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1、6.1 DigestionExplain why digestion of large food molecules is essential.Explain the need for enzymes in digestion.State the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase.Draw and label a diagram of the digestive system.6.1 DigestionOutline the fun
2、ction of the stomach, small intestine and large intestine.Distinguish between absorption and assimilation.Explain how the structure of the villus is related to its role in absorption and transport of the products of digestion.Why is digestion necessary?1. If you eat other organisms (plants/animals),
3、 we need to break it down into a form suitable for our human body.2. Most of what we eat is food that is made up of large/complex organic molecules, which our body cannot use.Large molecules cannot pass into your cell membranes that line the intestine (absorb nutrients) which pass into the bloodstre
4、am. Have to be small enough to pass into our cells through diffusion, facilitated transport, or active transport.6.1 DigestionDigestion is the chemical breakdown of large, insoluble food molecules into small, soluble molecules (stuff our body can use and absorb!).Food molecules before and after dige
5、stion/breakdown6.1 DigestionMolecule typeMolecular form ingestedMolecular form after digestionproteinproteinamino acidslipidstriglyceridesglycerol and fatty acidscarbohydratespoly/di/monosaccharidesmonosaccharidesnucleic acidsDNA/RNAnucleotidesThe last meal you ate probably had food from plants and/
6、or animals - once living things.These living things have their own DNA which codes for their specific proteins.Digestion allows you to breakdown individual amino acids so that your own DNA can use them as building blocks to synthesize proteins your body can recognize and use.6.1 DigestionOrder of di
7、gestion:Ingestion: you eat the foodDigestion: series of chemical reactions, whereby you convert the ingested food to smaller and smaller molecules.Absorption: small molecules are absorbed through cells of your digestive system and pass into nearby blood vessels.Transport: your circulatory system del
8、ivers the small molecules/nutrients to your body cells.6.1 DigestionNeed for enzymes in digestion:Digestion of large molecules happens naturally at our body temperature but only at a very slow rate. Enzymes are needed to speed up this process!Remember, enzymes are proteins that are catalysts - they
9、speed up chemical reactions.As catalysts, the real function of enzymes is they lower the activation energy needed for the reaction to occur.6.1 DigestionDigestive enzymes all help to catalyze hydrolysis reactions.You studied hydrolysis - so what is it?Hydrolysis is the breakdown of a larger molecule
10、 into smaller molecules, losing water in the process.6.1 DigestionExamples of Digestive Enzymes6.1 DigestionAmylaseProteaseLipaseExample of this enzymeSalivary amylasePepsinPancreatic lipaseSourceSalivary glandWall of stomachPancreasSubstrateStarchProteinsTriglycerides (fats or oils)Productsmaltose
11、and glucoseSmall polypeptidesFatty acids and glycerolOptimum pHneutral (pH 7)Acidic (pH 3)Neutral (pH 7)Draw and label the digestive system6.1 DigestionIn order:MouthEsophagusStomachSmall IntestineLarge Intestine (colon)RectumSTOMACH1. In the mouth, food is broken down mechanically (teeth) and chemi
12、cally (amylase)2. When you swallow, food is passed through the esophagus through muscle contractions called peristalsisMuscles squeeze around your food, pushing it down - why it hurts sometimes when you swallow a ridged chip.6.1 Digestion3. Digestion of proteins starts in the stomach, with the help
13、of gastric juice - a mixture of 3 things:Pepsin - enzyme most active in high acid, a high acidic environment is the right condition for it to work.Hydrochloric acid - breaks down food, creates the acidic environment, kills bacteria that could cause food poisoning. This is what burns your throat when
14、 you throw up.Mucus - lines the inside of stomach to prevent stomach damage from the hydrochloric acid6.1 Digestion4. The muscular wall of the stomach creates a churning motion on order to mix the food with the gastric juice.5. After a period of time, a valve at the lower end of the stomach opens an
15、d the food enters the small intestine.6.1 DigestionSMALL INTESTINE6. Digestion continues in the small intestines with more secretions: bile form the liver/gall bladder and lipase from the pancreas break down food further.7. Now some molecules are small enough to be absorbed. The inner wall of the in
16、testine is made up of thousands of finger-like extensions called villi.6.1 Digestion8. Each villus contains a capillary bed so absorbed molecules can be taken from the small intestine, and pass through a layer of cells into other body cells through the bloodstream. Once a nutrient molecule enters a
17、body cell, it leaves the circulatory system and the cell may use it for energy (ex: glucose) or maybe its used as a building block to build a larger molecule (ex: amino acids)If the nutrient molecule is used for building larger molecules, the process of bringing the nutrient to a body cell then usin
18、g it is called assimilation.6.1 DigestionLARGE INTESTINE (COLON)9. Most of the useful nutrients in food has already been absorbed by the small intestine. What remains of the original food by the time it gets to the beginning of the large intestine is undigested (unabsorbed).10. Primary function of t
19、he large intestine is to absorb water.The LI is also home to many bacteria (ex: E.coli) that we provide nutrients/water to while they make vitamin K and maintain a overall healthy environment in our LI.6.1 Digestion11. Any food undigested by us or the bacteria in your LI exits the body as solid wast
20、e through the rectum then out the anus.6.1 Digestion1. What does the digestion of starch by amylase produce?A. LactoseB. SucroseC. CelluloseD. MaltoseAnswer: D6.1 Digestion2. Which of the following is correct for lipase?Answer: A6.1 DigestionSubstrateSourcepH optimumAtriglyceridespancreaspH = 7Bfatt
21、y acidssmall intestinepH = 7Ctriglyceridessmall intestinepH = 9Dfatty acidspancreaspH = 93. Which of the following parts of the digestive system secrete proteases?Answer: C6.1 DigestionStomachSmall IntestineLarge IntestineAYesYesYesBYesNoYesCYesNoNoDNoNoNo4. The diagram below shows parts of the huma
22、n digestive. Which points are linked by the small intestine? A. I and IIIB. II and IIIC. II and IVD. III and IVAnswer: B6.1 Digestion5. What are the names of the organs labelled I and II in the diagram below?Answer: C6.1 DigestionIIIApancreasliverBsmall intestinelarge intestineCgall bladderpancreasD
23、esophagusstomach6. Celiac disease causes the destruction of the villi cells. Which of the following is most likely to happen to people with celiac disease?A. Incomplete digestion of fatsB. Poor absorption of calciumC. Increased levels of glucose in bloodD. Damage in the esophagus caused by increase
24、in acid content of the stomachAnswer: B6.1 Digestion7. What processes occur during assimilation and absorption of lipids?Answer: B6.1 DigestionAssimilationAbsorptionAlipids are broken down by enzymeslipids are ingestedBlipids are incorporated into new membraneslipids pass into the viliClipids pass i
25、nto the villilipids are incorporated into new membranesDlipids are ingestedlipids are broken down by enzymes8. What is the main function of the large intestine?A. Absorption of waterB. Digestion of fats and proteinsC. Absorption of nutrientsD. Recycling of digestive enzymesAnswer: A6.1 Digestion6.3
26、Defense against infectious diseaseDefine pathogen.Explain why antibiotics are effective against bacteria but not against viruses.Outline the role of skin and mucus membranes in defense against pathogens.Outline how phagocytic leucocytes ingest pathogens in the blood and in body tissues.6.3 Defense a
27、gainst infectious diseaseDistinguish between antigens and antibodies.Explain antibody production.Outline the effects of HIV on the immune system.Discuss the cause, transmission and social implication of AIDS.Pathogen and AntibioticsPathogen: any living organism or virus that is capable of causing a
28、disease.EX of Pathogens: viruses, bacteria, fungi, and various worms.BUT exposure to most pathogens do not result in a disease.Our body has amazing defenses for most pathogens that enter out body and in the case when they do enter, we usually have already developed an immunity to that pathogen.6.3 D
29、efense Against Infectious DiseasesFor some, like bacteria, there are chemicals called antibiotics that can work against living bacterial cells that do not affect our own body cells.How antibiotics work against bacteria:1. Bacteria are prokaryotes and our body cells are eukaryotes. Antibiotics take a
30、dvantage of the differences between our cells and bacteria. Can you some of those differences?Prokaryotes: Cell wall, nucleoid (free floating DNA), no nucleusAntibiotics are chemicals produced by microorganisms, Example: Pencillium fungus produces penicillin to kill bacteria6.3 Defense Against Infec
31、tious Diseases2. There are different categories of antibiotics - some block protein synthesis in bacteria (but have no effect on ours because our DNA is in a nucleus), others may stop the production of a new cell wall by bacteria (thus blocking their ability to grow and divide.3. This also explains
32、why antibiotics do not work on viruses. Viruses use your own body cells as a host to create new viruses. Any chemical that would stop viruses would also damage your own cellsWhen you get a cold - doctors cant do anything for you because antibiotics dont work on the influenza virus, you just have to
33、let it run its course!6.3 Defense Against Infectious DiseasesPreventing Pathogens From Entering Our BodiesIt isnt possible to isolate yourself and stay away from every possible source of infection, so your body has some awesome ways to make it difficult for pathogens to enter your body and start an
34、infection.Skin: it is a barrier to infection with 2 layersUnderneath layer (dermis) is very alive with sweat glands/capillaries/sensory receptors.Top layer (epidermis) is constantly being replaced as the dead cells from the dermis keep moving up. So this layer of dead cells is a great barrier agains
35、t pathogens because it isnt truly alive.As long as our skin remains intact, it defends against pathogens.This is why it is so important to clean and take care of cuts to the skin to quickly heal the top layer of skin or else pathogens enter our blood stream through that cut.Stomach Acid: some pathog
36、ens enter the body in food and water.The very acidic environment of the stomach helps to kill most of these ingested pathogens.Mucus: other pathogens enter in the air we breathe (either through nose or mouth)This route is lined with a type of tissue known as mucous membrane.Why its better to breathe
37、 through your nose than mouth: the hairs in your nose serve as the first filter to separate pathogens from the air going into your lungs.6.3 Defense Against Infectious DiseasesCells of mucus membranes produce and secrete a lining of sticky mucus which can trap incoming pathogens and prevent them fro
38、m reaching cells they could infect.Some mucus membranes are lined with cilia - hair like extensions with a wave-like movement that traps pathogens too.Also, the cells that secrete mucus also secrete an enzyme called lysozyme - which chemically damages many pathogens.Area w/ Mucus MembraneWhat it is/
39、doesTracheaTube carried air to and from lungsNasal PassagesTubes allow air to entier the nose and then the tracheaUrethraTube carried urine from bladder to outsideVaginaReproductive tract leading from uterus to the outside6.3 Defense Against Infectious DiseasesWhat Happens When Pathogens Do Get In?B
40、esides your skin/mucus/stomach acid, our body has another defense against pathogens!Leucocytes (white blood cells) are in out blood to help us fight off pathogens that make it that far, and also remember them when they enter again helping us keep an immunity against repeat pathogens.Some of the leuc
41、ocytes in blood are phagocytes.Phagocytes can identify pathogens, determining if they are a natural part of the body, and if not, ingest them by endocytosis.6.3 Defense Against Infectious DiseasesThe pathogens are then killed and digested inside the phagocytes by enzymes.Phagocytic leucocytes can in
42、gest pathogens in the bloodUsing their flexible cell membrane, they easily change shape and can squeeze out through the walls of capillaries and move through tissues to get to the site of the infection.Large numbers of phagocytes at the infection site is PUS!6.3 Defense Against Infectious DiseasesAn
43、tigens and AntibodiesAntigens are proteins found in the cell membranes or cell walls of bacteria/viruses .These antigens allow your body to recognize a pathogen as being an invader in your body or not self, which give a clear signal to switch on your immune response with a rapid production of antibo
44、dies.Antibodies are protein molecules that are produced by your body in response to any pathogen antigens that enters your body.6.3 Defense Against Infectious DiseasesThere are millions of different antibodies and each one is specific to an antigen.EX: the antibodies produced in response to infectio
45、n by the chicken pox pathogen is very different from the influenza virus antibodies.Each antibody molecule has a basic Y shape, and the tops of the Y are specific binding sites that give every antibody its unique properties.These specific binding sites attach to the corresponding antigen site, and o
46、nce it is bound to the pathogens antigens, it can destroy it (deactivate its DNA or cause their cell wall to explode.6.3 Defense Against Infectious Diseases6.3 Defense Against Infectious DiseasesHIV and AIDSAIDS shows just how crucial the bodys defenses are against diseases. Destruction of the immun
47、e system eventually leads to death, which ultimately is what AIDS does.A syndrome, like AIDS (acquired immunodeficiency syndrome), is a group of symptoms that are found together.6.3 Defense Against Infectious DiseasesCause of Aids - HIV: HIV (human immunodeficiency virus) causes AIDS.The virus infec
48、ts a type of lymphocyte that plays a vital role in antibody production.Over a period of years, these lymphocytes are destroyed and antibodies cannot then be produced.Without a functioning immune system, the body is vulnerable to pathogens that normally would be controlled easily.Individuals with AID
49、S have low numbers of lymphocytes, weight loss, and other diseases caused by viruses/bacteria is what leads to their death.6.3 Defense Against Infectious DiseasesTransmission of AIDS:HIV does not survive long outside the body and cannot easily pass through the skin, so it requires body fluids to be
50、transferred from one person to another.Through small cuts, tears in the vagina/penis/mouth during vaginal/anal/oral sex.In traces of blood from sharing needles through drug use.Across the placenta from mother to baby, through cuts during childbirth, or in milk during breast-feeding.In transfused blo
51、od - rarely happens today as donated blood goes through several tests until it is give to a patient6.3 Defense Against Infectious DiseasesSocial Implication of HIV/AIDS:Families and friends suffer grief from prolonged sickness than can last decades, then eventually death.Families become poorer if th
52、e individual with AIDS was the wage earner and is refused life insurance, or if that person has no medical insurance to pay for the medicine to prolong their life.Individuals infected with HIV may become stigmatized and not find partners, housing or employment.Sexual activity in a population may be
53、reduced of the fear of AIDS.6.3 Defense Against Infectious Diseases1. Which factors related to mucus membranes protect the body against microbes?I. Production of lysozymeII. Secretion of alkaline solutionsIII. Trapping of microbesA. I and II C. I and IIIB. II and III D. I, II and IIIAnswer: C6.3 Def
54、ense Against Infectious Diseases2. What prevents antibiotics from being effective against viruses?A. Viruses have a high rate of mutation.B. Viruses have no RNA.C. Viruses have no metabolism.D. Viruses have a protein shell that protects them.Answer: C6.3 Defense Against Infectious Diseases3. Which t
55、erm describes a molecule capable of triggering an immune response?A. AntibodyB. AntigenC. PathogenD. AntibioticAnswer: B6.3 Defense Against Infectious Diseases4. What does the nucleus of a human lymphocyte contain?A. Only the genes to produce a specific antigenB. Only the genes to produce a range of
56、 antibodiesC. Only the genes that control the growth and development of a lymphocyteD. The whole genetic information for a human.Answer: D6.3 Defense Against Infectious Diseases5. Which of the following statements about antibodies is correct?A. Antibodies are polypeptidesB. Antibodies are produced b
57、y the bone marrow.C. Antibodies are pathogenic foreign substances.D. Antibodies kill bacteria but not viruses.Answer: A6.3 Defense Against Infectious Diseases6. What stimulates the production of antibodies?A. AIDSB. AntibioticsC. AnticodonsD. AntigensAnswer: D6.3 Defense Against Infectious Diseases7
58、. What are 2 effects of HIV on the immune system?A. Reduction in antibody production and increase in active lymphocytes.B. Increase in antibody production and decrease in red blood cells.C. Reduction in antibody production and decrease in active lymphocytes.D. Increase in antibody production and increase in red blood cells.Answer: C6.3 Defense Against Infectious Diseases8. Where in a cell are antigens found?A. In the nucleusB. In the cytoplasmC. In the plasma membraneD. On the surface of the golgi apparatusAnswer: C6.3 Defense Against Infectious Diseases
