Biology Unit 2: Sperm And Ovum

Front 1

Describe and explain twoadaptations of the human egg cell.

Back 1

D: 23 chromosomes in nucleus.

E: 46 chromosomes can be restored at fertilisation.

D: Food store/ Lipid droplets.

E: Supplies energy and nutrients

D: Large surface area.

E: Increase chance or fertilisation.

D: Release chemical.

E: To attract sperm.

D: Membrane with sperm receptors.

E: To allow sperm to bind.

Front 2

Describe three structural differences between a human sperm cell and a humanegg cell.

Back 2

1. Flagellum.

2. Streamlined shape.

3. Acrosome.

4. Sperm cell has less cytoplasm.

5. Egg cell has Zona Pellucida

Front 3

When a sperm cell reaches an egg cell, enzymes are released from the head of thesperm. Explain the reasons for the release of these enzymes.

Back 3

1. enzyme {digest / eq}{ zona (pellucida)

2. idea that sperm can get through to egg {cell /nucleus

3. {contact with / receptor on} {zona pellucida /(glycoprotein) jelly coat / surface of ovum }

4. (causes) {acrosome / eq to {rupture / open /

Front 4

Describe what happens in the egg cell once the sperm cell nucleus has entered it

Back 4

Meiosis II is completed.

Both nuclei fuse.

Chemicals released from cell surface membrane.

Zona Pellucida thickens then hardens.

Makes cell impenetrable (other sperm cant get in.

Egg cell membrane changes its charge to positive.

Front 5

One fertilisation involves a male gamete nucleus fusing with the egg cellnucleus. Give two functions of this fertilisation.

Back 5

1. To produce a zygote.

2. Allow mixing of genetic material.

3. To produce a diploid. 2n number.

Front 6

Explain the function of mitochondria in sperm cells

Back 6

1. (they carry out) (aerobic) respiration

2. provide {ATP / energy

3. to {move / drive the / eq} {flagellum / tail}

4. allows sperm to swim

5. towards the {egg / eq} / {towards /along} theoviduct / eq ;

Front 7

Explain the importance of meiosis in the formation of human sperm and egg cells.

Back 7

1. Halves the chromosome number

2. so that at fertilisation the {full complement /eq} of chromosomes is restored

3. allows genetic variation (in gametes)

4. through independent assortment

5. through crossing over

Front 8

Describe how the acrosin is released from the acrosome

Back 8

1. idea of stimulus e.g. receptors, contact with{zona presence of chemicals

2. reference to acrosome swells

3. reference to acrosome} fuses

4. with (sperm) cell (surface) membrane

5. exocytosis ;

Front 9

Describe and explain three ways in which a human sperm cell is specialised for its function.

Back 9

1. shape qualified e.g. hydrodynamic, streamlined ; 2. idea of reduced resistance

3. {acrosome containing {enzyme / acrosin}4. involved in {digestion / break down} of the {zona pellucida / jelly layer}

5. {haploid / eq} nucleus 6. allows restoration of {diploid / full complement / 46 / eq} chromosomes at fertilisation

7. mitochondria qualified e.g. large number, correct location 8. to supply {ATP / energy} for {movement / eq}

9. {flagellum / eq} present 10. for propulsion / swimming / motility / eq

11.{markers / receptors} in cell surface membrane 12.to bind to egg cell surface membrane / detect chemicals released by ovum

Front 10

Describe and explain how, in mammals, events following the acrosome reactionprevent more than one sperm fertilising an egg

Back 10

1. sperm cell fuses withegg cell (membrane) 2. corticalgranules

3. idea of (cortical granules){moving towards / fusingwith } egg cell (surface)membrane

4. reference to exocytosis (ofcortical granules / vesicles /lysosomes)

5. idea of contents (of corticalgranules) {secreted/released into jelly layer /eq}

6. idea of { hardening /thickening / eq } of { zonapellucida / jelly layer } ORformation of fertilisationmembrane

7. reference to change incharge across egg cellmembrane

Front 11

Describe the function of mitochondria in spermcells.

Back 11

1. (they carry out) (aerobic) respiration

2. provide {ATP / energy / eq}

3. to { move / drive the / eq }{ flagellum / tail }

Front 12

Explain the importance of meiosis in the production of gametes.

Back 12

1. halves the chromosome number 2. to produce a haploid nucleus 3. so that at fertilisation the {fullcomplement / diploid number / eq} ofchromosomes is restored 4. allows genetic variation (in gametes) / 5. through independent assortment / 6. through crossing over