photosynthesis Flashcards
bbc bitesize
algae
definition
A group of organisms that photosynthesise but lack the complex range of cell types and organs found in land plants. Most algae are aquatic. All have chloroplasts.
biomass
definition
The dry mass of an organism.
carbon dioxide
definition
A gaseous compound of carbon and oxygen, which is a by-product of respiration, and which is needed by plants for photosynthesis.
cell
definition
Basic unit of life. Unicellular organisms only have one cell. Multicellular organisms have many cells.
chlorophyll
definition
The green chemical inside the chloroplasts of plant cells. It enables photosynthesis to take place.
chloroplast
definition
Contains the green pigment chlorophyll; the site of photosynthesis.
denature
definition
If a substance is denatured, its structure and function is altered. This can be caused by heat, altered pH or by chemical agents.
enzymes.
endothermic
definition
Reaction in which energy is taken in from the surroundings.
enzyme
definition
A protein which catalyses or speeds up a chemical reaction.
glucose
definition
A simple sugar used by cells for respiration.
light
definition
Visible electromagnetic radiation.
limiting factor
definition
A factor which, if in short supply limits or reduces the rate of photosynthesis, eg temperature, light intensity and carbon dioxide concentration.
organ
definition
A group of different tissues that work together to carry out a particular function, eg heart and lungs.
photosynthesis
definition
A chemical process used by plants to make glucose and oxygen from carbon dioxide and water, using light energy. Oxygen is produced as a by-product of photosynthesis. Algae subsumed within plants and some bacteria are also photosynthetic.
respiration
definition
The chemical change that takes place inside living cells, which uses glucose and oxygen to release the energy that organisms need to live. Carbon dioxide is a by-product of respiration.
stomata
definition
Tiny holes in the epidermis (skin) of a leaf. They control gas exchange by opening and closing and are involved in loss of water from leaves. Singular is stoma.
xylem vessels
definition
Narrow, hollow, dead tubes with lignin, responsible for the transport of water and minerals in plants.
Photosynthesis
overview
Green plants and algae use light energy to make glucose and oxygen from carbon dioxide and water. Temperature, carbon dioxide concentration and light intensity can affect the rate of photosynthesis.
Photosynthesis
Algae
Algae can also make their own food by the process of photosynthesis. Plant biomass will increase as a result of photosynthesis.
Photosynthesis equation
Carbon dioxide + water →(light)→ Glucose + oxygen
Is photosynthesis a endothermic or exothermic reaction?
Photosynthesis is an endothermic reaction as it requires light energy to react carbon dioxide and water to produce glucose and oxygen.
Photosynthesis
Chlorophyll
The light energy required is absorbed by a green pigment called chlorophyll in the leaves. Chlorophyll is located in chloroplasts in plant cells.
What is the main organ for photosynthesis?
Plant leaves are the main organ for photosynthesis.
Photosynthesis
carbon dioxide
The carbon dioxide required for photosynthesis comes from the air. It enters leaves through the stomata. Water enters the plant through the roots, and is transported to the leaves in the xylem.
Photosynthesis
oxygen
Oxygen is formed as a product. Some is used for respiration. During the day, provided the rate of photosynthesis is high enough, plant and algae give out oxygen.
Photosynthesis
glucose
Glucose is the starting point for making the materials that plants need to live. These materials are used to make cell walls and other cell components and will enable the plant to growth and increase in biomass.
The glucose not used for respiration is used in the following ways:
- cellulose
- starch
- Amino acids→Proteins
- Lipids (fats/oils)
Cellulose in plants
Many glucose molecules joined together makes cellulose which is to build cells walls and adds strength to cell walls
Starch in plants
Many glucose molecules joined.
insoluble
storage form of carbohydrate
Lipids (fats/oils) in plants
Used for storage in seeds
Amino acids and proteins in plants
Glucose plus nitrates absorbed from the soil makes amino acids.
many amino acid molecules joined makes proteins.
There are several ways of measuring the rate of photosynthesis in the lab. These include:
- the rate of oxygen production (number of bubbles or volume of oxygen gas given off in a set time)
- the rate of carbon dioxide uptake
- the rate of glucose production
Several factors can affect the rate of photosynthesis:
- light intensity
- carbon dioxide concentration
- temperature
Light intensity
Without enough light, a plant cannot photosynthesise very quickly - even if there is plenty of water and carbon dioxide.
Increasing the light intensity increases the rate of photosynthesis, until some other factor - a limiting factor - becomes in short supply.
The rate of photosynthesis is directly proportional to the light intensity until another factor becomes limiting.
At very high light intensities, photosynthesis is slowed, but these light intensities do not occur in nature.
Carbon dioxide concentration
Carbon dioxide is one of the reactants in photosynthesis. If the concentration of carbon dioxide is increased, the rate of photosynthesis will therefore increase. At some point, another factor may become limiting
Direct proportion
As light intensity increases the rate of photosynthesis also increases. This is because photosynthesis is an energy requiring reaction, endothermic. More light energy will increase the rate at which oxygen is given off so more bubbles of oxygen will be produced per minute.
Inverse proportion
There is an inverse relationship between distance and light intensity - as the distance increases, light intensity decreases. This is because as the distance away from a light source increases, light energy becomes spread over a wider area.
Features of leaves
Name the purpose of the adaptation large surface area
To absorb more light
Features of leaves
Name the purpose of the adaptation thin (leaves)
Short distance for carbon dioxide to diffuse into leaf cells
Features of leaves
Name the purpose of the adaptation chlorophyll
Absorbs sunlight to transfer energy into chemicals
Features of leaves
Name the purpose of the adaptation Network of veins
To support the leaf and transport water and sugars
Features of leaves
Name the purpose of the adaptation Stomata
Allow carbon dioxide to diffuse into the leaf and oxygen to diffuse out
Structure of leaves
Name the purpose of the adaptation Epidermis is thin and transparent
To allow more light to reach the palisade cells
Structure of leaves
Name the purpose of the adaptation Thin cuticle made of wax
To protect the leaf from infection and prevent water loss without blocking out light
Structure of leaves
Name the purpose of the adaptation Palisade cell layer at top of leaf
To absorb more light and increase the rate of photosynthesis
Structure of leaves
Name the purpose of the adaptation Spongy layer
Air spaces allow carbon dioxide to diffuse through the leaf
Structure of leaves
Name the purpose of the adaptation Palisade cells contain many chloroplasts
To absorb all the available light
What is the rate of photosynthesis directly proportional to?
Rate of photosynthesis is directly proportional to light intensity.
What is light intensity proportional to?
Light intensity is proportional to 1/d^2.
What is light in tensity inversely proportional to?
d^2
