Plant Cells

1. Plant Cells By Jessica McAllister

2. Images

3. structure • Plant cells are eukaryotic cells that differ in several key respects from the cells of other eukaryotic organisms. Their distinctive features include: • A large central vacuole, a water-filled volume enclosed by a membrane known as the tonoplast maintains the cell's turgor, controls movement of molecules between the cytosol and sap, stores useful material and digests waste proteins and organelles. • A cell wall composed of cellulose and hemicelluloses, pectin and in many cases lignin, and secreted by the protoplast on the outside of the cell membrane. This contrasts with the cell walls of fungi (which are made of chitin), and of bacteria, which are made of peptidoglycan. • Specialized cell-cell communication pathways known as plasmodesmata, pores in the primary cell wall through which the plasma lemma and endoplasmic reticulumof adjacent cells are continuous.

4. structure • Plastids, notably the chloroplasts which contain chlorophyll and the biochemical systems for light harvesting and photosynthesis, but also amyloplasts specialized for starch storage, elaioplasts specialized for fat storage and chloroplasts specialized for synthesis and storage of pigments. As in mitochondria, which have a genome encoding 37 genesplastids have their own genomes of about 100-120 unique genesand probably arose as prokaryotic endosymbionts living in the cells of an early eukaryotic ancestor of the land plants and algae. • Unlike animal cells, plant cells are stationary • Cell division by construction of a phragmoplast as a template for building a cell plate late in cytokinesis is characteristic of land plants and a few groups of algae, notably the Charophytes and the Order Trentepohliales. • The sperm of bryophytes have flagellae similar to those in animals, but higher plants, (including Gymnosperms and flowering plants) lack the flagellae and centrioles that are present in animal cells.

5. Function • Nucleus-The nucleus is a highly specialized organelle that serves as the information processing and administrative center of the cell. This organelle has two major functions: it stores the cell's hereditary material, or DNA, and it coordinates the cell's activities, which include growth, intermediary metabolism, protein synthesis, and reproduction (cell division). • centrosome - (also called the "microtubule organizing center") a small body located near the nucleus - it has a dense center and radiating tubules. The centrosomes is where microtubules are made. During cell division (mitosis), the centrosome divides and the two parts move to opposite sides of the dividing cell. Unlike the centrosomes in animal cells, plant cell centrosomes do not have centrioles. This is an important function of the cell like others. • Golgi body - (also called the golgi apparatus or golgi complex) a flattened, layered, sac-like organelle that looks like a stack of pancakes and is located near the nucleus. The golgi body packages proteins and carbohydrates into membrane-bound vesicles for "export" from the cell. • mitochondrion - spherical to rod-shaped organelles with a double membrane. The inner membrane is infolded many times, forming a series of projections (called cristae). The mitochondrion converts the energy stored in glucose into ATP (adenosine triphosphate) for the cell.

6. Function • rough-endoplasmic reticulum - (rough ER) a vast system of interconnected, membranous, infolded and convoluted sacks that are located in the cell's cytoplasm (the ER is continuous with the outer nuclear membrane). Rough ER is covered with ribosomes that give it a rough appearance. Rough ER transport materials through the cell and produces proteins in sacks called cisternae (which are sent to the Golgi body, or inserted into the cell membrane). • smooth endoplasmic reticulum - (smooth ER) a vast system of interconnected, membranous, infolded and convoluted tubes that are located in the cell's cytoplasm (the ER is continuous with the outer nuclear membrane). The space within the ER is called the ER lumen. Smooth ER transport materials through the cell. It contains enzymes and produces and digests lipids (fats) and membrane proteins; smooth ER buds off from rough ER, moving the newly-made proteins and lipids to the Golgi body and membranes

7. Diffusion • Diffusion is the movement of molecules from an area of higher concentration to that of a lower concentration. Once there are the same number of molecules on both sides, there is no longer any net movement because a gradient no longer exists. Osmosis is a special case of diffusion. Osmosis is the movement of water through a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration. Adding particles to one side of a membrane can establish a concentration gradient for water. The increase in particles on one side results in a decrease in water for that area.

8. Osmosis • Plant cells are surrounded by rigid cellulose walls, (unlike animal cells), but plant cells still take in water by osmosis when placed in pure water. • cell walls limit how much water can move in. The cell walls exert pressure, called turgor pressure, as the cells take up water. Turgor pressure is analogous to the air preasure of an inflated tire. • If particles are added to the plant then the osmotic pressure would decrease which causes the supportive structure of the plant diminish and the plant becomes limp and shriveled.

9. Cellular Respiration • one of the key ways a cell gains useful energy. It is the set of the metabolic reactions and processes that take place in organisms' cells to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions that involve the oxidation of one molecule and the reduction of another. • Nutrients commonly used by animal and plant cells in respiration include glucose, amino acids and fatty acids, and a common oxidizing agent (electron acceptor) is molecular oxygen (O2). Bacteria and archaea can also be lithotrophs and these organisms may respire using a broad range of inorganic molecules as electron donors and acceptors, such as sulfur, metal ions, methane or hydrogen

10. Photosynthesis • (Photosynthesis is the process where green plants use sunlight, carbon dioxide, and water to make food and oxygen.) • A process that takes place inside of the chloroplasts in plant cells is called photosynthesis. This process helps green plants make their own food. • Chlorophyll takes in energy from sunlight. The energy comes in the form of a tiny bundle known as a photon. The photon hits a molecule of water inside the chlorophyll. The photon's energy splits the water molecule into hydrogen and oxygen. The hydrogen combines with carbon dioxide (which the plant has absorbed from the air) to make sugars or glucose. The oxygen is released back into the atmosphere to give us more air.