Biology - Module 3
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Biology - Module 3 - Leaderboard
Biology - Module 3 - Details
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| Exchange surfaces in single celled organisms | - substances diffuse directly into (or our of) the cell across the cell surface membrane - the diffusion rate is quick because of the short distances substances have to travel - relatively high surface area to volume ratio |
| Exchange surfaces in multicellular organisms | - some cells are deep within the body = big distance between them and the outside environment - larger surface area to volume ratio - they have higher metabolism rate, so they use up oxygen and glucose faster |
| Exchange surface of root hair cells | - has large surface area which helps increase rate of absorption of water (by osmosis) and mineral ions (by active transport) from the soil |
| Exchange surface of alveoli | - made from a single layer of thin, flat cells called alveolar epithelium - this helps decrease the distance over which oxygen and carbon dioxide diffusion takes place |
| Blood supply to alveoli | - alveoli are surrounded by a large capillary network, giving each alveolus its own blood supply - this allows oxygen to be taken away and bring more carbon dioxide - the lungs are also ventilated, so air in each alveolus is constantly replaced - this helps maintain concentration gradient of oxygen and carbon dioxide |
| Blood supply in fish gills | - fish gills contains a large network of capillaries keeping them well supplied with blood - they are also well ventilated as fresh water is constantly passing over them - this helps maintain concentration gradient of oxygen, increasing the rate of diffusion |
| Describe goblet cells | - they secrete mucus - the mucus traps microorganisms and dust particles in the inhaled air, stopping them from reaching the alveoli |
| Describe cilia | - beats mucus on the surface of cells lining the airway - they move mucus upward away from the alveoli towards the throat, where it's swallowed - this helps prevent lung infections |
| Describe elastic fibres | - they are in the walls of the trachea, bronchi, bronchioles and alveoli - it helps the process of breathing out - on breathing in, the lungs inflate and the elastic fibres are stretched - then, the fibres recoil to help push air out when exhaling |
| Describe smooth muscles | - they are in the walls of the trachea, bronchi and bronchioles allowing their diameter to be controlled - during exercise they relax, making the tubes wider. This means there's less resistance to airflow |
| Describe goblet cells | - they secrete mucus - the mucus traps microorganisms and dust particles in the inhaled air, stopping them from reaching the alveoli |
| Describe cilia | - beats mucus on the surface of cells lining the airway - they move mucus upward away from the alveoli towards the throat, where it's swallowed - this helps prevent lung infections |
| Describe elastic fibres | - they are in the walls of the trachea, bronchi, bronchioles and alveoli - it helps the process of breathing out - on breathing in, the lungs inflate and the elastic fibres are stretched - then, the fibres recoil to help push air out when exhaling |
| Describe smooth muscle | - they are in the walls of the trachea, bronchi and bronchioles allowing their diameter to be controlled - during exercise they relax, making the tubes wider. This means there's less resistance to airflow |
| Describe cartilage | - in the walls of trachea and bronchi - provides support - its strong but flexible as it stops the trachea and bronchi from collapsing when you breathe in and the pressure drops |
| Explain process of inspiration | - external intercostal and diaphragm muscles contract - this causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thorax - the lung pressure decreases - this causes air to flow into the lungs |
| Is inspiration passive or active | - it is an active process, meaning it requires energy |
| Explain process of expiration | - the external intercostal and diaphragm muscles relax - the ribcage moves downwards and inwards and the diaphragm becomes curved again - the thorax volume decreases, causing the air pressure to increase - air is forced out of the lungs |
| Is expiration passive of active | - normal expiration is passive, meaning it doesn't require energy - however, it can also be forced |
| Define tidal volume | The volume of air in each breath |
| Define vital capacity | The maximum volume of air that can be breathed in or out |
| Define breathing rate | How many breaths are taken per unit of time |
| Define oxygen uptake | The rate at which a person uses up oxygen (dm3min-1) |
| How does a spirometer work | - when a person breathes in and out using a spirometer, the lid of the chamber moves up and down. - these movements are recored by a pen attached to the lid, creating a spirometer trace |
| What does the soda lime do | It absorbs the carbon dioxide the subject breathed out |
| How have fish adapted to low concentration of oxygen in water | - each gill is made of lots of thin branches called gill filaments or primary lamellae, which give a big surface area for exchange of gases - the gill filaments are covered with lots of tiny structures called gill plates or secondary lamellae, which increases the surface area more - the gill plates have lots of blood capillaries and a thin surface layer of cells to speed up diffusion |
| Explain counter current system | - blood flows through the gill plates in one direction and the water flows over in the opposite direction - this maintains a large concentration gradient between water and the blood - the concentration of oxygen in the water is always higher than in the blood, so as much oxygen as possible diffuses from the water into the blood |
| Explain ventilation in fish | - fish opens its mouth, which lowers the floor of the buccal cavity - the volume of the cavity increases, decreasing the pressure inside it - water is then sucked into the cavity - when the fish closes its mouth, the floor of the buccal cavity is raised again - volume inside decreases, pressure increases, and water is forced out of the gill filaments |
| What is the operculum | - it is a bony flap that covers each gill filament protecting it - the increase in pressure forces the operculum on each side of the head to open, allowing water to leave the gills |
| Explain ventilation in insects | - they have microscopic are filled pipes called trachea - air moves into the trachea through pores on the insect's surface called spiracles |
| Why do multicellular organisms need a transport system | - they have a large surface area to volume ratio - they have a higher metabolic rate - they are very active, so a large number of cells are all respiring quickly, therefore they need a constant supply of oxygen and glucose |
| Define single circulatory system | Blood only passes through the heart once for each complete circuit of the body |
| Define double circulatory system | Blood passes through the heart twice for each complete circuit of the body |
| Define closed circulatory system | Blood is enclosed inside blood vessels. Example: in fish |
| Define open circulatory system | Blood isn't enclosed in blood vessels all the time. Instead, it flows freely though the body cavity. Example: in insects |
| What are arteries | - they carry blood from the heart to the rest of the body. - their walls are thick, muscular and have elastic tissue to stretch and recoil as the heart beats, which helps maintain the high pressure |
| What are arterioles | - they have a layer of smooth muscle and less elastic tissue - this allows them to expand or contract, controlling the amount of blood flowing |
| What are capillaries | - they are the smallest of the blood vessels - substances like glucose and oxygen are exchanged between cells and capillaries - their walls are one cell thick |
| What are venules | - they join together to form veins |
| What are veins | - they take blood back to the heart under low pressure - they have a wider lumen, less elastic and muscle tissue - they contain valves, which prevent back flow |
| How does blood flow through veins | - blood flows with the help of contractions of the body muscles surrounding them |
| What is tissue fluid | - the fluid that surrounds cells in tissue - it's made from substances that leaves the blood, for example: oxygen, water and nutrients |
| What does tissue fluid not contain | - red blood cells and big proteins |
| How is tissue fluid formed from plasma | - at the start of the capillary bed, the hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid - this difference in hydrostatic pressure forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid - after tissue fluid leaves, the hydrostatic pressure reduces in the capillaries (being much lower at the end nearest to the venules) |
| Describe pressure filtration | - as water leaves the capillaries, the concentration of plasma proteins in the capillaries increases, and the water potential decreases - plasma proteins in the capillaries generate a form of pressure called oncotic pressure - as water potential in the capillaries is lower than the tissue fluid, some water re-enters the capillaries from the tissue fluid at the venule end by osmosis |
| What are lymph vessels | Excess tissue fluid |
| Describe the cardiac cycle | 1) ventricles diastole and atrium systole 2) ventricle systole and atrium diastole 3) ventricle diastole and atrium diastole 4) whole process start again |
| Explain what happens when ventricles relax and atrium contract | - volume decreases and pressure increases in the atrium - this pushes blood into the ventricles through the atrioventricular valves - there's a slight increase in ventricular pressure and volume |
| Explain what happens when ventricles contract and atrium relax | - volume decreases and pressure increases in the ventricles - pressure becomes higher in ventricles than in atria, which forces atrioventricular valves shut to prevent back flow - the high pressure opens the semi lunar valves and blood is forced through the pulmonary artery and aorta |
| Explain what happens when ventricles relax and atrium relax | - the high pressure in the pulmonary artery and aorta causes the semi lunar valves to close - the atria fills with blood due to high pressure in the vena cava and pulmonary vein |
| What is systole | Contraction |
| What is diastole | Relax |
| How is heart action initiated and coordinated | - process starts in the sino-atrial node (SAN), in the walls of the right atrium - SAN sends out regular waves of electrical activity to the atrial walls - this causes the right and left atrium to contract at the same time - the waves of the electrical activity are transferred from the SAN to the atrioventricular node (AVN) - AVN passes electrical activity to bundle of His, but there's a slight delay - this ensures that ventricles contract after atria have emptied - bundle of His conducts waves of electrical activity to Purkyne tissue - Purkyne tissue carries waves of electrical activity to walls of right and left ventricles, causing them to contract simultaneously from bottom up |
| How can doctors check someone's heart function | Using an electrocardiograph (ECGs), a machine that records the electrical activity of the heart |
| What happens to the heart muscle when is contracts | It depolarises, loses electrical charge |
| What happens to the heart muscle when is relaxes | It repolarises, regains charge |
| What is P wave caused by | The contraction of the atria |
| What is the QRS complex | The main peak of the heartbeat, together with the dips on either side. This is caused by the contraction of the ventricles. |
| What is the T wave caused by | The relaxation of the ventricles |
| How do you calculate heart rate | 60/time taken for one heartbeat |
| What is tachycardia | When the heartbeat is very fast. Problems include heart not pumping blood efficiently. |
| What is bradycardia | When the heartbeat is very slow. Problems include something may be preventing impulses from the SAN being passed on properly. |
| What is an ectopic heartbeat | When there is an extra heartbeat caused by earlier contraction of the atria or ventricle. |
| What is fibrillation | When the heartbeat is really irregular. The atria and ventricles have completely lost their rhythm and stop contracting properly, resulting in chest pain, fainting or death. |
| What is a haemoglobin | - a large protein with a quaternary structure - it's made up of 4 polypeptide chains - each chain has a haem group which contains iron - each molecule of haemoglobin can carry 4 oxygen molecules |
| What is the role of haemoglobin | To carry oxygen around the body. |
| What is oxyhemoglobin | When oxygen joins the iron in the haemoglobin |
| What does association or loading mean | When an oxygen molecule joins to haemoglobin |
| What does dissociation or unloading mean | When oxygen leaves oxyhemoglobin |
| Define affinity for xygen | The tendency a molecule has to bind with oxygen |
| What is the partial pressure of oxygen | PO2 - the measure of oxygen concentration |
| Where does oxygen load onto haemoglobin to form oxyhemoglobin | Where theres a high pO2 |
| Where is oxygen unloaded | Where there's a low pO2 |
| What happens when carbon dioxide and water react | With the help of carbonic anhydrase, they form carbonic acid which dissociates into HCO3- and H+ ions |
| How is haemoglobinic acid formed | When H+ ions combine with haemoglobin |
| Why is the dissociation curve shaped the way it is | - when haemoglobin combines with the first O2 molecule, its shape alters to make it easier for other molecules to join - but as haemoglobin starts to become saturated, it gets harder for more oxygen molecules to join |
| Explain the Bohr effect | When carbon dioxide levels increase, the dissociation curve shifts to the right, showing more oxygen is released from the blood |
| Explain chloride shift | To compensate fore the loss of HCO3- ions from the red blood cells, chloride ions diffuse into the red blood cells. |
| Why do plants need transport systems | Plants need substances like water, minerals, and sugar to live. They also need to get rid of waste substances. They also have a small surface area to volume ratio with a relatively high metabolic rate. Exchanging substances by direct diffusion would be too slow. |
| What is the xylem tissue responsible for | Is transport water and mineral ions in solution. These substances move up the plant from the roots to the leaves. |
| What is the phloem tissue responsible for | It transports sugars (mainly sucrose) up and down the plant. |
| What is the vascular system | The xylem and phloem together |
| Where is the xylem and phloem located in the roots and why is it there | It is located in the centre surrounded by the phloem to provide support for the root as it pushes through the soil |
| Where is the xylem and phloem located in the stems and why is it there | They are located near the outside, with phloem being on the outer edge, to provide a sort of scaffolding that reduces bending |
| Where is the xylem and phloem located in the leaves and why is it there | They make up a network of veins, with phloem being on the underside, which support the thin leaves |
| How are xylem vessels adapted for their function | - they are very long, tube like structures formed from cells joined end to end - there are no end walls on these cells, making an uninterrupted tube that allows water to pass through the middle easily - the cells are dead, so they contain no cytoplasm - their walls are thickened by lignin, which helps with support and stops them from collapsing inwards - water and ions move in and out of the vessels through pits in the walls |
| How is phloem tissue adapted for its function | - contains phloem fibres, phloem parenchyma, sieve tube elements and companion cells - sieve tube elements have no nucleus, and only has a very thin layer of cytoplasm and few organelles - companion cells provide energy for active transport of solutes |
| How do you dissect plant stems | - use scalpel to cut a cross section of the stem as thinly as possible - use tweezers to gently place them in water, this stops them from drying out - transfer to dish containing stain ( TBO- stains the lignin in the walls of xylem blue-green) and leave for a minute - rinse off the sections in water and mount each one onto a slide |
| Why is water important for plants | - to keep turgor pressure to support the plant - to transport substances - photosynthesis - help plants to cool down in hot conditions |
| Where does water enter the plant | Water enters through the root hair cells and then passes through the root cortex, including the endodermis, to reach the xylem |
| How is water drawn into the roots | Through osmosis |
| Define symplast pathway | Water moves through the living parts of cells (he cytoplasm) via osmosis. The cytoplasm of neighbouring cells connect through plasmodesmata. |
| Define plasmodesmata | Small channels in the cell walls |
| Define apoplast pathway | Water moves through the non-living parts of the cell, the cell walls as well as intracellular spaces. It is the fastest movement of water as it provides the least resistance. |
| How does water move through the apoplast pathway | The water can carry solutes and move from areas of high hydrostatic pressure to areas of low hydrostatic pressure, example of mass flow. |
| Describe and explain the function of the casparian strip | When water in the apoplast pathway gets to the endodermis cells in the roots, it is blocked by a waxy strip in the cells walls called casparian strip. Now water has to enter through the symplast way. This prevents toxins from entering further as the cell membrane is partially permeable. |
| How is water transported through the leaves and out the stomata | - water leaves the xylem vessel and moves across the leaf cell either through apoplast or symplast pathway - water evaporates from the cell walls into the spaces between the cells - when the stomata opens, water diffuses out of the leaf into the surrounding air |
| How does water move up the plant | Water molecules form hydrogen bonds with the carbohydrates in the walls of the xylem (adhesion) as well as each other (cohesion). The combined effects of which cause water to move up the xylem via capillary action. |