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Flashcards by Maddie Wright, updated more than 1 year ago
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Created by Maddie Wright
almost 6 years ago
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| Question | Answer |
| How is size related to SA:V in animals? | Larger animals have a smaller SA:V. A large SA means cells will be supplied with sufficient oxygen. As size increases, the V rises quicker than the SA. As an animal gets larger its SA:V decreases, so larger animals need a specialised exchange system because they can't rely on diffusion alone. |
| What 3 factors make up a good exchange system? | Short diffusion distance. Large SA. Able to maintain a steep concentration gradient. |
| What changes occur during inspiration? | External intercostal muscles contract, internal intercostal mucles relax, ribs move up an out, diaphragm contracts (flattens), volume of thorax increases, air pressure in lungs decreases below atmospheric pressure, air moves down pressure gradient into lungs. |
| What changes occur during expiration? | External intercostal muslces relax, internal intercostal muscles contract, ribs move down and in, diaphragm relaxes (domed), volume of thorax decreases, air pressure in lungs increases above atmospheric pressure, air moves down pressure gradient out of the lungs. |
| What features of the trachea are there? | It's a flexible airway made of C-shaped cartilage rings, the walls are made of ciliated epithelia cells and goblet cells - the goblet cells produce mucus and the cilia waft dirty mucus up to throat to be swallowed. |
| What are the features of the bronchioles? | They are branching subdivisions of the bronchi, muscle walls lined with epithelial cells, muscle allows for constriction to control air flow in and out of alveoli. |
| What are the features of the alveoli? | Minute air sacs at the end of bronchioles. contain elastic fibres and are lined with epitheliail cells (1 cell thick), the elastic fibres allow for stretch and recoil when breathing. |
| Why is diffusion from alveoli to blood rapid? | The walls if alveoli and capillaries are very thing and RBC's are squeezed flat against the walls - making a short diffusion pathway. RBC's are slowed as they pass through - allowing more time for diffusion. Alveoli and capillaries have a large SA. There is a constant blood flow - maintains a steep conc. gradient. |
| What is and how do you calculate breathing rate? | It is the number of breaths per minute. To calculate = count the number of peaks in each minute. |
| What is and how do you calculate oxygen uptake? | it is the volume of oxygen absorbed by the lungs in 1 minute. To calculate = gradient (change in y/change in x). |
| What is the tidal volume? | The volume of air inhaled or ehaled in 1 breath during normal breathing. |
| What is a spirometer? | A device that measures the movement of air into and out of the lungs. |
| What is the total lung capacity? | Vital capacity + residual volume |
| What is vital capacity? | The maximum volume of air that can be moved by the lungs in 1 breath. |
| What is residual volume? | The volume of air that remains in the lungs even after forced expiration. it prevents the lungs from collapsing. |
| What is inspiratory reserve volume? | The volume which can be inhaled additionally after normal inspiration. |
| What is expiratory reserve volume? | The volume which can be exhaled additionally after nornal expiration. |
| What is and how do you calculate minute ventilation? | The volume of air inhaled in 1 minute. Tidal volume x breathing rate. |
| How does oxygen reach the muscles in the wings of insects? | Air enters through spiracle. Respiring cells have a low concentration of oxygen. The oxygen passes along the trachea/tracheole along a concentration gradient. The gases diffuse into tracheole fluid and then into muscle cells. |
| What is the trachea of insects made of? | Circular bands of chitin. |
| What are spiracles? | Little holes in the exoskeleton of insects. The opening of them can be controlled to regulate water loss. |
| How do insects respond to high oxygen demand? | Tracheal fluid can be withdrawn, increasing the SA for exchange. Wing movements change the volume of the thorax, forcing air down trachea. Alter abdomen volume forcing air down trachea. |
| How do fish take in water? | Operculum (gill flaps) shut. Mouth opens. Floor of mouth moves down - increasing volume and decreasing the pressure. So water moves in to the buccal cavity. |
| How do fish get the oxygenated water over their gills? | Mouth closes. Floor is raised again - decreasing the volume. Opercular valves open - reducing the pressure in the opercular cavity. |
| What are the gills like in bony fish? | They have 4 gill arches on either side of their head. Filaments are attached to these gill arches. They come in pairs and many filaments provide a large SA. Lamella are perpendicular to filaments. Blood flows through them. This is where gas exchange occurs. |
| What is the countercurrent exchange system? | Water and blood flow in opposite directions along the whole length of the gill. Water is always next to the blood with a lower oxygen concentration. (Oxygen enters the blood by diffusing from the water). In this way, the concentration gradient is maintained. |
| What is an open circulatory system? | Blood isn't kept within the vessels all the time. It flows freely in the body. E.g. in insects. |
| What is a closed circulatory system? | The blood is maintained inside vessels. E.g. in mammals. |
| What are the advantages of a closed system? | Flow can be directed faster if necessary. Higher blood pressure can be maintained. |
| What is a single circulatory system? | Blood passes through the heart once for each circulation of the body. E.g. in fish. |
| What is a double circulatory system? | Blood passes through the heart twice for each circulation of the body. E.g. in mammals. |
| What are the advantages of a double system? | Blood pressure is higher as its 'pressurised' twice per cycle - increases flow rate to tissues. Can separate oxygenated and deoxygenated blood so there is an increased diffusion rate. Both of these are needed for animals with high metabolism rate. |
| What is an artery? | Thin layer of elastic tissue allows wall to stretch and recoil - helps maintain blood pressure. Thick layer of smooth muscle also helps maintain BP. Thick layer of collagen and elastic tissues - provide strength to withstand high pressure. Lumen size is relatively small to maintain high BP. Inner wall is folded to prevent damage. |
| What is an arteriole? | Branches off from artery. Smaller in diameter than arteries. No elastic tissue. Control blood flow to capillary beds via smooth muscle sphincters. Primary site of blood flow restriction. |
| What are capillaries? | Branch from arterioles. Very narrow lumen so that RBCs squeeze against the walls as they pass along. Increase diffusion rate. Walls are made of a single layer of flattened endothelial cells - reducing diffusion distance. leaky to allow substances to leave the blood. |
| What are venules? | Branch from capillary bed. Contain a thin outer layer of collagen, thin layers of muscle and elastic tissue, and a thin single layer of endothelial cells. |
| What is a vein? | Branches from venules. Carry blood back to the heart. Don't need to stretch and recoil as blood is at low pressure. Lumen is large to ease blood flow. Contain valves to help blood flow to the heart and prevent backflow. Skeletal muscles contract to help move blood. |
| What is tissue fluid? | Fluid that surrounds the cells in tissues. Made from plasma fluid and small molecules dissolved in the fluid. The plasma fluid in the capillaries move down a pressure gradient and surround the tissues. |
| What is hydrostatic pressure? | The pressure that fluid exerts when pushing against the sides of a vessel. Generated in the heart by the contraction of the ventricle wall. |
| What is oncotic pressure? | The pressure created by the osmotic effects of the solutes in a solution. Generated by plasma proteins, which are present in the capillaries, lowering the water potential. |
| What happens at the arteriole end of the capillary bed? | Hydrostatic pressure inside the capillary is greater than in the tissue fluid. The difference in hydrostatic pressure forces fluid out of the capillaries and into the spaces around cells, forming tissue fluid. |
| When happens at the venule end of the capillary bed? | Hydrostatic pressure inside the capillary is low (as fluid has been forced out). The water potential inside the capillaries is lower than in the tissue fluid (due to fluid loss from capillaries and the remaining plasma proteins inside the capillary). Water moves from the tissue fluid (high water potential) to the capillaries (low water potential) by osmosis. |
| Heart diagram. | |
| What do valves have to prevent them from turning inside out? | Tendinous cords. |
| What is the order of the cardiac cycle? | 1. Atrial systole - both atria contract, blood flows from the atria into the ventricles. 2. Ventricular systole - both ventricles contract, the atrio-ventricular valves close, the semi-lunar valves open, blood flows from the ventricles into the arteries. 3. Ventricular diastole - atria and ventricles relax, blood flows from the veins through the atria and into the ventricles. |
| How is the cardiac cycle coordinated? | 1. Sinoatrial node initiates the heartbeat. 2. SAN sends a wave of electrical activity. 3. Wave spreads across both atria, causing them to contract. 4. Wave reaches the atrioventricular node. 5. The septum prevents the wave crossing into the ventricles (delaying their contraction). 6. The AVN delays the impulses. 7. AVN sends a wave of electrical activity down the bundle of His to the Purkyne fibres at the apex of the heart. 8. This causes the ventricles to contract from the base up. |
| What do the letters on an ECG represent? | P wave - atrial systole. QRS complex - ventricular systole. T wave - diastole. |
| What is Bradycardia? | Slow heart rate. 4 beats per second = 48bpm (normal is 72bpm). reduced heart rate could indicate - good aerobic fitness, drug taking. Could be caused by - stagnation, risk of blood clots. |
| What is tachycardia? | Fast heart rate. 9 beatas per 5 seconds = 108bpm. Increased heart rate is a normal response to - exercise, excitement, stress, drugs. Tachycardia is elevated heart rate for no reason. Treatment may involve relaxation therapy of beta-blocker. |
| What is fibrillation? | Uncoordinated contraction of the atria and ventricles. This means little blood is pumped. Defibrillation may work to fix this.. |
| What is an ectopic heartbeat? | An extra beat or an early beat of the ventricles. The patient may feel as if a heart beat was missed. |
| Describe haemoglobin. | A quaternary protein made of 4 polypeptide chains, each one has a haem group containing FE2+. The haem group has a high affinity (attraction) for oxygen. Each haem can carry one oxygen molecule, so each Hb can carry 4 oxygen molecules. |
| Briefly describe the movement of haemoglobin from the lungs to the tissues. | At the lungs: Hb associated with oxyegn. Hb has a high affinity for oxygen (readily combines). Forms oxyhaemoglobin. At respiring tissues: Hb dissociates from oxygen. Hb has a low affinity for oxygen (removes oxygen from RBCs). |
| What is partial pressure? | The amount of gas that is present in a mixture of gases is measured by the pressure it contributes to the total pressure if the gas mixture. Normal atmospheric pressure in 100kPa, as oxygen makes up 21% of the atmosphere, its partial pressure is around 21kPa. |
| Explain the oxygen dissociation curve. | At low ppo2, the 4 polypeptide chains of Hb are tightly associated. This makes it hard for the 1st oxygen molecule to load. the 2nd and 3rd then load easier. The 4th is hard to load due to the space already taken up. It takes a ppo2 of around 12/14kPa to fully saturate Hb. |
| Explain the difference between foetal Hb and adult Hb. | Foetal Hb has a higher affinity for oxygen than adult Hb. This is because the ppo2 at the placenta is low, so it must be able to associate with o2 in this environment. Adult Hb will dissociate with o2 at low ppo2. |
| What effects does carbon dioxide have on the ppo2 in the blood? | Hb has a reduced affinity for o2 in the presence of co2. The greater the conc. of co2, the more readily the Hb releases o2 (the Bohr effect). Dissolved co2 is acidic and the low pH causes Hb to change shape. If co2 is high, O2 is readily unloaded from the Hb and the o2 dissociation curve moves to the right. |
| Describe the transport of CO2 in the blood. | Co2 diffuses into RBC and combines with water to form carbonic acid. This reaction is catalysed by the enzyme carbonic anhydrase. Carbonic acid dissociates to form hydrogencarbonate ions and hydrogen ions. Hydrogencarbonate ions diffuse out of RBC into the blood plasma. Chloride ions move in to the RBC to maintain the change. Deoxygenated Hb has a high affinity for hydrogen ions and mops up proteins, forming haemoglobinic acid. This acts as a buffer to maintain the blood pH. |
| What are the features of a palisade cell? | Many chloroplasts to absorb light for photosynthesis. Large SA for light absorption. Large vacuole presses chloroplasts to sides of cell. Thin cell walls, so co2 can easily enter. |
| What are the features of guard cells? | Found in pairs, with a gap between to form a stoma. Potassium ions actively transported into guard cell, lower the water potential. In the light, guard cells take up water and become turgid. Thin outer walls and thickened inner wall force them to bend outwards, opening the stoma - allowing the leaf to exchange gases. STomatal closure is stimulated by abscisic acid. |
| What are the features of root hair cells? | Each hair is an extension of an epidermal cell. Large SA for absorption of water from the soil. Thin, permeable cell wall, for entry of water and ions. Cytoplasm contains many mitochondria to provide energy for active transport of ions. |
| What are the features of epidermal tissue? | Derived from flattened cells that form a protective layer on the surface of leaves, stems and roots. Most lack chloroplasts. Some produce a wax that forms a cuticle to reduce water loss. |
| What are the features of the vascular tissue? | Comprised of xylem and phloem. Xylem vessels carry water and minerals from roots to all parts of the plant. Phloem transfer the products of photosynthesis to the non-photosynthesising parts of the plant. |
| What are the features of the meristematic tissue? | It contains the plants stem cells. Found in tips of roots and shoots and within the cambium of the vascular bundle. These undifferentiated cells give rise to all types of plant cells in response to plant growth factors such as auxin and cytokinin. |
| Why do plants need transport systems? | Plants are multicellular, so have a small SA:V and a relatively big metabolic rate. Exchanging substances by direct diffusion would be too slow, so plants need transport systems. |
| Describe a xylem vessel. | Transport water and minerals up the plant. Contains lignified cell walls, which are waterproof, provides support and prevents collapse under tension. Are empty and form a continuous column for ease of flow - also allows tension to pull water up. Bordered pits in the cell walls allow movement of water sideways. |
| Describe a phloem vessel. | Carries sugars (properties of photosynthesis). Contain sieve tube elements which allow movement of sap from 1 element to the next. Companion cells surround them and have many mitochondria to produce ATP for active processes. |
| Describe the structure of xylem and phloem in the roots. |
Xylem and phloem are enclosed in a cylinder made of endodermis cells. Spaces between the endodermis and the xylem and phloem are packed with meristem cells called the pericycle. Between the endodermis and epidermis are several layers of large parenchyma cells, forming the cortex. Air spaces allow diffusion of o2 across the root for respiration.
Image:
Stem3 (binary/octet-stream)
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| Describe the arrangement xylem and phloem in stems. | In young shoots the xylem and phloem are close to each other in a vascular bundle. A thin layer of meristematic tissue lies between the xylem and phloem (cambium). As the shoot gets older, the cambium in the bundle spreads out to form a complete ring. Xylem and phloem then form from the ring of cambium. |
| What is parenchyma tissue for? | Packaging and supporting tissue, e.g. cortex pith. Fills spaces between other tissues. In roots, may store starch. |
| What is collenchyma tissue for? | Tissue thickened with cellulose cell walls to provide support and structure. Mainly found under the epidermis in young stems in the large veins of leaves. Strengthen the vascular bundles and outer parts of stems, whilst allowing some flexibility. |
| What is sclerenchyma tissue for? | Thickened with lignified cell walls to provide strength. |
| What is the order that water moves in a plant? | 1. Water -> root hair cell. 2. Root hair cells -> endodermis. 3. Endodermis -> xylem. 4. Xylem -> up stem to leaf. 5. Water leaving leaf. |
| How does water move into the root hair cells? | Root hair cells take up ions by active transport. This lowers the water potential inside root hair cells. Water moves down the water potential gradient from high water potential to low water potential by osmosis. |
| How does water move from the root hair cells to the endodermis? | 3 pathways: Apoplastic pathway - via the cell walls but is blocked at the endodermis by the casparian strip. Water is then forced into the endodermal cells by mass flow. Symplastic pathway - goes through the cytoplasm via the plasmodesmata. By osmosis. Vacuolar pathway - through the cytoplasm via the plasmodesmata and vacuoles. |
| How does water move from the endodermis to the xylem? | Endodermal cells actively transport ions into the xylem. This lowers the water potential of the xylem. Water then moves from the endodermal cells into the xylem by osmosis. |
| How does water move from the xylem up the stem to the leaf? | At the leaves, water leaves the xylem and moves into th cells, mainly by the apoplast pathway. Water evaporates from the cell walls into the spaces in the leaf (spongy mesophyll cells). When stomata are open this water diffuses out of the leaf, down a water potential gradient, into the surrounding air. This reduces the hydrostatic pressure, and water moves along this pressure gradient up the xylem vessels. This movement is aided by the cohesive and adhesive properties of water. This is known as the transpiration pull/ =cohesion-tension theory. |
| How do you prepare a potometer correctly? | 1. Cut a healthy shoot at a slant, underwater. 2. Check potometer is full of water with no air locks. 3. Insert shoot into potometer underwater. 4. Use vaseline to ensure seal between shoot and potometer is airtight. 5. Dry leaves. 6. Allow time for shoot to acclimatise. 7. Shut screw clip. 8. Keep ruler fixed and record position of air bubble on scale. 9. Start timing and record distance moved per unit of time. |
| What plant features are there that may affect transpiration rate? | Leaf SA - larger area means more surface for evaporation and diffusion. Number of leaves - larger area means more surface for evaporation and diffusion. Number of stomata - more available allow greater loss of water vapour by diffusion. Thickness of cuticle - thinner cuticle allow more evaporation. |
| What effects can weather conditions have on transpiration rate? | Increased temp and sunlight - water molecules will have KE and so will diffuse faster. Sunlight will result in the stomata opening wider, allowing more water vapour out. Reduced humidity - steeper water potential gradient and increased rate of diffusion. Wind - moves saturated air resulting in steeper water potential gradient and increased rate of diffusion. |
| What is translocation? | The movement of assimilates to where they are needed in a plant. Movement is from source to sink. |
| What are the plant assimilates? | Sucrose - assimilation of inorganic carbon as a result of photosynthesis. Amino acids - assimilation of inorganic nitrogen actively taken up by root hair cells. |
| What is the source and what is the sink? | The source is the part of a plant that loads assimilates into the phloem sieve tubes. The sink is the part of a plant that removes assimilates from the phloem sieve tubes. |
| What is active loading? | Hydrogen ions are actively transported out of companion cells to the source (leaf cell). This generates a conc. gradient (high hydrogen conc. grad. outside cell, low hydrogen conc. inside). Hydrogen ions diffuse back in with sucrose molecules through special cotransport proteins (moving sucrose against its sucrose grad.). Sucrose then diffuses through plasmodesmata into the sieve tube. |
| Describe the movement from source to sink. | Sucrose entering the sieve tube element from the source, makes the water potential inside lower. Water moves into the sieve tube by osmosis, increasing the hydrostatic pressure at the source. At the sink, sucrose is removed by either diffusion or active transport, making the water potential of the sap higher. Water moves out of the sieve tube by osmosis into the surrounding cells, reducing the hydrostatic pressure. Sap flows down the pressure gradient from higher to lower pressure (by mass flow). |
| How can a plant root be a source or a sink? | Source - when root converts starch into sugars which are transported around plant. Sink - when root stores sugars as starch. When loading it is a source and when unloading it is a sink. |
| What evidence is there for translocation in phloem? | Ringing a tree - results in sugars collecting above the ring. An aphid feeding on the plant stem contained many sugars when dissected. Radioactively labelled carbon from CO2 can appear in phloem. |
| What are xerophytes? | PLants that have adapted to live in dry conditions. E.g. cacti. |
| How can plants limit water loss? | Thick cuticles -reduce water loss, especially in the winter, when water is hard to absorb because it is frozen in the soil. Its a barrier to evaporation and increases diffusion distance. Sunken stomata and hairy leaves - trap water vapour next to the leaf, reduce the water potential gradient between the inside and outside of the leaf, reducing transpiration. Leaves reduced to spines or needles - provides a small SA, so will reduce transpiration. |
| What is marram? | A xerophyte. Stomata are sunken in pits, the leaves have a tough cuticle, they curl tight when the air is dry. The root system is extensive. |
| What are hydrophytes? | Plants that are adapted to live in water. E.g. lilies. |
| What problems are there for the roots of hydrophytes (and adaptations)? | Many of the cells are underwater where O2 levels are low. Without o2 the cells cannot respire and will die. Hydrophytes have air spaces in the roots and stems to allow o2 to move from the floating leaves down to the parts of the plant that are underwater. |
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