7 Transport Flashcards
Role of Phloem vessels
Glucose made by photosynthesis is converted into sucrose and transported to other parts of plants through phloem vessels.
Position of Xylem vessels in cross sections
In root: star shaped.
In stem: inner part.
In leaf: upper part but below strengthening cells.
(Check textbook)
Function of Xylem
Xylem tissue contain long, hollow xylem cells that for long tubes through the plant. Tubes are hollow remains of dead cells. Thick strong cell walls to help support plant. Tubes are important as they transport water and mineral ions from roots through stem to all parts of the plant that need them. Supply water for leaf cells for photosynthesis.
Function of Phloem
Phloem cells are living cells linked together to for continuous phloem tissue. Dissolved food materials: sucrose and amino acids, are transported all over the plant from leaves. This is called translocation.
Structure and function of Root hair cells
Root hair cells are adapted for absorption of substances. They have a fine extension that sticks out into the soil. This greatly increases surface area for absorption. Water enters through osmosis because water potential is higher outside the root; water molecules are moving down their water potential gradient. Water enters root hair cells, passes through root from cortex cell and then into xylem tissue. Dissolved mineral ions are absorbed through active transport because there is usually a higher concentration inside the root cells.
Explain what is meant by Transpiration
Water molecules in the leaf cross the cell membranes of the spongy mesophyll cells into the air spaces. This is called evaporation as the liquid water in cells becomes water vapour in the air spaces. When the stomata opens, water vapour diffuses out.
Factors that affect the rate of transpiration
Temperature
Wind
Humidity.
Effect of temperature on Transpiration
Increased temperature means increased kinetic energy which means faster movement of particles. The more they move, the easier it is for them to evaporate from cell surfaces into air space and diffuse out of leaf.
Effect of Humidity on Transpiration
If humidity is decreased, there is less water vapour in the air, so a lower concentration of water molecules outside the leaf than inside, so more transpiration occurs.
Define Cohesion
Water molecules show cohesion meaning that they stick together. So as water molecules move out of xylem cells in a leaf vascular bundle, they create a tension at the top of xylem tube, pulling water molecules up the plant.
Role of Sucrose
Glucose is converted into sucrose because it is less reactive so it can be transported without causing problems for other cells.
Used to be converted back for respiration, and production of other molecules in the cell for cell growth.
Role of Amino acids in plants
Used to produce proteins for formation of new plant tissue during growth and produce enzymes to control cell reactions.
Main sinks for glucose
Root, shoot tips and flowers.
Define the Circulatory system
A system of continuous blood vessels, with a pump (the heart) and valves to ensure one-way flow of blood.
Describe Double circulation
Blood passing through the heart twice for each time that it passes through body tissues. This is because when blood leaves left side of heart, it passes through tissues of the lungs before returning to the heart for pumping around the rest of the body.
Reason for separating circulation to lungs from circulation to body
Allows blood circulation to be at different pressures.
Blood leaving left side is normally below 4 kPa. This is because the blood doesn’t travel far to lung tissue, so there is little loss of pressure before reaching capillaries surrounding the alveoli. Also prevents damage to the delicate capillaries.
Blood leaving right side has to travel all around body so needs pressure of about 16 kPa. When it reaches the capillaries within body tissues, pressure dropped to below 3 kPa so no damage done to them.
Role of Heart
A muscular organ that pumps blood through blood vessels: away from heart in arteries, into heart through veins. Has two pumps separated by septum tissue. Right side pumps blood into lungs to collect oxygen. Left side pumps oxygenated blood around body, which arrives back to right side deoxygenated.
What are the four chambers in the heart?
Left atrium, right atrium, left ventricle and right ventricle.
How is one-way flow of blood ensured?
There are valves at points where blood vessels enter and leave heart that close when heart contracts to prevent backflow of blood.
Describe the blood flow through the heart
Blood from body arrives at heart via vena cava and enters right atrium. Contraction of right atrium passes blood to right ventricle. Contraction of right ventricle forces blood out through pulmonary artery to lungs. Blood enters left atrium from lungs through pulmonary vein. Contraction of left atrium passes blood to left ventricle. Contraction of left ventricle forces blood out through aorta toward rest of body. (Mention one-way valves at all times).
Define Heart rate
Measure of how frequently the heart beats per minute.
Factors that affect the resting heart rate
Age - Children usually faster.
Fitness - trained athletes have more muscle and can pump more blood out so have low.
Illness - Infection can raise, some diseases can slow.
Drugs.
Effect of activity on heart rate
More activity increases heart rate, which increases amount of blood pumped, increases speed at which it reaches body tissues. Supplies oxygen and glucose faster to respiring cells and removes waste products more rapidly.
Role of Coronary arteries
Arteries that pass through the heart muscle to give it blood supply to provide oxygen and sugars for respiration.
Describe Coronary heart disease
Blockage of coronary arteries caused by layers of cholesterol deposited in inner lining of the blood vessel. Reduces amount of oxygen and sugars getting to muscle cells and so reduce amount of energy they can release through respiration. Any sort of blockage can cause problems such as angina (heart pains) or high blood pressure. A full blockage causes a heart attack which may result in death.
Factors that can increase risk of a blockage in coronary arteries
Diet - high level of saturated fats.
Smoking - chemicals in tobacco smoke that pass into blood can damage delicate lining of arteries, cholesterol is more likely to be laid down at those points.
Genes - can be inherited
Structure of Arteries
Large blood vessels that carry blood flowing away from heart. Thick muscular and elastic walls, with a narrow lumen through which blood flows.
Structure of Capillaries
Tiny blood vessels that form a network throughout every tissue and connect arteries to veins. Very thin walls to increase rate of diffusion by keeping distance between blood and cell cytoplasm to a minimum. All exchange of substances between blood and tissues occur here.
Structure of Veins
Large blood vessels that carry blood flowing back to heart. Large lumen. Have valves that prevent backflow.
Explain how the structure of arteries helps reduce and even out blood pulses from heart
Arteries have thick elastic walls and the recoil of the elastic wall after the pulse of blood passes through helps maintain blood pressure and even out pulses.
Substances carried in blood and where they are carried from and to
Molecules absorbed from digested food - carried from small intestine to apob.
water - carried from intestines to apob.
oxygen - carried from lungs to apob.
Carbon dioxide - carried from apob to lungs.
Urea - carried from liver to kidneys.
Hormones - carried from glands to apob.
Function of Plasma
Straw-coloured liquid part of blood, mainly consisting of water which makes it a good solvent for many substances.
Function of Red blood cells
Most common cell in blood. Biconcave shape and have no nucleus, makes them flexible and carry more haemoglobin to transport oxygen.
Function of White blood cells
Defend the body against disease. Many types. Part of immune system that respond to infection by trying to kill pathogens using phagocytosis (engulfing), or produce antibodies that attack pathogens.
Function of Platelets
Small fragments of much larger cells that are also important in protecting us from infection by causing blood to clot when there is damage to a blood vessel.
