, . Topic 1: Movement across Membranes .
Cell membranes are selectively permeable meaning that they allow certain substances to pass through
& prevent other substances from entering. Membranes are 1 cell thick
Molecules enter or leave the cell through: Osmosis; Diffusion; Active Transport
● Diffusion- Movement of molecules from an area of high
concentration to low concentration until concentration is
equal on both sides
● Osmosis- Movement of water molecules from an area of
high water potential to an area of low water potential
across a semipermeable membrane. Cell membranes do
not allow dissolved substances. Eg. sugar to pass through
● Active Transport- Transport of molecules against a concentration gradient,
which therefore requires energy. Some organic molecules eg. amino acids &
glucose are too large to fit through the membrane. Protein in the membrane
will gain energy from the mitochondria to move these molecules through the
membrane
Topic 2: Cell Division
Cell Cycle
A series of processes that take place in a cell between 1 cell division & the next
● During the cell cycle, cells grow & prepare for cell division & after cell division, the new cell
grows and the cycle carries on
● The cell cycle has 4 main stages
○ Growth of cell & production of new materials
○ Replication of DNA & duplication of chromosomes
○ Final growth & preparations for cell division
○ Mitosis & Cytokinesis
Interphase- The period between cell divisions during which the cell grows & prepares to divide
(preparation for mitosis)
● During the first parts of interphase, Cells are active & continue regular activities
● Nerve cells & blood cells DO NOT go through mitosis
Chromosomes
Are found in the cell nucleus & contains info that controls cell processes
● Structure- When not undergoing division, chromosomes form a tangled ball
called the chromatin network. But during interphase, The chromosomes
untangle and replicate themselves. Chromosomes are made up of DNA & protein
Mitosis
Process where 1 cell divides to form 2 identical cells
● Identical cells have the same number & type of chromosomes
● Meiosis is the cell division process that halves the chromosome number to produce
reproductive cells, such as sperm and eggs.
○ Zygote- result of the sperm & egg fusing. It undergoes
mitosis for several weeks to form an embryo which
will grow into a foetus thru mitosis
○ Meiosis produces sperm cells & egg cells
Cell membranes are selectively permeable meaning that they allow certain substances to pass through
& prevent other substances from entering. Membranes are 1 cell thick
Molecules enter or leave the cell through: Osmosis; Diffusion; Active Transport
● Diffusion- Movement of molecules from an area of high
concentration to low concentration until concentration is
equal on both sides
● Osmosis- Movement of water molecules from an area of
high water potential to an area of low water potential
across a semipermeable membrane. Cell membranes do
not allow dissolved substances. Eg. sugar to pass through
● Active Transport- Transport of molecules against a concentration gradient,
which therefore requires energy. Some organic molecules eg. amino acids &
glucose are too large to fit through the membrane. Protein in the membrane
will gain energy from the mitochondria to move these molecules through the
membrane
Topic 2: Cell Division
Cell Cycle
A series of processes that take place in a cell between 1 cell division & the next
● During the cell cycle, cells grow & prepare for cell division & after cell division, the new cell
grows and the cycle carries on
● The cell cycle has 4 main stages
○ Growth of cell & production of new materials
○ Replication of DNA & duplication of chromosomes
○ Final growth & preparations for cell division
○ Mitosis & Cytokinesis
Interphase- The period between cell divisions during which the cell grows & prepares to divide
(preparation for mitosis)
● During the first parts of interphase, Cells are active & continue regular activities
● Nerve cells & blood cells DO NOT go through mitosis
Chromosomes
Are found in the cell nucleus & contains info that controls cell processes
● Structure- When not undergoing division, chromosomes form a tangled ball
called the chromatin network. But during interphase, The chromosomes
untangle and replicate themselves. Chromosomes are made up of DNA & protein
Mitosis
Process where 1 cell divides to form 2 identical cells
● Identical cells have the same number & type of chromosomes
● Meiosis is the cell division process that halves the chromosome number to produce
reproductive cells, such as sperm and eggs.
○ Zygote- result of the sperm & egg fusing. It undergoes
mitosis for several weeks to form an embryo which
will grow into a foetus thru mitosis
○ Meiosis produces sperm cells & egg cells
