Plant cell structure

plant cell structure

label this image

plasma membrane is found

inside cell wall

vacuoles have a

large volume

middle lamella

glue holds adjacent plant cells together

plasmodesmata

pores between adjacent plant cells

ribosomes

sites for protein synthesis

Plant cells, like all cells, are surrounded by a

membrane

Plants are

eukaryotes

because plants are eukaryotes they have

membrane-enclosed organelles

biological membranes are composed of a

phospholipid fluid bilayer with proteins

phsopholipids are

amphibathic

membrane has many instrinsic _

membrane-spanning proteins

two types of transport proteins

carrier, channel

carrier proteins what it is and when its used

substrate-specific binding sites + secondary active transport

secondary active transport

facilitated diffusion, active transport, or co-transport

channel proteins what it is and when its used

allow specific molecules to pass + facillitated diffusion

3 names for the membrane

plasma membrane (PM)

cell membrane

plasmalemma

Phospholipid bilayers have a hydrophobic _ and hydrophilic _

core, surfaces

semi-permeable or selectively permeabl

some molecules can diffuse across a membrane, while other molecules cannot

osmosis

water molecules can freely diffuse a membrane, while solutes cannot

differentially

permeable

almost any molecule can diffuse across a membrane, given enough

time but different molecules will diffuse at different rates

what would diffuse more slowly

Charged molecules, polar molecules

diffusion of water across a membrane

despite being a polar molecule, can slowly diffuse across an artificial

phospholipid bilayer, partially due to the fact that it is a very small molecule.

aquaporins

membrane-spanning proteins that act as moderately selective water channels.

DNA of plant cells is found largely in the _ but also in the _ and _

nucleus, plastids, mitochondria

Plant cells, like all cells, also have _ and a _ both with no membrane and composed of microtubules and acitin filaments.

ribosomes, cytoskeleton

Organelle movement is via the

actin (micro)filaments.

Microtubules are essential for

cell division.

Unlike animal cells, plant cells seem to not have

intermediate filaments

Chloroplasts 3

site of photosynthesis. surrounded by a double membrane (= the chloroplast envelope).  have DNA and ribosomes.

2 things that are descended from chloroplasts

chromoplasts and amyloplasts

amyloplasts

starch storage below ground

chromoplasts

pigmented but not photosynthetic

Photosynthetic tissues tend to have

dozens of chloroplasts per cell

Chromoplasts

tend to have a very high

carotenoid content

example of where we find chromoplsts

fruits

 plant cells have a cell wall that is located

to the outside of the plasma

membrane

all plant cells have a _ and some also have a _

primary cell wall (living) and a secondary cell wall (usually dead at maturity).

In those cells that have a secondary cell wall, this wall is located

to the inside of the

primary cell wall

3 examples of cells with secondary cell walls

tracheids, vessel elements and xylem fibres

Mature plant cells tend to have a large central vacuole, that can be as large as

70% of

cell volume

Developing plant cells may have several

small vacuoles

The membrane that surrounds the vacuole is called the

tonoplast

The interior of the vacuole is typically slightly

acidic

The vacuole is an area of fairly low _ compared to other parts of the cell

metabolic activity

The vacuole plays a central role in: 3

1) water relations

2) as a storage area for ions (inorganic or organic)

3) location of anthocyanins

In many plant species, the type of anthocyanin determines

flower colour

ATP Synthase found in two places and which membrane

 chloroplasts (thylakoid

membrane) and mitochondria (inner

membrane).

Plasmodesmata

 cytosolic connections to adjacent plant cells. Channels run through the cell walls and are lined with plasma membrane.

Diffusion of molecules through the plasmodesmata is regulated by the

desmosomes

desmosomes/desmotubules

endoplasmic reticulum-based organelles that run through

the channels

mitochondria is often close to the

chloroplasts

mitochondria are the site of

aerobic cellular respiration

aerobic cellular respiration, which functions to

regenerate ATP

mitochondria have two things

DNA and ribosomes

Golgi apparatus 

 protein modification and protein sorting

endoplasmic reticulum

membrane network that runs through the cytosol.

Rough ER 

has ribosomes and is involved in protein synthesis

Smooth ER

 no ribosomes, and has

varied roles in cellular metabolism.

Microbodies

small organelles that have various sub-types Peroxisomes and Glyxysomes

Peroxisomes

 involved in photorespiration

Glyoxysomes

involved in fat breakdown

where is fat breakdown typically important

seeds

Protein bodies

protein storage organelles

where are protein bodies commonly found

In the fall trees shed leaves. Nitorgen is pulled out and stored as protein bodies to be used again in the spring. Cells of the inner bark of woody plants in winter.

Oleosomes

 lipid-storing organelles;

Oleosomes are also known as 2 things

spherosomes or oil

bodies

Oleosomes are mostly found in

oilseeds

Oleosomes have

half a membrane

cytosol

water-based gel-like fluid in which the organelles are found,

and is an active site of metabolism

cytoplasm includes 3

cytosol, cytosolic ribosomes, cytoskeleton

cytoplasm does not include

interiors of organelles

-protoplasm

everything to the inside of the plasma membrane

2 examples of what is considered protoplasm

nucleus, chloroplast

protoplasm does not include

cell wall

possible to experimentally isolate suspensions of plant cells by using cell

wall degrading enzymes → these cells are known as

protoplasts

all plant cells have a

primary cell wall,

where is the primary cell wall located

 outside of the plasma

membrane

The cell wall is fairly

rigid

rigitity plays a critical role in allowing plant cell cells to be

pressurized

The rigid cell wall prevents the pressurized cell from

rupturing

animal cells cannot be pressurized without

rupturing

The major components of the primary plant cell wall are 4

ajor components of the primary plant cell wall are:

o cellulose microfibrils - carbohydrate

o hemicelluloses (cross-linking glucans/glycans) carbohydrates

o pectin - carbohydrate

o a small amount of various proteins

Cellulose

 chains, organized as microfibrils,

are largely responsible for the strength and

rigidity of the cell wall.

Cellulose is a

linear glucose polymer

Parallel cellulose chains are held together

by

H bonds

These parallel chains are arranged as _ which are packaged

together as _

elementary fibrils, microfibrils

Microfibrils are composed of parallel chains of elementary fibrils, which in turn are

composed of

cellulose chains.

Especially in woody plants, microfibrils may also further bundled into 

larger groupings, macrofibrils

Cellulose microfibrils have different orientations in different cell types (2)

• Sometimes there is a criss-cross pattern.

• Sometimes the microfibrils are largely parallel to each other.

Hemicelluloses (cross-linking glycans) 

carbohydrates, but are smaller and shorter

than cellulose microfibrils, and function to cross-link adjacent microfibrils.

The cross-linking affects

cell wall rigidity

Cross-linking by hemicelluloses anchors

adjacent microfibrils relative to each other.

More cross-linking = greater rigidity = 

less extensibility

Pectin

carbohydrate, composed mainly of polygalacturonic acid

Pectin, with water, produces a jelly-like matrix in which the other

cell wall components

are embedded.

Pectin is also the major component of the

middle lamella

middle lamella

glue between

adjacent plant cells.

Pectin used in the manufacture of jellies (e.g. apple or grape jelly), and can be

purchased

in grocery stores.

The secondary cell wall is laid down to the

 inside of the primary cell wall, and after the primary wall