Digestion Flashcards
1
Q
What is digestion
A
The breakdown of large organic molecules into small soluble molecules to be absorbed by cells
- these are then synthesised to be used by the body
2
Q
What are the stages of digestion for a holozoic feeder
A
- Ingestion- large food particles taken into the mouth and broken down by teeth and tongue which is mechanical digestion
- Digestion- chemical breakdown (enzymes) of large organic molecules into small soluble molecules
- Absorption- small molecules move from the gut into blood stream
- Egestion- removal of undigested waste food molecules
3
Q
What are the main forms of digestion
A
Physical
Chemical
4
Q
What is mechanical digestion
A
Muscular action which pounds food into a semi-solid state
5
Q
Why does mechanical digestion take place
A
To increase surface area of food over which enzymes may act to chemically digest food
6
Q
How are carbohydrates broken down and what enzyme
A
Polysaccharide - disaccharide- monosaccharide
Using amylase
7
Q
Specific carb breakdown examples with amylose
A
Amylose- maltose- glucose
Using amylase-maltase
8
Q
How are lipids broken down and using what enzyme
A
Lipids- fatty acids + glycerol
Using lipase
9
Q
How do protein breakdown and using what enzyme
A
Polypeptides- dipeptides- amino acids
Using peptidase
10
Q
What is endopeptidase
A
An enzyme which hydrolyses peptide bonds within/ at the middle of a protein molecule
Tor produce shorter polypeptides
11
Q
What is exopeptidase
A
An enzyme that hydrolyses peptide bonds at the terminal end of the shorter polypeptide chains
To produce dipeptides or individual amino acids
12
Q
What two organs make up the small intestine
A
Duodenum and ileum
13
Q
What is the structure of the gut wall from outer to inner
A
Serosa
Muscular layer- circular muscle and longitudinal muscle
Submucosa
Mucosa
Lumen
14
Q
What’s the structure of serosa
A
- layer of tough connective tissue
15
Q
What is the function of serosa
A
Protect the gut wall from friction from other organs
16
Q
What is the muscle layer structure
A
- two layers of muscle running in different directions
- inner/circular- fibres in rings
- outer/longitudinal- fibres lengthways
- both have smooth involuntary muscle
17
Q
What’s the function of muscle layer
A
Cause a wave of muscular contraction that moves food along the gut
18
Q
What’s the structure of submucosa
A
- contains blood and lymph vessels
- contains a rich network of nerve fibres
19
Q
What’s the submucosa function
A
- takes away absorbed food products
- coordinate the muscular contractions involved in peristalsis
20
Q
What is the structure of mucosa
A
- lines the gut wall
- epithelia cells of the mucosa are layered (stratified) for protection
21
Q
What is the function of mucosa
A
- secretes mucus which lubricates the passage for food
- helps to protect the gut from damage
- some regions secrete digestive juices, others absorb digested food
22
Q
examples of chemical digestion in the buccal cavity
A
- slaivary amylase
23
Q
What is an autotroph
A
Use simple inorganic materials to manufacture complex organic compounds
24
Q
What is a heterotroph
A
Consume complex organic food molecules
25
Type of autotrophs
Photoautotrophic and chemoautotrophic
26
What is photoautotrophic
Use light energy to convert simple inorganic molecules into complex organic ones
Eg photosynthesis
27
What is chemoautotrophic
Use the energy derived from oxidation to convert simple inorganic molecules into complex organic ones
28
Types of heterotrophs
Holozoic feeders
Parasites
Saprotrophytes/saprotrophs/saprobionts
29
What are holozoic feeders
- nearly all animals
- take food into their bodies and break it down
- have specialist digestive systems
- follows process of ingestion, digestion, absorption, assimilation and egestion
30
What are parasites
- Organism that feed o another organism (host)
- host always suffers harm and often dies
- highly specialised
31
What are saprophytes
- Feed on dead/decaying matter and don’t have specialised digestive system
- feed by secreting enzymes onto food outside the body then absorbing the soluble products across the cell membrane by diffusing
- extracellular digestion
32
What is fungal feeding
Fungi secretes enzymes from the growing tip of hyphae
33
Process of fungal feeding
1. The growing tip of the hyphae penetrates the food, secreting enzymes
2. Enzymes diffuses out thorough cell wall onto the surface of the food (substrate)
3. The enzymes digest food into soluble products
4. These products are absorbed into the hyphae through cell wall by facilitated diffusion/active transport
5 soluble products are transported within the fungi and excess are stored (extracellular digestion)
34
How do unicellular organism digest food
Ingest food particles by endocytosis then digest them. Waste is digested
35
How can protease be divides
Into endopeptidases and exopeptidases
36
examples of chemical digestion in the stomach
-pepsinogen
37
examples of chemical digestion in the duodenum
- pancreatic amylase
- trypsiongen
- lipase
38
examples of chemical digestion in the ileum
- maltase
- sucrase
- lactase
- lipase
39
Function of salivary glands
Produce saliva
40
Function of oesophagus
Carries food from the mouth to the stomach
41
Function of stomach
Produces hydrochloric acid
42
Function of pyloric sphincter muscle
Controls amount of food leaving the stomach
43
Function of duodenum
Receives juices from the gall bladder and pancreas
44
Function of ileum
Is where most digested food is absorbed
45
Function of bile duct
Takes bile from the gall bladder to the duodenum
46
Function of pancreas
Produces enzymes which pass into the duodenum
47
Function of gall bladder
Stores bile
48
Function of the colon
Is where most waters absorbed
absorbs vitamin k and folic acids
49
Function of rectum
Stores water faeces for several hours
foods in semi-solid state taht consists of residues of undigested cellulose, bacteria, dead cells
50
Function of anus
Controls the passing of faeces
51
what do peptic/cheif cells do
secrete pepsinogen (inactive form of pepsin)
which is activated into pepsin which hydrolyses larger polypeptides into smaller polypeptides
52
what do oxyntic cells do
secrete hydrochloric acid
kills bacteria
provides an optimum for pepsin
activates pepsinogen into pepsin
53
what do goblet cells do
secrete mucus
forms a protective layer on the stomach wall against pepsin and hydrochloric acid
aid food movement
54
what does muscularis do
contracts and relax
churns food in the stomach to provide a lager surface area for chemical digestion
55
what does the pyloric sphincter do
contracts and relax
food exits the stomach
56
where is trypsinogen secreted by and enters
secreted by pancrease
enters duodenum via pancreatic duct
activated by enterkinase
to become trypsin
57
why must enzymes be secreted as inactive enzymes
otherwise enzymes digest the proteins in the cells their made
- autolysis- damage to stomach lining
58
where is dipeptides do and where are they found
break down dipeptides into amino acids
found in membrane of epithelial cells in duodenum and ileum
59
where is dimers do and where are they found
all dimers are hydrolysed into their momomers intracellularly in the membranes of epithelial cells in duodenuma and ileum
60
where is salivary amylase secreted
salivary glands into the buccal cavity
61
where is pancreatic amylase secreted
produced in pancrease and enter duodenum via pancreatic duct
62
where is lipase produced
secreted by pancrease into duodenum
63
where is bile contained, stored, produced
contains- bile salts and water
stored- gall bladder
produced by- liver
64
what is the process of bile breaking down lipid globules
1. bile salts attach to lipid
2. they break down into smaller globules
3. increase suface area
4. lipase chemically digests
65
structure of villi in ileum
- microvilli
- capillaries
- epithelium
- lacteal- lymphatic vessel to absorb lipids
- globlet cells
- ateriole and venule end
66
what features of the ileum make it a good excahnge surface
- microvilli- increase SA
- capillaries- good blood supply
- long villi- increase SA
- folded lining
epithelial cell thickness- 1 cell thick
67
where does nutrient absorption happen
ileum/duodenum an small intestine
68
what molecules are absorbed by ileum, duodenum, small intestine
- amino acids
- glucose
- glycerol
- fatty acids
- fructose
- galactose
- vitamin k
- folic acid
- water
69
how are these nutrients absorbed
- water- osmosis
- monosaccharides and amino acids- cotransport, active transport, facilitaed diffusion
- vitamin k and floic acid- simple diffusion
- fatty acids and glycerol- lymphatic vessels/lacteal
70
how are carbohydates and proteins digested finally
1. the dimers are broken by their respective enzymes using intrinsic/intracellular enzymes
2. na/k pumps are activated by ATP - na conc inside cell deacreaes
3. cotransport proteins allow diffusion of na coupled to glucose or amino acids
4. high conc of glucose and amino acids inside the cell
5. facilitated diffusion into interstitual space then blood cells
6. solute conc decreases, water potential increases so more water will flow into blood via osmosis
71
how are lipids absorbed into ileum
1. fatty acids and monoglycerides are diffusing into mucosal cells
2. triglycerides are synthesised in smooth endoplasmic reticulum
3. formation of chylomicrons
4. exocytosis of vesicles that contain chylomicrons (ATP is used)
5. entering the lymphatic vessels
72
what are chylomicrons
collection of triglycerides and phospholipids
73
what are intrinsic enzymes
embedded within the cell membrane of the epithelium
74
how are faceaes passed
passes along colon and is egested as solidified faeces (defaecation)
- cellulose fibre is required to provide bulk and stimulate peristalsis
75
what are the 4 parts the large intestine is divided into
- caecum
- ascending colon
- transverse colon
- descending colon
76
what are parasite
an organism that feeds on or in another organism, the host. the parasite gains nutrition at the expense of the host
77
whats the differebce between primary, secondary hosts and vectors
- The PRIMARY host organism is where the adult forms of the parasite develop.
- SECONDARY hosts are where larval / intermediate forms of the parasite are found.
- VECTORS are secondary hosts which actively and directly transfer the parasite from one primary host to another primary host (e.g. Malaria).
78
whats the difference between ectoparasites and endoparasites
ectoparasites live on another organism
endoparasites live in another organism
79
what is an example of an ectoparasite
a head louse (pediculus) which feeds by sucking blood from the scalp of the host
it claws to hold onto the haors and lays eggs which are glued to the base of hairs
transfer between hosts is direct contact
80
whats an example of an endoparasite
tapeworm
live in guts of humans- primary host
a larval form developed in pigs- secondary host
infection in humans occurs from eating undercooked pork containing live larval forms
81
how is a tapeworm adapted to live in the gut of humans
- thick cuticle to produce anti-enzymes
- a scolex (suckers) to attach to gut wall
- reduced gut and feeds by absorbing pre-digested nutrients through its cuticle
- produces large numbers of eggs that pass out in faeces to increase change of infection
- flat to incraes surface areas for absoprtion
- anaerobic respiration as no oxygen in gut lumen
82
what is the lifecycle of tapeworms
1. eggs released into the environment in faeces
2. secondary hosts eat vegetation contaminated with tapeworms
3. eggs hatch and larvae burrow through gut wall- then carried by blood around the body
4. larvae develop into cysts in muscle
5. humans eat undercooked or raw meat and get infected
6. scolex develops and attaches to wall of the small intestine
7. adults grow to 5cm and can survive for many years
