Plant Cell Lecture 2 PDF

Lecture 2 a Introduction to Plant Biology and Anatomy Prepared and presented by : Dr. Abdelaziz Mohamed Nasr Lesson Objectives Understand the basic plant cell and the function of its organelles. Understand the concept of plant classification. Plan...

Lecture 2 a Introduction to Plant Biology and Anatomy Prepared and presented by : Dr. Abdelaziz Mohamed Nasr Lesson Objectives Understand the basic plant cell and the function of its organelles. Understand the concept of plant classification. Plant kingdom Naked seeds Bryophyt es Algae Life Cycle of Mosses Life Cycle of angiosperm Plant cell Cell wall It provides the most significant difference between plant cells and other eukaryotic cells. The cell wall is rigid (up to many micrometers in thickness) gives plant cells a very defined shape. Cell wall Cellulose fibrils deposited in alternating layers for strength contains pits (openings) and provides protection from physical injury Cellulose is made up from glucose chains. This first cell wall of these growing cells is called the primary cell wall. When the cell is fully grown, it may, it may deposit new layers as secondary cell wall. Cell wall Secondary cell wall Primary cell wall Middle lamella Cell wall Primary cell wall which is generally a thin, flexible and extensible layer composed of cellulose, pectin and hemicellulose. Secondary cell wall which is a thick layer rich in lignin that strengthens and waterproofs the wall. In between the primary walls is a middle lamella which is a pectin-rich intercellular material that glues the adjacent cells together. The cell wall is very essential in plants as it helps resist osmotic pressure. Functions of cell wall Structural and mechanical support Maintain and determine cell shape. Resist internal turgor pressure of cell. Control rate and direction of growth. Regulate diffusion of materials. Carbohydrate storage Protect against pathogens, dehydration, and other environmental factors Source of biologically active signaling molecules and cell-cell interactions. Nucleus Surrounded by nuclear envelope, which is made up of inner and outer membrane. Contains pores (fusion between outer and inner membrane) Allow the macromolecules movement. Maintains the shape of the nucleus. Nucleus Nucleus It contains the genetic material (DNA) along with associated proteins (histones), which are called chromatin. The chromatin fibers coils up at the time of cell division to produce chromosomes. Nucleolus It is a dark part of the nucleus. It is involved in ribosome production. Ribosomes Made up of rRNA (ribosomal RNA), and proteins. They could either be free in the cytoplasm or bound to the ER. They are the main producers of protein in the cell. Endoplasmic reticulum a system of narrow tubes and sheets of membrane that form a network throughout the cytoplasm. If ribosomes are attached, they are called Rough ER, which are involved in producing proteins which are mainly secreted outside of the cell. If no ribosomes are attached, it is called Smooth ER, which are involved in lipid production. Dictyosomes a stack of thin vesicles held together in a flat or curved array. The receive the vesicles on their forming face, and release them from their maturing face. They help in modify proteins from the endoplasmic reticulum, and may also polymerize sugars to polysaccharides. They then package these materials for delivery to destinations within the cell (e.g. the cell wall), for secretion, or for storage. Dictyosomes Peroxisomes Membrane-bound sacs. Peroxisomes are involved in detoxifying certain byproducts of photosynthesis and are found closely associated with chloroplasts. Mitochondria Mitochondria (singular, mitochondrion) are the organelles that carry out this cell respiration. Help the cell breakdown highly energetic compounds such as sugars and starches and produce ATP which can be better used by the cell. Mitochondria Plastids Plastids are a group of dynamic organelles able to perform many functions. One prominent activity is photosynthesis, carried out by the green plastids, chloroplasts. There is also chromoplasts (colored), and leucoplasts (translucent). Plastids Central Vacuole It contains primarily water and salts, the central vacuole can expand rapidly, forcing the cell to grow rapidly as well. They can also exert turgor pressure on cell wall. In addition to cell growth, the central vacuole functions in storage of both nutrient reserves and waste products. In seed cells, vacuoles may be filled with protein that will be used when the seed germinates. They can also store calcium, potassium, and water-soluble pigments and help What is the take-home message from today’s lecture. Let’s discuss. Pre-reading for next class Plant growth, division and differentiation. Plant biology Any more questions?