Topic 4 - plant cells and transport Flashcards
Which structures does a plant cell contain that an animal cell doesn’t?
Cell wall
Plasmodesmata
Chloroplasts
Amyloplasts
Vacuole
Function of the chloroplasts and explanation
Site of photosynthesis
Have stacks of thylakoids called a grana, containing chlorophyll
These grana are connected by extensions of thylakoid membranes called lamellae
Grana are surrounded by a colourless fluid called stroma which contain the enzymes required for photosynthesis
Chloroplasts are bound by a membrane
Function of amyloplasts
Produces and stores starch
Surrounded by a double membrane
Features of vacuole
Contains cell sap and is surrounded by a tonoplast (single membrane). Provides the cell with strength and support
Features of the cell wall
Rigid outer covering made of peptidoglycan which provides the cell with strength and support
Features of the plasmodesmata
An extension of cytoplasm between the cell wall of adjacent cells involved in the transport of substances between them
What are plasmodesmata?
Gaps between cells
Describe the structures in a chloroplast that are involved in the light dependent reactions of photosynthesis (3 marks)
Granum provides increased SA for photosynthesis
A granum is a stack of thylakoids
Thylakoid membrane contains proteins and chlorophyll
Explain the features of the chloroplast
Have a double membrane
Site of photosynthesis
Contain stacks of thylakoid membranes called grana
Grana are connected by lamella
Grana are surrounded by a colourless fluid called stroma which contains all the enzymes required for photosynthesis
What causes plant fibres to have so much strength?
The arrangement of microfibrils in a mesh-like pattern
Secondary thickening which results in a thick secondary cell wall developing which often contains lignin
What is the function and structure of the xylem vessel?
Vascular tissue that transports dissolved minerals and water around that plant
Structural support - lignin allows the vessel to withstand high pressure created by the moving column of water
Xylem vessels form long, hollow straw like structures that are formed by dead cells
Don’t contain any cytoplasm or organelles that could slow down the flow of water
Describe the structure and function of a plants cell wall
Made of cellulose. Outer layer is called middle lamella. Holds adjacent cells together as well as providing support and protection
Structure and function of sclerenchyma
Sclerenchyma fibres provide support
They consist of bundles of dead cells
They form long, hollow tubes, but they do have end walls present
Lignification of cell walls occur, but they do not have pits like xylem vessels
They have more cellulose in their walls compared to other plant cells
Structure and function of phloem tissue
Transport organic compounds (assimilates), particularly sucrose, from sources (e.g. leaves) to sinks (e.g. roots).
The transport of these compounds can occur up and down the plant. This is known as translocation
No support function in a plant
Phloem is a complex tissue made up of various cell types; its bulk is made up of sieve tube elements which are the main conducting cells and companion cells
Function of the vascular bundles in a stem
Vascular bundles consist of xylem vessels which are group together with phloem tissue
In a stem, xylem vessels are always located towards the middle of the stem, while the phloem is located closer towards the outside of the stem
Sclerenchyma fibres are associated with the vascular bundles and provide additional support to the stem
Relate the structure of cellulose to its function
Made of long beta glucose chains which are held together by hydrogen bonds to form microfibrils. Hydrogen bonds are strong meaning cellulose is suitable for providing structural support within the cell walls
Relate the structure of xylem and sclerenchyma fibres to their function
Cellulose microfibrils form an arrangement of net like structures in the cell walls of the fibres
Secondary thickening further strengthens the fibres by adding lignin
Explain starch
Starch is the storage polysaccharide of plants
It is stored as granules in plastids (e.g. chloroplasts) and amyloplasts (small, membrane bound organelles containing starch granules)
Due to starch molecules being large polymers consisting of thousands of glucose monomers, starch takes longer to digest than glucose
Starch contains:
Amylose (10 - 30% of starch)
-Unbranched helix-shaped chain with 1,4 glycosidic bonds between α-glucose molecules
-The helix shape enables it to be more compact and thus it is more resistant to digestion
Amylopectin (70 - 90% of starch):
-1,4 glycosidic bonds between α-glucose molecules (as found in amylose) but also 1,6 glycosidic bonds form between glucose molecules creating a branched molecule
Explain features/structure of cellulose
Cellulose is a polymer consisting of long chains of β-glucose joined together by 1,4 glycosidic bonds
Component of well walls in plants and is composed of long, unbranched chains of beta glucose which are joined by glycosidic bonds.
Microfibres formed of microfibrils are strong threads which are made up of long cellulose chains joined together by hydrogen bonds and they provide structural support in plant cells
Due to the inversion of the β-glucose molecules many hydrogen bonds form between the long chains, giving cellulose it’s great strength
Explain the function of cellulose
Cellulose is the main structural component of cell walls due to its strength, which is a result of the many hydrogen bonds found between the parallel chains of microfibrils
The high tensile strength of cellulose allows it to be stretched without breaking which makes it possible for cell walls to withstand turgor pressure
The cellulose fibres and other molecules (e.g. lignin) found in the cell wall form a matrix which increases the strength of the cell walls
These strengthened cell walls provide support to plants
What conditions do bacterial cells require for growth?
-Nutrients
-Sufficient supply of oxygen for bacteria which respire aerobically
-Temp and PH cant be too high or too low so that enzymes that control metabolic processes to function optimally
Explain the relationship between the structure and functions of a granum in photosynthesis (3)
-Granum is formed from many layers of thylakoid membranes to increase surface area for absorbing light
-Thylakoid membranes contain chlorophyll to absorb light
-Electron carrier molecules in thylakoid membrane involved in ATP production
Some plant cells contain the polymer starch.
Explain how the structure and properties of starch are related to its function as a storage molecule (3)
-Contains glucose needed for respiration/energy
-Insoluble so there is no osmotic effect
-Amylose is coiled making starch compact so more can be stored
-Amylopectin is branched/has 1-4 and 1-6 glycosidic bonds so it can be rapidly hydrolysed
What is meant by tensile strength?
The total amount of force a fibre can withstand without breaking
