Chapter 19 Viruses and Bacteria. Viruses Viruses are NOT cells! A virus is made up of: 1.Nucleic...
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Transcript of Chapter 19 Viruses and Bacteria. Viruses Viruses are NOT cells! A virus is made up of: 1.Nucleic...
Viruses• Viruses are NOT cells!
• A virus is made up of:
1.Nucleic acid
(RNA or DNA)
2. Protein coat
What is a virus?
• Made of nucleic acid (DNA OR RNA), protein coat (capsid) and sometimes lipids
• MUST enter living cells in order to reproduce
• Very small
• Range from a few to 100s of genes Bacteriophage = virus that
infects bacteria
Viruses: Living or Non-living?
• No cell membrane or other living cell components
• Host cells required for reproduction
• Do not metabolize or respond to stimuli
• BUT, they do have genetic info and can change over time
Virus Infection: Lytic vs. Lysogenic Cycles
• Lytic Cycle: virus enters cell, makes copies of itself, and causes the cell to “lyse” or burst
• Lysogenic Cycle: virus integrates into host cell DNA and viral genetic info is copied along with host cell’s DNA
Lytic Cycle of a Cold or Influenza
Virus
The cold or flu virus infects cells lining of the nose and throat, reproducing more cold viruses and destroying body cells.
• What are the two things all viruses have?
• Are viruses living or non-living?
• What are the two ways viruses infect a living host cell?
• What are the two ways viruses can reproduce?
Retrovirus• A virus that contains
RNA instead of DNA
• Human Immunodeficiency Virus (HIV) is a retrovirus
• HIV causes AIDS
ENVELOPE
RNA
CAPSID
HIV Virus and Immune System
The thymus gland by the heart and the bone marrow produce the white blood cells that protect us from infection.
HIV attacks the T cell of the immune system.
Retroviruses• When enter cells, produce
DNA copy of RNA then integrate into host cell
• Can remain dormant until replicate and burst open cell
• “Retro” because genetic info is copied backwards RNA => DNA
• Destroys helper T cells–Makes getting other diseases really easy
• Transmitted by blood, breast feeding, sexually, and other bodily fluids• Can happen to anyone!
Mouth sores common to AIDS patients
Viruses as Parasites
• Take advantage of host cell’s respiration, nutrition and other cellular functions
• Depends entirely on another organism for its existence
Chicken Pox
• Symptoms– Fever and weakness– Red, itchy rash
• Transmitted by– Direct contact– Droplet inhalation
Common Cold
• Symptoms– Sneezing– Sore throat– Fever– Muscle and headaches
• Transmitted by– Direct contact– Droplet inhalation
Warts/HPV
• Symptoms– Noncancerous growths on
skin; can become cancerous
• Transmitted by– Direct contact– Sex
Hepatitis
• Symptoms– Jaundice– Fatigue– Abdominal pain– Diarrhea and nausea
• Transmitted by– Human waste, contaminated
food and water (Hep A)– Contact w/ bodily fluids (B & C)
Herpes
• Symptoms– Blister like sores (can
actually be on any part of the body)
– Fever– Fatigue
• Transmitted by– Direct contact– Sex
Measles
• Symptoms– High fever– Sore throat– Rash– Swollen eyelids
• Transmitted by– Droplet inhalation
Polio
• Symptoms– Fever– Headache– Muscle weakness– Difficulty swallowing
• Transmitted by– Droplet inhalation
Virus Prevention
• Vaccination – Injection of weakened or dead pathogen
• Hygiene– Wash your hands!
• Safe sex– Use condoms or other prophylactic contraceptives
• Abstinence – Only method that is 100% effective against
transmission of sexually transmitted viruses
BacteriaBacteria are small PROKARYOTIC cells.
They have a cell wall and DNA.
Some bacteria are beneficial and some are pathogenic. *Pathogenic = disease causing
Bacteria
• Used as a common name to describe prokaryotes
• Usually range from 1-5 micrometers!
• Divided into two kingdoms: eubacteria and archaebacteria
Staphylococcus epidermidis
Eubacteria• Largest bacterial Kingdom• Wide range; many lifestyles,
live almost anywhere• Usually have cell wall for
shape and protection - cell wall contains peptidoglycan
• Have cell membrane- sometimes an extra membrane outside of it as well
Escherichia coli
Archaebacteria
• Look similar to eubacteria under microscope but chemically different
• No peptidoglycan & different membrane lipids
• DNA more like eukaryotes (Share a more recent common ancestor)
• Live in extreme/harsh environments
How Are Bacteria Identified?
Identified by:– Shape– Movement techniques – Way of obtaining energy– Oxygen Needs– Mode of Reproduction
Movement
• Not all prokaryotes can move
• Ones that move– Propelled by flagella (whiplike structures for
movement)– Lash, snake or spiral– Glide along layer of slime
Escherichia coli
Metabolic Diversity: Heterotrophs vs. Autotrophs
• Most are heterotrophic!• If autotrophic:
– Some are photoautotrophs (similar to plants)– Some are chemoautotrophs (make organic molecules
from CO2
• If heterotrophic:– Most are chemoheterotrophs (Take in organic
molecules for energy and carbon supply)– Humans are chemoheterotrophs, too!– Some are photoheterorophs (photosynthetic but need
organic compounds for carbon source)
Oxygen Needs
• Facultative anaerobes– Can survive with or without oxygen
• Obligate anaerobes– Must live in the absence of oxygen
• Obligate aerobes– Require constant supply of oxygen to live
Growth and Reproduction• Conjugation
– Hollow bridge forms between two cells and genes move from one cell to the other; increases genetic diversity
– IS a sexual process (NOT REPRODUCTION – does not produce gametes)
• Binary Fission– Grows to where it
doubles in size then replicates DNA and divides in half
Bacteria’s Importance
• Producers• Nitrogen Fixation• Human Uses
– Food and beverage production– Industry– Drug and chemical production– Live in our intestines; provide vitamins– Biotechnology
• Decomposers– Recycle nutrients in ecosystem– Sewage treatment
Bacterial Diseases
Two ways bacteria causes diseases:
1. Break down organism’s cells for food
2. Release toxins that affect the organism’s body
Examples of Bacterial Diseases
• Streptococcus– Symptoms – fever, sore throat, swollen glands
• Diphtheria– Symptoms – sore throat, low grade fever
***Both cause disease by releasing TOXINS
Circulatory SystemBacteria can infect the heart valves and the lining of the ventricles.
The circulatory system brings oxygen and nutrients to all body cells.
Left ventricle
Beneficial Bacteria in the Digestive System
Bacteria like E. coli make digestive enzymes and vitamin K in the large intestine.
Nervous SystemBrain
Spinal cord
Spinal& peripheral nerves
The nervous system responds to changes in the external and internal environment. It is “the communicator”.
Nervous System Infections
Both bacteria and viruses can infect the brain causing such diseases as meningitis and encephalitis.
Nerve cells or Neurons
Controlling Bacteria• Food storage and processing• Disinfectants
– Chemical solutions that kill bacteria
• Sterilization– Method to control growth of bacteria by heat
• Vaccines– Weakened or killed pathogens– Sometimes prompts body to produce immunity
• Antibiotics– Block growth of bacteria
Comparing VIRUSES and BACTERIA
1.Which is a virus?2.Which is a bacteria?3.Which is living?4.Which is non-living?
A. B.