Biology Unit 2 Topic 4

Front 1

what are the types of living organisms?

Back 1

Autotrophic organisms; photoautotrophic organisms and chemoautotrophic organisms

Heterotrophic organisms; saprotrophic organisms, parasitic organisms, and holozoic organisms.

Front 2

Explain photoautotrophic organisms

Back 2

Can make its own nutrients as it can convert simple inorganic molecules into complex molecules. Uses light energy to carry out photosynthesis.

Front 3

Explain chemoautotrophic organisms

Back 3

Can make its own nutrients as it can convert simple inorganic molecules into complex molecules. Uses energy from chemical reactions

Front 4

Explain saprotrophic organisms

Back 4

Gets their nutrients by secreting extracellular enzymes which break down decaying/dead matter and then reabsorb the digested products into the cell.

Front 5

Explain parasitic organisms

Back 5

Gets their nutrients from other organisms. Usually happens over a long period of time and can cause harm to the host. Includes endoparasites and ectoparasites.

Front 6

Explain holozoic organisms

Back 6

Ingest then digest their food, to absorb the nutrients. Includes, herbivores, omnivores and carnivores.

Front 7

Give an example of photoautotrophic organisms

Back 7

kelp

Front 8

Give an example of chemoautotrophicorganisms

Back 8

Nitrogen-fixing bacteria

Front 9

Give an example of saprotrophic organisms

Back 9

Mushrooms

Front 10

Give an example of parasitic organisms

Back 10

Tapeworms

Front 11

Give an example of holozoic organisms

Back 11

Lions

Front 12

Explain the differences between mechanical digestion and chemical digestion

Back 12

Chemical digestion uses enzymes and hydrolyses molecules into smaller molecules. This means chemical bonds are broken. Water is required. Mechanical digestion does not use enzymes. It uses the cutting and crushing action of teeth and rhythmic contractions of the gut. This increases the surface area of the food to aid chemical digestion by enzymes. This process is not featured on chemical digestion.

Front 13

Explain why chemical digestion is useful to help enzymes in digestion

Back 13

Mechanical digestion increases the surface area of the food which increases the area that enzymes can work on. This process, therefore, aids chemical digestion

Front 14

Why must food be digested?

Back 14

Insoluble and too big to cross membranes and be absorbed into the blood.

Polymers, and must be converted to their monomers, so they cant be rebuilt into molecules needed by body cells.

Front 15

What is the function of the Mouth

Back 15

Carriage of food to the stomach

Front 16

What is the function of the oesophagus

Back 16

Carriage of food to the stomach

Front 17

What is the function of the stomach

Back 17

Digestion of protein

Front 18

What is the function of the duodenum

Back 18

Digestion of carbohydrates, fats and proteins

Front 19

What is the function of the ileum

Back 19

Digestion of carbohydrates, fats and proteins; absorption of digested food and water

Front 20

What is the function of the colon

Back 20

Absorption of water

Front 21

What is the function of the rectum

Back 21

Storage of faeces

Front 22

What is the function of the anus

Back 22

Egestion

Front 23

Describe the structure of the gut

Back 23

Throughout its length, the gut wall consists of four tissue layers surrounding a cavity, the of the gut. The proportions of the different layers of the gut wall vary, depending on ± function of the part of the gut. The outermost layer, the serosa is tough connective tissue, protecting the gut wall. The gut moves while processing food and the serosa reduces friction with other abdominal organs. The muscle comprises two 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. The submucosa is connective tissue containing blood and lymph vessels, which remove absorbed products of digestion, and nerves that co-ordinate peristalsis. The mucosa is the innermost layer and lines the gut wall. Its epithelium secretes mucus, lubricating and protecting the mucosa. In some regions of the gut, it secretes digestive Juices and in others, absorbs digested food.

Front 24

Describe how digestion of carbohydrates using enzymes occurs

Back 24

polysaccharides are digested into disaccharides and then monosaccharides. Amylase hydrolyses starch and glycogen to the disaccharide maltose and maltase digests maltose to the monosaccharide glucose. Similarly, sucrase digests sucrose and lactase digests lactose. The general name for carbohydrate-digesting enzymes is carbohydrase.

Front 25

Describe how digestion of proteins using enzymes occurs

Back 25

Proteins are extremely large molecules. They are digested into polypeptides, then dipeptides and then amino acids. The general names for protein-digesting enzymes are protease and peptidase. Endopeptidases hydrolyse peptide bonds within the protein molecule, then exopeptidases hydrolyse the terminal or penultimate peptide bonds at the ends of these shorter polypeptides

Front 26

Describe the Regional specialisation of the mammalian gut

(the buccal cavity)

Back 26

Mechanical digestion begins in the mouth or buccal cavity, where food is mixed with saliva by the tongue and chewed with the teeth. The food's surface area increases, giving enzymes more access. Saliva is a watery secretion containing:

Amylase, beginning the digestion of starch and glycogen into maltose. HC03- and C032- ions.

The pH of the saliva varies between 6.2 and 7.4, although the optimum pH for salivary amylase is 6.7—7.0.

Mucus, lubricating the food's passage down the oesophagus.

Front 27

Describe the Regional specialisation of the mammalian gut

(The oesophagus )

Back 27

The oesophagus has no role in digestion, but it carries food to the stomach. Its wall shows the tissue layers in their simplest form.

Front 28

Describe the Regional specialisation of the mammalian gut

( The stomach )

Back 28

Food enters the stomach and is kept there by the contraction of two sphincters, or rings of muscles. The stomach has a volume of about 2 dm3 and food may stay there for several hours. The stomach wall muscles contract rhythmically and mix the food with gastric juice secreted by glands in the stomach wall. astric juice is secreted from glands in depressions in the mucosa, called gastric pits. Gastric juice contains: Peptidases, secreted by zymogen, or chief cells, at the base of the gastric pit. Pepsinogen, an inactive enzyme, is secreted and activated by ions to pepsin, an endopeptidase which hydrolyses protein to polypeptides. Hydrochloric acid, secreted by oxyntic cells. It lowers the pH of the stomach contents to about pH2, the optimum pH for the enzymes, and kills most bacteria in the food. Mucus, secreted by goblet cells, at the top of the gastric pit. Mucus forms a lining which protects the stomach wall from the enzymes and lubricates the food.

Front 29

Describe the Regional specialisation of the mammalian gut

(The small intestine - duodenum)

Back 29

The small intestine has two regions: the duodenum and the ileum. Relaxation of the pyloric sphincter muscle at the base of the stomach allows partially digested food into the duodenum, a little at a time. The duodenum is the first 25 cm and it receives secretions from the liver and the pancreas. Bile is made in the liver. It is stored in the gall bladder then passes through the bile duct into the duodenum. Bile contains no enzymes. Bile contains bile salts, which are amphipathic, i.e. their molecules have hydrophilic and hydrophobic parts. They emulsify lipids in the food, by lowering their surface tension and breaking up large globules into smaller globules, which increases the surface area. This makes digestion by lipase more efficient. Bile is alkaline and neutralises the acid in food coming from the stomach. It provides a suitable pH for the enzymes in the small intestine. Pancreatic juice is secreted by islet cells, which are exocrine glands in the pancreas. It enters the duodenum through the pancreatic duct.

Front 30

What does pancreatic juice contain?

Back 30

Enzymes and sodium hydrogen carbonate

Front 31

Name the enzymes that pancreatic juice contains

Back 31

trypsinogen

endopeptidases

amylase

lipase

Front 32

what is the function of trypsinogen

Back 32

Inactive enzyme converted into the endopeptidase trypsin by the duodenal enzyme, enterokinase

Front 33

what is the function of endopeptidases

Back 33

Hydrolyse protein polypeptides to peptides

Front 34

what is the function of amylase

Back 34

Digests any remaining starch to maltose

Front 35

what is the function of lipase

Back 35

Hydrolyses lipids into fatty acids and monoglycerides

Front 36

what is the function of sodium hydrogen carbonate

Back 36

Raises the pH to make pancreatic juice slightly alkaline and contributes to:

Neutralising acid from the stomach

Providing the appropriate pH for the pancreatic enzymes to work efficiently

Front 37

Describe the Regional specialisation of the mammalian gut (The small intestine - ileum)

Back 37

The region of the small intestine called the ileum is well adapted for absorption. In humans it is very long, several metres, and its lining is folded. On the surface of the folds are Villi and their epithelial cells have microscopic projections called microvilli. The folds, Villi and microvilli produce a very large surface area for absorption.

Front 38

Describe how glucose is absorbed in the small intestine

Back 38

Amino acids are absorbed into the epithelial cells by active transport and, as individual amino acids, they pass into the capillaries by facilitated diffusion. They are water-soluble and dissolve in the plasma. Glucose passes into the epithelial cells with sodium ions, by co-transport. They move into the capillaries, sodium by active transport and glucose by facilitated diffusion, and dissolve in the plasma. Diffusion and facilitated diffusion are slow and not all the glucose is absorbed. To prevent it leaving the body in the faeces, some is absorbed by active transport.