Which steps of the cell cycle is interphase composed of?
G1 (Gap 1), S (Synthesis), and G2 (Gap2).
What happens during the G1 phase?
Cells increase in size, produce RNA, and synthesise proteins.
What happens during the S phase?
DNA replication occurs.
What happens during the G2 phase?
The cell will continue to grow and synthesise new proteins required for cell division.
Which step follows interphase?
Mitosis.
What are the five stages of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytoplasmic division
Outline what happens during prophase.
- Chromosomes condense and become visible
- Chromatids are two strands of a chromosome joined at one region called the centromere
- Microtubules from the cytoplasm form a three-dimensional structure known as the spindle
- Centrioles move around the nuclear envelope and position themselves at opposite sides of the cell, forming the poles of the spindle
- Spindle fibres form between the poles
Outline what happens during metaphase.
- The nuclear envelope breaks down
- The chromosomes move and the chromosomes’ centromeres attach to spindle fibres
Outline what happens during anaphase.
- The centromeres split
- The spindle fibres shorten, pulling the two halves of the centromere in opposite directions
- One chromatid of each chromosome is pulled to each of the poles
- The separated chromatids reach the poles and the spindle breaks down
Outline what happens during telophase.
- Chromosomes unravel
- The nuclear envelope reforms
- The two sets of chromsomes become enclosed in seperate nuclei
Outline what happens during cytoplasmic division.
- The cell surface membrane contracts until the cell is divided
- Two new cells are formed
What are totipotent cells?
Cells which have the ability to develop into a total individual.
What does the outer blastocyst cell layer form?
The placenta.
Why are the cells in the inner cell mass of a blastocyst known as ‘pluripotent embryonic stem cells?’
They can potentially give rise to most cell types.
What are multipotent stem cells?
Cells which have the ability to give rise to a few different cell types (e.g. white blood cells can develop into red blood cells, platelets, and other types of white blood cells like phagocytes and lymphocytes).
What features do prokaryotic cells have?
- No nuclei
- Ribosomes
- Circular DNA
- Cytoplasm
- Infolded cell surface membrane
- Cell wall (which contains peptidoglycan)
- Pili*
- Flagellum*
- Capsule (slime layer on surface)*
- Plamids*
*Not always present
What features do eukaryotic cells have?
- Mitochondria
- Nucleus
- Nucleolus
- Rough endoplasmic reticulum
- Ribosomes
- Smooth endoplasmic reticulum
- Golgi apparatus
- Lysosomes
- Centrioles
- Cell surface membrane
What features do prokaryotic and eukaryotic cells have in common?
- Ribosomes
- Cytoplasm
- Vesicles
- Vacuoles
