B3: Living Together - Food and Ecosystems

    Cards (150)

    • Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
    • Diffusion can happen in both gases and liquids, for example, if you spray perfume it quickly diffuses across the whole room so you can smell it everywhere or if you put some food coloring in a beaker of water it will diffuse through the water until the whole glass is the same color.
    • Diffusion can also take place through some materials such as cell membranes, for example, if there is a cell membrane in between the inside and outside of a cell, only some molecules are able to diffuse through them, generally only very small molecules that are dissolved in the fluid inside or outside the cell can diffuse through, whereas larger molecules can't fit through the membrane because they're too big.
    • Diffusion is a passive process that doesn't require any energy from the cell, it's just the random movement of the particles themselves that results in diffusion.
    • The concentration gradient is the difference in concentration between two places, the larger the concentration gradient between two places, the higher the rate of diffusion.
    • Temperature is important because higher temperatures give the particles more energy and this means that all the particles will move around faster and so overall they'll diffuse more quickly, a higher temperature means a higher rate of diffusion.
    • The surface area is the last factor that affects the rate of diffusion, the larger the surface area, the higher the rate of diffusion, to see why, imagine that we have these two boxes, they both have the same volume but the bottom one has a much larger surface area, this means that a lot more particles can fit around its surface and so at any point in time more particles could be diffusing in and out at once, resulting in a higher rate of diffusion across a larger surface area.
    • Osmosis is the diffusion of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
    • Water concentration is the amount of water compared to the other molecules like sugars or salts that are dissolved in that water, also known as solutes.
    • In a cell, the concentration of water is determined by the proportion of water compared to solutes, not the volume of water.
    • Water particles will diffuse from the outside of the cell down the concentration gradient into the cell, a process known as osmosis.
    • Active transport is the movement of molecules against their concentration gradient from an area of lower concentration to an area of higher concentration, requiring energy from the cell.
    • Active transport always takes place across a membrane, such as the cell membrane, and requires special proteins that sit in the membrane and transfer the molecule from one side to the other.
    • Like all energy in the cell, the energy for active transport comes from solar respiration, which is the process that happens mainly in the mitochondria when they break down glucose to release energy.
    • Solar respiration is responsible for all of the energy that the cell uses and stores the energy in literal molecules called ATP, which act like little batteries taking the energy from the mitochondria to the different parts of the cell that need it.
    • Plants have networks of roots that protrude into the ground, and around the outside of these roots are special cells called root hair cells which absorb the water and mineral ions and are adapted to their role by having long hair-like protrusions where they stick out into the soil, providing a large surface area for absorption.
    • An adaptation of root hair cells is having lots and lots of mitochondria.
    • The minerals and nutrients that plants need like magnesium and nitrates are at a higher concentration inside the cell than they are outside in the soil, and they cannot absorb them by diffusion, instead they have to use energy to absorb them by active transport against their concentration gradient, with the energy coming from cellular respiration which happens in mitochondria.
    • Plants need to absorb large amounts of water and mineral ions to survive, which they obtain from the soil.
    • Photosynthesis is a process that takes place in the leaves and more specifically in the subcellular structures called chloroplasts.
    • Chlorophyll is a pigment that can absorb light, which it uses to convert carbon dioxide and water into glucose and oxygen.
    • The equation for photosynthesis can be written as: six co2 molecules combining with six h2o molecules to make a single molecule of glucose and in doing so also give out six o2 molecules.
    • The reaction requires light energy for it to take place, and when energy from the surroundings is used to help a reaction take place, it is called an endothermic reaction.
    • Energy is transferred from the environment to chloroplasts by light.
    • The carbon dioxide diffuses into the leaves through the stomata and the water is taken up from the soil by the roots and then transported to the leaves via the xylem.
    • The only product that the plants really want is the glucose, which they use for solar respiration, photosynthesis, and for making cellulose, starch, amino acids, and oils.
    • Glucose is essential for plants' growth rate, which is often dependent on how fast they can photosynthesize.
    • Plants need to carry out photosynthesis to survive, which is dependent on four main factors: light intensity, temperature, the concentration of carbon dioxide in the air, and the amount of chlorophyll that the plants have.
    • Chlorophyll is the pigment within chloroplasts that absorbs the light energy needed for photosynthesis, and its level within an individual plant can vary due to disease, environmental stress, or lack of nutrients.
    • When we talk about limiting factors for photosynthesis, we're normally referring to light, carbon dioxide, and temperature.
    • As light intensity increases, the rate of photosynthesis also increases, but after a certain point, the rate plateaus because when light is plentiful, something else becomes the limiting factor.
    • Carbon dioxide is one of the reactants for photosynthesis, and the more red a plant can get, the higher the rate of photosynthesis, but after a while, the rate plateaus because when carbon dioxide is plentiful, something else becomes the limiting factor.
    • Temperature affects the rate of photosynthesis, with the rate rising initially because the enzymes involved can work more quickly and the molecules can move faster, but after a while, the rate starts to drop again as the enzymes involved begin to denature.
    • More than one limiting factor can be represented within a single graph, for example, a graph can represent two different experiments where light intensity affects photosynthesis, one at 15 degrees Celsius and the other at 25 degrees Celsius.
    • Farmers often use greenhouses to create conditions for high rate of photosynthesis, trapping the sun's heat and providing artificial light so that photosynthesis can continue all through the day and night.
    • Farmers may also use fertilizers to ensure that the plants have enough essential minerals and pesticides to kill any unwanted bugs.
    • Mass transport systems of plants involve the transport of sugars, known as translocation, and water, through transpiration.
    • Plants make their own sugars through photosynthesis, which occurs in the leaves.
    • Translocation is the process by which these sugars are transported to other parts of the plant for use or storage.
    • Translocation is mainly achieved by phloem cells, which are arranged end to end to form long columns known as phloem tubes.
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