Exchange and Transport

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A-Levels Biology f211 Flashcards on Exchange and Transport, created by Gemma Bradford on 12/05/2013.
Gemma Bradford
Flashcards by Gemma Bradford, updated more than 1 year ago
Gemma Bradford
Created by Gemma Bradford over 11 years ago
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Resource summary

Question Answer
Explain the features on one heartbeat on an ecg P wave - contraction of atria QRS complex - contraction of ventricles T wave - relaxation of ventricles
How do you calculate heart rate Heart rate (bpm) = 60/ time taken for one heartbeat (s)
What is the normal range at rest for an adult heart rate 60-100 bpm
What is fibrillation An irregular heartbeat that can result in fainting
Describe an artery Carry blood from heart to rest of body, thick muscular walls with elastic tissue, endothelium is folded, small lumen
Describe a capillary Branched from arteries, connecting to veins, exchanges substances between itself and other cells, one cell thick endothelium, large lumen
Describe a vein Take blood back to the heart, thin muscular wall with little elastic tissue large lumen, contain valves
What is tissue fluid Fluid surrounding cells in tissues, made from substances that leave the blood
What is the difference between a source and a sink Source = where assimilates are produced Sink = Where assimilates are used up
What is a capillary bed Network of capillaries in an area of tissue, where substances move out of capillaries into tissue fluid by pressure filtration
What is translocation Movement of assimilates from source to sink
Give an example of translocation Source for sucrose is leaves, sinks are food storage organs/meristems
How do enzymes maintain a concentration gradient from source to sink By changing dissolved substances at the sink into something else/breaking them down to lower concentration at sink
What are assimilates Substances that become incorporated into the plant tissue - sugars
Describe the start of a capilalry bed Nearest to arteries, high hydrostatic pressure forcing fluid out of capilalries and into space around cells = forming tissue fluid
What is transpiration Evaporation of water from a plant's surface as a result of gas exchange for photosynthesis
How does light affect transpiration rate Stomata open more in more light = allowing for more water to evaporate out
Describe the end of a capillary bed Water potential is lower than in tissue fluid, so some water re-enters by osmosis, low hydrostatic pressure
How does temperature affect transpiration rate Warmer water molecules have more energy, so they evaporate from cells inside leaf faster = increasing water potential gradient between inside and outside of leaf
How does humidity affect transpiration rate If air around stomata is dry, water potential gradient between leaf and air is increased
Give a difference between blood and tissue fluid Tissue fluid does not contain any red blood cells or big proteins, as they are too large to be pushed out of capillary walls
How does wind affect transpiration rate Air movement blows away water molecules from around the stomata, increasing water potential gradient
Name 4 precautions to take when setting up a potometer 1. Cut shoot underwater and at a slant 2. Assemble potometer and insert shoot underwater 3. Dry leaves 4. Allow time for shoot to acclimatise before shutting tap
Name 4 adaptations of xerophytic plants 1. Stomata sunk in pits 2. Curled leaves 3. Layer of hairs on epidermis 4. Less stomata
What does a potometer test Estimates transpiration rate by water uptake of the plant, can test effect of different factors on rate
What is the lymphatic system Where the tissue fluid did not re-enter at end of capillary bed, so instead enters lymph vessel = becoming lymph
Why does rate of transpiration fluctuate at different times of the day Because factors are not constant
How does water enter a plant Soil - root hair cells - root cortex including endodermis - xylem Osmosis
Describe haemoglobin Found in red blood cells, carries oxygen around the body, can carry 4 oxygen molecules, large protein with quaternary structure, made of four polypeptide chains each with it's own haem group
Does soil have a high water potential or low High, so it diffuses into the root hair cells
Do leaves had a high or low water potential Low
Describe the symplast pathway Travels through cytoplasm of cells and through plasmodesmatas to reach xylem vessel
Describe the apoplast pathway Goes through cell walls, blocked by casparian strip where it takes the symplast pathway to reach the xylem vessels
Outline the association and disassociation of oxygen Lungs = oxygen joins to iron in hb to form oxyhb Body cells = oxygen leaves oxyhb and turns back into hb
What is a transpiration stream Movement of water from roots to leaves
What is association of oxygen Loading of oxygen onto hb
What is cohesion Where water molecules are attracted to eachother, so the whole column of water moves up the xylem
What is tension As water evaporates from leaves, this creates a suction pulling more water into leaf
What is disassociation Unloading of oxygen from oxyhb
What is adhesion Where water molecules are attracted to the xylem vessel walls, helping water to rise up through vessels
What is affinity for oxygen Tendency a molecule has to bind with oxygen
What is the casparian strip Waxy, waterproof strip in cell walls at endodermis
What are mesophyll cells Type of leaf cell
What is the affect of air bubbles in the xylem They can block the column of water, preventing water from reaching the cells
What is partial pressure of oxygen pO2 Measure of oxygen concentration, the higher the concentration of dissolved oxygen in cells = higher partial pressure
Why do plants need transport systems Need water, minerals and sugars to live, and need to get rid of waste substances. Multicellular with small SA:V ratio. If they exchanged substances directly, it would be too slow
How does pO2 affect haemoglobin's affinity for oxygen Oxygen loads onto hb in a high pO2, oxygen unloads in a low pO2
What is lignin Spiralled woody substance in xylem vessels, supporting the xylem walls and allowing flexibility to prevent stem from breaking
Where is there a high pO2 Alveoli in lungs
What are pits in the xylem vessel In walls where there is no lignin, allowing water and mineral ions to move in/out of vessels to supply other types of cells with water
Where is there a low pO2 Respiring tissue
What is the purpose of having no end walls in xylem vessels Making an uninterrupted tube allowing water to pass up through centre easily
What does an oxygen dissociation curve show How saturated hb is with oxygen at a given pO2
What are xylem vessels formed of Long tube like structures formed from vessel elements, dead cells containing no cytoplasm
What are dictoyledonous plants Green, non-woody plants bushes and trees
How is phloem formed From cells arranged in tubes, living cells
Why are disassociation curves S shaped instead of a straight line When oxygen first binds with hb, it alters it's shape to make it easier for other oxygen molecules to bind. As hb becomes more saturated with oxygen, it's shape makes it harder for other oxygen molecules to join. Steep part of curve is where it's easy for oxygen molecules to join
What living cells are in the phloem Phloem fibres, parenchyma, sieve tube elements and companion cells
Describe sieve tube elements Joined end to end to form sieve tubes, sieve plates have holes to allow sugars to pass through, no nucleus, few organelles, thing cytoplasm
Describe companion cells For every sieve tube element, carry out living functions for themselves and sieve tubes such as providing energy for active transport of sugars
Why does fetal haemoglobin have a higher affinity for oxygen than adult haemoglobin Fetus' gets oxygen from mother's blood across placenta, by the time it reaches placenta, oxygen saturation has decreased as it has been used up by the mother's body. Placenta has a low pO2, helping oxygen to unload. Curve is to the LEFT of adult hb curve.
Are the sugars transported in the phloem whole or dissolved Dissolved
What is a single circulatory system Blood only passes through the heart once for each complete circuit of the body
What is a double circulatory system Blood passes through the heart twice for each complete circuit around the body
What is the partial pressure of carbon dioxide pCO2 Measure of the concentration of CO2 in a cell
What is a closed circulatory system and give an example Blood is enclosed in blood vessels - fish
How does pCO2 affect disassociation of oxygen from oxyhb Hb gives up oxygen more readily in a higher pCO2
What is an open circulatory system and give an example Blood flows freely in body cavity - insects
Name features of the right side of the heart Inferior and superior vena cava, pulmonary artery, right ventricle, right atrium, semi lunar valve, tricuspid valve
Name features of the left side of the heart Aorta, pulmonary vein, left atrium, left ventricle, semi lunar valve, bicuspid valve
Outline the bohr effect CO2 in red blood cells converted to carbonic acid by carbonic anahydrase, carbonic acid splits into hydrogen and hydrogencarbonate ions, the increase in hydrogen ions causes oxyhb to unload oxygen so hb can take up hydrogen ions forming haemoglobonic acid
What is the purpose of heart valves Prevent backflow of blood
Why is the heart muscle thicker on the left As left ventricle pumps blood around the whole body
What is the main advantage of the bohr effect To get more oxygen to respiring tissues
What is the word equation for aerobic respiration glucose + oxygen ¬ carbon dioxide + water + energy
What is the purpose of coronary arteries To supply the heart with an oxygenated blood supply
What is hydrostatic pressure Where blood is under high pressure in arteries due to contraction of ventricle walls
Give the brief sequence of the cardiac cycle 1. Ventricles relax, atria contract 2. Ventricles contract, atria relax 3. Ventricles relax, atria relax
What is the SAN Sino atrial node in wall of right atrium, sending waves of electrical activity over the atrial walls
What is the purpose of non-conducting collagen tissue in the heart Prevents the waves of electrical activity from being passed directly from artia - ventricles. Causes delay which allows for the atria to empty before ventricles contract
What is the AVN Atrioventriclular node passing waves of electrical activity on to the bundle of HIS
What is the bundle of HIS Group of muscle fibres conducting waves to purkyne tissue
What is the purkyne tissue Carries waves of electrical activity in walls of ventricles, causing them to contract together from apex upwards
What is an elecctrocardiograph Machine recording electrical activity of the heart
What is an electrocardiogram Trace produced by an electrocardiograph
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