Topic 3 Flashcards
What are the common features in the cells of all living organisms?
Membranes, cytoplasm, ribosomes, some form genetic material
What are the types of cell?
Prokaryotic cells and eukaryotic cells
Which is more complex: prokaryotic or eukaryotic cells?
Eukaryotic- also bigger than prokaryotic cells
Where are prokaryotic cells found?
In simple organisms like bacteria
Where are eukaryotic cells found?
In all types of plants and animals
List the organelles found in prokaryotic cells
Cell wall, Capsule, Plasmid, Flagellum, Pili, Ribsomes, Mesosomes, Circular DNA
Function of cell wall
Supports the cell and stops it changing shape
Function of capsule
Helps to protect bacteria from attacks by immune system
Function of flagellum
Long hair-like structure that helps to move the cell
Function of pili
It’s used in the transfer of genetic material by helping stick prokaryotes stick together
Function of mesosomes
Inward folds in the plasma membranes with an unknown function
What’s the difference between the normal circular DNA and plasmids in bacteria?
Plasmids are smaller loops of DNA that can be passed between cells
List the organelles in eukaryotic cells
Nucleus, nucleolus, rough ER, smooth ER, mitochondria, centrioles, lysosomes, Golgi apparatus
Function of nucleus and nucleolus
Ribosomes and RNA are made in the nucleolus. The nucleus controls the cell’s activities because DNA is located here
Function of rough ER
Folds and processes proteins
Function of smooth ER
Synthesises and processes lipids
Function of ribosomes in prokaryotic and eukaryotic cells
Site of protein synthesis
Function of mitochondria
Site of later stages of aerobic respiration
Function of centrioles
The separation of chromosomes in cell division
Function of lysosomes
Ingestion of invading cells and break down of unwanted structures, both by digestive enzymes
Function of Golgi apparatus
Modifies proteins and packages them in vesicles for transport
How are proteins transported out of the cell?
- They enter the rER, assuming a 3D shape as they make their way through
- Vesicles containing the protein fuse to form flattened sacs of the Golgi apparatus
- Proteins are modified within the Golgi apparatus
- Vesicles with the modified protein pinch of the Golgi apparatus and fuse with the cell membrane, releasing it
How do sperm fertilise eggs?
1) Sperm reach the ovum
2) Chemicals are released from cells surrounding the ovum, triggering acrosome reaction
3) The acrosome swells, fusing with the sperm cell membrane
4) Digestive enzymes are released from acrosome
5) Sperm fuses with ovum membrane and enters
6) Enzymes released from ovum thicken zona pellucida stop any more sperm entering
7) The two nuclei fuse
Why is mitosis needed?
For growth of multi-cellular organisms, repairing damaged tissues, asexual reproduction
What are the stages of the cell cycle?
Growth phase 1- cell grows, new organelles and proteins are made
Synthesis- DNA replicates to prepare for mitosis
Growth phase 2- proteins for cell division made
Mitosis- cell cycle begins and ends here
What are the five stages of mitosis?
Prophase, metaphase, anaphase, telophase, cytokenesis
Describe how proteins are modified, packaged and secreted by the cell (4 marks)
- In the rER proteins are folded- forms 3-D shape
- The proteins is packaged into transport vesicles by the rER
- The vesicles move to the Golgi apparatus and fuse with it
- They are then changed in Golgi apparatus ;
- The protein is transferred in secretory vesicles from the Golgi apparatus to the cell membrane
- Vesicles fuse with cell surface membrane- protein is secreted
Describe what happens during prophase
Chromosomes condense to become shorter and fatter. Centrioles start moving to opposite sides of the cell, forming networks of spindle. The nuclear envelope breaks down
Describe what happens during metaphase
Chromosomes line up along the middle of the cell. They then become attached to the spindle by their centromere.
Describe what happens during anaphase
Centromeres divide, separating each pair of sister chromatids. Spindles contract, pulling chromatids to opposite poles of the cell.
Describe what happens during telophase
The chromatids reach opposite poles of the cell and uncoil. They are called chromosomes again. A nuclear envelope forms around the chromosomes, making two nuclei,
Describe what happens during cytokenesis
The cytoplasm divides to form two daughter cells that are genetically identical to each other and to the parent cell.
Describe the process of meisosis
1) DNA replicates to form two identical copies of each chromosome, called chromatids
2) The chromosomes pair up to form homologous pairs
3) The first division results in the separation of homologous pairs
4) The second division results in the pairs of chromatids being seperated
5) 4 genetically different gametes are produced.
