digestion and absorption

Question 1

what are CARBOHYDRATES broken down into?

Answer 1

disaccharides and then monosaccharides (sugars)

Question 2

what are LIPIDS/FATS broken down into?

Answer 2

fatty acids and glycerol (monoglycerides)

Question 3

what are PROTEINS broken down into?

Answer 3

amino acids

Question 4

what are CARBOHYDRATES broken down BY?

Answer 4

amylase and membrane-bound disaccharidases (enzyme)

Question 5

HOW are CARBOHYDRATES broken down by AMYLASE?

Answer 5

• AMYLASE is an enzyme that catalyses the conversion of STARCH (polysaccharide) into MALTOSE (disaccharide)
• this involves the HYDROLYSIS of the GLYCOSIDIC BONDS in starch

Question 6

WHERE is AMYLASE produced?

Answer 6

in the salivary glands and the pancreas

Question 7

HOW are CARBOHYDRATES broken down by MEMBRANE-BOUND DISACCHARIDASES?

Answer 7

• membrane-bound disaccharidases are enzymes attached to the cell membrane of epithelial cells lining the ileum (small intestine)
• they break down disaccharides into monosaccharides
• this involves the hydrolysis of glycosidic bonds

Question 8

what is MALTOSE catalysed by?

Answer 8

maltase

Question 9

what is SUCROSE catalysed by?

Answer 9

sucrase

Question 10

what is LACTOSE catalysed by?

Answer 10

lactase

Question 11

what are the MONOSACCHARIDE PRODUCTS of MALTOSE?

Answer 11

glucose + glucose

Question 12

what are the MONOSACCHARIDE PRODUCTS of SUCROSE?

Answer 12

glucose + fructose

Question 13

what are the MONOSACCHARIDE PRODUCTS of LACTOSE

Answer 13

glucose + galactose

Question 14

what are LIPDS broken down BY?

Answer 14

lipase and bile salts

Question 15

HOW are LIPIDS broken down by LIPASE?

Answer 15

• LIPASE enzymes catalyse the breakdown of LIPIDS into MONOGLYCERIDES (glycerol) and FATTY ACIDS
• this involves the HYDROLYSIS of ESTER BONDS in lipds

Question 16

where is LIPASE made?

Answer 16

pancreas

Question 17

where does LIPASE WORK?

Answer 17

small intestine

Question 18

where does AMYLASE WORK?

Answer 18

mouth and small intestine

Question 19

HOW do BILE SALTS help in the breakdown of LIPIDS?

Answer 19

• BILE SALTS emulsify lipids = cause lipids to form small droplets
• bile salts increase the available surface area for lipase to work on as small lipids droplets have a LARGER surface area than one big lipid droplet

Question 20

where are BILE SALTS produced?

Answer 20

liver

Question 21

what are PROTEINS broken down BY?

Answer 21

endopeptidases and exopeptidases (proteases/peptidases)

Question 22

what are PEPTIDASES?

Answer 22

enzymes that catalyse the conversion of PROTEINS into AMINOA CIDS by HYDROLYSING the PEPTIDE BONDS between amino acids

Question 23

how are PROTEINS broken down by ENDOPEPTIDASES?

Answer 23

ENDOPEPTIDASES hydrolyse peptide bonds WITHIN a protein

Question 24

how are PROTEINS broken down by EXOPEPTIDASES?

Answer 24

• EXOPEPTIDASES hydrolyse peptide bonds AT THE END of protein molecules
• they remove single amino acids from proteins

Question 25

what are 3 examples of **ENDOPEPTIDASES?**

Answer 25

**TRYPSIN, PEPSIN, CHYMOTRYPSIN**

Question 26

where are **TRYPSIN** and **CHYMOTRYPSIN** synthesised and secreted to?

Answer 26

they are **SYNTHESISED** in the **PANCREAS** and **SECRETED** to the **SMALL INTESTINE**

Question 27

where is **PEPSIN** produced and released to?

Answer 27

pepsin is **PRODUCED** by cells in the **STOMACH LINING** and is **RELEASED** into the **STOMACH**

Question 28

what **CONDITIONS** does **PEPSIN** work in?

Answer 28

pepsin **ONLY** works in **ACIDIC CONDITIONS** which is provided by **HYDROCHLORIC ACID** in the **stomach**

Question 29

what are **DIPEPTIDASES?**

Answer 29

- **DIPEPTIDASES** are **exopeptidases** that work on **DIPEPTIDES** - they separate 2 amino acids that make up a dipeptide by **HYDROLYSING** the **PEPTIDE BONDS** between them

Question 30

where are **DIPEPTIDASES** located?

Answer 30

the **CELL-SURFACE MEMBRANE** of **EPITHELIAL CELLS** in the **SMALL INTESTINE**

Question 31

how are **GLUCOSE** and **GALACTOSE** absorbed across cell membranes?

Answer 31

**glucose** and **galactose** are absorbed by **ACTIVE TRANSPORT** with **SODIUM IONS** via a **CO-TRANSPORTER PROTEIN**

Question 32

how is **FRUCTOSE** absorbed across cell membranes?

Answer 32

fructose is absorbed via **FACILITATED DIFFUSION** through a **DIFFERENT** transporter protein to glucose and galactose

Question 33

how are **MONOGLYCERIDES** and **FATTY ACIDS** absorbed across cell membranes?

Answer 33

- **MICELLES** help to **move monoglycerides** and **fatty acids towards** the **epithelium** - **micelles** constantly break up and reform so can **release monoglycerides** and **fatty acids** - **micelles** are **NOT** taken across the epithelium - **monoglycerides** and **fatty acids** are **LIPID-SOLUBLE** so can **diffuse** directly across the **epithelial cell membrane**

Question 34

how are **AMINO ACIDS** absorbed across cell membranes?

Answer 34

- **amino acids** are absorbed via **CO-TRANSPORT** - **SODIUM IONS** are **ACTIVELY TRANSPORTED** out of the ileum epithelial cells into the blood - this creates a **sodium ion CONCENTRATION GRADIENT** - sodium ions can then **DIFFUSE** from the lumen of the ileum into the epithelial cells through **SODIUM DEPENDENT TRANSPORTER PROTEINS, carrying the amino acids with them**