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Transcript
Cell Structure and Function Chapter 2 What do cells do? Plant cells and Animal cells A single cell is the smallest structure that carries out the activities necessary for life. A cell is like a tiny factory. Different parts of the factory produce or control different things. One part gets food or water. Another part keeps the cell clean. Still other parts are in charge of reproducing. All parts of the cell must work together to run smoothly. An organism cannot survive without cells doing their work. Animal and plant cells may look different but they share many similar features. They have at least 3 features in common: cell membranes, a nucleus and cytoplasm. Look at txt. Pg. A47 The cell membrane is the outer covering of the cell. Water and food enter through the cell membrane, and wastes leave through it. Plant cells have an additional structure called the cell wall which gives them extra support. Each animal cell and plant cell contains a nucleus. The nucleus is the control center for the cell. It carries information for reproduction and directs all cell activities. The cytoplasm is a gel-like material that surrounds all parts of the cell within the membrane, including the nucleus and the organelles. Organelles are small structures, each of which has a specific job. Cell structure Function Mitochondria Vacuoles Nucleus Provide energy Store materials Cell control center; reproduction Cell membrane Structure and transport Golgi Bodies & transport Endoplasmic Reticulum The nucleus is the cells control center and acts during reproduction. The cell membrane gives the cell structure and transports materials into and out of the cell. The Golgi Bodies and Endplasmic Reticulum transport materials with the cell. Cell transportation A cell membrane is a special kind of barrier. It holds important cell materials inside it, but allows water, gases, and wastes to pass through. In passive transport, materials move into or out of the cell without the cell using any energy. The simplest kind of passive transport is diffusion. Substances diffuse from regions of high concentration to regions of low concentration. Sometimes a cell needs to move materials opposite the way diffusion would move them. In active transport, substances move from regions of low to high concentration. This requires the cell to use its own energy. Sometimes large proteins in the cell membrane help move materials in and out. The proteins act as tunnels to allow only certain materials to pass. Using Energy All living things need energy to survive. Plants use a process called photosynthesis to make food by harnessing the energy from sunlight. This process takes place in chloroplasts, and depends on the green pigment chlorophyll. During photosynthesis, water from the ground is combined with carbon dioxide from the air. Oxygen is produced and released into the air. A molecule of glucose is also produced. Glucose is one of the high energy compounds called sugars. All plants and animals depend on the sugars made by the plants for their food. They get energy from the sugars by the process of cellular respiration. All plants and animals depend on the sugars made by the plants for their food. They get energy from the sugars by the process of cellular respiration. Mitochondria perform cell respiration, the reverse process of photosynthesis. This process combines oxygen from the air with glucose from food to form water and carbon dioxide. A lot of energy is released in the process Mitochondria store this energy in a molecule called ATP. This molecule acts like a battery. The cell tap into ATP whenever it needs to use energy. Cell Division New organisms usually begin when cells from two parents combine to form a new cell. Soon the single cell divides to form two cells. The two divide to form four, and the four divide into eight cells. Millions of divisions occur as the cells become a complete organism. As cells divide, they differentiate, which means they become different from one another. Early on the cells organize themselves into three groups, called germ layers. One layer will form the skin and nerves. Another layer becomes the lining of the digestive tract. The third layer becomes all the other body parts Bacteria and other single-celled organisms can also copy themselves. This copying results in new individuals. When conditions favor division, a bacterial colony can double very quickly. Lesson 2 Specialized Cells Different cells for different Job All multicellular organisms have specialized cells that work together. Both plants and animals have tissues that perform specific jobs. Most complex organisms have a variety of tissues. Epithelial tissues are sheets of cells that cover surfaces. They also line certain body cavities and blood vessels. Connective tissue, as the name implies, joins other tissues together. It also stores fat and make of specialized cells and fibers that stick to living cells. Bone is a type of connective tissue too. All muscle tissue creates movement in one direction only, either by getting longer or shorter. Electrical impulses that constantly run through your body are produced and routed by nervous tissue. Organs are made up of several tissue types that work together to perform one or more functions. The brain, heart, and liver are three human organs. Some organs, like kidneys, perform more than one function. Kidneys remove waste from the body and also help control blood pressure. Organ Systems The more complex the organism, the greater the number of organ systems that are needed to carry out life processes. Humans have 11 organ systems. The systems also influence one another. Some organs work for more than organ system. Urinary System This system helps regulate the amount of water and salt in the blood, as well as removing liquid wastes. Musculoskeletal system Supports all parts of your body and allows you to move different parts of your body. Bones anchor other body parts and provide the structure needed for movement Contracting your muscles makes your body parts move. The muscles also generate warmth for your body. Nervous System Your brain is an indispensable organ, the headquarters of the nervous system. All your senses feed information into the brain. The brain processes and responds to this information, often responding by sending signals down nerves to muscles. The brain also controls the other organ systems. Look at txt. Pg. A57 Four of the remaining organ systems help your body fight infection, and allow you to eat, breathe, and reproduce. Another system produces hormones that regulate many body functions. Endocrine System Your body’s endocrine system works like a chemical messenger system. The glands of the endocrine system act as a communication centers. Endocrine glands are a specialized group of cells that make and send out hormones. Hormones act as messages. They travel through the blood stream and are picked up only by certain cells. Humans use about 50 different hormones. Some help regulate growth and energy use. Others control blood sugar, minerals, and other chemicals. Some hormones cause specific changes in the body. Many plants use hormones, too. These may cause a stem to bend toward the light, or could direct a plant to grow taller instead of wider. Gland Function Pituitary Gland This gland in the brain makes at least 8 different hormones. Many control other glands. Thyroid gland This helps regulate the body’s use of energy. Thymus This gland helps the body’s immune system. Adrenal Glands These manufacture hormones that regulate glucose & respond to stress. They also influence reproductive hormones. Pancreas This produces insulin and other hormones that affect the level of blood sugar. Lack of insulin leads to a disease called diabetes. Lesson 3 How does disease affect cells? Cells and Diseases Causes of Diseases Many things can cause illness or disease. Some diseases result when the body is invaded by alien organisms or viruses. Other diseases result when body systems do not function properly. Infectious Diseases Infectious diseases are caused by harmful organisms or viruses. Bacteria & some types of fungi are common types of infections. Certain types of worms can lodge in the intestines or muscles, causing several serious diseases. Protozoa carried by mosquitoes cause malaria. Contagious diseases can be spread easily from one person to another. Other diseases, like those from food poisoning, are not contagious. Viruses are not living organisms because they are not made of cells. Viruses are common causes of infectious disease. Viruses contain generic instructions that take over a cell’s normal instructions. Typically, the virus instructs the cell to male more viruses. Many viral diseases are mild, like colds, the flu, & chicken pox. Other viruses are more dangerous or even deadly. Viral diseases such as hepatitis or AIDS have killed many people. Non-infectious Diseases Non-infectious diseases occur when a body system does not function properly. These types of diseases cannot spread from person to person. Sometimes the diseases are caused by a condition that is inherited. Other times the diseases appears as a person’s body ages. Healthy lifestyles and habits can help prevent many of these later-in-life diseases. Poor nutrition causes many non-infectious diseases. People who do not receive the proper vitamins in their food can suffer a variety of illnesses and impaired organ functions. Fighting Disease Your body has 3 main lines of defense against invasion by disease agents. The first line of defense is made up of your body’s physical and chemical barriers. These include your skin, tears, salvia, earwax, and mucus. Your body’s second line of defense consists of processes that kick in should harmful agents enter. One of these defenses is inflammation. The blood releases fluid and other products that enlarge the area and make it red and sore. The second line of defense can include the production of special cells called phagocytes. These cells surround and consume harmful disease agents that invade your body. Phagocytes are one type of white blood cells. The body has a very powerful defense weapon to fight specific harmful agents of disease. It’s called the immune system. And is your body’s 3rd line of defense. Immune System The immune system uses special cells that travel throughout the body & recognize invading pathogens. These cells can recognize harmful invaders because they have surface structures different from those of normal body cells. Certain types of white blood cells produce special proteins called antibodies that also fight invaders. After the body destroys invaders, the body begins to recover from illness. As an added benefit, some of the immune system’s special white blood cells remain in the body. If the same pathogens invade the body again, these cells can immediately produce the needed antibodies. This means that the body is now immune to, or protected from that particular illness. Disease Prevention or Treatment Many diseases that were once deadly are now under control. Fro example, smallpox killed hundreds of millions throughout history. Yet in 1980, the World Health Organization declared smallpox to be eradicated, meaning it was wiped out. A vaccine usually contains an inactive version of a pathogen. When the body is exposed to the vaccine, it slowly makes antibodies against it. Later, should the real pathogen enter the body, the antibodies are ready right away to stop it. Penicillin is an antibiotic that works by weakening the cell walls of bacteria, allowing water from outside to rush inside.