Write an essay on the control of
processes in cells and the importance of
these controls
The cell cycle - correct answer-- The cell cycle is a series of events that occur in order to
produce two genetically identical daughter cells
- Tightly controlled by specific genes and highly regulated
- During interphase, the cell prepares to divide by replicating DNA and organelles
- Then the mitotic phase begins, starting with prophase, where the nuclear envelope breaks
down and chromosomes condense. The centrioles move to opposite poles of the cell and
the microtubules form a mitotic spindle
- Metaphase involves chromosomes lining up along the equator of the cell, attached to the
spindle by the centromere
- When the chromosomes are aligned, anaphase begins where the chromosomes seperate
into two chromatids at the centromere
- During telophase the spindle disappears and a new nuclear envelope forms around the
chromosomes, the chromosomes decondense. The cytoplasm then splits and two daughter
cells are formed
- This process is useful for growth of an organism or repairing damaged cells, however must
be regulated
- Tumor supressor genes slow down the rate of cell division and repair mistakes in DNA by
destroying cells with faulty DNA (apoptosis), maintaining the normal rate of cell division
- If a tumour surpressor gene becomes mutated it is switched off and no longer expressed,
causing uncontrolled cell growth
- While most of the time these cells die, those that survive can continue dividing and form a
tumor which may be malignant (cancerous)
- Therefore the role of tumor surpressor genes are important in controlling cell division as
without them cells would divide uncontrollably and lead to health issues
Movement of substances across membranes - correct answer-- Useful substances such as
glucose and amino acids must be transported across the cell membrane so that they can be
used in processes like respiration
- However, the cell membrane must also prevent unwanted substances from entering the
cell, therefore it needs to be selectively permeable in order to control this
- Phospholipid membrane is arranged in a phospholipid bilayer, with hydrophilic fatty acid
tails facing inside and hydrophobic phosphate heads facing outside
- This acts as a barrier to large or charged molecules, but allows smaller, uncharged
molecules like oxygen and water to pass through
- If this bilayer wasn't present it would be difficult to control the passage of substances thus
difficult to regulate metabolism
- Channel proteins within the cell membrane are selective in controlling the molecules they
allow to cross
- e.g. aquaporins are channel proteins that allow water to rapidly pass through the cell
membrane
processes in cells and the importance of
these controls
The cell cycle - correct answer-- The cell cycle is a series of events that occur in order to
produce two genetically identical daughter cells
- Tightly controlled by specific genes and highly regulated
- During interphase, the cell prepares to divide by replicating DNA and organelles
- Then the mitotic phase begins, starting with prophase, where the nuclear envelope breaks
down and chromosomes condense. The centrioles move to opposite poles of the cell and
the microtubules form a mitotic spindle
- Metaphase involves chromosomes lining up along the equator of the cell, attached to the
spindle by the centromere
- When the chromosomes are aligned, anaphase begins where the chromosomes seperate
into two chromatids at the centromere
- During telophase the spindle disappears and a new nuclear envelope forms around the
chromosomes, the chromosomes decondense. The cytoplasm then splits and two daughter
cells are formed
- This process is useful for growth of an organism or repairing damaged cells, however must
be regulated
- Tumor supressor genes slow down the rate of cell division and repair mistakes in DNA by
destroying cells with faulty DNA (apoptosis), maintaining the normal rate of cell division
- If a tumour surpressor gene becomes mutated it is switched off and no longer expressed,
causing uncontrolled cell growth
- While most of the time these cells die, those that survive can continue dividing and form a
tumor which may be malignant (cancerous)
- Therefore the role of tumor surpressor genes are important in controlling cell division as
without them cells would divide uncontrollably and lead to health issues
Movement of substances across membranes - correct answer-- Useful substances such as
glucose and amino acids must be transported across the cell membrane so that they can be
used in processes like respiration
- However, the cell membrane must also prevent unwanted substances from entering the
cell, therefore it needs to be selectively permeable in order to control this
- Phospholipid membrane is arranged in a phospholipid bilayer, with hydrophilic fatty acid
tails facing inside and hydrophobic phosphate heads facing outside
- This acts as a barrier to large or charged molecules, but allows smaller, uncharged
molecules like oxygen and water to pass through
- If this bilayer wasn't present it would be difficult to control the passage of substances thus
difficult to regulate metabolism
- Channel proteins within the cell membrane are selective in controlling the molecules they
allow to cross
- e.g. aquaporins are channel proteins that allow water to rapidly pass through the cell
membrane
