Special topics

Question 1

Fertilisation

Answer 1

Occurs in fallopian tube, sperm must get through Corona radiata, zona pellucida, membrane of secondary oocyte, cytoplasm of secondary oocyte. Fusion of pro-nuclei.

Question 2

embryogenesis achievements

Answer 2

Patterning (spatial/temporal positioning), major axis (posterior, ventral, anterior, dorsal), 3 germ layers (ecto, meso, endoderm), rudimentary major organs form

Question 3

blastocyst formation

Answer 3

fertilisation produces diploid cell via pro-nuclei fusion –> cell divides via cleavage –> morula –> blastocyst

Question 4

blastocyst structure

Answer 4

Has blastocyst cavity, embryoblast (inner), trophoblast (outer), encompassed in zona pellucida

Question 5

gastrulation - bilayer embryonic disc to trilayer

Answer 5

bilayer embryonic disc consists of ectoderm and endoderm. Primitive streak causes formation of mesoderm.

Question 6

Stem cell hierarchy

Answer 6

Totipotent - gives rise to all cell types and extra embryonic tissue (zygote)
Pleuripotent - gives rise to all cell types (blastocyst)
Multipotent - all cell types of specific organ/tissue
Nullipotent - no more differentation, for replacement

Question 7

Unipotent in skin

Answer 7

Found in basement membrane, migrates/differentiates up over 2-4 weeks until dead. Express different types of keratain during migration. Constant renewal.

Question 8

Ex vivo gene therapy

Answer 8

treats monogenetic condition (only mutation in one cell) by correcting mutation and retaining 5% stem cells before grafting onto skin

Question 9

Disulphide bonds

Answer 9

between cysteine amino acids, covalent bonds so can be very strong in oxidising environments. Maintains tertiary structure by linking N terminus to C terminus

Question 10

Domains

Answer 10

Parts of tertiary structures, have different functions (e.g. binding, chewing bacterial cell wall), proteins may have more than one

Question 11

Intrinsically disordered proteins

Answer 11

Their structure comes from having no structure (temporarily), found covering nuclear pores for selective permeability, may fold upon binding to another protein

Question 12

4 major forces maintaining protein shape

Answer 12

hydrogen bonds and hydrophobic interactions (both weak), ionic interactions and disulphide bonds

Question 13

Tertiary structure

Answer 13

every atom affects every other atom, can’t tell tertiary structure from DNA sequence, determined mainly by hydrophobic interactions but also ionic interactions

Question 14

Secondary structure

Answer 14

Localised organisation, only involves main chain (N terminus, C terminus, alpha carbon). 3 types: beta strands, alpha helix, random coils.

Question 15

central alpha carbon

Answer 15

carbon bonded to NH group, carboxyl group, and R chain. Point of rotation, forms flat plane. Protein folds are limited due to limited angles/rotation.

Question 16

what processes occur in first week of embryogenesis/embryonic phase

Answer 16

fertilisation, cleavage of zygote, formation of morula and blastocyst, implantation

Question 17

what structures will ectoderm turn into

Answer 17

all nervous tissue (includes brain and spinal cord), epidermis, outer tissues

Question 18

mesoderm structures

Answer 18

all cardiovascular, lymphatic, and muscular systems, and kidneys

Question 19

endoderm structures

Answer 19

gut, bladder, endocrine function (pancreas, thyroid, thymus)

Question 20

trophoblast derivatives

Answer 20

chorion and therefore placenta. chorion + endometrium (uterus lining) = placenta

Question 21

embryoblast (inner cell mass) derivatives

Answer 21

embryo itself

Question 22

epiblast vs hypoblast

Answer 22

epiblast gives rise to ectoderm while hypoblast gives rise to endoderm

Question 23

trophoblast function

Answer 23

Thickens uterine wall, releases hormones to prevent menstruation (human chorionic gonadotropin), releases proteases for implantation

Question 23

primitive streak formation

Answer 23

ectodermal cells move from posterior to anterior forming a groove, pushes away endoderm cells for mesoderm to arise.

Question 23

umbilical cord is formed by..

Answer 23

connecting stalk (posterior) and yolk sac

Question 24

amnion function

Answer 24

amniotic cavity filled with fluid protects foetus from mechanical stress and temperature

Question 25

week 1 of embryogenesis

Answer 25

fertilisation 12-24 hours post ovulation, cleavage of zygote 30 hours post fertilisation, morula 3-4 days post fertilisation, blastocyst 4-5 days post fertilisation, implantation 6 days post fertilisation

Question 26

weeks 2-4 of embryogenesis

Answer 26

trophoblast development, embryonic disc, gastrulation,

Question 27

planarity of secondary structure

Answer 27

strong covalent peptide bonds form flat plane that restricts movement to two twists (pi, sine) called ramachandran angles. Restricted movement dictates protein folding

Question 28

Alpha helix and beta sheets, random coil structures

Answer 28

Alpha helix can very rarely be inverted
Beta strands come together to form beta sheets
Random coils are stable, locked in place so actually have structure

Question 29

primary structure

Answer 29

topological bond info, order of bonds

Question 30

protein denaturation factors

Answer 30

pH, salt concentration (+ or - charges), temperature

Question 31

chaperone proteins

Answer 31

proteins that help fold other proteins; contain hydrophobic residues; can change folding environment by diminishing hydrophobic effect temporarily

Question 32

fibrous protein structure

Answer 32

hydrophobic residues down (three) side chains making it insoluble, thin and long, metabolically inactive

Question 32

globular proteins structure

Answer 32

globular - strands curl so hydrophobic parts in core, surrounding water molecules make it soluble; metabolically active (e.g haemoglobin, insulin)