Lecture Seven

Question 1

cell wall

Answer 1

a rigid membrane that contains cellulose (a carbohydrate that is indigestible for humans). The cell wall is the outer covering of the cell. It protects the parts inside, and the cellulose molecules in the wall provide the support and rigidity needed to maintain the three dimensional structure of the cell.

Question 2

cell membrane

Answer 2

a flexible membrane made up of layers of protein and lipid (fats and oils are examples of lipids). The cell membrane is semi-permeable, meaning that it allows select compounds in and out, but not others. If the cell were like a bicycle tire, the cell wall would be the thick, protective outer tire tread part and the cell membrane would be the inner tube part.

Question 3

chloroplast

Answer 3

an organelle (“organelle” is the generic name for a plant organ) that contains chlorophyll. This is the organelle where light energy is captured and where the first steps are taken in the chemical pathway that converts the energy in light into chemical forms of energy that the plant can transport and store, like sugar and starch. Chloroplasts are not evenly distributed throughout the plant, but as you might expect are concentrated in parts of the plant that are exposed to the sun. A plant cell in the leaf blade will have many chloroplasts while cells in the middle of the stem will have few or none.

Question 4

mitochondria

singular = mitochondrion

Answer 4

Another organelle, this one is where the stored sugars are burned to produce forms of energy that the plant can use for growth. This is the cell’s powerplant. All cells will have many mitochondria.

Question 5

nucleus

Answer 5

An organelle that contains the chromosomes. Chromosomes contain the genetic code that is carried within each cell and that directs which chemical reactions are turned on and off in the cell. Chromosomes are also the hereditary material passed on to new cells and to subsequent generations. Each cell has one nucleus.

Question 6

vacuole

Answer 6

an organelle containing various fluids including stored chemical energy like starch and waste products from the cell. The vacuole takes up much of the cell volume and gives shape to the cell.

Question 7

cytoplasm

Answer 7

the fluid inside the cell membrane in which the organelles and other plant cell parts are suspended.

Question 8

middle lamella

Answer 8

a material containing pectin that forms between cells and that cements the cell wall of one cell to the cell wall of an adjacent cell. If bricks in a wall are like cells in a plant, the middle lamella in the plant is like the mortar between bricks in the wall.

Question 9

define “tissue”

Answer 9

a group of cells that share a function

Question 10

dermal tissue

Answer 10

“derma” is Greek for “skin”

outside of the plant providing protection for plant cells

Question 11

cutin

Answer 11

waxy polymer which coats the wall of the cell exposed to the environment

Question 12

epidermis

Answer 12

outermost layer of cells in the plant.

usually one cell thick

few if any chloroplasts

may have hairs or trichomes

Question 13

guard cells

Answer 13

contained in the epidermic on the underside of leaves

Question 14

stomata

Answer 14

a hole through which gasses can move into and out of the deeper cell layers in the leaf

Question 15

What unique feature of the epidermis is found in roots and not shoots?

Answer 15

root hairs

Question 16

cortex (sometimes called “ground meristem”)

Answer 16

found inside the epidermis and extends towards the interior stem and root

Question 17

pith

Answer 17

center of the stem

Question 18

parenchyma

cell type

Answer 18

most common type of cortex cell

very thin walls

alive and helps heal wounds by creating callus

site of photosynthesis and storage of starch and other chemical compounds

Question 19

collenchyma

cell type

Answer 19

living

thickened cell walls

they respond to external stimuli

Question 20

sclerenchyma (cell type)

Answer 20

has primary and secondary cell walls

primary is rich in cellulose

secondary is deposited just inside primary wall with high concentration of lignin giving the cell rigidity

Question 21

fibers

Answer 21

formed from long strands of sclerenchyma

used in fabrics, carpets, rope, etc.

comes from jute, hemp, flax, etc.

Question 22

Sclerenchyma comes in two types

Answer 22

fibers and sclerids

Question 23

sclerids

Answer 23

cells with hard, tough walls

coalesce and cover other plant parts

think of cherries, nuts, cocnut

Question 24

Are sclerenchyma cells typically alive or dead at maturity?

Answer 24

dead

Question 25

Which cells divide to initiate adventitious roots?

Answer 25

parenchyma

Question 26

vascular tissue

Answer 26

form the pluming system of a plant which water, nutrients, sugars, and other compounds flow (vascular bundle)

Question 27

three main types of vascular tissue

Answer 27

xylem
phloem
vascular cambium

Question 28

xylem

Answer 28

moves water to the plant in a unidirectional pattern (root to stem to leaf then out of the plant)

Question 29

do trees have xylem?

Answer 29

yes, it is the part we call wood

Question 30

vessels

Answer 30

elongated cells that connect end to end to form tubes

dead at maturity

walls are perforated so water can move freely from cell to cell

relatively large diameter compared to other xylem allowing greater movement of water

Question 31

xylem fibers

Answer 31

these are sclerenchyma cells lying near the vessels and tracheids

strung together end to end, but are without pits or perforations

they don’t move water, rather, they provide flexible support for the plant and its vascular bundles.

Question 32

xylem parenchyma

Answer 32

in woody plants there are parenchyma cels around the vascular bundles that extend horizontally through the xylem

develop into rays moving laterally from center to exterior of plant (not parallel)

Question 33

phloem

Answer 33

moves nutrients taken up by the roots to other parts of the plant

also moves sugars made in the leaves by photosynthesis and other hormones like auxin

Question 34

flow in phloem is…

Answer 34

bidirectional among lead, stem, and root

Question 35

four types of phloem tissue

Answer 35

sieve tube members - elongated cells that join end to end, alive, thin cell membrane containing living protoplasm

companion cells - contain nucleus, may direct the metabolism of sieve tube member, alive

phloem fibers (sclerenchyma cells) - provide support same as for xylem

phloem parenchyma cells - adjoin the sieve tube cells, same as for xylem

Question 36

vascular cambium

Answer 36

this third type of vascular tissue is a meristematic region (meaning that the cells can actively begin dividing to form new growth) where new vascular tissues originate in plants with secondary growth, like trees.

Question 37

What flows in the xylem, and does it flow both directions or only up from the roots to the leaves?

Answer 37

water, unidirectional