Adaptations For Nutrition

Question 1

• Give an example of a unicellular organism
• What kind of nutrition do amoeba use
• What celled are amoeba and how does this affect their surface area to volume ratio
• State three ways they obtain nutrients though their cell membrane and give 2 examples of these nutrients

Answer 1

• Amoeba is an example of a
  unicellular organism
• Amoeba like other protoctists use holozoic nutrition
• They are single - celled so have a large surface area to volume ratio
• They obtain nutrients such as oxygen and glucose through their cell membrane.via: diffusion, facilitated diffusion, active transport

Question 2

• Describe and explain how they take in large food molecules such as bacteria and microscopic algae
• What do the food vacuoles fuse with, what do they contain and what happens to the products of digestion
• What happens to the indigestible remains?

Answer 2

• Through endocytosis. The food molecules are surrounded by membranes, forming vacuoles
• The food vacuoles fuse with lysosomes containing hydrolytic enzymes which digest the contents of the food vacuoles. The products of digestion are absorbed into the cell cytoplasm
• Indigestible remains are egested by exocytosis

Question 3

• What are hydra ( shape, tentacles, digestive system)

Answer 3

• Hydra are multicellular fresh water animals. They are in the same phylum as jellyfish. They are cylindrical in shape and contain tentacles at the top of the body which contain stinging cells
• They have an undifferentiated digestive system

Question 4

• How do they ingest prey
• What happens to the products of digestion
• How are the indigestible remains egested
• What kind of opening do they have in their digestive system

Answer 4

• Their tentacles move paralysed prey in though the mouth and into the sac-like hollow body cavity where the prey is digested
• The products of digestion are then absorbed into the body cells
• Indigestible remains are egested through the mouth
• They have a single opening in their digestive system

Question 5

• Give examples of organisms that have a tube gut
• Most animals have a distinct ………….. and ……….. end
• How many opening does the digestive system have
• Where is food ingested
• Where is indigestible food egested

Answer 5

• Worms ( Earthworms and flatworms)
• Anterior and Posterior
• Digestive system that is a tube with two openings
• Food is ingested at the mouth
• Indigestible waste is egested at the anus

Question 6

• Give three reasons Why must food be digested

Answer 6

• Large polymers must be hydrolysed into their smaller monomers
• Large insoluble molecules in food are hydrolysed into smaller soluble molecules
• So that the molecules can be absorbed into the bloodstream and assimilated into molecules needed by body cells

Question 7

• List the 4 main functions that the Human gut performs in order
• What is ingestion and where does it take place in the digestive system

Answer 7

• Ingestion, Digestion, Absorption, Egestion
• Ingestion is the first part of the digestive system and it is the process of taking food into the body through the mouth

Question 8

• What is digestion and what stage does it occur at

Answer 8

• Digestion is the breakdown of large insoluble molecules into soluble molecules that are then small enough to be absorbed into the blood. It is the second stage of the digestive system

Question 9

• State and explain the two types of digestion

Answer 9

• Mechanical digestion: cutting and crushing by teeth and muscle contractions of the gut wall, increases the surface area over which enzymes can act
• Chemical digestion: breakdown using digestive enzymes. Bile and stomach acids also contribute to this

Question 10

• What is absorption?

- What is egestion?

Answer 10

• Absorption: The passage of small soluble molecules and ions through the gut wall into the blood
• Egestion: the elimination of indigestible waste e.g. cellulose (dietary fibre)

Question 11

• Where do digestion and absorption occur
• What is the gut
• State and explain the process which propels food along the gut
• What do the circular muscles do and what is bolus
• What aids peristalsis in the intestines

Answer 11

• They both occur in the gut
• The gut is a long hollow muscular tube which allows movement of its content in one direction only. Each section is specialised and forms particular steps in the process of chemical and mechanical digestion and absorption
• The process that propels food along the gut is peristalsis: is the wave of muscular contractions and relaxations of the gut which propel the contents along the whole length of the gut
• Circular muscles contract behind the bolus (ball of food) and then relax after the wave of contraction has passes
• Dietary fibre aids peristalsis in the intestines

Question 12

• Give another name for the human digestive system
• State the function of mouth (buccal cavity)
• State the function of the oesophagus

Answer 12

• Alimentary canal
• Mouth (buccal cavity): Ingestion. Mechanical digestion of food due to crushing action of the teeth. Chemical digestion of starch by salivary amylase
• Oesophagus: carriage of food to the stomach by peristalsis

Question 13

State the function of:

• Stomach
• Duodenum
• Ileum

Answer 13

• Stomach: contraction of stomach muscles to churn up the food - mechanical digestion. Secretion of hydrochloric acid. Chemical digestion of proteins by enzymes
• Duodenum: receives pancreatic juice from the pancreas and bile from the gall bladder. Chemical digestion of carbohydrates, fats and proteins by enzymes
• Ileum: chemical digestion of carbohydrates, fats and proteins by enzymes and absorption of digested food.

Question 14

State the function of:

• Colon
• Rectum
• Anus

Answer 14

• Colon: absorption of water
• Rectum: storage of faeces
• Anus: site of Egestion

Question 15

• What is the outermost layer of the mammalian gut wall called and what is its function and what does it contain
• What tissue layer comes after The outermost layer - how many layers is it composed off and what do both these layers do

Answer 15

• Serosa: outermost later contains tough connective tissue which protects the gut wall. It helps to reduce friction with other abdominal organs during peristalsis.
• Muscularis: composed of two layers: the inner circular muscles and the outer longitudinal muscles. They make coordinated waves of contraction (peristalsis), pushing the ball (bolus) of food along the alimentary canal.

Question 16

• What layer comes after the submucosa - what does the layer consist of and state the function
• What is the inner layer of the mammalian gut wall. What does it have that secretes mucus - function of the mucus and what does it do in different regions of the gut

Answer 16

• submucosa: consists of connective tissue containing blood and lymph vessels which remove the absorbed products of digestion. This layer also contains the nerves which
  coordinate peristalsis.
• Mucosa: innermost layer- Epithelium secretes mucus which lubricates and protects the mucus. In some regions of the gut, it secretes digestive juices and in others, it absorbs digested food.

Question 17

• How is absorption in the gut epithelial cells possible
• What is starch hydrolysed into and what enzyme is involved in this process
• What does the product of starch hydrolysis break down into and what enzyme is present in this process
• What is lactose hydrolysed to and by what enzyme
• What is sucrose hydrolysed into and by which enzyme

Answer 17

• Is only possible if larger molecules i.e. carbohydrates, fats and proteins are first digested into smaller molecules.
• Starch is hydrolysed into maltose by the enzyme amylase
• Maltose breaks down into Alpha Glucose and this reaction is hydrolysed by the maltase enzyme
• Lactose is hydrolysed into glucose + galactose by lactase
• Sucrose is hydrolysed into glucose + fructose by sucrase

Question 18

• Describe the breaking down of proteins
• What is an endopeptidase. Give 2 examples
• What is an exopeptidase?
• What are fats hydrolysed by and what are the products of this hydrolysis

Answer 18

• Polypeptides ——> Dipeptides ——> Amino Acids
• Endopeptidases hydrolyse peptide bonds within the protein molecule such as pepsin and trypsin
• Exopeptidases hydrolyse peptide bonds at the end of shorter polypeptide chains to make amino acids/ dipeptides
• Fats are hydrolysed by lipase and the products are fatty acids and glycerol.

Question 19

• What happens in the buccal cavity (type of digestion and how this affects surface area)
• Saliva is a watery secretion containing which enzyme and state the other two products stating their function
• What is the purpose of the oesophagus

Answer 19

• Mechanical digestion occurs in the mouth - Food is mixed with saliva by the tongue and chewed with the teeth which increases the surface area of the food for the enzymes to work on.
• Saliva contains : Amylase which breaks starch down to maltase, Bicarbonate ions which creates an optimum pH (slightly alkaline) for amylase and Mucus which lubricates the food
• Oesophagus has no role in digestion but connects the buccal cavity to the stomach

Question 20

• How is the bolus of food kept in the stomach (which muscle)
• How long can the swallowed food stay in the stomach for?
• Why do the stomach wall muscles contract rhythmically?
• Where is gastric juice secreted from?

Answer 20

• Bolus of food enters stomach and is kept there by contraction of the sphincter muscles.
• Swallowed food can remain in the stomach for several hours
• The stomach walls muscles contract rhythmically to churn food
• Gastric juice is secreted from gastric glands in the mucosa of the stomach wall.

Question 21

• Gastric juice contains: Mucus, Hydrochloric acid and Pepsin: State the function of all these
• How is active pepsin formed
• Why are enzymes secreted in an inactive form

Answer 21

• Mucus is secreted by goblet cells which line the mucosa. It forms a protective lining which protects the stomach wall from digestive enzymes and hydrochloric acid and helps to lubricate the food
• Hydrochloric acid - Lowers the pH of the stomach contents to pH2 to create an optimum environment for enzymes and kills bacteria.
• Pepsin is secreted as inactive pepsinogen. This is a peptidase which works optimally in the acidic environment of the stomach.
• Activation of pepsinogen by hydrochloric acid (HCl) forms active Pepsin
• As the active form would digest the cells of the stomach wall (autolysis)

Question 22

• What are the two regions that the small intestine consists of?
• How is the partially digested food released into the duodenum?
• ## What is partially digested food known as?

Answer 22

• The two regions are the duodenum and the ileum
• Relaxation of the sphincter muscles at the base of the stomach releases the partially digested food into the stomach
• Known as Chyme.

Question 23

• Which section of the duodenum is the small intestine and what is its function.
• What happens to the food coming from the stomach ( Mucus, HCl, Sub - Mucosa)
• Where is bile made, stored and how is it passed into the duodenum

Answer 23

• The duodenum is the first section of the small intestine and receives secretions from the liver and the pancreas.
• Food coming from the stomach is lubricated by mucus and the hydrochloric acid is neutralised by alkaline secretions (NaHCO3) from cells in the sub mucosa
• Bile is made in the liver, stored in the gall bladder and passed through the bile duct into the duodenum

Question 24

• What does bile contain and state two properties of this bile product
• What is the function of bile salts and how do they affect the surface area for lipase action
• Is bile acidic or alkaline and how does this affect enzymes in the small intestine.

Answer 24

• Bile contains Bile salts which are both hydrophilic and hydrophobic
• They emulsify lipids present in the partially digested food and breaking up large globules into smaller droplets, thus increasing the surface area for lipase action.
• Bile is alkaline and neutralises the acid in the food coming from the stomach creating an optimum pH environment for the enzymes in the small intestine.

Question 25

• How is pancreatic juice secreted and how does it enter the duodenum?
• ## State and explain the functions of 4 enzymes involved in pancreatic secretion?

Answer 25

• Pancreatic juice is secreted by specialised cells in the pancreas and it enters the duodenum through the pancreatic duct.
• The 4 enzymes are: Endopeptidase, Trypsinogen, Pancreatic amylase, Lipase.
• Endopeptidases: Hydrolyses protein to shorter polypeptides
• Trypsinogen: Inactive enzyme converted into the endopeptidase trypsin by enterokinase
• Pancreatic amylase: Chemically digests any remaining starch to maltose
• Lipase: Hydrolyses lipids into fatty acids and glycerol

Question 26

• What two products does the duodenum secrete (duodenal secretion) and give their function
• What is the function of enterokinase

Answer 26

• The Duodenum secretes Sodium Hydrogen Carbonate and enterokinase
• Sodium Hydrogen Carbonate - raises the pH to make pancreatic juice more alkaline
• Enterokinase is an enzyme that converts trypsinogen to trypsin.

Question 27

• List the 4 features which makes the ileum well adapted for absorption
• What are the 2 specialised cells found in the mucosa of the ileum.

Answer 27

• It is very long (around 6 metre)
• Its lining is folded
• On the surface of the folds are villi
• The epithelial cells lining the villi have microscopic projections called microvilli.
• The two specialised cells are : Columnar epithelial cells and Goblet cells

Question 28

• What are the two main adaptations of the columnar epithelial cells
• What do goblet cells secrete and how does this impact the small intestine

Answer 28

2 main adaptation:

• Microvilli providing a large surface area for absorption of the products of digestion
• Large numbers of mitochondria to produce ATP energy for Active Transport
• Goblet cells secrete mucus, which lubricates and protects the lining of the intestine.

Question 29

• Where are endopeptidases and exopeptidases secreted from and where into
• What are dipeptides hydrolysed into
• What do Carbohydrates on epithelial cell membranes hydrolyse. What then happens to the products of Carbohydrates Hydrolysis.

Answer 29

• Endopeptidases and exopeptidases are secreted by cells at the tips of the villi into the gut lumen and continue the digestion of polypeptides
• Dipeptides are hydrolysed to amino acids by enzymes on the cell membranes of epithelial cells.
• They hydrolyse disaccharides into monosaccharides (alpha glucose). The monosaccharides can then be absorbed into the epithelial cells.

Question 30

In Crohn’s Disease villi in the small intestine are destroyed. Suggest how this could lead to diarrhoea

Answer 30

• Less microvilli or shorter villi
• Reduced Surface area
• Less enzymes on the membranes
• Reduces digestion so less absorption of products of digestion (e.g. amino acids or glucose)
• More solute in the lumen so lower water potential
• Less water absorption so water moves from epithelial cells into lumen = Diarrhoea

Question 31

• What is the transport mechanism of Glycerol and fatty acids from the lumen into epithelial cells
• Then from epithelial cells into capillary/lacteal
• What is the transport mechanism of glucose and galactose from lumen into epithelial cells
• Then from epithelial cell into capillary/ lacteal

Answer 31

• Diffusion and then reassembled into triglyceride : from lumen into epithelial cells
• Diffusion into lacteal then carried via lymphatic system to the blood
• Co Transport with Na+ from lumen into epithelial cells
• Then facilitated diffusion into the capillary

Question 32

State the transport mechanisms from lumen into epithelial cells and then from epithelial cells into capillary/ lacteal for:

• Na+
• Amino Acids
• Water

Answer 32

• Na+ : Co Transport with glucose from lumen into epithelial cells and then facilitated diffusion into capillary
• Amino Acids: Active Transport from lumen into epithelial cells and then facilitated diffusion into capillary
• Water: Osmosis from lumen into epithelial cell and then osmosis into capillary from epithelial cells.

Question 33

• What is the name of the vein that transports substances absorbed in the blood into the liver
• Give 3 uses of products of digestion ( Glucose + Amino Acids
  + Lipids)

Answer 33

• Hepatic Portal Vein
• Glucose: Required for aerobic respiration. Excess stored as glycogen
• Amino Acids: Used for protein synthesis. Excess is deaminated in the liver.
• Lipids (Glycerol + Fatty acids): Energy storage, Protection of vital organs and thermal insulation under the skin.

Question 34

• What 4 sections are the large intestine divided into
• What happens to indigestible foods, cells bacteria and undigested cellulose when it reaches the rectum
• Give 3 substances absorbed in the large intestine

Answer 34

• Caecum, the appendix, the colon and the rectum
• By the time it reaches the rectum, indigestible food, cells, bacteria and undigested cellulose have become faeces, which will be egested
• Water, mineral ions and vitamins produced by symbiotic bacteria in the gut, like Vitamin K and folic acid.

Question 35

• What is nutrition the process of?

- What is autotrophic nutrition?

Answer 35

• Nutrition is the process by which organisms obtain energy to maintain life functions, and matter to create and maintain structure
• Autotrophic organisms synthesise their own complex organic molecules from simpler molecules using either light or chemical energy.

Question 36

• State the two different types of autotrophic nutrition describing the differences and giving examples for both

Answer 36

• Photoautotrophic organisms e.g. green plants, algae and some bacteria - use energy from sunlight to carry out photosynthesis to make organic molecules (glucose) from inorganic molecules carbon dioxide and water
• Chemoautotrophic organisms use energy from chemical reactions to synthesise organic molecules. Examples of these organisms are bacteria respiring in deep sea hydrothermal vents.

Question 37

• What is heterotrophic nutrition?

- Give 4 examples of heterotrophs

Answer 37

• Heterotrophic organisms cannot produce their own organic molecules so they consume complex organic molecules from other organisms. They then break this material down into smaller, soluble molecules which they can absorb and assimilate
• Animals, fungi, some protoctista and some bacteria

Question 38

Explain how active transport of Na+ from the epithelial cells into the blood helps with the passage of glucose from the lumen into the blood.

Answer 38

• Lower concentration of Na+ in epithelial cells, which creates concentration gradient for Na+
• Na+ and glucose enter epithelial cell from lumen by co-transport
• Increase glucose concentration in cell, which creates a concentration gradient for glucose
• Glucose moves into blood by facilitated diffusion

Question 39

State the 3 types of heterotrophic nutrition:

Answer 39

1- Holozoic Nutrition
2- Saprotrophic Nutrition
3- Parasitic Nutrition

Question 40

• What is holozoic nutrition?
• What organisms use holozoic nutrition?
  What is a:
• Carnivore
• Herbivore
• Omnivore
• Detritivore

Answer 40

• When organisms ingest food, digest it and then egest any indigestible remains
• Mostly animals, but also some protoctists such as amoeba
• Carnivore - only eat other animals
• Herbivore - Only eat plant material
• Omnivore - Eat both plant and animal material
• Detritivore - Feed on dead and decaying matter

Question 41

• What organisms carry out Saprotrophic nutrition?
• What do Saprotrophs feed on?
• What kind of digestion do they carry out and explain the process of this digestion
• Define Decomposers

Answer 41

• All fungi and some bacteria
• They feed on dead and decaying matter
• They carry out extracellular digestion
• Enzymes are secreted onto the food material outside of their body (e.g. amylases, proteases and cellulases)
• They can absorb the soluble products of digestion into their cells by diffusion or active transport
• Decomposers are microscopic saprotrophs that play an important role in decaying leaf litter and recycling nutrients such as nitrogen

Question 42

• What is a parasite
• Give some examples of parasites
• Difference between endoparasite and ectoparasite
• What are plants and animals parasitized by
• What are animals also parasitized by
• What is Bacteria parasitized by

Answer 42

• Parasites are organisms that live on or in another organism, called the host, and obtain nourishment at the expense of the host. Parasites therefore cause harm and often cause death.
• The pork tapeworm, fungus potato blight and human head-lice
• Endoparasites lives in the host whereas an ectoparasite lives on the host
• Plants and animals are parasitized by bacteria, fungi, viruses, nematodes and insects
• Animals are also parasitized by Protoctista, tapeworms and mites
• Bacteria can be parasitized by viruses called bacteriophages.

Question 43

• What is the pork tapeworm?
• State 3 features of a tapeworm
• What are the two hosts stating whether they are primary or secondary
• Explain the lifecycle of a tapeworm

Answer 43

• ## Is a gut endoparasite it is an example of a specialised parasite which has undergone considerable evolutionary changes in order to survive. Has no competition and cannot be preyed upon