Notes : 4.7 - 4.12 Properties of Plants

Question 1

Label the structures within the chloroplast.

Answer 1

Question 2

Name the two parts of the vacuole

Answer 2

Question 3

What structure is this ?

Answer 3

Amyloplast

Question 4

Plant Cell Wall Structure

Answer 4

● Middle lamella- outer cell wall layer that contains polysaccharides called pectins. Pectins aid in cell adhesion by helping the cell walls of adjacent cells to bind to one another.

● Primary cell wall*- layer formed between the middle lamella andplasma membranein growing plant
cells. composed of *cellulose microfibrils contained within a gel-like matrix of hemicellulose fibres and pectin polysaccharides. The primary cell wall provides the strength and flexibility needed to allow for cell growth.

● Secondary cell wall- layer formed between the primary cell wall and plasma membrane in some
plant cells. This rigid layer strengthens and supports the cell. some secondary cell walls contain lignin.

Question 5

What is Lignin

Answer 5

Lignin is a thick, woody substance which is found in the cell walls of xylem and schlerenchyma cells and provides strength to the plant stem.

Lignin strengthens the cell wall and aids in water conductivity inplant vascular tissuecells.

Question 6

Plant cell walls
Feature & Function.

Answer 6

Question 7

How do the microfibrils form the wall ?

Answer 7

1. Cellulose molecules are unbranched but are bonded to each other through hydrogen bonds.

2.This bonding between cellulose molecules forms a net-like arrangement called a microfibril.

3. Microfibrils are in form hydrogen bonded between other microfibrils to form larger structures called macrofibrils.

• The net-like arrangement and the strength of the cellulose microfibrils are what make plant fibres so strong.

Question 8

Plant Organelles

Answer 8

1. Cell wall
2. Chloroplast
3. Middle lamella
4. Amyloplasts
5. Permanent Vacuole
6. Tonoplast
7. Plasmodesmata
8. Pits

Question 9

Vacuole

Answer 9

• Stores cell sap. Surrounded by single membrane (tonoplast)
• Helps to keep plant cells turgid.
• Stores nutrients needed by plants as well as waste minerals.

Question 10

Tonoplast

Answer 10

• Membrane that surrounds the vacuole.
• It separates the vacuole from the rest of the cell.

Question 11

Plasmodesmata

Answer 11

• They are narrow channels of cytoplasm within the cell walls of plants.
• It allows two neighbouring plant cells to transport substances between them and to communicate.

Question 12

Pits

Answer 12

• regions of a plant cell where the cell wall becomes very thin.
• pits allow neighbouring plant cells to exchange substances.
• arranged in pairs so that the pit of one plant cell is aligned with the pit of another plant cell.

Question 13

Amyloplasts

Answer 13

• Plant storage granules which contain starch. Surrounded by a double membrane.
• Converts the starch back into glucose when the plant cell needs more glucose for respiration.

Question 14

Two examples of polysaccharides found in plants.

Answer 14

• Starch
• Cellulose.

Question 15

Relate the structure of cellulose to it’s function

Answer 15

• Composed of long beta-glucose chains that are held together by hydrogen bonds to form microfibrils.

Question 16

Xylem

Answer 16

• Transport water and mineral ions from the roots to the rest of the plant.
• Made up of dead cells with open ends. This forms one continuous tube when the xylem cells are stacked on top of each other.
• No organelles or cytoplasm, which creates more space inside the vessel for transporting water.
• The cell walls contain pits which allow water and mineral ions to move into and out of the vessel
• Contains lignin, which strengthens the xylem vessel and provides structure and support to the plant.

Question 17

Phloem

Answer 17

• Transport dissolved substances, such as sucrose and amino acids from parts of the plant where they are made (sources e.g leaves as they produce glucose) to the parts of the plant where they are used (sinks).
• Phloem vessels are made up of two types of cell - sieve tube elements and companion cells.

Question 18

Sieve Tubes

Answer 18

• The sieve tube are living cells and are joined end-to-end to form sieve tubes.
• The ends of each cell consist of a ‘sieve plate’ which contains lots of holes to allow solutes to move from one cell to the next.
• Contain no organelles and very little cytoplasm to create more space for solutes to be transported.
• The absence of a nucleus and other organelles means that these cells cannot survive on their own, so each sieve tube element is associated with a companion cell, which contains a nucleus and is packed full of mitochondria.
• The sieve tube element and the companion cell are connected through plasmodesmata (channels in the cell wall) which allow the two cells to communicate.

Question 19

Ions and Importance

Answer 19

Mineral ions are found in the soil and are absorbed by the plant through their roots.

• Nitrate ions : Supply nitrogen which is needed for the production of DNA, Proteins and chlorophyll.
• Calcium ions : Forms Calcium pectate for cell wall, used in growth.
• Magnesium : Production of chlorophyll, activation enzymes.

Question 20

Water importance

Answer 20

• Required for photosynthesis.
• Maintain rigidity of cells.
• Transport of substances.
• Thermoregulation.

Question 21

Sclerenchyma

Answer 21

• found within vascular bundles and provide structural support to the stem.
• made up of bundles of long, dead cells.
• The cells have a hollow lumen and the cell walls are thickened with lignin.
• The cell walls also contain more cellulose than a typical plant cell which makes sclerenchyma fibres particularly strong.

Question 22

Vascular Bundles

Answer 22

Question 23

Plant fibres

Answer 23

Question 24

How is the tonoplast broken down ?

Answer 24

The tonoplast is broken down by the autolysis (When it breaks down itself) of the cell contents.

Question 25

Answer 25

Question 26

What are substomatal spaces

Answer 26

The air sacs that we used to call in gcse`.