Lecture 8 Flashcards
The assemblage of microbes living in a habitat is referred to as:
microbiota / gut Microbiota
1-3% of body mass in and on the average adult human body is comprised of
microbes
Bacteria vastly outnumbers the other kinds of microorganisms; the ratio of bacterial cells to human cells is estimated to be around:
1.3 : 1
we have more bacterial cells than the cells that make up the structure of our body
what is the function of the colon
The colon is the site of breakdown of materials that escape digestion (dietary fibre, resistant starches, and non-carbohydrate substrates)
Colonic bacteria produce enzymes that ferment what?
colonic bacteria can produce enzymes that ferment soluble fibers
Colonic bacteria play a crucial role in the fermentation of soluble fibers, leading to the production of…
short-chain fatty acids (SCFAs)
colonic bacteria → soluble fibers → SCFAs
what are the three SCFAs
Acetate (2 carbons)
Propionate (3 carbons)
Butyrate (4 carbons)
95% of SCFAs are used by what?
colonic cells as a source of energy
and provide about 10% of the total daily calories for the host
Describe the function of Colonic cells
maintaining the structural integrity of the large intestine
serving as a protective barrier
role of SCFAs
- SCFAs serve as messengers between the microbiota and the immune system
- development and function of intestinal epithelial cells and leukocytes (immune cells)
Bacteria in the colon also produces which two vitamins
B vitamins (thiamine, riboflavin, niacin, biotin,
pantothenic acid, and folate)
vitamin K
Vitamins originating from the diet are absorbed where?
Vitamins originating from the diet are absorbed in the small intestine
microbe-produced vitamins are absorbed where
microbe-produced vitamins are absorbed in the colon
define Dietary fibre:
Dietary fiber refers to non-digestible carbohydrates and lignin that are intrinsic and intact in plant foods.
define Functional fibre:
Functional fibre: isolated, non-digestible carbohydrates, extracted, or manufactured that have beneficial effects to humans
What does the sum of dietary and functional fibres encompass
the total amount of fibre consumed by an individual
define Soluble fibre (soluble in water):
type of dietary fiber that dissolves or swells in water
examples of Soluble fibre (soluble in water)
➢ Pectin
➢ Gums
➢ Mucilages
what foods contain Soluble fibre (soluble in water)
Found in fruits, legumes, oats, and some vegetables
how are Soluble fibers fermented? What do bacteria gain from fermenting Soluble fibers?
Fermented by health-promoting bacteria residing in the colon
through fermentation of fibres, bacteria can obtain energy and other substances (like nitrogen) that promote their growth
what are the byproducts of this fermentation of soluble fibers
Fermentation produces SCFAs (acetic, butyric, and propionic acids), that can be used by the human host;
this occurs mostly in the cecum and the ascending portion of the colon
define Insoluble fibre:
type of dietary fiber that does not dissolve in water
Types of Insoluble Fiber:
➢ Cellulose
➢ Hemicellulose
➢ Lignin
are Insoluble fiber Non-Fermentable?
Yes
poorly or non-fermentable by gut bacteria
how does Insoluble fiber promotes colonic health
increasing fecal volume
exerting a detoxifying effect
increase peristaltic rate
how does insoluble fiber contribute to Detoxifying Effect
Insoluble fiber has a detoxifying effect in the colon.
It can absorb or attach to hydrophobic carcinogens, preventing them from interacting with the colonic mucosa
This process facilitates the excretion of these carcinogens in the feces
peristaltic rate:
the speed or frequency at which ingested food moves through the digestive system
