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Transcript
Unit 5 Notes I CAN A The Characteristics of Living Things Organisms = living things All living things: Have cellular organization Contain similar chemicals Use energy Respond to their surroundings Grow and develop Reproduce Cellular Organization Cell = the basic unit of structure and function in an organism A microscope is needed to see most cells Unicellular Organism = single-celled organism Ex: a bacterium or bacteria Multicellular Organism = many-celled organism In Multicellular organisms: Each cell is specialized to do a certain task Ex: muscle and nerve cells are found in humans The Chemicals of Life All cells are made of chemicals Carbohydrates provide cells with energy Proteins and lipids are the building materials of cells Nucleic acids carry genetic material which controls the cell’s activities The most abundant chemical found in living cells is water Energy Use An organism’s cells use energy to perform all functions Ex: stomach cells use energy to digest food Ex: blood cells use energy to move chemicals around your body Response to Surroundings Stimulus = a change in an organism’s surroundings that causes the organism to react Stimuli (plural) include: Temperature Light Sound Response = an action or change in behavior -Do some examples in class When a plant grows toward light. The light would be the stimulus The planting growing toward the light is the response Growth and Development Growth = the process of becoming larger Development = the process of change that occurs during an organism’s life to produce a more complex organism Ex: you have gotten taller with age (growth), but you have also gotten smarter (development) Reproduction Reproduce = the ability to produce offspring that are similar to the parents Ex: birds lay eggs that develop into birds who look like their parents Ex: apples produce seeds that develop into apple trees Four hundred years ago people believed that life could appear from a nonliving material call spontaneous generation however we now know that living things are only produced by other living things. This was proven by two scientist Francesco Redi and Louis Pasteur What Is Life? Four -hundred years ago people believed that life could appear from a nonliving material call spontaneous generation however we now know that living things are only produced by other living things. - What Is Life? I CAN B What is a Virus? Virus= a tiny, nonliving particle that enters and then reproduces inside a living cell. No organisms are safe from viruses! (remember an organism is a living thing) Characteristics of Viruses Viruses are considered non living because they do not have all the characteristics essential for life The only way in which viruses are like organisms is they are able to multilpy. Although viruses can multiply, they do so differently than organisms. Viruses can multiply only when they are inside a living cell. Virus Sizes Viruses are much smaller that cells (even the smallest cells in bacteria) Measured in units called “nanometers” one billionth of a meter. - Viruses Show size of viruses on “Cells Alive Web Page” - Viruses How Viruses Multiply Once inside a cell, a virus’s genetic material takes over many of the cell’s functions It instructs the cell to produce the virus’s proteins and genetic material. These proteins and genetic material then assemble into new viruses Some viruses take over immediately (Active Viruses) cold Some viruses wait for a while (Hidden Viruses) cold sore - Viruses - Viruses Viruses and the Living World Viruses and Disease Some viral disease keep people sick for only a short period of time; (such as a cold) Others can be fatal (such as AIDS) Viruses can also cause diseases in organisms other than humans such as: Apple trees infected by apple mosaic virus Dogs and cats can get rabies I CAN C The Bacterial Cell There are more bacteria in your mouth than there are people on Earth!! Although there are billion of bacteria on Earth, they were not discovered until the late 1600’s. Anton Van Leeuwenhoek discovered them by accident when looking at scrapings from his teeth under a microscope. Bacteria= single celled organism Bacteria are prokaryotes. The genetic material in their cells is not contained in a nucleus. - Bacteria Bacteria are prokaryotes. The genetic material in their cells is not contained in a nucleus Cell Shapes Three basic shapes: Spherical Rodlike Spiral The shape of the cell helps scientists identify the type of bacteria. For example, bacteria that cause strip throat are spherical. Live in guts of Surgeon Fish Found in intestines of humans and is used to manufacture yogurt. Can cause meningitis Cell Sizes The largest known bacterium is about as big as a period in your book. Most bacteria are much smaller. The bacterium that causes strep throat are about .5 to 1 micrometer in diameter. A micrometer is one millionth of a meter. Reproduction When bacteria have plenty of food, the right temperature, and other suitable conditions, they thrive and reproduce frequently. It is a good thing that growing conditions for bacteria are rarely ideal. Otherwise, there would be no room on Earth for other organisms! Asexual Reproduction Asexual Reproduction= a reproductive process that involves only one parent and produces offspring that are identical to the parent. During binary fission the cell first duplicates its genetic material and then divides into two new cells, each cell gets a complete copy of the genetic material as well as some of the parent’s ribosomes and cytoplasm. Reproduces by binary fission every 20 minutes. Sexual Reproduction Sexual Reproduction= involves two parents who combine their genetic material to produce a new organism, which differs from both parents. This results in new bacteria that are genetically different from the parent cells The Role of Bacteria in Nature Oxygen Production Food Production Pasteurization= food is heated to a temperature that is high enough to kill most harmful bacteria without changing the taste. Environmental Recycling Decomposers= organisms that break down large chemicals in dead organisms into small chemicals Environmental Cleanup Health and Medicine Treating Infectious Diseases Bacterial Diseases Can be cured with medications known as antibiotics Antibiotic= a chemical that can kill bacteria without harming a person’s cells Example: Penicillin (works by weakening the cell walls of some bacteria and causing the cells to burst. Antibiotic resistance= results when some bacteria are able to survive in the presence of an antibiotic. - Viruses, Bacteria, and Your Health Treating Infectious Diseases Cont. Viral Diseases Unlike bacterial diseases, there are currently no medication that can cure viral infections. Medications help relieve symptoms - Viruses, Bacteria, and Your Health Preventing Infectious Diseases Vaccine= a substance introduced into the body to stimulate the production of chemicals that destroy specific viruses or bacteria. May be made from dead or altered viruses or bacteria that puts our body on “alert” for that disease. Vaccines are important tools that help prevent the spread of infectious diseases. I CAN D,E and F In 1663, Robert Hooke observed the first cells while looking at cork under his microscope He called them “cells” because they reminded him of the small rectangular rooms called cells At about the same time, Anton van Leeuwenhoek observed pond water and teeth scrapings He saw “animalcules” (little animals) in the water and bacteria from the teeth Development of the Cell Theory In 1838, Matthais Schleiden concluded that all plants are made of cells In 1839, Theodor Schwann concluded that all animals are also made of cells Therefore, all living things are made of cells In 1855, Rudolf Virchow proposed that new cells are formed only from existing cells The observations and conclusions of these five men led to the cell theory: All living things are composed of cells Cells are the basic units of structure and function in living things All cells are produced from other cells Examples of Cells Amoeba Proteus Plant Stem Bacteria Red Blood Cell Nerve Cell Inside tiny cells are even smaller structures called organelles Organelles = tiny cell structures which carry out specific functions within the cell Organelles are to cells, as organs are to the human body! See pgs. 20 & 21 (know all structures/functions) Cell wall = in plant cells, a stiff wall that surrounds the cell membrane giving the cell a box-like shape Cell membrane = protects the cell and regulates what enters and leaves the cell “Typical” Plant Cell - Looking Inside Cells Nucleus = directs all of the cell’s activities, including reproduction Nuclear membrane = protects the nucleus and regulates what enters and leaves the nucleus Chromatin = strands of genetic material which direct the functions of the cell Nucleolus = where ribosomes are made Organelles in the Cytoplasm Cytoplasm = area between the cell membrane and the nucleus filled with a gel-like fluid - Looking Inside Cells Mitochondria = rod-shaped organelles which produce most of the cell’s energy - Looking Inside Cells Endoplasmic reticulum (ER) = network of passageways that carries materials from one part of the cell to another Ribosomes = produce proteins (can be free-floating or attached to the ER) - Looking Inside Cells Golgi bodies = receives materials from the ER and sends them to other parts of the cell Chloroplasts = in plant cells, the site of photosynthesis Vacuoles = stores food, water, waste and other materials Lysosomes = contain chemicals which break down food particles and worn-out cell parts - Looking Inside Cells Cellular Organization In many celled organisms, cells are often organized into cells, tissues, organs, and organ systems. Cells make tissues Tissues make organs Organs work together in an organ system Specialized Cells In many celled organisms, cells are often organized into tissues, organs, and organ systems. Cells – Tissues – Organs – Organ System Some cells serve specific functions, therefore have specific structures Examples: Figure 14 pg. 23 Nerve cells with “arms” through which to pass messages Red blood cells which are flexible to fit through blood vessels Elements and Compounds Element = any substance that cannot be broken down into simpler substances Examples: hydrogen (H), oxygen (O) Atom = the smallest unit of an element Examples: one atom of hydrogen, one atom of oxygen Compound = formed when two or more elements combine chemically Example: water (H2O) is made of hydrogen and oxygen Molecule = the smallest unit of a compound Example: one water molecule is made of two hydrogen atoms and one oxygen atom (see pg. 33) - Chemical Compounds in Cells Compounds Inorganic and Organic Compounds Organic compounds = compounds which contain carbon Four groups of organic compounds: Carbohydrates Lipids Proteins Nucleic acids Inorganic compounds = compounds which do not contain carbon Exception: Carbon dioxide (CO2) is considered inorganic Carbohydrates Carbohydrate = an energy-rich organic compound made of the elements carbon, hydrogen, and oxygen Examples: sugars, starches Proteins Protein = large organic molecule made of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur Amino acids = small molecules which make proteins (20 different kinds) Enzyme = type of protein that speeds up a chemical reaction in a living thing Lipids Lipid = an energy-rich organic compound made of carbon, hydrogen, and oxygen Examples: fats, oils, waxes, cholesterol Lipids contain even more energy than carbohydrates! Nucleic Acids Nucleic acid = very large organic molecule made of carbon, oxygen, hydrogen, nitrogen, and phosphorus Two kinds: DNA (deoxyribonucleic acid) – genetic material RNA (ribonucleic acid) – produces proteins - Chemical Compounds in Cells Analyze together using questions on page 29. - Chemical Compounds in Cells Water and Living Things * Water makes up about 2/3 of the human body * Without water, most chemical reactions within cells could not take place * Water also helps give cells their size and shape * Water helps keep the temperature of cells from changing rapidly I CAN G The Cell Membrane as a Gatekeeper Selectively permeable = describes the cell membrane’s ability to allow some substances through and not others Three methods by which substances move into or out of a cell: Diffusion Osmosis Active transport - The Cell in Its Environment Diffusion – Molecules in Motion Diffusion = the process by which molecules tend to move from an area of higher concentration to an area of lower concentration Molecules are always moving, so as they bump into each other they spread out Osmosis – The Diffusion of Water Molecules Osmosis = the diffusion of water molecules through a selectively permeable membrane - The Cell in Its Environment - The Cell in Its Environment Active Transport Passive transport = the movement of materials through a cell membrane without using energy Passive transport moves substances from high concentration to low concentration Active transport = the movement of materials though a cell membrane using energy Active transport moves substances from low concentration to high concentration Transport proteins can also “pick up” molecules and move them into or out of a cell Sometimes, cells can also engulf particles, taking them into the cell (Figure 19, p. 37) - The Cell in Its Environment I CAN H Photosynthesis Photosynthesis = the process by which a cell captures the energy in sunlight and uses it to make food Sources of Energy Nearly all living things obtain their energy either directly or indirectly from the energy of sunlight captured during photosynthesis Autotroph = an organism that gets its energy directly from the sun Example: plants make their own food Heterotroph = an organism that gets its energy indirectly from the sun Example: animals cannot make their own food - Photosynthesis The Two Stages of Photosynthesis Stage 1: Capturing the energy in sunlight The chlorophyll (green pigment) in the chloroplasts serve as solar cells to collect the sun’s energy Stage 2: Turning the captured energy into sugars Requires two raw materials, H2O and CO2 CO2 enters through stomata (leaf pores) The Photosynthesis Equation 6 CO2 + 6 H2O (light energy) C6H12O6 C6H12O6 = glucose (a sugar) + 6 O2 - Photosynthesis I CAN I Cellular Respiration Storing and Releasing Energy During photosynthesis, plants capture the energy from sunlight and store it as carbohydrates (like glucose) When the plant cells need energy, they “withdraw” the stored carbohydrates Similarly, your body burns carbohydrates when its cells need more energy (like when you’re running) Respiration Respiration = the process by which cells “withdraw” energy from glucose During respiration, cells break down simple food molecules and release the energy they contain The Respiration Equation C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy The Two stages of Respiration Stage 1: Glucose is broken down in the cytoplasm Stage 2: Molecules are broken down further in the mitochondria – energy is produced - Respiration Comparing Photosynthesis and Respiration Photosynthesis and respiration are opposites! The products of one are the raw materials of the other, creating a circular cycle - Respiration I CAN J The Cell Cycle Cell cycle = the regular sequence of growth and division that cells undergo See p. 58-59 Stage 1: Interphase Interphase is the first stage (of 3) of the cell cycle Interphase is the period before cell division occurs The cell grows into its mature size The cell makes a copy of its DNA (process called replication) The cell prepares to divide into two cells Stage 2: Mitosis Mitosis is the second stage (of 3) of the cell cycle Mitosis is the stage during which the cell’s nucleus divides into two new nuclei Four Phases of Mitosis: Phase 1 of Mitosis: Prophase Chromatin in nucleus condenses to make chromosomes Spindle fibers form a bridge between the ends of the cell Nuclear membrane breaks down - Cell Division Phase 2 of Mitosis: Metaphase Chromosomes line up across the center of the cell Each chromosome attaches to a spindle fiber at its centromere (holding the chromatids together) Phase 3 of Mitosis: Anaphase Centromeres split The two chromatids separate One chromatid moves along the spindle fiber to one end of the cell The other chromatid moves to the other end The cell becomes stretched out as the opposite ends pull apart Phase 4 of Mitosis: Telophase The chromosomes begin to stretch out and lose their rodlike appearance at the ends of the cell A new nuclear membrane forms around each region of chromosomes Stage 3: Cytokinesis Cytokinesis is the third stage (of 3) of the cell cycle The cytoplasm divides, distributing the organelles into each of the new cells Each new (daughter) cell has the same number of chromosomes as the parent cell - Cell Division Length of the Cell Cycle See Figure 11, p. 60 Example: a human liver cell completes one cell cycle in about 22 hours Notice how long interphase is (21 hours) compared to mitosis and cytokinesis together (1 hour)! DNA Replication A cell makes a copy of its DNA before mitosis occurs This ensures that each daughter cell has all the genetic information it needs to carry out its activities - Cell Division The Structure of DNA (Figure 14, p. 61) DNA resembles a twisted ladder called a double helix The two “sides” are made of a sugar called deoxyribose and phosphates The “rungs” are made of pairs of nitrogen bases Nitrogen bases: adenine (A), thymine (T), guanine (G) and cytosine (C) Note that A only pairs with T, and G only pairs with C During replication, the DNA is “unzipped” and new nitrogen bases attach See Figure 15, p. 62 - Cell Division - Cell Division Cancer What Is Cancer? Cancer = a disease in which cells grow and divide uncontrollably, damaging the parts of the body around them How Cancer Begins Scientists believe that cancer begins when something damages a portion of the DNA in a chromosome, changing the DNA Mutation = a change in the DNA following damage Mutations disrupt the normal cell cycle, causing cells to divide in an uncontrolled way How Cancer Spreads First, one cell develops abnormally As that cell divides, more and more abnormal cells like it grow nearby In time, these cells form a tumor Tumor = a mass of abnormal cells that develops when cancerous cells divide and grow uncontrollably - Cancer Treating Cancer Doctors usually treat cancer in one of three ways: Surgery Doctors can sometimes completely remove the cancerous tumor through surgery, and the person may be cured Radiation If the tumor cannot be completely removed, or the cancer has spread, doctors may use radiation Radiation (beams of high-energy waves) target fast-growing cells and destroy them Drugs that destroy cancer cells If neither surgery nor radiation are options, doctors may prescribe chemotherapy Chemotherapy = the use of drugs to kill cancer cells Chemotherapy has many, many bad side-effects Cancer Prevention Almost 2/3 of all cancer deaths are caused by tobacco or unhealthy diets Cancer-causing actions Using tobacco (smoking cigarettes) can cause lung cancer Drinking alcohol can cause liver or kidney cancer Eating fatty foods can cause stomach or intestinal cancer Tanning or not using sunscreen can cause skin cancer (melanoma)