Organisms exchange substances with their environment Flashcards
What is the role of the xylem tissue
Transports water and mineral ions in solution. These substances move up the plant from the roots to the leaves.
What is the role of the phloem tissue
Transports organic substances like sugars both up and down the plant
What is the structure of xylem vessels
Long, tube-like structures formed from dead cells joined end to end . No end walls, making an uninterrupted tube that allows. water to pass. up through the middle
How does water move up a plant against the force of gravity
-Water evaporates from the leaves at the top of the xylem (transpiration)
-Creates tension, which pulls more water into the. leaf
-Water is cohesive, so when some molecules are pulled others follow
-Column of water in the xylem moves upwards
-Water enters the stem through the roots
What is transpiration
The evaporation of water from a plant’s surface.
Water evaporates from the moist cell walls and accumulates in the spaces between cells in the leaf. When the stomata open, it moves out of the leaf down the concentration gradient.
What are the factors that affect transportation rate
-Light: The more light the faster the transpiration rate, because the stomata opens when it gets light to let in carbon dioxide for photosynthesis
-Temperature: The higher the temperature the faster the transpiration rate. Warmer water molecules have more energy so they evaporate faster. This increases the concentration gradient between the inside and outside of the cell.
-Humidity: The lower the humidity, the faster the transpiration rate. If the air around the plant is dry, the concentration gradient between the leaf and air increases.
-Wind: The windier it is, the faster the transpiration rate. Lots of air movement blows away water molecules.
What is the role of sieve tube and companion cells
Sieve tube elements are living cells that form the tube for transporting solutes. They have no nucleus and few organelles, so they have companion cells that carry out living functions for sieve cells
What is translocation
The movement of solutes (assimilates) to where they are needed in a plant. It requires energy and occurs in the phloem. Enzymes maintain concentration gradient from the source to the sink by changing solutes at the sink, to ensure the conc is lower at the sink.
Mass Flow Hypothesis
-Active transport is used to load the solute from companion cells into the sieve tubes of the phloem at the source.
-Lowers the water potential inside sieve tubes, so water enters the tubes via osmosis from the xylem and companion cells, creating a high pressure inside the sieve tubes at the source of the phloem.
-At the sink end, solutes are removed from the phloem to be used up, increasing water potential inside the sieve tubes, so water also leaves tubes by osmosis, lowering pressure in the sieve tubes.
-There’s a pressure gradient from the source the. the sink, which pushes solutes along sieve tubes. towards the sink.
What is a potometer
Apparatus used to measure transpiration rates by measuring water uptake
How to use a potometer
-Cut shoot (slanted to increase SA for water uptake) underwater to prevent air entering xylem.
-Assemble potometer with capillary tube end submerged in a beaker of water
-Insert shoot underwater
-Ensure apparatus is watertight and airtight
-Dry leaves and allow time for shoot to acclimatise, shut the tap
-Remove the end of the capillary tube from the water beaker until an air bubble forms, then put the tube back in water
-Record the start position of the air bubble
-Start a stopwatch and record the distance moved. by the bubble per unit time.
-Only change one variable at a time.
Evidence For Mass Flow
-If a ring of bark, including phloem and not xylem, is removed from a woody stem, a bulge forms above the ring. The fluid from bulge has a higher concentration sugars than fluid below the ring, evidence of downward flow of sugars
-Radioactive tracer can track the movement of organic substances in a plant.
-Pressure in phloem can be investigated with aphids. The sap flows out quicker nearer the leaves than further down the stem- evidence of pressure gradient.
-If a metabolic inhibitor (stops ATP production) is put in the phloem, translocation stops- evidence that active transport is involved
What does an aphid do
Pierces the phloem, then their bodies are removed leaving the mouthparts behind, allowing sap to flow out
Use this information and your knowledge of surface area to volume ratios to suggest an explanation for the position of mitochondria in large U. marinum cells.
Larger cells have a smaller surface area to volume ratio. Takes longer for oxygen to diffuse
Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake.
Larger animals have a smaller surface area to volume ratio, so a specialised system will help overcome long diffusion pathway
Mammals such as a mouse and a horse are able to maintain a constant body temperature.
Use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse.
Mice are smaller organisms and therefore have a larger surface area to volume ratio. This means that mice have a shorter diffusion pathway and heat can be lost more easily. Mice must have a high metabolic rate as a faster rate of respiration releases heat
The scientist used units of μmol g–1 h–1 for the rate of oxygen uptake.
Suggest why he used μmol in these units.
Measures small uptake
The scientist decided to use the ratio of surface area to mass, rather than the ratio of surface area to volume. He made this decision for practical reasons.
Suggest one practical advantage of measuring the masses of frog eggs, tadpoles and adults, compared with measuring their volumes.
Less error in measuring mass, easier to find mass because of irregular shapes
Explain why oxygen uptake is a measure of metabolic rate in organisms.
Oxygen is used in respiration which requires ATP
Explain how the counter-current principle allows efficient oxygen uptake in the fish gas exchange system.
Blood and water flow in opposite directions, blood always passes water with a higher oxygen concentration, there’s a diffusion gradient maintained along the length of lamella
The damselfly larva is a carnivore that actively hunts prey. It has gills to obtain oxygen from water.
Some other species of insect have larvae that are a similar size and shape to damselfly larvae and also live in water. These larvae do not actively hunt prey and do not have gills.
Explain how the presence of gills adapts the damselfly to its way of life.
Damselfly has a higher metabolic rate so uses more oxygen per unit mass
Explain two ways in which the structure of fish gills is adapted for efficient
gas exchange.
Many lamellae so large surface area, thin surface so short diffusion pathway
Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange
Tracheoles have thin walls so short diffusion distance to cell.
They are highly branched so short diffusion distance to cells.
Trachea provides tubes full of air so fast diffusion into insect tissues.
Fluid at the end of the tracheoles that moves out into tissues during exercise so larger surface area for gas exchange.
Gas exchange insects
Air moves through spiracles on the surface, air moves through the trachea, gas exchange at tracheoles directly to/from cells.
Rhythmic. abdominal movements increase the efficiency of gas exchange by increasing oxygen entering → maintains greater conc gradient for diffusion.
Insects; adaptations
-Thick waxy cuticle → increased diffusion distance → less evaporation
-Spiracles can open and close → open to allow Oxygen in, close when water loss is too much
Structure of gills
Each gill is made of lots of thin plates (vertical) called gill filaments which provide large surface area. Gill filaments covered in lamellae (horizontal). Thin. epithelium short diff. distance between water and blood. Vast network capillaries on lamellae, removes oxygen. to maintain a concentration gradient.
Gas exchange in plants
CO₂ and O₂. diffuse through stomata, which is opened by guard cells. CO₂ and O₂ diffuse into mesophyll layer into air spaces down conc gradient.
Plants exchange; adaptations
-Lots of stomata that are close together →large surface area for gas exchange → gases don’t have to pass through cellist reach mesophyll.
-Interconnecting air space in mesophyll layers → gases come into contact with mesophyll cells
-Mesophyll cells have a large surface area
Xerophytic plants; adaptations
-Thick waxy cuticle →increased diffusion distance so less evaporation
-Stomata in pits, rolled leaves & hairs →trap water vapour →water potential gradient decreases → less evaporation
-Spindles → reduces surface area to volume ratio
Describe and explain the mechanism that causes lungs to fill with air.
Diaphragm muscle contracts and external intercostal muscles contract. Volume increases and pressure decreases. Air moves down a pressure gradient
Describe the gross structure of the human gas exchange system and how we breathe in and out.
Air enters the trachea, which split into two bronchi- one bronchus leading to each lung. Each bronchus branches off into smaller tubes ‘bronchioles’, which end in air sacs called alveoli.
Breathing in- Diaphragm muscles and external intercostal muscles contract. Volume increases and pressure decreases in thoracic activity. Air moves down a pressure gradient.
Breathing out. Diaphragm muscles relax and internal intercostal muscles contract. Volume decreases and pressure increase in thoracic activity. Air moves up along concentration gradient
Tidal volume is..
volume of air in each breath
Ventilation rate is…
Number of breaths per minute
Forced expiratory volume is…
max volume of air breathed out in one second
Forced vital capacity is…
max volume of air possible to breathe out forcefully after a deep breath it
Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveoli.
Less CO₂ exhaled out the lung, so reduced conc gradient between blood and alveoli, slower movement of CO₂ out of the blood
Bonds
Between lipids- Ester
Between starch-glycosidic
Between amine group and carboxyl group-peptide
Between nucleotides-phosphodiester
Types of peptidases
Endopeptidase- hydrolyses bonds within a protein
Exopeptidases- hydrolyse bonds at the end of a protein molecule, and remove single amino acids from protein
Dipeptidase- Hydrolyse peptide bond between dipeptide
Adaptations and functions of arteries
They carry blood from the heart to the rest of the body.
Thick muscular walls, and elastic tissue to stretch and recoil to maintain high blood pressure.
Endothelium is folded, allowing artery to stretch, to maintain high pressure.
All arteries, but pulmonary, carry oxygenated blood
Adaptations and functions of veins
Veins take blood back to the heart under low pressure.
Wider lumen will very little elastic and muscle tissue.
Valves stop blood flowing backwards.
Blood flow is assisted by contraction of body muscles around them.
All veins, but pulmonary, carry deoxygenated blood.
Adaptations of the heart
Left ventricle has thicker, more muscular walls than the right ventricle as it needs to contract powerfully to pump blood all around the body and the right ventricle needs to get blood to lungs which is closer
Ventricles have thicker walls than the atria, as they have to push blood out of the heart and the atria only needs to push blood to the ventricles
Atrioventricular valves link the atria and ventricles and stop blood flowing back into the atria when contractions occur
Semilunar valves link the ventricles to the pulmonary artery and aorta, and stop blood flowing back into the heart after ventricles contract
Describe and explain features of the alveolar epithelium that makes the epithelium well adapted as a surface for gas exchange.
Single layer of cells, reduces diffusion distance
Permeable allows diffusion of carbon dioxide
Good blood supply from network of capillaries maintains conc gradient
Elastic tissue so recoils after expansion
Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveoli.
Less carbon dioxide exhaled out of the lungs, so there’s a reduced diffusion gradient between blood and alveoli, less movemement of carbon dioxide out of the blood.
Explain why death of alveolar epithelium cells reduces gas exchange in human lungs.
Reduced surface area, increases distance for diffusion, reduced rate of gas exchange
Describe the pathway taken by an oxygen molecule from an alveolus to the blood.
Diffuses out of the alveoli across alveolar epithelium, and the capillary endothelium and into haemoglobin.
Explain how one feature of an alveolus allows efficient gas exchange to occur.
One cell thick, short diffusion pathway
Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs.
Do not include descriptions of pressure changes in the heart or the role of heart valves in your answer.
Renal vein, vena cava to right atrium, right ventricle to pulmonary artery
Tissue fluid is formed from blood at the arteriole end of a capillary bed.
Explain how water from tissue fluid is returned to the circulatory system.
Plasma proteins remain, creates water potential gradient, water moves to blood by osmosis, returns to blood by lymphatic system
Suggest two ways the student could improve the quality of his scientific drawing of the blood vessels in this dissection.
Annotate diagram, do not use sketching, add magnification scale bar
Explain how an arteriole can reduce the blood flow into capillaries.
Muscle contracts and narrows arteriole
Relationship between SA:volume and metabolic rate
Rate of heat loss increases as SA:volume increases , so they need a higher metabolic rate to generate enough heat to maintain a constant body temperature
Gas exchange in the alveoli
Oxygen diffuses from alveoli down its conc gradient across the alveolar epithelium, across the capillary endothelium into the blood in Hb. Carbon dioxide diffuse from capillary down its conc gradient across the capillary endothelium, across the alveolar epithelium into the alveoli.
Why is ventilation needed
-Maintains an Oxygen conc gradient
-Brings in air containing higher conc of oxygen
-Removes air with lower conc of Oxygen
Alveolar epithelium; adaptations
-Squamos epithelium- one cell thick →short diffusion distance
-Large SA:volume → fast diffusion
-Permeable
-Good blood supply from network of capillaries maintains conc gradient
-Elastic tissue allows it to recoil after expansion
Lungs; adaptations
-Many alveoli/capillaries → large surface area → fast diffusion
-Alveoli/capillary walls are thin/ short distance between alveoli and blood →short diffusion distance
-Ventilation →maintains conc gradient so faster diffusion
Fibrosis effects
-Scar tissue in lungs → thicker and less elastic than normal. Increases diffusion distance → rate of diffusion decreases. Faster ventilation rate so enough Oxygen can get to lungs/blood
-Lungs can expand and recoil less → can’t hold as much air , reduced TD and FVC
Asthma effects
Inflamed bronchi, smooth muscle lining bronchioles contract → airways contrict → narrow diameter → airflow of lungs reduces →less Oxygen enters alveoli/blood.
What is the effect of less Oxygen entering the alveoli
Reduced rate of gas exchange in the alveoli → less Oxygen diffuses into the blood → cells receive less Oxygen → rate of aerobic respiration reduced → less energy released → fatigue
Digestion of starch
Amylase hydrolyses starch to maltose →membrane bound maltase hydrolyse maltose to glucose → hydrolysis of glycosidic bond
Where is amylase produced
Salivary glands, released into mouth
Pancreas, released into small intestine
Digestion of lipids
-Bile salts produced by liver emulsify lipid to smaller droplets →increasing SA:V of lipids speeding up lipase action
-Lipase made in pancreas is released to small intestine
-Lipase hydrolyses lipids → monoglycerides+ fatty acids, breaking ester bond
-Monoglycerides, fatty acids & bile salts stick together to form micelles
How is products of digestion absorbed by cells lining the ileum
-Monoglycerides and fatty acids diffuse out of micelles into epithelial cells as they are lipid soluble
-Monoglycerides and tryglycerides recombine to triglycerides to form globules
-Globules coated with proteins to form chylomicrons
-Leave via exotycosis and enter lymphatic vessels
-Return to blood circulation
How can atheroma result in a heart attack
-Atheroma causes narrowing of coronary arteries
-Restricts blood flow to heart muscle supplying glucose, oxygen etc.
-Heart anaerobically respires→less ATP produced→ not enough energy for heart to contract→lactate produced→damages heart tissue/muscle
What factor increases the probability of getting cardiovascular disease
-Age
-Diet high in salt or saturated
-High consumption of alcohol
-Stressful lifestyle
-Smoking cigarettes
-Genetic factors
How does high blood pressure increase atheroma
Increases risk of damage to endothelium of artery wall which increases atheroma which can cause blood clots
Causes of accumulation of tissue fluid
-Low concentration of protein in blood plasma
-Water potential in capillary not as low, so water potential gradient is reduced
-More tissue fluid its formed at arteriole end
-Less water absorbed into blood capillary by osmosis
How does high blood pressure lead to accumulation of tissue fluid
-High bp= high hydrostatic pressure
-Increases outward pressure from arterial end of capillary / reduces inward pressure at venule end of capillary
-So more tissue fluid formed/ less tissue fluid is reabsorbed
-Lymph system is not able to drain tissues fast enough
How does the atrial systole maintain unidirectional flow of blood
-Atria contracts→decreasing volume and increasing pressure inside aorta
-Atrioventricular valves forced open
-When pressure inside atria > pressure inside ventricles, atrioventricular valves open
-Blood pushed into ventricles (semilunar valves are shut)
How does the ventricular systole maintain an unidirectional flow of blood
-Ventricles contract from the bottom up→decreasing volume and increasing pressure inside ventricles
-Semilunar valves forced open, when pressure inside ventricles>pressure inside arteries
-Atrioventricular valves shut, when pressure inside ventricles> pressure inside atria
-Blood pushed out of heart through arteries
How does the diastole maintain an unidirectional flow of blood
-Atria and ventricles relax→increasing volume and decreasing pressure inside chambers
-Blood from veins fills atria (increasing pressure in atria slightly) and flows passively to ventricles
-Atrioventricular valves open, when pressure inside atria> pressure inside ventricles blood flows passively to ventricles
-Semilunar valves shut, when pressure inside arteries> pressure inside ventricles
Why do valves shut
Prevent back flow of blood into chamber/vein to maintain unidirectional flow of blood through the heart
Structure of capillaries and importance of capillary beds as exchange surfaces
-Thin layer of endothelial cells→short diffusion pathway→rapid diffusion
-Capillary bed made of large network of branched capillaries→increases sa:v → rapid diffusion
-Narrow lumen→reduces flow so more times for diffusion
-Capillaries permeate tissues (no cell is far from capillary)→short diffusion pathway
-Pores in walls between cells→allows substances to escape
What is tissue fluid
-Fluid surrounding cells/ tissues
-Provides respiring cells with water/oxygen/glucose/amino acids
-Enable waste substances to move back into blood
Formation and return of tissue fluid
-At arteriole end of capillaries thereigher hydrostatic pressure inside capillaries than tissue fluid
-Forces fluid out of capillaries into spaces around cells
-Large plasma proteins remain in capillary as they’re too large to leave
-At venule end, hydrostatic pressure reduces as fluid leaves capillary
-As water is lost, an increasing concentration of plasma proteins lowers water potentials in capillary below water potential of tissue fluid
-Water re-enters capillaries from tissue fluid by osmosis down gradient
-Excess water taken up by lymph system and is returned to circulatory system- through veins in neck
The closed double circulatory system
Pulmonary circulation
-Deoxygenated blood in right side of heart pumped to lungs→oxygenated blood returns to left side of heart
Systematic circulation
-Oxygenated blood in left side of heart pumped to tissues/organs→deoxygenated blood returns to RHS
Why is closed double circulatory system important for mammals
-Prevents missing of oxygenated and deoxygenated blood→ blood pumped to body is fully saturated with oxygen→ efficient delivery of oxygen and glucose for respiration
-Blood can be pumped at a higher pressure→substances taken to and removed from body cells quicker and more efficiently
Role of coronary arteries
Delivers oxygenated blood to cardiac muscle
Blood vessels which enter and leave heart
Aorta- takes oxygenated blood from heart to respiring tissues
Vena cava- takes deoxygenated blood from respiring tissues to heart
Blood vessels entering and leaving lungs
Pulmonary artery-takes deoxygenated blood from heart to lungs
Pulmonary vein-takes oxygenated blood from lungs to the heart
Blood vessels entering and leaving kidneys
Renal arteries takes deoxygenated blood to kidneys
Renal veins take deoxygenated blood to the vena cava from the kidneys
