nuovo deck

Question 1

where does the strength in plants come from?

Answer 1

from the thin cellulose walls of plant cells and the glue that holds them together

Question 2

what is cellulose?

Answer 2

polysaccharide, a polymer of beta glucose

Question 3

is cellulose short? is cellulose branched?

Answer 3

cellulose is short and unbranched

Question 4

does cellulose wind into a spiral? how many glucose units are in each molecule?

Answer 4

no, cellulose remains straight and has from 1 000 up to 10 000 glucose units

Question 5

how do microfibrils form? what do they make up?

Answer 5

they form thanks to hydrogen bonds between the OH groups in neighbouring cellulose chains.
Microfibrils make up the cell wall

Question 6

how do microfibrils arrange themselves around the cell? does something bind them?

Answer 6

they arrange themselves around the cell in a helical shape and are stuck together by a glue formed by hemicellulose and pectins that bind both to the surface of cellulose and to each others

Question 6

is the cytoplasm of a cell continuous with the next one’s ? why ?

Answer 6

yes, thanks to channels called plasmodesmata

Question 6

which bonds are stronger ? hydrogen bonds or glycosidic ?

Answer 6

Glycosidic but the large number of hydrogen makes for a pretty strong structure

Question 7

are cell walls permeable ?

Answer 7

yes, they are fully permeable to water and solutes

Question 8

what is a pit?

Answer 8

a thinning in cell wall because there is only one layer of cellulose deposited there

Question 9

where are plasmodesmata usually located ?

Answer 9

in pits, aiding movement of substances between cells

Question 10

what is the function of xylem vessels?

Answer 10

they form impermeable tubes for transport of water and inorganic ions (mineral ions) + support thanks to stiffened walls by lignin

Question 11

what is the function of phloem sieve tube cells?

Answer 11

form long tubes for the transport of organic solutes like sugars and amino acids, NO ROLE IN SUPPORT

Question 12

what is the function of sclerenchyma fibres?

Answer 12

columns of stiffened cells that provide support

Question 13

what does each vascular bundle contain ? on the outside?

Answer 13

xylem vessels and sieve tube elements, on the outside sclerenchyma fibres

Question 14

where is the vascular tissue in a young dicotyledon? in trees?

Answer 14

In a young dicotyledon, the vascular tissue is in bundles TOWARDS the OUTSIDE of the stem. In trees these separate bundles merge to form a continuous ring as the plant grows

Question 15

what do xylem vessels look like?

Answer 15

They are fluid-filled tubes in which water moves upwards from the roots to the shoots

Question 16

where does the most evaporation occur?

Answer 16

From the cells that line the substomatal cavities of the leaves , vapour diffuses through a diffusion gradient

Question 17

where do we get the energy to pull water up to the leaves?

Answer 17

from the evaporation of water from the cells in the sub stomatal cavities of the leaves

Question 18

what is capillary action and what can it do ?

Answer 18

capillary action is caused by the surface tension between the water and the walls of the capillaries, it helps drawing the water as the capillaries create a massive pull on water behind them

Question 19

how does water move up the stem in xylem ? what does it look like?

Answer 19

It looks like a continuous stream (capillary action is enough to bring it through the whole stem) and is called a TRANSPIRATION STREAM

Question 20

what is a transpiration stream?

Answer 20

it’s the stream of water that travels continously up the xylem and through the stem from the roots to the shoots thanks to capillary action and powered by the evaporation of water from the cells in the substomatal cavities of the leaves

Question 21

is the water that is being pulled up in the xylem under tension? why don’t the xylem vessels collapse inwards.
Why doesn’t the column of water break as it is pulled up?

Answer 21

yes, the water that is being pulled up is under tension but the xylem vessels do not collapse inwards because of this since they are heavily lignified. Water column does not break because of cohesion tension theory, when water it’s being pulled up under tension it brings with it the molecule behind because linked by cohesion

Question 22

what does the movement of water in the xylem provide?

Answer 22

a mass flow system for the transport of inorganic ions that are absorbed into the roots and required throughout the plant

Question 23

why is the movement of substances in the xylem only upwards?

Answer 23

Because it moves the water and inorganic ions captured by the roots all the way to the shoots

Question 24

what are nitrate ions in the plant needed for?

Answer 24

nitrate ions are needed to create all 20 amino acids when nitrogen is combined with products of photosynthesis. Cytoplasm is also made largely of proteins, created by joining two amino acids together, also ATP, nucleic acids, some plant growth substances

Question 25

what happens when a plant lacks magnesium ? nitrogen ? calcium?

Answer 25

if not supplied with enough inorganic ions the plant will show deficiency symptoms and in this case will not be able to produce chlorophyll, older leaves yellow between veins with reddish/brownish tints. Nitrogen = yellow leaves. Calcium = stunted growth because of the role of calcium ions in cell wall structure and permeability

Question 26

what is the main difference between xylem vessels and phloem sieve tube elements?

Answer 26

sieve tube elements remain alive thanks to the help of companion cells while xylem vessels are dead

Question 27

how does the material pass from one sieve tube element through to the other? what are they called?

Answer 27

material is moved thanks to holes in the end wall that are aligned with the ones of the other sieve tube elements. They are called sieve plates

Question 28

what is the transport of organic molecules in the phloem called ? what are the substances in the phloem produced by and where?

Answer 28

translocation.
The substances produced by the phloem (sugars, amino acids) are produced in the leaves thanks to photosynthesis

Question 29

where do the organic molecules in the phloem move to and why are they needed there?

Answer 29

The products of photosynthesis move in the phloem either to the roots or to the buds ALL STARTING FROM THE LEAVES. In the roots, they are used as a source of energy or converted into a polysaccharide such as starch for storage while they can also go towards the buds, developing flowers or fruits and their seeds

Question 30

where are mineral ions transported if they have to go from one part of the plant to the other?

Answer 30

If mineral ions have to move from one part of the plant to the other (like growing/developing leaves) they cannot use they xylem and thus resort to using the phloem

Question 31

why might mineral ions need to go from one part of the plant to the other?

Answer 31

To move from old leaves to young new ones or down tot he bulb before it goes dormant

Question 32

which organelles does the companion cell have ? what do they do?

Answer 32

The companion cell is a thin cell that still has the nucleus, mitochondria, ribosomes and RER. They perform the metabolic functions that maintain the sieve tube element

Question 33

what do the transfer cells have to improve their function?

Answer 33

-cell wall and cell surface have many infoldings to increase surface area
-a lot of mitochondria for energy
-a lot of plasmodesmata for transport

Question 34

what is a sink cell and also give an example

Answer 34

a sink cell is a place in which the substances are used/stored but not produced, like roots, buds, flowers and fruits

Question 35

how do many plants survive the winter ? (aka what state are they on) what happens in spring ?

Answer 35

In order to survive the winter many plants fall in a dormant state, storing starch in roots, bulbs and tubers. Once back in spring the starch is broken down and the bulb become momentarily the source, buds and new leaves the sink

Question 36

why don’t we use diffusion to move substances along the phloem ?

Answer 36

Because it would take too long

Question 37

how is a turgid cell?

Answer 37

completely full, with its contents pressing on the cell wall. Turgor supports leaves of all plants including trees but can be lost if the cell loses water

Question 38

what is the link between lignin and separation of fibres?

Answer 38

The bigger the lignin the more difficult it is to separate the fibres

Question 39

what can we use plant fibres for ?

Answer 39

clothing
paper
ropes
floor covering
mats to absorbe heavy materials or hydrocarbons from polluted waters
create biocomposites with other materials

Question 40

what is the active ingredient of garlic ?

Answer 40

allicin, only produced when plant is cut or damaged

Question 41

steps of testing medicines

Answer 41

1. pre clinical testing, made on animals or cells and tissue cultures = safety and whether effective on target disease
2. clinical trial phase one, small group, healthy, different doses = if absorbed, distributed, metabolised and excreted AS PREDICTED
3. clinical trial phase two, (100-300) small group with disease = effectiveness
4. double-blind randomised controlled trial (1000-3000)
5. after licensing trials continue for data on effectiveness and safety

Question 42

function of seeds

Answer 42

-aid dispersal
-protect the embryo (tough seed coat called tests)
-provide nutrition for new plant

Question 43

how is a seed made ?

Answer 43

In blooming plant is the ovule fertilised by the nucleus of a pollen grain while the ovary becomes the fruit

Question 44

how are the nutrients/food stored in seeds depending on plants?

Answer 44

if the plant is a monocotyledon then food is stored in the storage tissue called endosperm while, if the plant is a cotyledon, the nutrients are stored in endosperm but food in the seed leaves that sweel to fill the seed

Question 45

what are monocotyledon seeds (like cereals) also called?

Answer 45

endospermic

Question 46

what are the means of transport of seeds?

Answer 46

wind, water, animals and self dispersal

Question 47

when does the seed take in water?

Answer 47

when the conditions are suitable and dormancy has been broken the seed takes in water from a pore that triggers metabolic changes