BIOLOGY: Topic 1 ( cell biology ) : Cell structure , specialised cells , osmosis RP , microscopes

Name 2 types of cells

Prokaryotic and eukaryotic cells.

What is the difference between prokaryotic and eukaryotic cells ?

Prokaryotic cells are single-celled organisms without a nucleus, while eukaryotic cells can be unicellular or multicellular and contain a nucleus.

Give an example of eukaryotic cells ?

Animal and plant cells

Give an example of prokaryotic cells

Bacterial cells

What is the definition of a cell?

Basic unit / building block of all living organisms

What are the subcellular structures of an animal cell?

Nucleus , cell membrane , cytoplasm , mitochondria and ribosomes

What are the subcellular structures of an plant cell?

Nucleus , cell membrane , cytoplasm , mitochondria , ribosomes , chloroplasts , vacuole & cell wall

What are the subcellular structures of a bacterial cell ?

Cell wall , cell membrane , string of DNA , plasmids , flagellum , ribosomes & cytoplasm

What is the function of the nucleus?

Contains the DNA which controls the cells activities

What is the function of the cell membrane ?

Controls wht enters and leaves the cell

What is the function of the cytoplasm ?

Whewre chemical reactions occur

What is the function of the mitochondria ?

Rleases energy from aerobic respiration

What is the function of the ribosomes ?

Protien synthesis

What is the function of the chloroplasts ?

Where photosynthesis occurs

What is the function of the vacuole ?

To store water and other chemicals like cell sap

What is the function of the cell wall ?

strengthens and supports the cell

What is the function of the plasmids ?

• Loops of DNA

What is the function of the flagellum ?

• Tail like structure which allows it to move

What is a stem cell ?

A stem cell is an undifferentiated cell that can:

• divide by mitosis to produce more stem cells

• differentiate into specialised cells

What does differentiation mean ?

Differentiation is the process by which a cell changes to become a specialised cell for a specific function.

Examples:

• nerve cell

• muscle cell

• red blood cell

What are 2 properties of stem cells ?

• They can divide repeatedly by mitosis.

• They can differentiate into specialised cells.

Where are embryonic stem cells found ?

Embryonic stem cells are found in early embryos.

Why are embryonic stem cells useful ?

They can differentiate into almost any type of cell in the body.

Examples:

• nerve cells

• muscle cells

• skin cells

• blood cells

What are some possible uses of embryonic stem cells ?

Embryonic stem cells may be used to treat:

• paralysis

• diabetes

• damaged nerve tissue

• blood disorders

• damaged organs

State 3 advantages of embryonic stem cells ?

• Can differentiate into almost any cell type.

• Could treat many diseases.

• Large numbers can be grown in laboratories.

State 3 disadvantages of embryonic stem cells?

• Embryos are destroyed.

• Some people believe it is unethical.

• Cells may carry viruses.

Why are some people against embryonic stem cell research ?

Because embryos are destroyed during the process.

Some people believe embryos represent potential human life and therefore should not be used for research.

Where are adult stem cells found ?

Adult stem cells are found in some tissues of the body.

A common example is bone marrow.

What is bone marrow ?

Bone marrow is a soft tissue found inside bones that contains stem cells capable of producing blood cells.

What can bone marrow stem cells be used for ?

Bone marrow stem cells can be used to treat blood diseases such as:

• leukaemia

• some immune disorders

Why are adult stem cells less flexible than embryonic stem cells?

Adult stem cells can only differentiate into a limited range of cell types.

Embryonic stem cells can differentiate into almost any cell type.

State three advantages of adult stem cells.

• No embryos are destroyed.

• Fewer ethical concerns.

• Can be taken from the patient.

• Less risk of rejection.

State three disadvantages of adult stem cells.

• Can only form certain cell types.

• Can only treat a limited number of diseases.

• Small risk of infection.

Why is rejection less likely when adult stem cells are taken from the patient?

The cells have the patient's own genetic information, so the immune system is less likely to recognise them as foreign.

What are meristem cells?

Meristem cells are stem cells found in growing regions of plants.

Found in:

• root tips

• shoot tips

What is special about meristem cells?

Meristem cells can differentiate into any type of plant cell throughout the life of a plant.

State three benefits of using meristem cells.

• Cheap to grow.

• Can produce clones of plants quickly.

• Can conserve rare plant species.

Why can meristem cells help farmers?

They allow large numbers of genetically identical plants with desired characteristics to be produced quickly.

What is therapeutic cloning ?

Therapeutic cloning is a process used to produce stem cells that are genetically identical to a patient.

Describe therapeutic cloning.

• Remove nucleus from patient's body cell.

• Remove nucleus from egg cell.

• Insert patient's nucleus into egg cell.

• Cell begins dividing.

• Embryo forms.

• Stem cells are removed from embryo.

Why is thearapeutic cloning useful ?

The stem cells produced are genetically identical to the patient.

Therefore there is little or no risk of rejection.

State 2 advantages of therapeutic cloning ?

• Stem cells can become different cell types.

• Could replace damaged tissues and organs.

State three disadvantages of therapeutic cloning.

• Embryo is destroyed.

• Ethical concerns.

• Risk of transferring viruses.

What is meant by transplant rejection?

Transplant rejection happens when the immune system identifies transplanted tissue as foreign and attacks it.

Why are stem cells important in medicine?

• replace damaged cells

• repair tissues

• treat disease

• grow replacement tissues and organs

What is magnification?

Magnification is how many times bigger an image is than the actual object.

State the magnification equation.

Magnification = Image size ÷ Actual size

Rearrange the magnification equation to find image size.

Image size = Magnification × Actual size

Rearrange the magnification equation to find actual size

Actual size = Image size ÷ Magnification

How many micrometres (μm) are in 1 millimetre (mm)?

1 mm = 1000 μm

What is resolution?

Resolution is the ability to distinguish between two separate points.

Higher resolution means more detail can be seen.

What is the difference between magnification and resolution?

Magnification = makes the image bigger.

Resolution = makes the image clearer and more detailed.

Why isn't increasing magnification always useful?

increasing magnification does not always increase detail.

If resolution stays the same, the image becomes larger but not clearer.

Why are electron microscopes better than light microscopes?

Electron microscopes have:

• higher magnification

• higher resolution

What can electron microscopes see that light microscopes cannot?

• ribosomes

• internal cell structures in greater detail

• very small organelles

Why are electron microscopes not always used?

• expensive

• large

• require specialist training

• cannot easily observe living specimens

What is osmosis?

Osmosis is the net movement of water molecules through a partially permeable membrane from a dilute solution to a concentrated solution.

What is a partially permeable membrane?

A partially permeable membrane allows some molecules to pass through but not others.

Why does osmosis occur?

Water moves to equalise concentrations on both sides of a partially permeable membrane.

Which molecules move during osmosis?

Water molecules only.

What does a dilute solution mean?

A dilute solution contains:

• lots of water molecules

• low concentration of dissolved substances

What does a concentrated solution mean?

A concentrated solution contains:

• fewer water molecules

• high concentration of dissolved substances

Which direction do water molecules move during osmosis?

Dilute solution → Concentrated solution

What happens to an animal cell in a concentrated solution?

Water leaves the cell by osmosis.

The cell:

• shrinks

• becomes crenated

What happens to a plant cell in a dilute solution?

Water enters the cell by osmosis.

The vacuole expands.

The cell becomes:

✅ Turgid

What does turgid mean?

Turgid means swollen and firm because water has entered the plant cell.

Healthy plant cells are turgid.