Plants

Question 1

Name four structure which are plant cells but are not found in animal cells

Answer 1

Chloroplast

Permanent vacuole

Cellulose cell wall

Plasmid such as amyloplast

Question 2

Primary cell wall

Answer 2

Middle lamella

Middle lamella is first layer -when a plant cell divides into two new cells

Mainly consists of pectin (polysaccharides) which act as a glue and holds the cell walls of adajecent plant cell together

Pectin -negatively charged carboxyl group combine with positive calcium ion to make calcium pectate

Cellulose microfibrils and the matrix build up on both sides of the middle lamella
-walls are flexible with all microfibrils being arranged in the same direction

Question 3

Secondary cell wall

Answer 3

Secondary cell walls build up with the microfibrils densly laid at different angles to each other which makes the composition much more rigid

Hemicellulose helps harden it further

Lignin is added to cell wall to produce wood makes it more
—> rigid

Question 4

What are plasmodesmata?

Answer 4

Cytoplasmic bridges that connect the cytoplasm of neighbouring cells

The cell walls are thinner in the region of plasmodesmata

• channels of cytoplasm that pass between adjacent cells walls of plant cells that allows fast communication and exchange of substances between cells

Question 5

What are symplast?

Answer 5

Interconnected cytoplasm of the cells

Question 6

What is middle lamella

Answer 6

The first layer of the plant cell wall to be formed when a plant cell divides, made mainly of calcium pectate(pectin) that binds the layers of cellulose togther

Question 7

What are pits

Answer 7

In secondary thickening, area around the plasmodesmata dont have secondary thickening in them which leave thin areas of the wall called pits

There is no cytoplasm in xylem cells, but pits allow water to move between the vessel which is essential in maintaining a flow of water at even pressure

Thin areas of cell wall in plant cells with secondary thickening , where plasmodesmata msintian contact with adjacent cells, simple holes which allows water move out into the surrounding cell

Question 8

Describe the strcuture of the permanent vacuole found in plant cell

Answer 8

A membranous sac that contain cell sap -(dissolved sugar and salts)
—> which cause water to move inside the cell by osmosis, which keeps the cell turgid

Vacuole mainly maintain the shape of the cell, as well as store pigments which will prevent them from leaking to the cytoplasm unless it heated, they also store protein

Contain lytic enzyme and act similarit to lysosome and they also store waste product

Question 9

What are chloroplast

Answer 9

A small flattened structure that contains a double membrane. The inner membrane is stacked into thylakoid . Contain chlorophyll which is green pigment that absorb light for photosynthesis

Question 10

Similarities of chloroplast and mitochondria

Answer 10

Large organelle

• > diameter (4-10 um)
• > thick (2-3 um)

Contain their own DNA

Surrounded by an outer membrane

Have an enormously folded inner membrane that gives a greatly increased surface area where enzyme-controlled reaction take place

Question 11

Difference of chloroplast and mitochondria

Answer 11

Site of photosynthesis

Contain chlorophyll
-green pigment that is largely responsible for trapping the energy from light , making it available for plant to use

Question 12

Describe amyloplast

Answer 12

An organelle found in some plant cells that synthesises and stores starch molecule and breaks them down to glucose when the cell requires it

Question 13

Primary function of stem

Answer 13

Stem is support to hold the leaves in the best position for obtaining sunlight for photosynthesis

Movement of material such as water and mineral ions

Question 14

What is parenchyma

Answer 14

Relatively unspecialised plant cell that act as packing in stem and roots to give support
And can be modified suitabel for storage or photosynthesis

Question 15

What is collenchyma

Answer 15

Plant cells with areas of cellulose thickening that gives mechnical strength and support to the tissue
Due to the thick primary cellulose walls

Question 16

What are sclerenchyma

Answer 16

Plant cells that have very thick lignified cell walls and an empty lumen with no living content

Question 17

Propterties of sclerenchyma

Answer 17

Provide support to the plant, much like xylem vessel
-made of bundle of dead cells that run vertically up the stem

Have strong secondary walls made of cellulose microfibrils positioned at right angle

Ligin deposited on the cell walls of fibres , makes the fibre strong but flexible

The strength of the fibre depend on their length , how much ligin it contains

When the fibre liginfied , the cell content dies because water cannot pass through and so fibre becomes a hollow tibe

The cell can no longer grow so plant growth has to be highher up in the stem

Question 18

Structure of parenchyma

Answer 18

Consist of thin walled living cells

They are involed in food storage

Comprises a thin cell wall and made up of cellulose

Question 19

Sturcutrw of collenchyma

Answer 19

Consist of thin walled living cells

Mechanical tissue in particulary dicot stems

Comprises an uneven thick primary cell wall and is made up of pectin and hemicellulose

Question 20

Strucutre of sclerenchyma

Answer 20

Consists of dead cells

Mainly mechnical tissue

Comprises a hard and thick cell qall and is made up of lignin

Question 21

Function of parenchyma

Answer 21

Is to store and assimilate food. Hence , they are referrd to as food storage tissue

Stores waste product of plants

Serves as a packing tossie to fill the spaces between other tissues and maintian the plant shape and firmess

Question 22

Function of collenchyma

Answer 22

Provides mechanical support and elascitt to the stems of dicot plants

Cells possess chloroplast the involved in manufacturing sugar and starch

Provides tensile strength and flexibility to the plant body

Question 23

Function of sclerenchyma

Answer 23

Provides mechical strength to the plant

It makes the plant body rigid, flexible and elastic

Question 24

Structure of xylem

Answer 24

Vessel are long tube like strucutre that are formed from dead cells, joined end to end but they have no end walls, making for an uninterrupted tube that allows water and minerals ion to pass up through it easily

Walls are thickened by ligin which helps support the plant

Question 25

What is a protoxylem

Answer 25

Not fully ligified (can stretch and grow) The cellulose microfibrils in the walls of the xylem vessel are arranged vertically in the stem —> increasing strength of the tube Allowing it to resist the compression force from the weight of the plant pressing down on it

Question 26

What is Metaxylem

Answer 26

Increasing amount of lignin are incorporated into the cell walls as the stem ages and the cells stop growing Means that the cells become impermeable to water and other substances —> tissue becomes stronger and more supportive but the content of the cell dies The end walls between the cells mostly break down so the xylem forms hollow tubes which go from the roots to the tip of the stems and leaves

Question 27

What transport in xylem and system

Answer 27

Water and mineral ions are transported from the roots to the leaves and shoots in the transpiration stream Water moves out of the xylem into the surrounding cells through the specialised pits in the walls of the xylem vessels

Question 28

Where are xylem located

Answer 28

Located around stem and part of the vascular bundle

Question 29

What does phloem transport and

Answer 29

Phloem is made of living tissue and transport food molecules around the plant, both up and down in active process - translocation —> from leaves to tissue where needed

Question 30

Structure of phloem

Answer 30

Phloem is made up of many cells that are joined togther to form very long tubes Cells dont get lignifed and this the content remain living As a result of the cell walls being pirced , specilaised sieve plates will form and the phloem sap flows through the holes in these plates Mature phloem cells have no nucleus, tonoplasat and some other organelle as they break down while the gaps in the sieve plate are being made, filling the phloem sieve tube with phloem sap The phloem surivial relies on the companion cells which are very active cells with orgnelles, they are connected to the phloem sieve tubws through the plasmodesmata The cell membrane of the companion cells have many inner foldings that increase the surface area over which they transfer sucrose into the cell cytoplasm, as well as many mitochondria to provide the needed ATP

Question 31

Similarities of plant stem

Answer 31

Both are plant transport tissue Both have lot of water moving through them Both found togther in vascular bundles in plants

Question 32

Difference in xylen

Answer 32

Xylem - water mineral ions are transported in the xylem - xylem cells are living when first formed but become heavily lignified , so cell contents die - comprises hollow tube running through plants - water moves through xylem in transpiration stream carrying minerals with it Water leaves xylem through pits -provide important structural support for plant

Question 33

Difference in phloem

Answer 33

Contains product of photosynthesis Eg suvrose transported in the phloem in the solution in water Phloem sieve tubes are made of many cells joined togther to form tubes with perforated sieve plates between them Phloem sieve elemnts are not dead but have lost most their functions; they are a tube filled woth phloem sap - cell habe no nuclei Phloem cells only survive because they are supoorted by companion cells which are very active and lunked to phloem cells by many plasmodesmata

Question 34

Parenchyma structure

Answer 34

Found throughout the body —> outer layers of parenchyma cells in the stem may contain chloroplast —> stem is modified into collenchyma and schlerenchyma Can differentiate into other kinds of cells Alive;metabolically active Functions in photosynthesis, storage, and secretion

Question 35

Sclerenchyma

Answer 35

Specialised for strucutural support - cells have primary walls and strong thick secondary walls - pits allow exchange of substances between adjacent living sclerenchyma cells -mature functioning cells are dead

Question 36

What does sclerenchyma contain

Answer 36

Lignin deposited on the cell walls of these fibre in a spiral which makesthe fibre strong and flexible

Question 37

Sclerenchyma how does the strength of the fibres depends what

Answer 37

Strength of the fibre - length - how much it is lignified ( how much lignin it contains)

Question 38

Schlerenchyma what happens when the fibre is lignified

Answer 38

When it is lignified the cell content die because water cannot pass through lignin —> fibres become hollow tube -once this happen cell can no longer grow , so plants growth has to be higher up in the stem