Nutrition Flashcards
1
Q
What is autotroph?
A
An organism that makes it’s own complex organic materials by photosynthesis or chemosynthesis.
2
Q
What is a photoautotroph?
A
An organism that uses light energy to make complex
organic materials.
3
Q
What is a Chemoautotroph?
A
An organism that uses chemical energy to make complex organic materials.
4
Q
What is a Heterotroph?
A
An organism that consumes ready-made complex organic
material (its food).
5
Q
What is Holozoic?
A
Feeding method of many animals, involving ingestion, digestion and egestion.
6
Q
What are Saprophytes?
A
Organism that feeds on dead, decaying matter by
extracellular digestion and absorption of the products of digestion.
7
Q
What are Parasites?
A
An organism that obtains nutrients from another living organism, its host, to which it causes harm.
8
Q
How do Unicellular organisms (Amoeba) gain nutrition?
A
Holozoic nutrition; obtain nutrients via diffusion/ facilitated diffusion/ active transport across the cell surface membrane; larger molecules/ microbes absorbed by endocytosis into food vacuoles; Products absorbed into cytoplasm and indigestible remains egested via exocytosis.
9
Q
How do simple multicellular organisms (Hydra) gain nutrition?
A
Extends its tentacles, discharges stinging cells
to paralyse prey; Tentacles move prey through the mouth to hollow body cavity; Endodermal cells secrete protease and lipase and prey is digested extracellularly; products of digestion absorbed into the cells and indigestible remains egested through the mouth.
10
Q
Why do larger, more complex organisms (humans) require a more complex digestive system?
A
More complex organisms have a more varied, complex diet.
11
Q
What is Saprotrophic nutrition?
A
Feed on dead or decaying matter. No specialised digestive system; Extend branching hyphae into the food material, secrete digestive enzymes from the tip of the hypha; Enzymes include proteases, lipases, amylases and cellulases;
Soluble products of digestion absorbed via diffusion and active transport.
12
Q
What is a decomposer?
A
Microscopic saprotrophs involved in decaying leaf litter and recycling nutrients.
13
Q
What is a detritivore?
A
A holozoic organism that feeds on decaying matter, that gets digested internally in a digestive system.
14
Q
What is the function of the Salivary Gland?
A
Produces saliva.
15
Q
What is the function of the oesophagus?
A
Carries food from the mouth to the stomach.
16
Q
What is the function of the stomach?
A
Produces hydrochloric acid.
17
Q
What is the function of the pyloric sphincter muscle?
A
Controls amount of food leaving the stomach.
18
Q
What is the function of the duodenum?
A
Receives juices from the gall bladder and pancreas.
19
Q
What is the function of the ileum?
A
Is where most digested food is absorbed.
20
Q
What is the function of the bile duct?
A
Takes bile from the gall bladder to the duodenum.
21
Q
What is the function of pancreas?
A
Produces enzymes which pass into the duodenum?
22
Q
What is the function of the gall bladder?
A
Stores bile.
23
Q
What is the function of the colon?
A
Is where most water is absorbed.
24
Q
What is the function of the rectum?
A
Stores waste faeces for several hours.
25
What is the function of the anus?
Controls the passing of faeces.
26
What is the Serosa and what's it's function?
Tough connective tissue, protecting the gut wall. The gut moves while processing food and the serosa reduces friction with other abdominal organs.
27
What is the muscle of the gut wall and what's it's function?
Comprises of 2 layers in different directions, the inner circular muscles and the outer longitudinal muscles. They make coordinated waves of contractions, peristalsis. Behind the ball of food, circular muscles contract and longitudinal muscles relax, pushing the food along.
28
What is the Submucosa and what's it's function?
Connective tissue containing blood and lymph vessels, which remove absorbed products of digestion and nerves that coordinate peristalsis.
29
What is the Mucosa and what's it's function?
The innermost layer and lines the gut wall. It's epithelium secretes mucus, lubricating and protecting the mucosa. In some regions of the gut, it secretes digestive juices and in others, absorbs digested food.
30
What are Peptic/chief cells?
They secrete pepsinogen, which is activated into pepsin, which hydrolyses large polypeptides into smaller polypeptides.
31
What are Oxyntic cells?
Secrete Hydrochloric acid. This kills bacteria, provides an optimum pH for pepsin and activates pepsinogen to pepsin.
32
What are Goblet cells?
They secrete mucus. This forms a protective layer on the stomach wall against pepsin and hydrochloric acid, In addition it aids in the movement of food within the stomach (lubrication).
33
What is Muscularis?
Contract and relaxes. It churns the food in the stomach to provide a larger surface area for chemical digestion.
34
What is the Pyloric Sphincter?
Contract and relaxes. So, food exists the stomach.
35
What are the features of the ileum which make it a good exchange surface?
Has a good blood supply (capillary network)-increases conc gradient. Has villi and microvilli to increase SA. Epithelial cells are one cell thick-decreases diffusion distance. Has blood and lacteal immediately under epithelial cells -decreases diffusion distance. It's permeable= has enzymes on surface to break it down and proteins for absorption embedded in membrane.
36
What is the process of the absorption of lipids/fats in the ileum?
-The fatty acids and glycerol (as a monoglyceride) diffuse across the membrane of the epithelial cells.
-Inside the cells they enter the SER and are recombined to form triglycerides.
-They are packaged into vesicles along with phospholipids and cholesterol.
-They are called Chylomicrons.
-The lipids are transferred from the cells into the lacteals in chylomicrons. They leave the cell by exocytosis.
-In the lymph system they are transferred to the subclavian vein from the thoracic duct.
37
What is the process of final digestion and absorption of carbohydrates and proteins (in the ileum)?
The enzymes which hydrolyse the dimers maltose, sucrose, lactose and dipeptides are cell membrane proteins of the small intestine epithelium. The monomers formed (various monosaccharides and amino acids) enter the epithelium by co transport and then pass to the blood by facilitated diffusion. To understand this process it's necessary to start with a sodium potassium pump.
-Na+ are actively transported out of the epithelial cells and into the blood.
-Against their concentration gradient. This requires ATP.
-This creates a low conc of NA+ inside the cell.
-Na+ move into the epithelial cells from the lumen of the ileum by cotransport with glucose.
-Na+ move down their conc gradient, bringing glucose with them.
-Glucose moves by facilitated diffusion from a high conc inside the epithelial cell to a low conc in the capillaries.
38
Describe mechanical digestion in the buccal cavity:
Salivary glands produce salivary amylase which breaks down starch to maltose.
Optimum pH 7-8 for salivary amylase.
-Mechanical digestion = chewing = mastication.
39
Describe mechanical digestion in the stomach:
Salivary amylase is denatures.
Large polypeptides are broken down to smaller polypeptides by pepsin. The inactive form of pepsin is pepsinogen, it is activated by HCL.
Optimum pH of 1-2 for pepsin.
40
Describe chemical digestion in the duodenum:
Pancreatic amylase breaks down starch/glycogen to maltose.
Trypsin breaks down large polypeptides to smaller polypeptides.
Exopeptidases break down smaller polypeptides to dipeptides and amino acids.
Lipase breaks down triglycerides to glycerol and fatty acids.
pH 8-optimum for all enzymes.
Endopeptidases of pepsin and trypsin hydrolyse the peptide bonds in the central/middle regions of the PPC. Exopeptidases hydrolyse the bonds at the terminal ends of the PPC.
Bile emulsifies the fat globules into smaller fat globules to increase surface area for the lipase enzymes to act on, therefore increasing the rate of hydrolysis.
41
Describe the chemical digestion in the ileum:
Maltase breaks down maltose into glucose + glucose.
Lactase breaks down lactose into glucose + galactose.
Sucrase breaks down sucrose into glucose + fructose.
Dipeptidases break down dipeptides into amino acids.
pH8 for all enzymes to work at optimum.
42
What is the fate of glucose in digestion?
Glucose is absorbed from
the blood by the cells for energy release in respiration and any excess is stored in fat cells.
43
What is the fate of amino acids in digestion?
Amino acids are absorbed by cells for protein synthesis. However, excess cannot be stored. Excess amino acids are taken to the liver where deamination occurs producing a respiratory substrate and urea (which is excreted).
44
What is the fate of lipids in digestion?
Lipids are used for membranes and hormones, excess are stored as fats.
45
What is the structure and function of the stomach?
Structure: continuous with oesophagus and duodenum. Located in the abdominal cavity, just below diaphragm. Described as a J shaped organ. Has muscular walls and gastric pits that secrete HCL and protease enzymes (pepsin).
Function: Muscular walls churn food and mechanically digest it. Oblique muscle layer. Contains HCL to kill any bacteria ingested. This is also the optimum pH (2) for protease enzymes, which start protein digestion.
46
What is the structure and function of the pancreas?
Structure: leaf shapes organ, below the stomach, has a pancreatic duct leading to the duodenum. Contains lobes known as islets of Langerhans-produce enzymes (exocrine).
Function: Contains both exocrine glands (that secrete digestive enzymes endopeptidase pancreatic amylase and lipase into the duodenum via the pancreatic duct) and endocrine glands (that secrete insulin and glucagon into the blood) to regulate blood glucose levels.
47
What is the structure and function of the Gall bladder?
Structure: underneath the liver with a bile duct that leads to the pancreatic duct.
Function: Stores bile produced by the liver and releases it via the bile duct, then pancreatic duct, into the duodenum. The bile has a pH of 3 to neutralise the stomach acid.
48
What is the structure and function of the duodenum?
Structure: first 25cm of small intestine. Curves from the stomach around the pancreas. Secretions from the gall bladder and pancreas are added via the pancreatic duct.
Function: connects the stomach to the rest of the small intestine. Site of neutralisation of the stomach acid using the bile from the gall bladder. Site of action for endopeptidase (trypsin), pancreatic amylase and lipase secreted from the pancreas.
49
What is the structure and function of the ileum?
Structure: Majority of small intestine. Highly folded into villi with a vast blood supply. Villi covered by epithelial cells with many microvilli to increase the surface area.
Function: Microvilli-site of absorption of the products of digestion, which then move into the bloodstream (glucose and amino acids) or lymphatic system (lipids via chylomicrons) and removed.
50
What is the structure and function of the colon?
Structure: Starting on the lower right side of the body, the colon goes up, across and then down the left side of the body, surrounding the small intestines. It as very muscular walls.
Function: Site of water absorption. Pushes faeces along using the muscular wall to the rectum. Large number of beneficial bacteria that produce vitamins such as B12 and folic acid.
51
Describe Carbohydrate digestion:
-In the mouth the enzyme salivary amylase starts to hydrolyse (break a bond by inserting water) starch to maltose.
-In the duodenum, pancreatic amylase continues to hydrolyse the glycosidic bonds in starch to maltose.
-Maltose is then hydrolysed to glucose by maltase enzymes embedded in the membrane of the epithelial cells lining the ileum.
52
Describe glucose absorption:
Only glucose is small enough to move across the epithelial cell membrane, and be absorbed (carried across the cell into the blood). They are absorbed by facilitated diffusion and active transport using specific carrier proteins. One mechanism responsible for absorption of glucose is a process called co transport. Through this mechanism glucose is absorbed into the epithelial lining of the small intestine. Sodium ions actively transported out of epithelial cell into the blood by sodium potassium pump, this action uses energy in the form of ATP. The active transport of sodium ions out of the cell maintains the diffusion gradient/conc gradient which drives the facilitated diffusion of sodium ions into the cell from the lumen. As the sodium ions are carried into the epithelial cell via a co transport carrier protein they carry glucose molecules with them passively. The movement of glucose into the cell (from the lumen) creates a conc gradient which drives the facilitated diffusion of glucose from the cell into the blood.
53
Describe protein digestion:
Proteins are hydrolysed by enzymes called protease. This process begins in the stomach. Pepsin, an endopeptidase with an optimum pH of 2 hydrolyses the peptide bonds within a polypeptide chain. This produces many smaller polypeptide chains. Pepsin has acidic optimum pH and so it does not denature in the stomach acid and can still function.
In the duodenum, trypsin is added, this is another endopeptidase. It's optimum pH is 8, the pH of the pancreatic juice and bile added to the duodenum. Exopeptidases are also found in the pancreatic juice, they hydrolyse the peptide bonds at the end of the protein.
If any dipeptides are produced, then dipeptides-embedded in the cell surface membrane of the epithelial cells of the ileum hydrolyse these into amino acids.
54
Describe amino acid absorption:
(Similar to co transport with Na+ and glucose, just different proteins for amino acids).
Only amino acids are small enough to move across the epithelial cell membrane, and be absorbed into the blood. Amino acids are absorbed by facilitated diffusion and active transport using specific carrier proteins. This process also occurs during selective reabsorption in the PCT of the kidney nephron.
55
Describe lipid digestion:
Lipids are only digested within the lumen of the small intestine. Bile is produced in the liver, stored in the gallbladder, it is released into the duodenum via the bile duct, then pancreatic duct.
Bile contains bile salts which emulsify fat droplets=increase SA:V for lipase enzymes to act on.
The enzyme lipase from the pancreatic juice, hydrolyses ester bonds in lipids into glycerol, fatty acids and monoglycerides. This happens in the duodenum at pH 8.
56
Describe lipid absorption:
Fatty acids and monoglycerides are emulsified by bile salts to form micelles.
Fatty acids enter the epithelial cells and link to form triglycerides.
Triglycerides combine with proteins inside the Golgi body to form chylomicrons.
Chylomicrons enter the lacteal and are transported away from the intestine.
57
What is an Ectoparasite?
Organisms that live on another organism.
58
What is an Endoparasite?
Organisms that live in another organism.
59
What is a primary host?
Where the adult forms of the parasite develop.
60
What is a secondary host?
Where larval/intermediate forms of the parasite are found.
61
What does a head louse feed on and how is it adapted for this?
Both adults and larval stages of headlice feed on blood. It lives on the head where it clings to hairs using strong claws. The eggs are laid and glued to the base of hairs.
Gut-feeds by holozoic nutrition.
Piercing mouthparts (feeds on blood).
62
How is a tapeworm adapted to prevent it being dislodges by peristalsis?
The scolex is embedded in the gut wall and has hooks and suckers to prevent it being dislodged by peristalsis.
63
Why doesn't a tapeworm have a digestive system?
There is no digestive system or mouth as the tapeworm only needs to absorb nutrients that have already been digested.
64
Why is the body of a tapeworm flattened?
To increase the surface area for absorption of nutrients from the gut contents.
65
Why do tapeworms secrete mucus and other chemicals?
They secrete mucus and enzyme inhibitors to reduce the risk of digestion.
66
Why does a tapeworm not need another tapeworm to sexually reproduce?
Each proglottid is hermaphrodite containing both male and female reproductive organs. Therefore it doesn't need to find a mate as it can self-fertilise.
67
Why are so many eggs released from a tapeworm?
Each proglottid can contain about 50,000 eggs, this increases the chance of infecting another host.
68
Describe sequence of events tapeworm goes through to infect a host:
Eggs released into the environment in faeces. Secondary hosts eat vegetation contaminated with tapeworm eggs. The eggs hatch and larvae burrow through gut wall-then carried in the body. Larvae develop into cysts in muscle. Humans eat undercooked or raw meat and get infected. Scolex develops and attaches to the wall of the small intestine. Adults grow to 5cm long and can survive for many years.
69
Why is the tapeworm body surface folded and has projections called microtriches?
Further increase of surface area for absorption.
