Special topics Flashcards
Fertilisation
Occurs in fallopian tube, sperm must get through Corona radiata, zona pellucida, membrane of secondary oocyte, cytoplasm of secondary oocyte. Fusion of pro-nuclei.
embryogenesis achievements
Patterning (spatial/temporal positioning), major axis (posterior, ventral, anterior, dorsal), 3 germ layers (ecto, meso, endoderm), rudimentary major organs form
blastocyst formation
fertilisation produces diploid cell via pro-nuclei fusion –> cell divides via cleavage –> morula –> blastocyst
blastocyst structure
Has blastocyst cavity, embryoblast (inner), trophoblast (outer), encompassed in zona pellucida
gastrulation - bilayer embryonic disc to trilayer
bilayer embryonic disc consists of ectoderm and endoderm. Primitive streak causes formation of mesoderm.
Stem cell hierarchy
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
Unipotent in skin
Found in basement membrane, migrates/differentiates up over 2-4 weeks until dead. Express different types of keratain during migration. Constant renewal.
Ex vivo gene therapy
treats monogenetic condition (only mutation in one cell) by correcting mutation and retaining 5% stem cells before grafting onto skin
Disulphide bonds
between cysteine amino acids, covalent bonds so can be very strong in oxidising environments. Maintains tertiary structure by linking N terminus to C terminus
Domains
Parts of tertiary structures, have different functions (e.g. binding, chewing bacterial cell wall), proteins may have more than one
Intrinsically disordered proteins
Their structure comes from having no structure (temporarily), found covering nuclear pores for selective permeability, may fold upon binding to another protein
4 major forces maintaining protein shape
hydrogen bonds and hydrophobic interactions (both weak), ionic interactions and disulphide bonds
Tertiary structure
every atom affects every other atom, can’t tell tertiary structure from DNA sequence, determined mainly by hydrophobic interactions but also ionic interactions
Secondary structure
Localised organisation, only involves main chain (N terminus, C terminus, alpha carbon). 3 types: beta strands, alpha helix, random coils.
central alpha carbon
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.
what processes occur in first week of embryogenesis/embryonic phase
fertilisation, cleavage of zygote, formation of morula and blastocyst, implantation
what structures will ectoderm turn into
all nervous tissue (includes brain and spinal cord), epidermis, outer tissues
mesoderm structures
all cardiovascular, lymphatic, and muscular systems, and kidneys
endoderm structures
gut, bladder, endocrine function (pancreas, thyroid, thymus)
trophoblast derivatives
chorion and therefore placenta. chorion + endometrium (uterus lining) = placenta
embryoblast (inner cell mass) derivatives
embryo itself
epiblast vs hypoblast
epiblast gives rise to ectoderm while hypoblast gives rise to endoderm
trophoblast function
Thickens uterine wall, releases hormones to prevent menstruation (human chorionic gonadotropin), releases proteases for implantation
primitive streak formation
ectodermal cells move from posterior to anterior forming a groove, pushes away endoderm cells for mesoderm to arise.
umbilical cord is formed by..
connecting stalk (posterior) and yolk sac
amnion function
amniotic cavity filled with fluid protects foetus from mechanical stress and temperature
week 1 of embryogenesis
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
weeks 2-4 of embryogenesis
trophoblast development, embryonic disc, gastrulation,
planarity of secondary structure
strong covalent peptide bonds form flat plane that restricts movement to two twists (pi, sine) called ramachandran angles. Restricted movement dictates protein folding
Alpha helix and beta sheets, random coil structures
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
primary structure
topological bond info, order of bonds
protein denaturation factors
pH, salt concentration (+ or - charges), temperature
chaperone proteins
proteins that help fold other proteins; contain hydrophobic residues; can change folding environment by diminishing hydrophobic effect temporarily
fibrous protein structure
hydrophobic residues down (three) side chains making it insoluble, thin and long, metabolically inactive
globular proteins structure
globular - strands curl so hydrophobic parts in core, surrounding water molecules make it soluble; metabolically active (e.g haemoglobin, insulin)
