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1

Metabolism

The total of all chemical reactions in the cell that result in energy and synthesis of new macromolecules.

2

Why do we study metabolism?

-pathogens acquire energy and nutrients at the expense of their host
-metabolic enzymes are targets for antimicrobials
-biochemical testing is used to help identify pathogens in clinical speicmens

3

Categorize organisms based on carbon source, energy source and electron source.

-Carbon Source: Autotrophs (CO2), heterotrophs (organic molecules)
-Energy Source: Phototrophs (light) , chemotrophs (chemicals inorganic and organic)
-Electron Source: Lithotrophs ( Inorganic Molecules), Organotrophs (organic molecules)

*note: all pathogenic bacteria are chemoheterothrophs

4

Describe the 3 major stages in aerobic heterotrophic catabolism (aerobic respiration) as it occurs in chemoheterotrophs. What happens, where does it happen and what is the final outcome?

Stage 1: Uptake of Nutrients
-release of exoenzymes and breakdown of macromolecules
-outside the cell
-exoenzymes (ex: amylase) begin digestion outside of the cell
ex: proteins --> peptides --> amino acids

Stage 2:
-glycolysis
-occurs in the cytoplasm
-produces 2 ATP

Stage 3:
-Krebs Cycle and electron transport chain
-occurs on the surface of plasma membrane
-produces 32-34 ATP

5

Describe 2 anaerobic catabolic pathway used by some bacteria.

Anaerobic Respiration:
- does not use oxygen
- it is the terminal electron acceptor is an inorganic molecules uses ETS to create ATP. however, this is shorter and less efficient and generates less ATP.
ex: Ecoli in our intestine reduce nitrates --> nitrites

Fermentation:
-Partial oxidation of glucose when no external terminal electron acceptor is available
-Lactic acid fermentation: dental caries, (Streptococci and lactobacillus) yogurt and cheese

6

List the characteristics and major components of the first line of defence (innate immunity). What is the purpose of the 1st line of defence?

The first line of defense if designed to prevent pathogens from entering the body.

7

Describe Physical Barriers (1st line).

Physical barrier
-intact skin: thick, several layers, composed of mainly keratin, dry surface
-mucous membrane: thinner and less efficient barrier, lined with mucus/cilia that trap and propel microbes, line body cavities that are open to the environment: respiratory tract, digestive tract, urinary tract, reproductive

8

Describe Chemical Defense (1st line)

Chemical Defences:
-Lysozyme: found in tears, saliva, sweat, mucous, etc.
-Acids: skin (sebum with fatty acids pH 4), stomach (pH 1.5), vagina (lactic acids pH 4)

9

Describe Microbial Antagonisms (1st line)

Microbial Antagonism: symbiosis = to live together
-Mutualism: both organisms benefit (bacteria in colon)
-Commensalism: 1 organism benefits, other effected (staph. Epidermis on skin)
-Parasitism: lives at expense of host, may be harmful or harmless (pathogen - a parasite that causes harm to its host)

10

Describe any other other following roles from first line of defense

Other:
-swallowing physically removes epithelial cells of the oral cavity and attached microbes, blinking, vomiting, urination, nasal hairs, coughing and sneezing

11

List and describe the role of the major components of the second line of defense

Cells, processes and antimicrobial chemicals that operate against any microbes that has evaded the body's first line of defense.

12

What is the purpose of inflammation?

Initiated in response to injury and or infections.
Purpose:
-removes. contain any invading microbes
-repair tissue damage

13

Describe the process of phagocytosis.

Phagocytosis: ingestion of foreign materials by macrophages, neutrophils and monocytes

Process:
1.Chemotaxis: directed migration of phagocytic cells toward microbe due to chemical attractants
2.Attachment: mediated by complement fragments or antibodies
3.Ingestion: pseudopodia surround microbe (endocytosis)
--> phagosome formation
4.Digestion: phagosome fuses with lysosome containing various enzymes --> phagolysosome (digestive vacuole)
5. Elimination: degraded bits eliminated by exocytosis. Some microbial components may remain attached by cytoplasmic membrane, playing a role in the adaptive immune response

14

What cells are considered 'professional phagocytes'?

macrophagus (in tissue), neutrophils and monocytes (in blood)

15

List the effects of inflammation and the resulting signs

-Acute: develops quickly, in short lived ex: misquote bite
-Chronic: can cause tissue damage, linked to many chronic disease ex: gingivitis and periodontal disease

16

Adaptive Immune System:
Differentiate between humoral and mediated immunity.

Human Oral Antibody Response (B-cells):
-leads to the formation of specific circulating antibodies that will recognize and bind to and inactive or destroy microbes or their toxins
-act against extra cellular antigens (ex: most bacteria)

Oral Mediated Immunity:
Recognizes and attack intracellular pathogens (ex: viruses), abnormal or altered host cells (cancer) and transplanted cells

17

What is the purpose of the humoral system?

To make antibodies against agents

Cell involved:
- B-cells
- plasma
- memory cells
- helper T cells

Chemical involved: antibodies and antigens

18

What is the purpose of the cell mediated system?

To recognize and attack:
- intracellular pathogens
- abnormal host cells
- transplanted cells

3 types of cells:
- cytotoxic
- helper T
-memory T cells

19

What determines virulence?

A virulence factor is any structure or physiological characteristic that helps a pathogen to enter, attach, multiple, invade and evade host defense mechanisms resulting in damages to host tissue (disease)

20

Give examples of virulence factors the enable:
A: transmission
B: entry
C: attachment
D: how they invade and spread, etc
E: how host cells are damaged

Transmission: mucous membrane to mucous membrane (ex: oral herpes, mono, STI),

Entry: break in the skin/mucous membrane (ex: STI)

Attachment: fimbriae/pili

How they invade: flagella/capsules

How host cells are damaged: toxin production

21

Describe invasive exoenzymes

Causes damage to host tissues, allow spread of pathogen away from initial site of infection (ex: exotoxin B, hemolysin)

22

Describe endotoxins

Gram negative bacteria of lipid A and lipopolysaccharide. This is released only when cells die. Cause fever inflammation, diarrhea, etc.

23

Describe exotoxins

Proteins produced mostly by gram positive bacteria, released from living bacterial cell, soluble in body fluids, may act far from site of infection.

24

What factors influence our oral flora?

-consistent supply of nutrients
-consistent removal of waste products
-controlled moisture, temperature, pH and oxygen

25

Describe dental plaque biofilm and the steps in its formation

Dental plaque is a non-calcifed mixed microbial biofilm on the surface of the tooth. It plays a major role in dental caries and periodontal disease.

Steps:
-acquired pellicle formation
-bacterial colonization
-plaque maturation

26

What is the role of mutans streptococci and lactobacilli?

Mutans streptococci: primary indicator of dental caries. Able to rapidly ferment many sugars with production of more acids. Able to split sucrose into glucose and fructose using enzyme glucosyl transferase

Lactobacilli: not a primary indicator of dental caries, but important in advancing caries once started. It is a prolific lactic acid producer, aciduric and gram positive bacillus

27

What is the function of sucrose and glucosyl transferase?

Glucosyl transferase enzyme can split sucrose into glucose and fructose, and is able to join the monosaccharide glucose units into long chain glucans

28

Describe the etiology of dental caries

-dental caries is a chronic infection of the enamel or dentin in which the microbial agents are responsible for members of the oral flora, resulting in demineralization of enamel by acids produced by plaque microbes as they garment dietary carbohydrates
-etiology: enamel structure, saliva, diet, oral hygiene, microbial flora (ex: mutans streptococci and lactobacilli)

29

What are some of the ways in which we can control/reduce incident of caries?

-self care
-fluoride
-diet
-DH visits
-sealants
-antimicrobial anti plaque agents

30

List factors involved in periodontitis

-bacteria virulence factors
-host: poor oral hygiene, stress, diet, etc
-microbial: porphyromonas gingivalis

31

Differenciate between gingivitis and periodontal disease

gingivitis: inflamed gingiva (reversible)

periodontitis: inflammation and infection of ligaments and bones that support teeth, the major cause of tooth loss in adults