Topic 3: Cell Structure, Reproduction and Development Flashcards
Explain why J can be seen using the electron microscope but not the light microscope
- because electron microscope has a high magnification
- because this structure is small
Explain why the nuclear envelope cannot be seen as two membranes using this electron microscope
- two membranes are close together
- resolution of this microscope is not high enough.
The student describe one organelle that was seen as “several curved membrane-bound sacs decreasing in size (1)
B- golgi apparatus
(ii) Explain why this organelle cannot be seen using a light microscope.
(2)
because the magnification of the light microscope is not high enough
because it is very small.
Give two differences between an organ and a tissue
1- Organ has many functions whereas a tissue has fewer
2- Organ has several groups of cell types whereas a tissue has one cell type.
(b) Plant cells can also be studied using an electron microscope.
Name two structures present in animal cells that are not present in a plant cell.
(2)
- flagellum
- cilia
State the function of these cells:
Slimy capsule
Pili
Slimy capsule prevents dehydration of the cell.
Pili allows bacteria to adhere to surfaces.
Name three structures found in a prokaryotic cell but not in a eukaryotic cell.
(3)
- plasmid
- pili
- slimy capsule
Describe what occurs during prophase (4 marks)
- chromatin condenses
- chromosome becomes visible
- nuclear envelope breaking down.
- centrioles moving to poles.
- nucleolus disappears.
Describe the process of crossing over. (3 marks)
- homologous chromosomes pair up.
- chromatids from a pair of chromosomes overlap.
- chiasmata break in chromatid.
- recombination of chromatids.
Explain what is meant by the term chromatid
one of two DNA molecules that make up a chromosome.
DNA replicates in S phase.
Explain why several divisions of mitosis are involved in the production of sperm cells.
- to increase the number of primary spermatocytes.
- there is are many sperm cells produced.
1.Heat the root tip of the acid
2. warm gently to intensify the stain.
3. press down gently on the cells.
4. cover with a glass coverslip
5. add the stain to the root tip
6. tease the cell apart.
What is the correct order for these steps.
A. 1,5,6,4,3,2
B. 1,6,3,4,5,2
C. 5,2,6,1,4,3,
D.6,1,5,4,3,2
A - 1,5,6,4,3,2
Describe the role of the rough endoplasmic reticulum
for protein synthesis
to fold the protein
for protein transport
to package the protein into vesicles.
Explain the importance of mitosis in budding
- mitosis result in two cells that each have a nucleus.
- each bud contains a full set of chromosome.
- so each bud are genetically identical to the parent yeast cell.
Explain the role of meiosis in the production of genetically varied sperm cells. (5 marks)
- to produce haploid cells
- chiasmata break in chromatid which leads to the formation of chromatids.
- homologous chromosomes maternal and paternal chromosomes line up in different combinations.
- New combinations of alleles in the gametes.
Describe the structure of plasmodesmata.
- pores in the cell wall between adjacent cells.
- there is cytoplasm running through the plasmodesmata.
Describe the role of structure S
- structure S is flagellum enabling the sperm to swim.
- to transfer the male genetic material from the cervix to the ovum.
Give two difference other than size between the structure of a sperm cell and the structure of a female gamete (2)
Sperm cell has flagellum whilst female gamete does not have.
Sperm cell has an acrosome but a female gamete does not have.
Compare mitosis with meiosis (3)
- mitosis produces two cells but meiosis produces four cells.
- mitosis produces diploid cells but meiosis produces haploid cells.
- no crossing over in mitosis but there is in meiosis.
Describe the process of fertilisation in mammals.
release of enzymes from sperm.
sperm digests the zona pellucida
fusion of sperm cell and female gamete membrane.
cortical reaction occurs allowing the zona pellucida to harden.
