Biochem revision - Week 2 Macromolecules and Nutrients

Question 1

Define catabolism and anabolism.

Answer 1

Catabolism is the breakdown of complex molecules in living organisms to form simpler ones; releases E; destructive metabolism

Anabolism is the synthesis of complex molecules in living organisms from simpler ones together with the storage of energy; constructive metabolism.

Question 2

What are the three buildings blocks/levels of carbohydrates? How many of each carbon do they contain?

Answer 2

Monosaccharides - the simplest carbs that contain 3-7 carbon atoms Ex. Trioses, Pentoses, Hexoses, Heptoses

Oligosaccharides - contain 2-10 monosaccharides linked covalently
Ex. Maltose

Polysaccharides - contain 10 or more oligosaccharides
Ex. Cellulose, glycogen

Question 3

What are carbohydrates?

Answer 3

Carbohydrate are compounds that contain at least two hydroxyl groups that share the common molecular formula: (CH2O)2

Question 4

How are oligosaccharides linked? What does this mean?

Answer 4

Oligosaccharides are covalently linked through glycosidic linkages.

This means that a water molecule is shed and an oxygen molecule bonds with the hydrogen of another oligosaccharide

Question 5

What kind of saccharide are sucrose and lactose? What monosaccharides are they made up of?

Answer 5

Disaccharides

Sucrose: Glucose and Fructose

Lactose: Glucose and Galactose

Question 6

What structures make up glycogen and cellulose? What kind of saccharide are they?

Answer 6

Both glycogen and cellulose are polysaccharides

Cellulose is a mixture of amylose and amylopectin; main carb in plants

Glycogen is similar to amylopectin; main storage of carbs in animals

Question 7

What are the four categories of lipids?

Answer 7

Fatty acids

Triacylglycerols

Phospholipids

Steroids

Question 8

What is the general structure of a fatty acid? What does it mean to be saturated and unsaturated?

Answer 8

Fatty acids are long carbon chains with H atoms all around and a carboxyl group at the end

Saturated fatty acids are when all the C’s are linked by single bonds (no room for more H atoms)
Unsaturated fatty acids are when some C atoms are double-bonded and can receive H to become single bonds

Question 9

What does a triacylglycerol consist of? How are these components linked?

Answer 9

• 1 Glycerol
• 3 fatty acids

They are linked through Ester linkages

Question 10

Which lipid is the most abundant in the human body? What is their purpose?

Answer 10

Triacylglycerols are the most abundant, making up 95% of dietary fat.

TAG’s serve as E depots

Question 11

What are steroids and phospholipids?

Answer 11

They are key components of cell membranes

Steroids are derivatives of cholesterol and participate in membrane formation

Question 12

What is one of the role of vitamins and minerals?

Answer 12

Although they have no energy value, vits/mins are involved in E provision during exercise and numerous other bodily functions

Question 13

What is hyponatremia?

Answer 13

The sodium level in the blood is below normal

Question 14

What are the thick and thin filaments of muscle contractile proteins composed of?

Answer 14

Thick filaments are composed of myosin heavy and light chain filaments

Thin filaments are made up of actin, troponin (pulls tropomyosin out of the way of myosin binding site) and tropomyosin (covers the binding site)

Question 15

Which is the most abundant protein in muscle tissue?

Answer 15

Myosin

Question 16

What is the make up of myosin?

Answer 16

Myosin is asymmetric with a double-headed region linked to a very long tail. The heads are made up of one heavy chain and two light chains.

Light meromyosin - constitutes the trunk of the thick filaments and can self-assemble

Heavy meromyosin - corresponds to the x-bridges and can be further divided into two S1 fragments that hydrolyze ATP/bind to F-actin and one S2 fragment that links the segments

Question 17

What is the structure of actin?

Answer 17

Actin is the main component of the thin filaments and exists as:

G-actin (globular/monomer)
and
F-actin (fibrous/polymer)

F-actin also increases the ATP turnover rate by emptying products from the active site.

Question 18

What bands/zones shorten during muscle contraction and what lines stay the same?

Answer 18

The I band and the H zone shorten while the A band remains the same length

Question 19

Describe the order of events for force generation

Answer 19

1. Rest: no actin myosin binding
2. ATP hydrolyzed on the heads of HMM at a slow rate because the binding of actin is hindered
3. Muscle excitation causes Ca2+ release from the SR.
   Increased Ca2+ ions bind to TnC causing it to have a conformational change that detaches Tnl from F-actin. This detachment lets tropomyosin move out of the way of the binding site for myosin
4. Myosin binds to F-actin
5. Conformational change in S1, causing power stroke, at the same time, ADP and Pi leave active site
6. Once active site is empty, ATP enters, hydrolyses, and attachment is broken
7. Ca2+ATPase pumps Ca2+ back into SR, causing muscle relaxation

Question 20

There are myosin isoforms. True or False?

Answer 20

True. Adults have Myosin Heavy Chain 1, 11a and 11x fiber types

i.e low, intermediate and high shortening V, respectively

Question 21

What are the three components to troponin?

Answer 21

TnC - binds to Ca2+
TnT binds to tropomyosin
Tnl - binds to actin