Topic 2 - Cells, Viruses and Reproduction

• One male gamete fuses with two polar nuclei to form triploid endosperm nucleus • One male gamete fuses with female gamete to form diploid zygote

Spermatogenesis Oogenesis

1) Primodial germ cell > Spermatogonia 2) Spermatogonia > Primary spermatocyte 3) Primary spermatocyte > Secondary spermatocyte 4) Secondary spermatocyte > Spermatids 5) Spermatids > 4 Spermatozoa

1) PGC > Oogonia 2) Oogonia > Primary oocyte 3) Primary oocyte > Secondary oocyte & 1 polar body 4) Secondary oocyte & 1 polar body> 1 ovum & 3 polar bodies

PGC divides by mitosis - forms spermatogonia Then continues to grow without further division - forms primary spermatocyte

• Pollen • Anthers

• Ovules • Ovaries

M - Spermatozoa F - Ova

Sexual reproduction that reproduces 4 genetically different haploid cells

Meiosis forms male microspores and female megaspores which then produce gamete’s

Large multi-enzyme complexes cut and rejoin parts of the maternal and paternal chromatids at the end of prophase 1

1) Meiosis of diploid microspore cells in the anther forms 4 haploid microspores 2) Haploid microspores mature into pollen grains via mitosis

• Outer protective coating • Pollen tube cell (which has its own nucleus) elongates to penetrate ovule

• A series of flattened sacs enclosed by a membrane with ribosomes on the surface • Folds and processes proteins made on the ribosomes

• A series of membrane bound sacs • Synthesises and processes lipids and steroids

• A series of fluid-filled, flattened and curved sacs called cisternae, with vesicles surrounding the edges • Sorts, processes and packages proteins and lipids • Also produces lysosomes

• Oval-shaped and bound by a double membrane called the envelope • Inner membrane folded to form projections called cristae, with matrix on the inside containing the enzymes needed for cellular respiration

• Hollow cylinders containing a ring of microtubules arranged at right angles to each other • Involved in cell division

• Large subunit (60S) and small subunit (40S) • Site of protein synthesis

• Vesicles containing digestive enzymes bound by a single membrane

• Nucleus • RER -SER • Golgi apparatus • Mitochondria • Centrioles • 80S ribosomes • Lysosomes

• Cell wall • Slime capsule • Plasmid • Flagellum • Pili • 70S ribosomes • Mesosomes

Rigid outer covering made of peptidoglycan Provides the cell with strength and support

Protective slimy layer which helps the cell to retain moisture and adhere to surfaces