Module 3 Special Topic

Question 1

What is embryogenesis?

Answer 1

Is the process of the embryo forms starting with a single cell

Question 2

What does embryogenesis achieve?

Answer 2

Patterning- The cells that are forming acquire identity in space and time

The major axis are defined - anterior/posterior and dorsal and ventral. Three germ layers are identified (Gastrulation). Rudiments (undeveloped forms) of the major organs.

Question 3

Gastrulation generates three germ layers, what are these called?

Answer 3

Ecto (Outside), Meso (Between), Endo (Inside)

Question 4

At what completed stage of meiosis does the sperm enter the oocyte?

Answer 4

Metaphase Meiosis II

Question 5

What process happens after fertilisation of the egg (hint: in the fallopian tube)?

Answer 5

Cleavage and formation of the Blastocyst

Question 6

What special types of formations are formed in the cleavage cell division process?

Answer 6

Morula (latin for raspberry) (3-4 days), and Blastocyst

Question 7

What are trophoblasts?

Answer 7

Cells that form around and create the outer layer of blastocyst

Question 8

When does implantation occur?

Answer 8

Usually 6 days after fertilisation

Question 9

What are the two components of the bilaminar embryonic disc and why are they formed?

Answer 9

Epiblast and Hypoblast, these give the rise to the three types of germ layers (ecto, meso, endo)

Question 10

What happens to the layers of the embryo in embryonic folding?

Answer 10

Lateral folding- The embryo folds in itself creating a tubular common-like structure making the endoderm the inner layer of what will become the lining of the gastrointestinal tract and the ectoderm now on the outside of the structure which will build the embryo’s outer layers.

Question 11

Differentiated cells have limited ____

Answer 11

Divisions

Question 12

What types of cells can replace themselves, and create differentiated daughter cells?

Answer 12

Stem cells

Question 13

What are the purpose of stem cells?

Answer 13

For growth, renewal and repair

Question 14

What is meant by ‘decreasing developmental potential’ during embryonic development?

Answer 14

This refers to the process by which cells become more specialized and therefore lose the ability to develop into different types of cells.

For example, a totipotent cell can develop into any cell type, but as it specializes, it becomes pluripotent, then multipotent, and finally unipotent, with each stage having a narrower range of cell types it can become.

Question 15

What is the stem cell hierarchy?

Answer 15

It is the organisation of stem cells according to their potential to differentiate into different cell types

Question 16

What is the Totipotent stem cell?

Answer 16

The most potent of the stem cells, it is capable of giving rise to all the cell types of the body and EXTRA embryonic tissues

Question 17

What is the Pluripotent stem cell?

Answer 17

The second most potent of the stem cells, it is capable of giving rise to all cell types of the body

Question 18

What is the Multipotent stem cell?

Answer 18

The third most potent of the stem cells, it is only capable of giving rise to cell types of a particular tissue or organ

Question 19

What is the Nullipotent stem cell?

Answer 19

The least potent stem cell, unable to give rise to other cell types

Question 20

What type of stem cell is in the skin, allowing for constant renewal?

Answer 20

Unipotent (eg: Differentiating Keratinocytes)

Question 21

Recap of embryogenesis: How does it all start?

Answer 21

With fertilisation n+n=2n

Question 22

Recap of embryogenesis: What happens next?

Answer 22

Cleavage and formation of blastocyte

Question 23

Recap of embryogenesis: What happens after cleavage?

Answer 23

Blastula formation/implantation

Question 24

Recap of embryogenesis: How do we create three germ layers and what are they?

Answer 24

Gastrulation (endoderm: gut, ectoderm: skin, mesoderm: connective tissues)

Question 25

Recap of embryogenesis: What happens after Gastrulation?

Answer 25

Organogenesis (Lateral folding)

Question 26

Recap of embryogenesis: Why do we need stem cells?

Answer 26

To replace differentiated cells, Growth, Repair, Renewal

Question 27

Recap of embryogenesis: Clinical utility of stem cells?

Answer 27

Long lasting skin grafts (gene edited)

Question 28

How do amino acids polymerise to form proteins?

Answer 28

Through condensation reactions. The carboxyl group (-COOH) of one amino acid reacts with the amino group (-NH₂) of another. A water molecule is removed (H₂O). A peptide bond (—CO—NH—) is formed. Repeating this creates a polypeptide chain (protein).

Question 29

What type of bond forms between amino acids in a protein?

Answer 29

A peptide bond. ## Footnote Formed by a condensation reaction between —COOH and —NH₂ groups.

Question 30

What is a hydrolysis reaction in proteins?

Answer 30

The reverse of condensation. Breaks peptide bonds. Water is added to split the bond. Turns polypeptides back into amino acids.

Question 31

What’s the role of water in condensation vs hydrolysis?

Answer 31

Condensation: water is removed to form bonds. Hydrolysis: water is added to break bonds.

Question 32

Rank these by relative strength (strongest to weakest): Peptide bond, disulfide bond, hydrogen bond, dipole-dipole interaction, intermolecular forces (Van der Waals)

Answer 32

1. Peptide bond (strongest) → Covalent bond between amino acids 2. Disulfide bond → Strong covalent bond between sulfur atoms (cysteines) 3. Hydrogen bond → Weaker than covalent bonds, important for secondary structure 4. Dipole-dipole interaction → Attraction between polar side chains 5. Intermolecular forces (Van der Waals) (weakest) → Temporary, induced dipoles between nonpolar groups