Cells & Tissues

• plant is a living, multicellular organism containing chlorophyll adapted to life on land with a nutritionally dependent multiceullar embryo (embryo phytes)
• plants are rooted in place, have modular growth (grows in units), they continue to grow throughout life, reproduce sexually or vegetatively (from the plant body), and have rigid cellulose rich cell walls
• tissue systems of plants include dermal (cover outside), vascular (conduct water nutrients), and ground (around vascular)
• cells were first observed in plant tissue (cork cells) in 1665 by Robert Hooke
• in 1838, Matthias Schleiden, a german botanist, discovered that plant tissues are comprised of organized masses of cells. He first introduced the cell theory in plants.
• In 1839, Theodor Schwann, extended the Cell theory to animal cells.
• In all cells, the middle lamella is the first cementing layer as the plant develops and is pectin rich
• The primary cell wall is composed of 25% of cellulose and it can be formed as the cell grows
• The secondary cell wall is composed of 50% cellulose and lignin, and it is only found in some cells and formed after growth stops.
• Secondary cell walls have three layers to the inside of the primary cell wall and it is strengthened by lignin
• plasmodesmata is a membrane lined "pore" that allows cell to cell communication through primary cell walls
• simple pits and bordered pits are found in the secondary cell wall
• simple pits have a gap between 2 different cell walls associated with the plasmodesmata
• bordered pits have a narrower gap between cells due to elongated boundaries. it prevents air bubbles from forming in cells.
• phragmoplast are microtubules within which the new cell wall is formed
• protoplast is the living contents of the cell, except the cell wall
• symplast is the interconnected protoplast and their plasmodesmata
• apoplast is the cell wall continuum and everything outside of protoplast (dead parts of the tissue)
• cytoplasm is everything inside living parts of the cell, except the nucleus
• plasma membrane or plasmalemma is a single membrane surrounding cell contents and it regulates transport in and out of the cell
• cytosol is the matrix suspending organelles
• plastids are a group of membrane bound organelles commonly found in photosynthetic organisms and mainly responsible for the synthesis and storage of food. they are surrounded by two membranes
• proplastids are undifferentiated plastids that are small, often colourless, membrane sacs that can divide and mature into functional plastids. they are self reproducing
• chloroplasts are a type of plastid and are the site of photosynthesis
• chromoplasts are plastids that contain pigment and that may or may not take part in photosynthesis
• leucoplasts are non pigmented plastids containing proteins (proteoplasts), starch (amyloplasts), oils (elaioplasts)
• Mitochondria is the cite of cellular respiration and source of ATP
• vacuole is important in cell expansion, turgor, storage and recycling. it helps maintain water balance
• turgor is the pressure exerted by fluid in a cell that presses the cell membrane against cell wall. it makes living plant tissue rigid which helps stop wilting
• vacuole is surrounded by tonoplast (vacuolar membrane)
• micro bodies contain oxidation reactions, peroxisomes (important for sequestering oxidative reactions), glyoxysomes (seeds where fats get broken down to sugars).
• Major components of endomembrane system: endoplasmic reticulum, Golgi body, vesicles, cytoskeleton, and cytoplasm
• Endoplasmic reticulum is a system of membranes that is found in a cell's cytoplasm and assists in the production, processing, and transport of proteins and production of lipids
• Rough ER is associated with ribosomes and is involved in protein synthesis
• Smooth ER has no ribosomes and is involved in lipid synthesis
• Golgi apparatus consists of a number of separate units called dictyosomes and is where glycoproteins and polysaccharides are assembled and secreted
• Vesicles are small membrane sacs that specialize in moving materials between rough ER, Golgi, and plasma membrane or vacuole
• Cytoskeleton is a network of protein filaments in the cytosol that help maintain the shape of the cell and keep it organized. It is made up of microtubules and microfilaments
• Microtubules are composed of tubulin
• Microfilaments are composed of globular actin