in the tracheal system of an insect
During respiration, carbon dioxide is produced so the carbon dioxide concentration at tracheole ends increases so now there is a concentration gradient for carbon dioxide so carbon dioxide diffuses down the cocnnetrarion gradient from cells, along tracheoles and trachea, into the atmosphere
What are the advantages and disadvantages of the tracheal system in insects
ADVANTAGES: Short diffusion pathway for gases, maintains diffusion concentration gradient
DISADVANTAGES: When spiracle valves open water can evaporates which causes dehydration (this can be overcome as spiracles remain closed most of the times as air stored in air sacs can be used), relies on diffusion so diffusion pathway has to be short so the size of the insect is limited
Why is the tracheal system insufficient for larger insects
-Diffusion pathway is longer
-More active so needs more energy
-Needs more oxygen
Describe two methods large insects use for the movement of gases
-Rings of muscles that can contract or relax (rhythmic abdominal movement) which allows a large movement of air in and out of the trachea which increases the concentration gradient
-Muscle cells carry out anaerobic respiration which produces lactate, water potential in muscles decreases, water moelcules osmosis from the tracheoles into muscle cells, this increases the exposed surface area for air, gases diffuse faster in air than water so a greater volume of oxygen is supplied(goes back to aerobic respiration)
Give 3 adaptations in insects for efficient Gas exchange
-Large number of fine tracheoles which gives a larger surface area
-Walls of tracheoles are thin and short distance between spiracles and tracheoles
-Use of oxygen and production of carbon dioxide creates steep diffusion gradients
What are two features of bony fish
Waterproof scales and small surface area to volume ratio
Gills are made from … that are …..
Each Gill filament is covered in … which are …. to the filament
As water passes through the gills, … occurs at the lamellae
Gills are made from Gill filaments that are stacked upon eachother
Each Gill filament is covered in lamellae which are perpendicular to the filaments
As water passes through the gills, gas exchange occurs at the lamellae
List the adaptations for efficent gas exchange in fish
-Many Gill filaments covered in lamallae which increases surface area
-Single layer of epithelial cells which provides a short diffusion pathway
-Dense capillary network which provides a short diffusion pathway
-Fish pushes water over gills which means there’s constant ventilation
-Counter current flow maintains a concentration gradient
What is counter current flow
The flow of blood in capillaries and water over lamellae in opposite directions
Explain how counter current enables efficient diffusion of gases
It ensures that that the equilibrium is not reached as the diffusion gradient is maintained across the entire length of the lamellae so almost all of the oxygen diffuses into the blood
Explain why parallel flow in fishes leads to inefficient diffusion of gases
The diffusion gradient is not maintained across the entire length of the lamella so only some of the oxygen diffuses in
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Define ventilation
Define respiration
Ventilation is the physical movement of air in and out the lungs
Respiration is the chemical reaction to release energy in the form of ATP
Explain the structure of trachea and bronchus
-contains goblet cells which produces mucus that traps dirt
-made of smooth and elastic muscles which are lined with ciliated epithelium and cilia removes mucus
-flexible
-c shaped cartilage which holds it open and prevents it from collapsing
Explain the structure and function of bronchioles
Made from muscle which constrict to control air flow
What are alveoli made from
How is it adapted for efficient Gas exchange
Collagen and elastic fibres
Capillary is one cell thick and alveoli epithelium cells are very thin providing a short diffusion pathway
Alveoli surrounded by a network of capillaries which maintains a concentration gradient
Lots of alveoli with a large surface area to volume ratio which increases surface area
Where is the thorax located
What is the diaphragm
Between the neck and abdomen
Dome shaped muslce that seperates thorax from abdomen
Intercostal muscles are a ….. pair of muscles
Antagonistic
Is it inspiration or expiration when external intercostal muscles contract and when internal intercostal muscles contract
External intercostal muscles contract - Inspiration
Internal intercostal muscles contract - Expiration
Explain the process of inhalation
-External intercostal muscles contract and internal intercostal muscles relax
-Diaphragm contracts and flattens
-Volume of thorax increases as ghe ribcage moves up and out
-Pressure of thorax decreases to below atmospheric pressure
-Atmospheric air is forces into lungs down pressure gradient
Explain the process of exhalation
-External intercostal muscles relax and internal intercostal muscles contracts
-Diaphragm relaxes
-Volume of thorax decreases as the ribcage moves in
-Pressure of thorax increases to above atmospheric pressure
-Air is forces out of the lungs down pressure gradient
Define pulmonary ventilation
What is the formula for pulmonary ventilation
Give the units
Define each part in the formula
Pulmonary ventilation is the total volume of air that moves into lungs in one minute
Pulmonary ventilation(dm³min-¹) = Tidal volume(dm³) × Breathing rate(min-¹)
Tidal volume is the volume of air takin in at each breath
Breathing rate is the number of breaths taken in a minute
What does a spirometer do
Records the volume of air in and out the lung
Define correlation, causation and risk factors
CORRELATION: Change in one variable is linked to the change in another
CAUSATION: One variable directly causes another
RISK FACTORS: Something that correlates with an increased chance of developing a disease
When do you use and what is measurements, what two tests
When do you use and what is frequencies, what test
MEASUREMENTS: Investigation Involved in taking measurements
-Looking for differences between mean values(t test)
-Looks for associations between different measurements from the same sample - correlation coefficient
FREQUENCIES: Finds the number of individuals in different categories(chi squared test)
For correlation coefficient, give a conclusion for when the result of a statistical analysis is larger than the critical value
There is less than 5% probability that the correlation is due to chance
We reject the null hypothesis
For correlation coefficient, give a conclusion for when the result of a statistical analysis is smaller than the critical value
There is more than 5% probability that the correlation is due to chance
Accept null hypothesis
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What does the pulmonary vein do
Carries oxygenated blood from the lungs to left atrium
What does the Aorta do
Carries oxygenated blood from left ventricle to rest of the body
What does the vena cava do
Carries deoxygenated blood from body to right atrium
What does the pulmonary artery do
Carries deoxygenated blood from right ventricle to lungs
Describe the structure of atria in the heart
Thin muscular walls, elastic walls to stretch when blood enters
Describe the structure of ventricles
Thicker muscular walls (compared to atria)
Explain the size of muscle in the right and left ventricle
Right ventricle: Thinner muscle than LV as blood is transported to lungs at lower pressure to prevent damage to capillaries and slower blood flow to allow diffusion to occur
Left ventricle: Thicker muscle than rv as it transports blood to body at higher pressure to travel a greater distance
Where is the semi lunar valve located
Aorta and pulmonary artery
Where are atrioventricular valves found
Where are bicuspid valves and tricuspid valves found
Between atria and ventricles
Bicuspid - left
Tricuspid - right
Which way do atrioventricular valves and semilunar valves point
AV-Downwards
SL-Upwards
What is meant by the heart working as a closed circuit and double circuit
Closed circuit: Blood is is blood vessels
Open circuit: Transports blood to lungs and body
What does the coronary artery do
Delivers oxygenated blood to the heart muscle
What connects the kidneys to the heart
Renal veins
Renal arteries
Explain two features of cardiac muscle
Myogenic as it can contract and relax without nervous stimulation or hormonal stimulation
Never fatigues as coronary arteries constantly supply them with oxygen
Where are coronary arteries found
What happens if this is blocked
Branches of the aorta
If is blocked, cardiac muscles starved of oxygen, no respiration occurs, myocardial infarction(heart attack)
What do valves do
When do they open and close
Valves prevent backflow
They open when there is a higher pressure behind
They close when there is a higher pressure infront
What does the septum do
Seperates oxygenated blood and deoxygenated blood
Maintains a high concentration of oxygen in oxygenated blood to maintain a steep concentration gradient
What is the cardiac cycle
What is systole and diastole
What are the 3 stages of the cardiac cycle
System of events that make up 1 heart beat
Systole - Contration
Diastole - Relaxation
Diastole, Atrial systole, Ventricular systole
Explain the diastole, atrial systole and ventricular systole in the cardiac cycle
DIASTOLE: The atria fills and pressure increases, pushed av valves to open, blood enters ventricles, atrium and ventricle walls relax, pressure in ventricles is lower than pressure in aorta and pulmonary artery, sl valves close - ‘dub’ sound
ATRIAL SYSTOLE
-Muscular walls of atria contract so remaining blood goes to ventricles
-Muscular walls of ventricles relax so they fill with blood
VENTRICULAR SYSTOLE
Ventricle contracts after a delay and pressure in ventricle increases. Pressure in the ventricle is higher than the atrium so av valve closes - ‘lub’sound, pressure in ventricle increases forcing sv valves to open as blood is pushed into the aorta and pulmonary artery
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What is the formula for cardiac output
Cardiac output = stroke volume × heart rate
Cardiac output = stroke volume × heart rate
Give the units
Cardiac output dm³ min‐1
Stroke volume dm³
Heart rate bpm
Define
Cardiac output
Stroke volume
Heart rate
Cardiac output is the volume of blood pumped by the heart in 1 minute
Stroke volume is the volume of blood that leaves the heart at each beat
Heart beat is beats per minute
What does the electrocardiogram do
The electrocardiogram shows electrical changes in a heart during each beat
What is cancer caused by
The mutation in genes that regulate mitosis
If these genes mutate and non functioning proteins are made, mitosis is not regulated which results in uncontrollable division of cells which forms a tumour
Explain benign tumours
-Can grow very large but at a slow rate
-Non cancerous as they produce adhesive moelcules sticking them together and to a particular tissue
-Often surrounded by a capsule so remain compact
-Can be removed by surgery + rarely return
Explain benign tumours
-Can grow very large but at a slow rate
-Non cancerous as they produce adhesive moelcules sticking them together and to a particular tissue
-Often surrounded by a capsule so remain compact
-Can be removed by surgery + rarely return
Explain malignant tumours
-Cancerous and spread quickly
-Do not produce adhesive moelciles so metastasis occurs where the tumour breaks of and spreads to other parts of the body through the bloodstream to form secondary tumours
-Tumour is not encapsulated and isn’t easy can grow projections into surrouding tissues and develop its own blood supply
-Supplementary treatment to remove tumour (radiotherapy and chemotherapy) and recurrence is more likely
-Cell nucleus becomes larger and the cell becomes unspecialised again
What 3 ways cab mutations be induced by
Radiation: High energy ionising radiation affects bidning of correct base pairs
Chemicals
Virus: Change base sequence in DNA
What happens when a stem cell divides by mitosis
One cell has the potency to remain as a stem cell, the other cell differentiates to form a specialised cell
What are proto oncogens
Cells that regulate cell growth and development of the cell
What do arteries do
Arteries carry blood away from the heart
What do veins do
Veins carry blood back into the heart
State the order blood flows through blood vessels
Arteries - Arterioles - Capilaries - Venules - Veins
Compare the shape of the lumen in a vein to an artery and how this affects speed of blood flow in veins
Vein lumen is an irregular shape and is bugger than arteries so there is greater friction against blood so slower blood flow
What is the endothelium in blood vessels
A smooth layer that prevents friction
ARTERIES
Muscular layer
Elastic layer
Thickness of wall
Valves
-Thick muscle layer that contacts and relaxes to control blood flow
-Thick elastic layer that stretches syringe systole and recoils during diastole to maintain blood pressure
-Hicker walls to prevent vessels from bursting due to high pressure
-No valves
ARTERIOLES
Muscular layer
Elastic layer
Thickness of wall
Valves
-Thicker muscle layer than arteries to restrict blood flow
-Thinner elastic layer that arteries as pressure is lower
-Thinner walls as pressure is slightly lower
-No valves
VEINS
Muscular layer
Elastic layer
Thickness of wall
Valves
-Thin muscle layer
-Thin elastic layer as pressure is lower
-Thinner walls as pressure is lower so low risk of vessels bursting
-Valves to prevent backflow
CAPILARIES
Muscular layer
Elastic layer
Thickness of wall
Valves
-No muscle layers
-No elastic layer
-One cell thick - short diffusion pathway
-Highly branched - large SA
What is tissue fluid and what does it contain
Fluid that bathes in cells and allows the exchange of substances between blood cells
Contains water, glucose, amino acids, fatty acids, salts and oxygen
Capillaries gave small gaps in their walls so what can be forced out
Liquids and small molecules
What is hydrostatic forces
Force of a liquid on a surface
Explain the formation of tissue fluid and where does this occur
As blood enters capillaries from arterioles, smaller diameter causes a high hydrostatic pressure so water, glucose, amino acids, fatty acids, salts, oxygen and small proteins are forced out, RBC, platelets and large proteins are left in blood
Occurs at arteriole end of capillary
During the formation of tissue fluid, what molecules are left in the blood
Red blood cells
Platelets
Large proteins
Describe the reabsorption of tissue fluid and where does this occur
-Loss of fluid inside capillaries lowers water potential so water in tissue fluid moves into capillaries by osmosis
-Hydrostatic pressure in capillaries at venule is lower than Hydrostatic pressure outside capillaries so tissue fluid is forces back in
Occurs towards venule ends of capillaries
What is the purpose of the lymphatic system
Not all the tissue fluid will be absorbed as equilibrium will be reached
Rest of the tissue fluid is absorbed into the lymphatic system and eventually drains back into the bloodstream near the heart
How are lymph vessels similar to veins
They both contain valves
What is lymphodema
Lymph system is damaged and prevents fluid from returning to blood
What is lymphoma
Cancer of the lymphatic system
Lymph contains lymphocytes
What are lymphocytes made in and what role do they play
Made in lymph nodes
Play a role in immunity (WBC)
What is lymph moved by
Hydrostatic pressure
Contraction of lymph vessels
What are the components of lymph system
Lymphatic vessels
Lymph nodes
Lymphatic tissue
What structure is haemoglobin
Quaternary structure
How many polypeptide chains does haemoglobin have and what do they contain
4
Each polypeptide chain contains a heme group which has an iron
What does affinity of haemoglobin for oxygen mean
The ability of haemoglobin to bind to oxygen
What does saturation of haemoglobin with oxygen mean
When haemoglobin is holding the maximum amount of oxygen it can bind to
Describe the oxyhaemoglobin dissociation curve
Oxygen in loaded in regions with a high partial pressure of oxygen and unloaded in regions with low partial pressure of oxygen
Give an example of where oxygen is loaded and unloaded
Loaded in alveoli
Unloaded in respiring tissue
What is the cooperative nature of oxygen binding to oxyhaemoglobin due to
Haemoglobin changes shape when the first oxygen binds
This makes it easier for further oxygen to bind
Explain the bohr effect
Oxyhaemoglobin curve shifts to the right
Affinity for oxygen decreases because the acidic carbon dioxide slightly chnages the shape of haemoglobin
Explain the difference between the fetal haemoglobin curve and mother haemoglobin curve
Fetal curve shifts to the left, has a higher affinity for oxygen because a fetuses only source of oxygen is from its mothers haemoglobin in the placenta so its affinity for oxygen needs to be higher than its mother
Explain the oxyhaemoglobic curve for llamas
Live in high altitudes where there is a lower partial pressure of oxygen
Curve shifts to the left so haemoglobin have higher affinity for oxygen
Explain the oxyhaemoglobic curve for smaller mammals
Curve shifts to the right, haemoglobin has less affinity for oxygen
Have faster metabolism so more oxygen for more respiration
What are two types of plants
Dicotyledonous
Xerophyte
What are the 3 main layers in a dicotyledonous leaf
Palisade mesophyll
Spongy mesophyll
What is the stomata
Pore in epidermis of leaves
How is the spongy mesophyll adapted for gas exchange
It has lots of space for gases to diffuse and this helps maintain the concentration gradient
Where does photosynthesis occur in a dicotyledenous leaf
Palisade mesophyll
What does the xylem and phloem transport and where is it found in a dicotyledonous leaf
Xylem transports water and dissolved mineral ions
Phloem transports sucrose
Found in vascular bundle
What is the adaptations of palisade mesophyll
Tightly packed, oblong shape with lots of chloroplast for photosynthesis
Explain the gas exchange in the stomata
Oxygen diffuses out and carbon dioxide diffuses in
To maintain concentration gradient
How does stomata reduce water loss from evaporation
It closes at night when photosynthesis wouldn’t be occurring
Where are xerophyte plants adapted to survive in
Environments with limited water, dry places
What are the 5 structural features adaptations of xerophytic plants
Curled leaves to trap moisture to increase local humidity
Hairs to trap moisture to increase local humidity
Sunken stomata to trap moisture to increase local humidity
Thicker cuticle go reduce evaporation
Longer root network to reach more water
WATER POTENTIAL INSIDE AND OUTSIDE LEAF IS THE SAME AS IT REDUCES WATER POTENTIAL GRADIENT SO LESS EVAPOURATION AND TRANSPIRATION
What do guard cells do
They open and close the stomata
What is special about gaurd cells
The only epidermal cells with chloroplast
What is transpiration
The loss of water vapour from the stomata by evaporation
What are the 4 factors that affect transpiration
Light intensity
Temperature
Humidity
Air movement
How does light intensity affect transpiration
High light intensity
More stomata open
Larger surface area for evaporation
Increase transpiration
How does temperature affect transpiration
High temperature
Water moelcules have more kinetic energy and move faster
More evaporation
Increased transpiration
How does humidity affect transpiration
Low humidity
Water potential is higher in lead than outside leaf, increasing water potential gradient
Increased transpiration
How does air movement affect transpiration
Increased air movement
Moist air is removed from around the leaf
Water potential gradient is maintained
Increases transpiration
What are the 2 features of water enabling water to move up against gravity
What is this called
Cohesion
Adhesion
Cohesion tension theory
How does cohesion help pull water up against gravity
Hydrogen bonds form between the oxygen of one molecule and Hydrogen of another molecule
This means water can travel up the xylem as a continuous column
How does adhesion help pull water up against gravity
Water molecules sticks to xylem walls
The narrower the xylem, the bigger the impact of adhesion
Describe the movement of water up the xylem
I. Water vapour evaporates out of stomata on leaves. This loss in water volume creates a lower pressure.
2. When this water is lost by transpiration more water is pulled up the xylem to replace it (moves due to negative pressure).
3. Due to the hydrogen bonds between water molecules, they are cohesive (stuck together).This creates a column of water within the xylem.
4. Water molecules also adhere (stick) to the walls of the xylem. This helps to pull the water column upwards.
5. As this column of water is pulled up the xylem it creates tension, pulling the xylem in to become narrower.
What do you use to measure transpiration
Potometer
When using a potometer, why must the shoot be cut underwater
To prevent any air entering the xylem and breaking tbe column of water
Why must a potometer be air tight
No air bubbles get in
No water leaks out so doesn’t affect accuracy of measure of uptake of water
How do you reset a potometer
Open the reservoirs tap so water moves into the capillary tube and pushes the air bubble back to the starting position
As the xylem vessel matures, what is it strengthened by
Lignin
How is xylem formed
The vessels join end to end - as the vessel matures, end walls break down - forms a long, continuous hollow tube
Talk about the organelles in a xylem
There are no organelles
Talk about the organelles in a xylem
There are no organelles
Explain some adaptations of the xylem
-Lignin in the xylem walls to withstand tension of water as it is pulled up as a continuous column
-Lignin in xylem walls prevent xylem from collapsing
-No living contents in cell - little resistance to water movement
-End walls break down to form a long continous hollow tube
-Pits allow water to move sideways out of the xylem which prevents air bubble being former
What are pits
Pores in the side walls of xylem
