Topic 3B - More Exchange and Transport Systems Flashcards

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1
Q

How are carbohydrates digested? (2)

A
  1. Amylase — Amylase catalyses the breakdown of starch. It works by catalysing hydrolysis reactions that break the glycosidic bonds in starch to produce maltose.
  2. Membrane-bound disaccharidases — These are enzymes which help breakdown disaccharides into monosaccharides. This is done by catalysing the hydrolysis of glycosidic bonds.
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2
Q

Where is amylase produced? (2)

A
  1. The salivary glands — this releases amylase into the mouth.
  2. The pancreas — this releases amylase into the small intestine.
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3
Q

Where are membrane-bound disaccharidases found?

A

Attached to the cell membranes of epithelial cells lining the ileum.

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4
Q

What makes up sucrose?

A

Glucose + Fructose

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5
Q

What makes up maltose?

A

Glucose + Glucose

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6
Q

What makes up lactose?

A

Glucose + Galactose

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7
Q

What is the disaccharidase of sucrose?

A

Sucrase

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8
Q

What is the disaccharidase of maltose?

A

Maltase

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9
Q

What is the disaccharidase of lactose?

A

Lactase

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10
Q

How are lipids digested? (2)

A
  1. Lipase enzymes — They catalyse the breakdown of lipids into monoglycerides and fatty acids. This is done by catalysing the hydrolysis of the ester bonds in lipids.
  2. Bile salts — These emulsify lipids (form small droplets), which are then easier to be hydrolysed by lipases as they’ll have a greater surface area.
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11
Q

Where are lipases produced?

A

The pancreas — they are then secreted into the small intestine.

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12
Q

Where are bile salts produced?

A

The liver

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13
Q

How are proteins digested? (3)

A
  1. Endopeptidases — They act to hydrolyse peptide bonds within a protein.
  2. Exopeptidases — They hydrolyse peptide bonds at the end of protein molecules. They remove single amino acids from proteins.
  3. Dipeptidases — They are exopeptidases that work specifically on dipeptides. They act to separate the two amino acids that make up dipeptides by hydrolysing the peptide bond between them.
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14
Q

Where are endopeptidases produced? (2)

A
  1. Some endopeptidases (Trypsin & Chymotrypsin) are produced in the pancreas — they are secreted into the small intestine.
  2. Another endopeptidase (Pepsin) is produced in the cells lining the stomach — it is then secreted directly into the stomach.
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15
Q

How are monosaccharides absorbed into the bloodstream? (3)

A

Glucose is absorbed by active transport with sodium ions via a co-transporter protein.

Galactose is absorbed in the same way by the same co-transporter protein.

Fructose is absorbed via facilitated diffusion through a different transporter protein.

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16
Q

How are monoglycerides and fatty acids absorbed into the bloodstream?

A

Micelles help to move monoglycerides and fatty acids towards the epithelium. As micelles constantly break up and reform they can ‘release’ monoglycerides and fatty acids, allowing them to be absorbed. Monoglycerides and fatty acids are lipid-soluble, so can diffuse directly across the epithelial cell membrane.

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17
Q

How are amino acids absorbed into the bloodstream?

A

Sodium ions are actively transported out of the epithelial cells into the ileum itself. They then diffuse back into the cells through sodium-dependent transporter proteins in the epithelial cell membranes, carrying the amino acids with them.

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18
Q

What is the role of haemoglobin?

A

To carry oxygen around the body.

19
Q

Describe the structure of haemoglobin.

A

Haemoglobin is a protein with a quaternary structure, made up of four polypeptide chains. Each chain has a haem group which contains an iron ion and gives haemoglobin its red colour. Each haemoglobin molecule can carry four oxygen molecules.

20
Q

How many oxygen molecules can each haemoglobin molecule carry?

A

Four

21
Q

How is oxyhaemoglobin formed?

A

When oxygen associates/loads onto haemoglobin in the lung.

22
Q

How is haemoglobin reformed?

A

When oxygen disassociates/unloads from oxyhaemoglobin in respiring tissue.

23
Q

What does affinity for oxygen mean?

A

The tendency a molecule has to bind with oxygen.

24
Q

What is partial pressure of oxygen?

A

A measure of oxygen concentration.

25
Q

A high partial pressure of oxygen means a _____ concentration of oxygen.

A

High

26
Q

A low partial pressure of oxygen means a ____ concentration on oxygen.

A

Low

27
Q

When does oxygen load onto haemoglobin?

A

When there’s a high partial pressure of oxygen (in the lungs).

28
Q

When does oxygen unload from oxyhaemoglobin?

A

When there’s a low partial pressure of oxygen (in respiring tissue).

29
Q

What are the conditions in the lungs? (4)

A
  • High oxygen concentration
  • High partial pressure of oxygen
  • There is a high affinity for oxygen
  • Oxygen loads onto haemoglobin
30
Q

What are the conditions in respiring tissue? (4)

A
  • Low oxygen concentration
  • Low partial pressure of oxygen
  • There is a low affinity for oxygen
  • Oxygen unloads from oxyhaemoglobin……
31
Q

What does a dissociation curve show us?

A

How saturated the haemoglobin is with oxygen at any given partial pressure

32
Q

What does 100% saturation of haemoglobin with oxygen mean?

A

Every haemoglobin molecule is carrying the maximum of 4 molecules of oxygen.

33
Q

What does 0% saturation of haemoglobin with oxygen mean?

A

None of the haemoglobin molecules are carrying any oxygen.

34
Q

Describe and explain the appearance of a dissociation curve.

A

It has the appearance of an s-shape and not a straight line as the saturation of haemoglobin can also affect the affinity.
When haemoglobin combines with the first oxygen molecule, it’s shape alters in a way that makes it easier for the other oxygen molecules to join too. But as the haemoglobin starts to become saturated, it gets harder for more oxygen molecules to join.
This means there is a shallow area at the start and end where it is hard for oxygen to bind and a steep area in the middle where it is easier for oxygen to bind.

35
Q

When there is a high partial pressure of oxygen, haemoglobin has a _________________ so it also has a _______________________.

A

High affinity for oxygen

High saturation of oxygen

36
Q

When there is a low partial pressure of oxygen, haemoglobin has a _________________, so it has a _____________________.

A

Low affinity for oxygen

Low saturation of oxygen

37
Q

What is the partial pressure of carbon dioxide?

A

A measure of the concentration of carbon dioxide in a cell.

38
Q

How does pCO2 affect oxygen loading and unloading?

A

Oxyhaemoglobin unloads it’s oxygen more readily in higher pCO2.
Haemoglobin loads oxygen more readily in a lower pCO2.

39
Q

What is the Bohr effect?

A

The Bohr effect describes the observation that increases in the partial pressure of carbon dioxide results in a lower affinity for oxygen.

40
Q

What does it mean when the dissociation curve shifts?

A

The further the curve is to the left, the higher the haemoglobin’s affinity for oxygen is.
The further the curve is to the right, the lower the haemoglobin’s affinity for oxygen is.

41
Q

What are the different types of haemoglobin that exist in different environments? (3)…

A
  1. Low oxygen environments — they have haemoglobin with a higher affinity for oxygen than human haemoglobin. This is because there isn’t much oxygen available, so the haemoglobin has to be very good at loading any available oxygen.
42
Q

What does a dissociation curve for an organism living in a low oxygen environment look like? Why does it look like this?

A

Further to the left than the dissociation curve for human haemoglobin. They have a higher affinity for oxygen as they have less oxygen available so they they have to be good at loading whatever oxygen they can.

43
Q

What does a dissociation curve for an organism smaller than a human look like?

A

Further to the right than the dissociation curve for human haemoglobin. This is because they respire more (to maintain their heat) than humans so they need their haemoglobin to be able to unload easily at respiring tissue.

44
Q

What does a dissociation curve for an organism with higher activity levels than humans look like?

A

Further to the right than the dissociation curve for human haemoglobin. This is because they have a high oxygen demand as they respire a lot to provide ATP for their muscles. So oxygen needs to be able to unload easily at the respiring muscles.