2.4 Adaptations For Nutrition Flashcards
1
Q
Define an autotroph
A
An organism that synthesises its own complex organic molecules from simpler molecules using either light or chemical energy
- photoautotrophs and chemoautotophs
2
Q
Define hetereotrophs
A
An organism that obtains complex organic molecules by consuming other organisms
3
Q
Define sapotrophs
A
An organism that derives energy and raw materials for growth from the extracellular digestion of dead or decaying material
4
Q
Explain parasitic nutrition
A
- obtaining nutrition from another living organism, the host
- endoparasites live in the body of the host whereas exoparasites live on the surface
- host tends to suffer harm and occasionally death
5
Q
Explain holzoic nutrition
A
- used by most animals
- ingest food, digest food and egest the indigestible remains
- herbivores, carnivores, omnivores
6
Q
How do single celled organisms like amoeba obtain nutrients?
A
- diffusion, facilitated diffusion or active transport across cell membrane
- take in larger molecules and microbes by endocytosis into food vacuoles which fuse with lysosomes
- indigestible remains egested by exocytosis
7
Q
Nutrition in single body opening organisms like Hydra
A
- tentacles paralyse prey
- tentacles move prey into mouth and into hollow body cavity
- prey digested extracellularly and products are absorbed
- indigestible remains are egested through mouth
8
Q
What is used for many multicellular organisms?
A
- tube gut
- posterior and anterior opening
- variable complexities
9
Q
Why must food be digested?
A
- molecules are insoluble and too big to cross membranes and be absorbed by blood
- many are polymers and must be converted to monomers
10
Q
What propels food along gut?
A
Peristalsis
11
Q
What are the functions of the gut?
A
- ingestion
- digestion
—> mechanical and chemical - absorption (gut wall to blood)
- egestion
12
Q
Outline function of parts of digestive system
A
- mouth: ingestion, digestions of starch and glycogen
- oesophagus: carriage of food to stomach
- stomach: digestion of protein
- duodenum: digestion of carbs, fats and proteins
- ileum: digestion of carbs, fats and proteins, and absorption of digested food and water
- colon: absorption of water
- rectum: storage of feces
- anus: egestion
13
Q
What are the 4 layers surrounding the lumen of the gut?
A
Mucosa, sub mucosa, muscle, serosa
14
Q
What is serosa?
A
- outermost layer of the gut
- tough connective tissue protecting gut wall
- reduces friction with other abdominal organs
15
Q
What is muscle?
A
- inner circular muscles and outer longitudinal muscles
- make coordinated contractions of the gut known as peristalsis
- circular muscles contract and longitudinal relax
16
Q
What is submucosa?
A
- connective tissue containing blood and lymph vessels which remove absorbed products of digestion
- nerves that coordinate peristalsis
17
Q
What is mucosa?
A
- innermost layer that lines the gut wall
- epithelium secretes mucus to lubricate and protect the mucosa
18
Q
Explain the digesting of carbohydrates
A
- poly to di to mono
- amylase hydrolyses starch and glycogen to maltose which is hydrolysed to glucose by maltase
- sucrase and lactase
- carbohydrate enzymes as the umbrella term
19
Q
Explain the digestion of proteins
A
- poly to di to amino
- protease and peptide enzymes
- endopeptidases hydrolyse peptide bonds within protein molecules and exopeptidases hydrolyse terminal peptide bonds
20
Q
Explain the digestion of fats
A
- digested to fatty acids and monoglycerides by lipase
21
Q
How is the buccal cavity specialised for digestion?
A
- mechanical digestion occurs here - food mixed with saliva by tongue and chewed by teeth
—> saliva contains amylase (digestion of starch and glycogen), HCO3- ions and CO32- ion, and mucus to lubricate food down oesophagus
22
Q
How is the stomach specialised for digestion?
A
- food kept in by contraction of 2 sphincters (rings of muscle)
- walls contract rhythmically and mix food with gastric juice secreted by gland in stomach walls
—> peptidases secreted by zygmogen cells, pepsinogen (inactive) is secreted and activated by H+ ions to pepsin, HCl secreted by oxyntic cells to lower pH of stomach acid and kill bacteria in food, mucus secreted by goblet cells to form a lining that protects the stomach walls from enzymes
23
Q
What are the 2 regions of the small intestine?
A
Duodenum and ileum
24
Q
Where is bile made and stored?
A
- made in liver
- stored in gall bladder
25
Describe bile
- no enzymes
- bile salts which are amphipathic
—> emulsify lipids to increase SA for digestion by lipase
- alkaline and neutralises food coming from stomach
26
What is pancreatic juice?
- secreted by islet cells (exocrine glands in pancreas)
- enters duodenum via pancreatic duct
27
Describe pancreatic juice
- trypsinogen - inactive enzyme converted to the endopeptidase trypsin by enterokinase
- endopeptidases - hydrolyse proteins
- amylase - digests any remaining starch to maltose
- lipase - hydrolyses lipids to fatty acids and monoglycerides
- sodium hydrogen carbonate - raises pH to make slightly alkaline to neutralise stomach acid and provide appropriate pH for pancreatic enzymes
28
What are villi?
- finger like projections on the ileum
- synthesise digestive enzymes
29
What happens to food coming from the stomach to small intestines?
- lubricated and neutralised by alkaline solutions from cells at the base of the crypts of Lierberkuhn called Brunners glands
30
Role of endo and exo peptidases in the small intestine
- peptidases secreted by villus epithelial cells and digestion continues in the gut lumen
- dipeptidases in cell surface membranes digest peptides to amino acids
31
Where does absorption occur?
- mainly in the small intestine via diffusion, facilitated diffusion and active transport
32
How are amino acids absorbed in SI?
- epithelial cells by active transport and pass into capillaries by facilitated diffusion
- water soluble and dissolve into plasma
33
How is glucose absorbed in SI?
- passes into epithelial cells with sodium ions by co transport in facilitated diffusion
- not all absorbed so some bought into cells by active transport to prevent being egested
34
How are fatty acids absorbed in SI?
- diffuse into epithelial cells and lacteal
—> lacteal: blindly ending lymph capillary in the villi
- part of lymphatic system that transports fat soluble molecules to left subclavian vein near heart
35
How are vitamins absorbed by the SI?
- A and B: absorb into blood
- A,D,E: fat soluble so absorbed into lacteals
36
Use of lipids once digested
- membranes
- some hormones
- excess stored
37
Many absorbed substances are taken in hepatic portal vein to liver. What happens to glucose and amino acids?
- glucose to body cells for energy or glycogen storage, excess as fat
- amino acid taken to cells for PS. Excess cannot be stored so converted to urea and excreted by kidney
38
What are the components of the large intestine?
- caecum
- appendix
- colon
- rectum
39
Explain role of colon
- stores undigested food, bacteria, mucus and dead cells
- less villi but large role in water absorption
- vitamin K and folic acid are secreted by mutalistic microorganisms in colon
- water and minerals absorbed
- semi-solid material reaches rectum and is egested by defecation
40
Carnivore
- only animals so high protein diet
- short SI, straight and smooth LI
41
Herbivore
- eat only plant material
- long SI, pouched LI
42
Describe the dentition of herbivores
- teeth modified to grind plant cell walls before enter stomach
- grazing herbivore has incisors on lower jaw and the canine teeth are indistinguishable from incisors in shape and size
—> cut the grass
- diastema separates front teeth from side teeth (premolars)
- molars interlock like a W in an M
—> circular grinding action on horizontal plane over time exposes sharp edged enamel ridges to increase grinding efficiency
—> open unrestricted lots so teeth contour to grow, replacing worn material
- smooth skull as no need for jaw muscle
43
Describe dentition of carnivores
- adapted for catching and killing prey, cutting/crushing bones and tearing meat
- sharp incisors to grip and tear muscle from bone
- canine teeth are larger and curved, pointed for piercing
- premolars and molars have cusps which crush
- specialised cheek teeth called carnassials that are like scissor blades
- lower jaw moves vertically
- well developed jaw muscles, protrusions on skull
44
Define a ruminant
- a cud chewing herbivore possessing a ‘stomach’ divided into 4 chambers
—> rumen is the largest, contains mutualistic microbes
- adapted to enable digestion of beta glycosidic bonds in cellulose
45
Ruminant digestion of cellulose
- grass cut by teeth, mixed with saliva to form cud
- food mixed with microbes in rumen - secrete enzymes which digest cellulose to glucose
- glucose fermented to organic acids that are absorbed in blood
C6H12O6 ——> 2CH3COOH + CH4
- fermented grass pass to reticulum and reformed to cud, then regurgitate to mouth for more chewing
- cud to omasum where water and organic acids absorbed to blood
- the obomasum is true stomach where protein is digested by pepsin
- SI and LI function comparable to human
46
Structural modifications of the pork tapeworm
- scolex with suckers and hooks to attach to duodenum wall
- thick cuticle to protect from enzymes and hosts immune system
- makes enzyme inhibitors
- reduced gut to allow absorption on whole body
- hermaphrodite - male and female reproductive organs
- eggs have resistant shells
47
Why does tapeworm rely on anaerobic respiration?
Oxygen levels too low for aerobic in the intestije
48
Features that are important to the functioning of the villus
- microvilli to increase surface area for absorption
- larger capillary network to maintain diffusion gradient
- lacteal to absorb lipids
- thin epithelium for short diffusion pathway
49
Brunners glands and their role
- tubular submucosal glands found in duodenum
- secrete alkaline solution containing bicarbonate, protect from acidic stomach content
- could conditions for intestinal enzymes
50
What is food called during digestion
- bolus
- chyme
