Download Chapter 2 Plant Cells and how they work

Chapter 2 Plant Cells and how they work
Robert Hook first termed the word cell in 1665 and later went on to describe
cell structure.
Cells were defined as the basic unit of life in the 1800s.
Developments in microscopy have provided much more detailed information
since then.
Cell Structure *fig 2.3
Walls
Cell Wall: Structure that contains all other parts of the plant cell :protoplast
Made of cellulose (starch)
Primary cell wall: Laid down first and made mostly of cellulose
Secondary cell wall: laid down internally to the primary wall
Present only in support tissues
Made mostly of lignin that provides support….gives wood its strength
Pits: openings in the cell walls
Plasmodesmata: channels that pass through pits and connect adjacent cells
thereby allowing for intercellular transport
Middle Lamella: sticky substance found between adjacent cells made of
Pectin which is used in making jelly
Protoplast
All of the plant cell enclosed by the cell wall
-nucleus
-cytoplasm: organelles, cytosol (fluid component), microtubules and
microfilaments: cytoskeleton which lends support and cell shape
plasma membrane *fig 2.6: located internal to the cell wall and is made of
a phospholipid bilayer with protein channels, intermembrane proteins,
glycoproteins etc
-semipermeable structure providing regulation of transport in and out of the
cell
Organelles: membrane bound structures in the cell with specialized
functions
Chloroplasts: Photosynthesis: CO2 + H2OCH2O (sugar) + O2
-pigment containing disc shaped organelles found in many
copies/phosynthetic cell
-chlorophyll is the main pigment that gives plants their green color
-have their own DNA which is inherited maternally
internal structure:
Grana: are interconnected stacks where chlorophyll is concentrated
Stroma: protein rich fluid outside the grana and inside the membrane
Leucoplasts: starch storage structures
Chromoplasts: contain various pigments and are abundant in colored plant
parts such as flowers and fruits
Mitochondrion: Respiration CH2O (sugar) + O2: CO2 + H2O + ATP
-break down of sugar to produce the universal energy carrying molecule
ATP
-membrane bound
-many copies/cell
-have their own maternally inherited DNA
internal structure:
-inner and outer membrane
-cristae: inner membrane containing proteins of the electron transport chain
-matrix: contained within the inner membrane = site of ATP formation
Central Vacuole: large membrane enclosed structure containing sap: water
based solution of sugar, salt , amino acids, proteins, and crystals.
-composes up to 90% of some plant cells
-serves as storage of waste as well as source of reserves
-anthocyanins which are water soluble pigments are stored in the vacuole
Internal Membrane System: Synthesis packaging and transport of
substances
Endoplasmic reticulum: network of membranes connecting to the nucleus
which transports messages from the nucleus to the ribosomes attached to the
rough ER
Ribosomes: site of protein synthesis
-made of RNA and protein
Smooth ER: transport and packaging of proteins
Golgi Apparatus: storage, modification and packaging of proteins
Nucleus: Contains the chromosomes the cell's instructions and the material
of inheritance
Cell Division
Mitosis: nuclear reproduction associated with asexual somatic cell growth
-produces 2 daughter cells that are genetically identical to the original
mother cell
Cell Cycle
Interphase: Cell growth and preparation to divide
-during interphase the chromosomes replicate(duplicate)
*fig 2.9
Prophase: Chromosomes condense and sister chromatids and centromeres
can be seen, the nucleus disintegrates
Metaphase: Dyads (replicated chromosomes) align on the equatorial plane
of the cell, spindle fibers grow from the centrioles and attach to the
centromeres of each chromosome or dyad
Anaphase: spindle fibers pull in opposite directions thereby separating the
sister chromatids and creating a whole new set of chromosomes
Telophase: the nuclear membrane begins to reform creating 2 distinct and
identical nuclei
Cytokinesis: Cell division
Osmosis and Diffusion
All things in nature seek an equal concentration
Diffusion: The movement of molecules across a semipermeable membrane
from a region of higher concentration to a region of lower concentration
-this process is spontaneous and releases energy in the process
-the reason it release energy is that it requires energy to create a gradient
(concentration difference between 2 adjacent areas) to begin with. Some of
this energy is release as the gradient diffuses
Osmosis: The diffusion of water in response to a gradient when the solutes
cannot diffuse
-if the membrane is not permeable to the solutes involved in the gradient,
water will diffuse to equalize concentrations.
Hypertonic: solution with a greater solute concentration than within a cell
or reference solution
Hypotonic: solution with a lower solute concentration than within a cell or
reference solution
Diffusion and Osmosis are passive transport processes and therefore
release energy. Active transport which requires the pumping of
molecules against a gradient requires energy. This is normally
accomplished with the assistant of protein pumps and uses an energy
source such as ATP