Cells & Compartments (Module 2 Lecture 5)

Question 1

Give two examples to highlight the difference in specificity of metabolic fuels in the human body.

Answer 1

1. Brain cells need glucose.

2. Resting muscle cells prefer fatty acids.

Question 2

Give four examples of specialized metabolic functions in the human body.

Answer 2

1. Liver converts extra nitrogen into urea.
2. Adipocytes store triglycerides.
3. Adrenal cortex makes glucocorticoids (a corticosteroid that metabolizes fats, proteins, and carbohydrates as well as contains anti-inflammatory properties).
4. Fasting liver makes glucose out of carbon skeletons of amino acids.

Question 3

What gives the nucleus its shape?

Answer 3

Lamin, which are fibrous proteins lining the inner surface of the inner nuclear membrane.

Question 4

What provides additional mechanical support for the external nuclear envelope?

Answer 4

A network of intermediate filaments.

Question 5

What connects the two nuclear membranes and allows for transport of materials to and from the cytosol?

Answer 5

Nuclear pores

Question 6

Describe the development of rRNA.

Answer 6

It is synthesized primarily in the nucleolus and acquires some proteins before passing through nuclear pores into the cytosol to continue and become fully developed.

Question 7

Give two examples that describe protein transport into the nucleus.

Answer 7

1. Histones are made in the cytoplasm and then imported into the nucleus.
2. NF-AT proteins migrate back and forth between cytosol and nuclear depending upon specific conditions.

Question 8

What is NF-AT proteins?

Answer 8

Nuclear factor of activated T-cells, which is a family of proteins involved in the immune response as well as development of cardiac, skeletal muscles, and nervous system

Question 9

Contrast between the two mitochondrial membranes.

Answer 9

1. Outer = permits relatively large molecules to enter

2. Inner = provides major barrier function

Question 10

Describe two points to remember about the development of the mitochondria.

Answer 10

1. Mitochondrial DNA encodes some of the specific mitochondrial proteins.
2. Other proteins are synthesized outside and then imported into the mitochondria.

Question 11

What is a peroxisome?

Answer 11

A small, single-membrane organelle that has a high content of oxidases to oxidize organic substrates and generate toxic H2O2 (RH2 + O2 –> R + H2O2).

Question 12

List three types of peroxisomal enzymes.

Answer 12

1. Catalase (degrades hydrogen peroxide, which is especially important for the liver and kidneys to detoxify the body)
2. Enzymes that specifically oxidize long-chain fatty acids without generating ATP
3. Two enzymes involved in the synthesis of plasmalogens (phospholipids that have a sn-1 unsaturated ether-linkage instead of an acyl group.

Question 13

How to peroxisomes grow and divide?

Answer 13

1. They uptake peroxisomal proteins from the cytosol to grow (which have specific proteins required to catalyze import).
2. They undergo fission to divide into daughter cells.

Question 14

Describe the environment and functions of lysosomes.

Answer 14

1. pH ~ 5 to digest four types of macromolecules into subunits using acid hydrolase enzymes
2. Functions to destroy infectious agents like bacteria and yeast, recover from injury, involute tissues, and turnover cells and organelles

Question 15

List the five pathways of lysosomal digestion.

Answer 15

1. Proteins –> amino acids –>
2. Polysaccharides –> monosaccharides –>
3. DNA & RNA –> nucleotides –> nucleosides + Pi –>
4. Triacylglycerols –> fatty acids + diacylglycerols –> fatty acids + monoacylglycerols –> fatty acids + glycerol –>
5. Phosphoacylglycerol –> Pi + Head group (choline/etc) + diacylglycerols –>