Plants Structure and Function Flashcards
How does suberin in the cell wall of cork tissues and lignin in the cell wall of wood affect its permeability
reduces the permeability so that water and dissolved substances cannot pass through
What is the first layer of the cell wall?
the middle lamella
when is the middle lamella made
when the plant cell divides into two new cells
What is the middle lamella made of and what does the substance do
pectin
it is a polysaccharide that acts like glue and holds the cell wall of adjacent plant cells together
How does pectin hold plant cells together
pectin has lots of negatively charged carboxyl groups and these combine with positive calcium ions to form calcium pectate. the calcium pectate binds to the cellulose on either side
What is the primary cell wall
the first very flexible cell plant cell walls to form, with all the cellulose microfibrils orientated in a similar direction
What is the secondary cell wall
the older plant cell wall in which the cellulose microfibrils have built up at different angles to each other, making the cell wall more rigid. Hemicellulose help to harden it further
What are the two isomers of glucose
a-glucose
b-glucose
what is the difference between a-glucose and b-glucose
a-glucose has hydrogen on top for both sides while hydroxide is on the bottom for both sides
b-glucose has hydrogen on top for one one side and hydroxide on top for the other side. a hydrogen is also on the bottom on one side and a hydroxide is on the bottom on the other side.
Difference between starch and cellulose
starch is made up of alpha glucose while cellulose is made up of beta glucose held together by 1,4-glycosidic bonds
What happens as a result of cellulose being made from beta glucose
one of the monomer units has to be inverted so the bonding can take place. This means that the hydroxyl groups stick out on both sides of the molecule
because of this, hydrogen bonds can be made between the partiallt positively charged hydrogen atoms of the hydroxyl grouos and the partially negatively charged oxygen atoms in other areas of the glucose molecule. this is called cross linking and it holds the neighboring chains firmly together
what is the function of hemicellulose and other short chain carbohydrates in the cell wall
the matrix of hemicellulose and other short chain chain carbohydrates hold together the cellulose microfibers that are deposited in layers. they act like glue, binding to each other and to the cellulose molecules. mannose, xylose, and arabinose are examples of the sugars involved.
What is the plasmodesmata
cytoplasmatic bridges between plant cells that allow communication between the cells
How does the plasmodesmata form
it is produced as cells divide- the two cells do not divide completely and threads of cytoplasm remain between them. The threads pass through gaps in the newly formed cell wall and signaling substances can pass from one cell to another through the cytoplasm
When secondary thickening takes place hemicellulose and lignin are deposited in the cell wall making it thicker. In the areas around the plasmodesmata, this process doesn’t happen, leaving thin areas of the cell wall called pits
What is the symplast
the interconnected cytoplasm of the cells
What is the membrane that surrounds the permanent vacuoles
the tonoplast
what is the function of the tonoplast
controls the movement of cells into and out of the vacuole, and so it controls the water potential of the cell.
what is the vacuole filled with
cell sap, which is a solution of various substances in water.
what is the function of the cell sap
it causes water to move into and out of the cell by osmosis, and this keeps the cytoplasm pressed against the cell wall. This keeps the plant cell turgid and the whole plant stays upright
What are chloroplasts
organelles adapted row carry out photosynthesis. containing the green pigment chlorophyll
Which plants contain the genetic information to make chloroplasts
almost all plant cells
List 5 similarities between mitochondria and chloroplasts
Large organelles with a biconcave shape
contain their own DNA
are surrounded by an outer membrane
have an enormously folded inner membrane that gives a greatly increased surface area where enzyme controlled reactions takes place
are thought to have been free living prokaryotic organisms that were engulfed by and became part of other cells
Differences between chloroplasts and mitochondria
Chloroplasts are the site of photosynthesis
Chloroplasts contain chlorophyll
What are amyloplasts
organelles that store starch
