Dental Biochemistry

Front 1

1. How are most intracellular compartments in the cell?

What does this establish?

Back 1

Membrane-bound

A barrier between cytoplasm and interior of compartment

Front 2

2. What are advantages to having these compartments membrane-bound?

Back 2

1. Existence of specialized environments where specialized functions can take place

2. Same metabolites can be earmarked for different fates w/in different compartments

Front 3

3. What is a consequence of having membrane-bound compartments?

Back 3

Need a mechanism for moving molecules across membrane barriers

Front 4

4. What is the most notable non-membrane-bound compartment?

Back 4

Nucleolus

Where ribosome assembly takes place

Front 5

5. What are three properties of membranes?

Back 5

1. Form permeability barriers (wall off interior compartment of cell)

2. Composed of lipids, proteins, and carbohydrates

3. Different membranes within the cell and surrounding the cell have different components (esp. proteins)

Front 6

6. What is the basic structure of all biological membranes?

What are the components?

Back 6

Phospholipid bilayer

1. Other lipids (cholesterol) are embedded into bilayer

2. Proteins embedded into bilayer and attached to surface

3. Carbohydrates are covalently attached to proteins on outer surface of cytoplasmic membrane

Front 7

7. What is the structure of phospholipids?

Back 7

1. Polar head group
-either negatively charged or zwitterionic (both neg and pos)

2. Pair of hydrocarbon tails

Front 8

8. What are the solubility properties of phospholipids?

Back 8

Hydrocarbon tails are hydrophobic
-associate in interior of lipid bilayer

Head groups are hydrophilic
-form an interface with water on either side of bilayer

Front 9

9. How do the hydrophobic tails packs?

Back 9

To form a flat planar structure (double layer)

**Structure of phospholipids requires them to form this bilayer

Front 10

10. In a laboratory, what happens when purified phospholipids are mixed with water?

Back 10

Spontaneously form lipid bilayers which round up to form vesicles

Spherical shells of lipid bilayers surrounding an aqueous compartment

Front 11

11. What types of proteins do membranes contain?

Which type are most membrane proteins?

Back 11

1. Integral

2. Peripheral

Integral (interact with hydrophobic core of membrane)

Front 12

12. Describe integral membrane proteins.

Back 12

1. Go all the way through membrane

2. Have 2 hydrophilic ends separated by a hydrophobic region

3. Polypeptide chain may go back and forth through the membrane many times

Front 13

13. Describe peripheral membrane proteins.

Back 13

1. Generally do not interact with hydrophobic core

2. Loosely bound to other membrane proteins by non-covalent bonds

3. Some are covalently attached to phospholipid head groups

4. Some are attached to networks of fibers that run throughout cell, conferring shape and strength

Front 14

14. Are membrane symmetrical?

Back 14

No, asymmetrical

Phospholipids distribute asymmetrically

Integral membrane proteins are also asymmetrical with specific orientation

Front 15

15. How are newly synthesized phospholipids added to the membrane?

Back 15

Added to inner leaflet then flipped to outer leaflet by enzymes embedded in membrane

*Newly synthesized proteins are inserted into membrane with correct orientation

Front 16

16. What is and is not permeable through the phospholipid bilayer membrane?

Which proteins are responsible for passing polar and charged molecules through membrane?

Back 16

Non-polar molecules are freely permeable

Impermeable to polar molecules and charged ions

Integral membranes (have high substrate specificity)

Front 17

17. What are the three types of transport?

Back 17

1. Simple diffusion

2. Facilitated diffusion

3. Active transport (directional and can transport up gradient)

*First two are functionally symmetrical and only transport down a concentration gradient

Front 18

18. What are membrane channels?

What type of diffusion is this?

What does the rate depend on?

Back 18

Channel that allow hydrophilic molecules passage through membrane

Very specific (i.e aquaporin)

Simple diffusion


Concentration of diffusing molecule and number of channel proteins

Front 19

19. What happens in facilitated diffusion?

Back 19

Transporter protein binds specific molecule on one side

Undergoes conformational change

Releases molecules on other side of membrane

Front 20

20. How does facilitated diffusion differ from simple diffusion through a channel?

What does the rate of facilitated diffusion depend on?

Back 20

Only one molecule at a time is bound and a conformational change must take place

Front 21

21. How would a rate of transport - concentration of transported molecule curve look like for facilitated diffusion?

Simple diffusion?

Back 21

Hyperbolic - saturation properties

Linear - law of mass

Front 22

22. What is active transport?

Why is energy required?

Back 22

Energy is expended to push a molecule through the membrane against its gradient

Expenditure of energy confers directionality

Front 23

23. What is secondary transport?

Back 23

A molecule is transported against its concentration gradient, coupled to transport of another molecule down a concentration gradient maintained by primary active transport

Front 24

24. What is an example of secondary transport?

Back 24

Glucose transport into cells of intestinal epithelium in conjunction with Na+ ions

Sodium-potassium ATPase is active transport

Front 25

25. What occurs in the Na - K ATPase?

Back 25

Hydrolysis of ATP provides energy to simultaneously pump Na+ out of the cell and K+ into the cell

Maintain a low Na+ concentration in cell and high K+ concentration

Front 26

26. What is the function of the mitochondria?

Back 26

1. Produces most of cell's energy

2. Many important metabolic processes are compartmentalized inside (or outside) mitochondria

Front 27

27. How is the mitochondria structurally?

Back 27

1. Envelop of outer and inner membranes with distinctly different properties

2. Matrix is material enclosed by inner membrane

Front 28

28. Where is the site of energy production in the mitochondria?

Back 28

Inner membrane

Gradient of H+ across inner membrane is used to drive ATP synthesis

Front 29

29. What is the function of the nucleus?

Back 29

1. Stores genetic information (DNA)

2. Site of RNA synthesis

Front 30

30. How is the nucleus structured?

Back 30

1. Largest organelle in cell

2. Surrounded by double membrane

3. Nuclear envelope has pores (metabolites and small proteins can pass freely in and out

Front 31

31. What is the endoplasmic reticulum?

How is it structured?

Back 31

Network of membranous tubules within the cell

Inner portion (near nucleus) is rough ER

Outer portion is smooth ER

Front 32

32. What occurs at the rough ER?

Back 32

Synthesis of cytoplasmic membrane proteins and proteins destined for export

After synthesis they're passed to golgi

Front 33

33. What is the function of the golgi complex?

Back 33

1. Modify proteins produced in rough ER

2. Distributes these proteins to other parts of the cells

Front 34

34. How is the lysosome structured?

What is its function?

Back 34

Enclosed by a single membrane with a proton pump that keeps pH near 5

Involved in intracellular digestion

Contains a wide variety of hydrolitic enzymes that digest cellular waster and extracellular debris

Front 35

35. What are peroxisomes involved in?

What do they produce?

Back 35

Oxidative reactions using molecular oxygen or reactive oxygen species

Hydrogen peroxide (very toxic)