Slides Flashcards
(213 cards)
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How do plants
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get energy?
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Plants get their energy through
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photosynthesis.
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In this process
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plants convert light energy
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from the sun into chemical energy
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producing
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their food in the form of glucose.
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How does it occur?
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Source of Energy
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• Living organisms rely on each other.
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• The sun is the ultimate source of energy for all living things.
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• The sun provides this energy in the form of light and heat –
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this is know as RADIANT ENERGY.
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• The interaction and interdependence between organisms in
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ecosystems are driven by the need for energy.
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• Energy must be changed into a source that can be used.
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• Energy cannot be created or destroyed but can be converted
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from one form into another.
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How do plants
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get energy?
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The process by which green plants (and some
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microorganisms) produce food in known as photosynthesis.
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Food contains stored energy.
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Plants and animals obtain their energy from food.
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Animals eat plants and other animals as food.
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Plants however
do not eat food as animals do. How then do
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plants acquire their food?
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In the past people thought that plants acquire food from the
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soil.
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To find out whether this is true
a Belgian scientist
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Baptiste van Helmont carried out an investigation.
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Jean-Baptiste Von Helmont
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The Process of
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Photosynthesis
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STEP 1
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Absorption of Light
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Plant cells contain chloroplasts.
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Chlorophyll
the green pigment in
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chloroplasts
captures and absorbs the
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light energy and converts the sunlight
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into chemical energy.
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water
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The Process of
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Photosynthesis
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STEP 2
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Splitting of Water
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The energy from sunlight is used
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to split water molecules (H₂O)
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into oxygen (O₂) and hydrogen
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+
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ions (H ).
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The Process of
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Photosynthesis
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STEP 3
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Glucose Production
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The carbon dioxide (CO₂) taken in by
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the plant is combined with other
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organic compounds to produce
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glucose (C6H12O6) through a series of
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chemical reactions.
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Some of the food (glucose) molecules
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are used by the plant and some are
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stored for later use.
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oxygen
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carbon
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dioxide
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The Process of
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Photosynthesis
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STEP 4
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Release of Oxygen
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As a result of photosynthesis
plants
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release oxygen (O₂) into the
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atmosphere.
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This is the oxygen we breathe and is
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essential for all living things.
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How do water and nutrients reach plants?
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Water Absorption
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Plants absorb water from the soil
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through their roots.
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Water then travels up the plant’s
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stem through a network of tiny
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tubes called xylem.
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Nutrient Uptake
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Nutrients (phosphorus
nitrogen
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and potassium) dissolved in soil
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water move into the plant root
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cells. The dilute solution of
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nutrients in water
also known as
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sap
moves from the root tissue
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through the xylem to reach plant tissues
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Light energy captured by chlorophyll transforms six carbon dioxide molecules
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and six water molecules into a sugar molecule and six oxygen molecules.
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6CO2
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6H O 2
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SUNLIGHT
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C H O 6 12 6
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6O2
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CARBON DIOXIDE
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WATER
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GLUCOSE
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OXYGEN
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CHLOROPHYLL
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Plants require the following resources in order
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to photosynthesise:
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Sunlight
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which supplies the energy
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(radiant/light energy) for the
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process
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Carbon dioxide (CO2)
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plants absorb carbon dioxide
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from the atmosphere through a
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pore on the leaf called the
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stomata.
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Chlorophyll
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Plants appear green because
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they have a green pigment in
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their cells. This pigment is called
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chlorophyll. It traps and absorbs
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the radiant energy from the sun.
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Water (H2O)
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Plant roots absorb water from
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the soil and is then sent up to
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leaves via the xylem.
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. Importance of Photosynthesis
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Produces oxygen and
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uses up carbon dioxide
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Impacts food
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production and
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economy
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Supports
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biodiversity and
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makes ecosystems
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stable
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Provides food
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for a wide variety of
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organisms
including
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humans
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Importance of Photosynthesis
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Plants convert glucose into starch
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and other chemical compounds:
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• Glucose is a sugar and is the simplest form of food
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• Plants convert glucose into starch
cellulose and other chemical
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compounds that they need for processes such as growth and
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reproduction (MRS GREN)
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• Plants change glucose molecules into starch because starch is the
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chemical compound in which plants store energy.
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Importance of Photosynthesis
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• Many glucose molecules bond together to form starch molecules. For
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example
the sugar and starch that is produced is stored in leaves and
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other parts of plants such as apples
potatoes
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• Glucose is also converted into the chemical compound cellulose.
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• Cellulose is part of the cell walls of plants
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• Cellulose is the main building material of plants and is used to provide
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structure and support to plants.
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• This is the reason plants can grow without falling over
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• Wood consists of about 50% cellulose.
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Review
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Photosynthesis
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It is a process where plants
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turn sunlight
carbon dioxide
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and water into their food
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(glucose) and release
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oxygen.
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Water and
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Importance
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Nutrient Uptake Photosynthesis and other
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Plants absorb water and
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related processes impact the
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essential minerals from the
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ecosystem and the lives of
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soil through their roots.
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organisms in various ways.
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Four factors affect
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photosynthesis
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1. 2. 3. 4. Light – if there is more light photosynthesis happens faster
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Water – if there is not enough water photosynthesis slows down
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Temperature – the best temperature is about 300C – anything above 40ºC will
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slow photosynthesis right down
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CO2 – if there is more carbon dioxide photosynthesis will happen quicker
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Plants without chlorophyll
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• Plants that do not contain chlorophyll must use other ways to obtain their food.
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• Saprophytes
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–Plants that survive on dead organic tissue e.g. sugar stick
Indian pipe and certain orchids.
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• Parasites
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–Parasitic plants live on living organic tissue and obtain all their nutrients from the host. The host is harmed in the relationship. E.g. dodder and mistletoe
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Terminology
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• Interdependent – two or more things that depend or rely on each other.
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• Radiant energy – energy obtained from the sun in the form of heat and light.
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• Photosynthesis – radiant energy is converted into potential energy which is stored in food and
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oxygen is released.
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• Chemical reactions – chemical changes that take place when two or more compounds react and
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form new substances.
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• Cells – smallest units of living organisms.
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• Chlorophyll – green pigment in plant cells that absorbs radiant energy.
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• Chloroplast – a plastid in green plant cells which contains chlorophyll and in which photosynthesis
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takes place
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• Potential energy – energy that is stored in an object or system.
