Cell Structure Chp4-part1 PDF

Chapter 4 A Tour of the Cell © 2016 Pearson Education, Inc. 10 to 100 μm 0.1 to 5 μm The Microscopic World of Cells Cell theory states that all living things are composed of cells and that all cells come from earlier cells every cell in our body (and...

Chapter 4 A Tour of the Cell © 2016 Pearson Education, Inc. 10 to 100 μm 0.1 to 5 μm The Microscopic World of Cells Cell theory states that all living things are composed of cells and that all cells come from earlier cells every cell in our body (and in every other living organism on Earth) was formed by division of a previously living cell © 2016 Pearson Education, Inc. What kind of organism do you think this is? And this one?? Valonia ventricosa, also known as bubble algae, sea grape, or sailor's eyeballs – one of the largest known UNICELLULAR organisms!! Caulerpa taxifolia, an algal species – green seaweed, often bred for use in aquariums – also consists of just a single cell with many nuclei!! In fact, it is the LARGEST KNOWN single-celled organism! PHOTOGRAPH BY UNIVERSAL HISTORY ARCHIVE/UNIVERSAL IMAGES GROUP VIA GETTY IMAGES - HTTPS://EDUCATION.NATIONALGEOGRAPHIC.ORG/RESOURCE/CELL-  The Two Major Categories of Cells All cells have several basic features. They are all bounded by a thin plasma membrane. Inside all cells is a thick, jelly-like fluid called the cytosol, matrix of cytoplasm surrounding organelle -in which cellular components are suspended. All cells have one or more chromosomes carrying genes made of DNA. All cells have ribosomes, tiny structures that build proteins according to the instructions from the genes. Most organelles are found in both animal and plant cells. But there are some important differences. Only plant cells have chloroplasts (where photosynthesis occurs). Only animal cells have lysosomes (bubbles of digestive enzymes surrounded by membranes). © 2016 Pearson Education, Inc. Figure 4.3 IDEALIZED ANIMAL CELL Centriole Not in most Ribosomes Lysosome plant cells Cytoskeleton Plasma membrane Nucleus Cytoplasm Mitochondrion Rough endoplasmic Smooth reticulum (ER) endoplasmic IDEALIZED PLANT CELL Golgi reticulum (ER) Cytoplasm apparatus Cytoskeleton Mitochondrion Central vacuole Not in Cell wall animal cells Nucleus Chloroplast Rough endoplasmic reticulum (ER) Ribosomes Plasma membrane Smooth endoplasmic Channels between cells reticulum (ER) Golgi apparatus BioFlix Animation: Tour of an Animal Cell © 2016 Pearson Education, Inc. BioFlix Animation: Tour of a Plant Cell © 2016 Pearson Education, Inc.  CHROMATIN ORGANIZATION NUCLEUS  The Nucleus : Genetic Control of the Cell The nucleus is the control center of the cell. Contains DNA (contain genes) that stores the Nuclear envelope information necessary to produce a particular protein. Nuclear pore Chromatin fiber separated from the cytoplasm by a double membrane called the nuclear envelope. Nucleolus Pores - allow certain materials to pass between the nucleus and the surrounding cytoplasm long DNA molecules and associated proteins form fibers called chromatin. Each long chromatin fiber constitutes one chromosome. The nucleolus is a prominent structure within the nucleus and the site where the components of ribosomes are made. © 2016 Pearson Education, Inc. Ribosomes Ribosomes are responsible for protein synthesis In eukaryotic cells, the components of ribosomes are made in the nucleus and then transported through the pores of the nuclear envelope into the cytoplasm Some ribosomes are suspended in the cytosol, making proteins that remain within the fluid of the cell. Ribosomes attached Others are attached to the outside of the nucleus & to endoplasmic the endoplasmic reticulum, making proteins that are reticulum visible as incorporated into membranes or secreted by the tiny dark blue dots cell. Both these types of ribosomes are structurally identical © 2016 Pearson Education, Inc. How DNA Directs Protein Production DNA DNA transfers its coded Synthesis of information to a molecule mRNA in the nucleus called messenger RNA (mRNA). mRNA mRNA exits the nucleus through pores in the nuclear envelope and travels to the cytoplasm, where Movement of it binds to a ribosome. mRNA into cytoplasm via Ribosome nuclear pore A ribosome moves along the mRNA, translating the genetic Synthesis of protein in the Protein message into a protein with a cytoplasm specific amino acid sequence. © 2016 Pearson Education, Inc. Actively transcribing DNA (viewed under a microscope) The Endomembrane system The Endomembrane System: Manufacturing and Distributing Cellular Products The endomembrane system-internal network of membranes in a cell consists of the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles. These membranous organelles are either physically connected or linked by vesicles, sacs made of membrane. © 2016 Pearson Education, Inc. The Endoplasmic Reticulum The endoplasmic reticulum (ER) - one of the main manufacturing facilities in a cell. connected to the nuclear envelope composed of interconnected rough and smooth ER that have different structures and functions. Cells specializing in the production of proteins - have a larger amount of rough ER (With ribosomes attached) Cells producing lipids (fats) and steroid hormones - have a greater amount of smooth ER. Some products manufactured by rough ER are chemically modified and then packaged into transport vesicles- Vesicles - sacs made of membrane that bud off from the rough ER. These transport vesicles may be dispatched to other locations in the cell. © 2016 Pearson Education, Inc. cells of the pancreas and digestive tract produce a high Figure 4.12 3 Secretory 4 Vesicles bud off proteins depart. from the ER. 2 Proteins are modified in the ER. Transport Ribosome vesicle 1 A ribosome links amino acids. Protein Rough ER Polypeptide  Smooth ER The smooth ER lacks surface ribosomes - produces lipids, including steroids (hormones in the adrenal cortex and endocrine glands) Cells of ovaries and testis –enriched with SER- produce steroid sex hormones detoxifying a number of organic chemicals converting them to safer water-soluble products. Large amounts of smooth ER are found in liver cells – Enzymes of SER functions to detoxify products of natural metabolism (drugs /antibiotics) It contains enzymes that catalyze a number of reactions ; that can make lipid-soluble drugs and metabolic wastes into water-soluble, so that these (drugs and waste) can easily be expelled out of the body. To assist with this, smooth ER can double its surface area within a few days, returning to its normal size when the assault has subsided detoxify overloads of ethanol derived from excess alcoholic drinking and also barbiturates from drug overdose. © 2016 Pearson Education, Inc.  Figure 4.11 contains enzymes that catalyze a number of reactions ; that can make lipid-soluble drugs and metabolic wastes into water- soluble, so that these (drugs and waste) can easily be expelled out of the body. Nuclear envelope Ribosomes Rough ER Smooth ER  The Golgi Apparatus Rough ER “Receiving” side of the “Receiving” side of Golgi apparatus the Golgi apparatus Golgi apparatus Transport vesicles carry enzymes and 1 other proteins from Transport the rough ER to the vesicle Golgi for processing. “Shipping” side of the Golgi apparatus 2 Lysosomes carrying 3 digestive enzymes Plasma can fuse with other Colorized SEM membrane vesicles. “Shipping” side of Glogi apparatus Secretory protein Figure 4.13 The Golgi apparatus works in partnership with the ER and The Golgi Apparatus The Golgi apparatus consists of a stack of membrane plates. Products made in the ER reach the Golgi apparatus in transport vesicles. Proteins within a vesicle are usually modified by enzymes during their transit from the receiving to the shipping side of the Golgi apparatus. The shipping side of a Golgi stack is a depot - finished products can be carried in transport vesicles to other organelles or to the plasma membrane. © 2016 Pearson Education, Inc. Lysosomes A lysosome is a membrane-enclosed sac of digestive enzymes found in animal cells. Most plant cells do not contain lysosomes, they contain lytic vacuoles Lysosomes originate from vesicles that bud off from the Golgi apparatus Enzymes in a lysosome can break down large molecules such as proteins, polysaccharides, fats, and nucleic acids Lysosomes provide a safe compartment for breakdown of these molecules, without putting the cell’s other organelles and important molecules in danger of being broken down by these enzymes! © 2016 Pearson Education, Inc.  Digestive enzymes Lysosomes Lysosome have several types of digestive functions: Digestion 1) Many single-celled protists engulf nutrients in tiny cytoplasmic sacs called food vacuoles. Food vacuole Lysosomes fuse with the food vacuoles, exposing the food to digestive enzymes. A lysosome digesting food Small molecules that result from this digestion, such as amino acids, leave the lysosome and nourish the cell. Lysosomes can also 2. destroy harmful bacteria (e.g. WBCs - immunity), 3. engulf and digest parts of another organelle (recycling) and, 4. sculpt tissues during embryonic development, helping to form structures such as fingers. © 2016 Pearson Education, Inc.  A lysosome digesting food Digestive Lysosome enzymes In lower eukaryotes like Protista (Paramecium) Digestion Food vacuole Lysosome Digestive enzymes Digestion Vesicle containing damaged organelle A lysosome breaking down the molecules of damaged organelles In higher eukaryotes Lysosomes Lysosomes are important to cell function and human health as suggested by a group of hereditary disorders called lysosomal storage diseases. A person with such a disease: is missing one or more of the digestive enzymes normally found within lysosomes, and has lysosomes that become engorged with indigestible substances, which eventually interferes with other cellular functions. Most of these diseases are fatal in early childhood For example, in Tay-Sachs disease, deficiency of a lipid-digesting enzyme results in accumulation of excess lipids in nerve cells, leading to their death. © 2016 Pearson Education, Inc. Vacuoles Vacuoles are large sacs made of membrane that buds off from the ER or Golgi apparatus. They have many types of functions in different cell types: 1) Certain freshwater protists like Paramecium, amoeba etc. have contractile vacuoles - pump out excess water that flows into the cell from the outside environment. The contractile vacuole acts to regulate the quantity of water inside the cell. In freshwater environments - the concentration of solutes inside the cell is high concentration than outside the cell (i.e., the environment is hypotonic). water flows from the environment into the cell by osmosis. The contractile vacuole acts as part of a protective mechanism that prevents the cell from absorbing too much water and possibly lysing (rupturing) through excessive internal pressure. © 2016 Pearson Education, Inc. Figure 4.15-1 A vacuole filling with water LM A vacuole contracting LM (a) Contractile vacuole in Paramecium Vacuoles 2) A central vacuole can account for more than half the volume of a mature plant cell. The central vacuole of a plant cell is a versatile compartment that may: store organic nutrients like proteins, absorb water causing cells to expand, thus contributing to plant growth, and contain pigments (e.g., in cells of flower petals) that attract pollinating insects contain poisonous chemicals that protect against plant-eating animals/bugs (e.g., nicotine, caffeine etc.) 3) A food vacuole which buds into the cell from plasma membrane as a vehicle for ingesting food particles from outside © 2016 Pearson Education, Inc.  Rough ER “Receiving” side of the Golgi apparatus Golgi apparatus Transport vesicles carry enzymes and other proteins from the rough ER to the Transport Golgi for processing. vesicle “Shipping” side of the Golgi apparatus Lysosomes carrying digestive enzymes Plasma can fuse with other membrane vesicles. Secretory protein