Mammalian gametes + fertilisation Flashcards
how are mammalian eggs adapted for function
zona pellucida (protective coating) to prevent polyspermy
haploid nucleus to restore full set of chromosomes at fertilisation
how are mammalian sperm adapted for function
contain many mitochondria for energy required for moving
acrosome head contains digestive enzymes which break down the zona pellucida of the egg
describe the process of mammalian fertilisation
acrosome reaction - enzymes in acrosome digest the zona pellucida. Sperm nucleus enters the egg cell
cortical reaction - causes zona pellucida to harden to prevent polyspermy
nucleic fusion - restores full set of chromosomes which forms a diploid zygote
what is the importance of the egg cell being large
increases chance of fertilisation
contains lipid droplets which provides energy for a developing embryo
what is a feature of the zona pellucida an why is this important
hardens when one sperm cell has entered
prevents polyspermy
what is the roll of vesicles in the ovum and there importance
contain cortical granules
enzymes cause zona pellucida to harden
this prevents polyspermy
why is it important for the cytoplasm to contain proteins and lipid droplets in it
food source which supplies energy for cell division of the fertilised ovum
importance of the ovum having a haploid nucleus
diploid number can be restored at fertilisation
mixing of alleles allows for genetic differentiation
why is the flagellum important in a sperm cell
allows sperm to swim to reach the ovum
why do sperm contain many mitochondria
to carry out aerobic respiration to release energy in the form of glucose
this lets the flagellum move so the sperm can swim to the egg
what is a acrosome and what is its importance in sperm
it is a specialised lysosome
contains and releases digestive enzymes
these enzymes hydrolyse the zona pellucida which allows sperm to enter the ovum
what is the process of the acrosome reaction
ovum releases enzymes which attracts sperm
receptors on the head of the sperm bind to the zona pellucida of the ovum
the acrosome in the head of the sperm swells then the acrosome membrane fuses with the sperm cell membrane
digestive enzymes in a vesicle are released from the acrosome by exocytosis
the zona pellucida of the egg is digested by the enzymes which allow the sperm to reach, bind and fuse with the ovum membrane
genetic material of one sperm passes through the ovum cell membrane and enters the ovum
what is the process of the cortical reaction
genetic material from the sperm head enters the ovum
cortical granules of the lysosomes/vesicles of the ovum move towards and fuse with egg cell surface membrane which releases enzymes by exocytosis into the zona pellucida
zona pellucida hardens which prevents polyspermy
change in charge occurs across the cell membrane
