4.1.1.1 eukaryotes and prokaryotes
Plant and animal cells [eukaryotic cells] have a cell membrane, cytoplasm and genetic material enclosed in the
nucleus.
Bacterial cells [prokaryotic cells] are much smaller, they have a cytoplasm and a cell membrane surrounded by a cell
wall, the genetic material is not enclosed in a nucleus. It's a single DNA loop and there may be one or more small
rings of DNA called plasmids.
Cells are measured in micrometers. [um but u has a line under it like p]
1m = 1000mm
1mm = 1000 um
1um = 1000 nm
4.1.1.2 animal and plant cells
Most animal cells have these parts:
Nucleus, - contains the genetic material and controls the activities of the cell
Cytoplasm, - where chemical reactions take place
cell membrane, - holds the cell together and control what comes in and out of the cell
Mitochondria, - powerhouse of the cell provides energy for the cell to perform chemical reactions and is where
aerobic respiration takes solace.
ribosomes. - site of protein synthesis
Plant cells have the ones above as well as: chloroplasts - contains green chlorophyll to absorb light energy
and a permanent vacuole filled with cell sap. - helps support the shape of the cell and is used for storage of certain
materials.
Plant and algal cells have a cell wall made of cellulose which strengthens the cell and gives it extra support.
4.1.1.3 cell specialization
Cells specialize by going through a process called differentiation.
Specialized cells examples in animals:
Nerve cells: conduction of impulses.
Adaptations:
1. Has a cell body where most of the cellular structure is located and most protein synthesis occurs.
2. Extensions of the cytoplasm from the cell body form dendrites which receive signals and axons which
transmit signals allowing the neuron to communicate with other nerve cells, muscles or glands.
3. The axon is covered with a fatty sheath which speeds up nerve impulses which can be up to 1m long.
Muscle cells: contraction for movement
Adaptations:
1. 3 different types of muscle in animals: skeletal, smooth and cardiac [heart]
2. All have a high density of mitochondria to provide sufficient energy via respiration for muscle contraction.
3. All muscle cells have protein filaments in them, which the layers can slide over each other causing muscle
contraction.
Sperm cell: reproduction [to pass on the fathers genes]
Adaptations:
1. Head contains a nucleus which contains half the number of chromosomes [haploid no chromosome pairs]
2. The acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so
that the haploid nucleus can enter to fuse with the egg's nucleus.
3. The mid-piece is packed with mitochondria to release energy by respiration for the tail.
4. The tail rotates, propelling the sperm cells forwards allowing it to swim.
Specialized cells in plants:
Root hair cell: to absorb water and mineral ions form the soil.
, Adaptations:
1. Root hair increases the surface area so the rate of water uptake by osmosis is greater.
2. Thinner walls than other plant cells so water can move through more easily due to shorter diffusion distance.
3. Mitochondria for active transport of mineral ions.
4. Permanent vacuole containing cell sap which is more concentrated than soil water so maintaining a water
potential gradient.
Xylem vessel: is a transport tissue for water and dissolved ions
Adaptations:
1. No top or bottom walls between cells to form continuous hollow tubes through which water is drawn upwards
toward steh leaves by transpiration
2. Cells are essentially dead without organelles to allow free passage of water
3. Outer walls are thickened with lignin strengthening the tubes to help support the plant.
Phloem cells: transports dissolved sugars and amino acids
1. Made Of Living cells which are supported by companion cells
2. Cells are joined end to end and contain holes in cell walls [sieve plates] forming tubes which allow sugars
and amino acids to flow easily through by translocation.
3. Cells have few subcellular structures to aid the flow of materials.
4.1.1.4 cell differentiation
As an organism develops, cells differentiate to form different types of cells.
Most animal cells differentiate at an early stage.
Most tulips of plant cells retain the ability to differentiate through life.
In mature animals, cell division is mainly restricted to repair and replacement. As a cell differentiates it acquires
different subcellular structures to enable it to carry out a certain function, becoming a specialized cell.
Structural differences enable different types of cells to perform specific functions within the organism. It's important as
a cell changes to become specialized.
4.1.2.1 chromosomes
The nucleus of a cell contains chromosomes made of DNA molecules. Each chromosome carries a large number of
genes.
In body cells the chromosomes are normally found in pairs. One from each pair is inherited from the mother and the
other from the father. Humans have 46 chromosomes found in 23 pairs. Different species have different numbers of
chromosomes. Before a cell divides the genetic material needs or doubles which results in the X characteristic
shaped chromosomes we see in diagrams.
4.1.2.2 mitosis and the cell cycle
Cells divide in a series of stages called the cell cycle.
During the cell cycle the genetic material is doubled and then divided into two identical cells. Before it divides it needs
to grow and increase the number of subcellular structures such as ribosomes and mitochondria. The DNA replicates
to form two copies of each chromosome.
In mitosis, one set of chromosomes is pulled at each end of the cell and the nucleus divides. Finally, the cytoplasm
and cell membrane divide to form two new identical cells.
Cell division by mitosis is important in the growth and development of multicellular organisms.
1. Growth phase : the chromosomes are doubled, two copies of each chromosome are made which remain
attached to each other then will eventually be divided between the two genetically identical daughter cells.
The number of subcellular structures increases.
2. Mitosis: one chromosome from each set is pulled to each cell and a new nucleus forms around each group
of chromosomes.
3. Cytokinesis :the cytoplasm and cell membranes divide which result in the formation of two genetically
identical daughter cells.
Plant and animal cells [eukaryotic cells] have a cell membrane, cytoplasm and genetic material enclosed in the
nucleus.
Bacterial cells [prokaryotic cells] are much smaller, they have a cytoplasm and a cell membrane surrounded by a cell
wall, the genetic material is not enclosed in a nucleus. It's a single DNA loop and there may be one or more small
rings of DNA called plasmids.
Cells are measured in micrometers. [um but u has a line under it like p]
1m = 1000mm
1mm = 1000 um
1um = 1000 nm
4.1.1.2 animal and plant cells
Most animal cells have these parts:
Nucleus, - contains the genetic material and controls the activities of the cell
Cytoplasm, - where chemical reactions take place
cell membrane, - holds the cell together and control what comes in and out of the cell
Mitochondria, - powerhouse of the cell provides energy for the cell to perform chemical reactions and is where
aerobic respiration takes solace.
ribosomes. - site of protein synthesis
Plant cells have the ones above as well as: chloroplasts - contains green chlorophyll to absorb light energy
and a permanent vacuole filled with cell sap. - helps support the shape of the cell and is used for storage of certain
materials.
Plant and algal cells have a cell wall made of cellulose which strengthens the cell and gives it extra support.
4.1.1.3 cell specialization
Cells specialize by going through a process called differentiation.
Specialized cells examples in animals:
Nerve cells: conduction of impulses.
Adaptations:
1. Has a cell body where most of the cellular structure is located and most protein synthesis occurs.
2. Extensions of the cytoplasm from the cell body form dendrites which receive signals and axons which
transmit signals allowing the neuron to communicate with other nerve cells, muscles or glands.
3. The axon is covered with a fatty sheath which speeds up nerve impulses which can be up to 1m long.
Muscle cells: contraction for movement
Adaptations:
1. 3 different types of muscle in animals: skeletal, smooth and cardiac [heart]
2. All have a high density of mitochondria to provide sufficient energy via respiration for muscle contraction.
3. All muscle cells have protein filaments in them, which the layers can slide over each other causing muscle
contraction.
Sperm cell: reproduction [to pass on the fathers genes]
Adaptations:
1. Head contains a nucleus which contains half the number of chromosomes [haploid no chromosome pairs]
2. The acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so
that the haploid nucleus can enter to fuse with the egg's nucleus.
3. The mid-piece is packed with mitochondria to release energy by respiration for the tail.
4. The tail rotates, propelling the sperm cells forwards allowing it to swim.
Specialized cells in plants:
Root hair cell: to absorb water and mineral ions form the soil.
, Adaptations:
1. Root hair increases the surface area so the rate of water uptake by osmosis is greater.
2. Thinner walls than other plant cells so water can move through more easily due to shorter diffusion distance.
3. Mitochondria for active transport of mineral ions.
4. Permanent vacuole containing cell sap which is more concentrated than soil water so maintaining a water
potential gradient.
Xylem vessel: is a transport tissue for water and dissolved ions
Adaptations:
1. No top or bottom walls between cells to form continuous hollow tubes through which water is drawn upwards
toward steh leaves by transpiration
2. Cells are essentially dead without organelles to allow free passage of water
3. Outer walls are thickened with lignin strengthening the tubes to help support the plant.
Phloem cells: transports dissolved sugars and amino acids
1. Made Of Living cells which are supported by companion cells
2. Cells are joined end to end and contain holes in cell walls [sieve plates] forming tubes which allow sugars
and amino acids to flow easily through by translocation.
3. Cells have few subcellular structures to aid the flow of materials.
4.1.1.4 cell differentiation
As an organism develops, cells differentiate to form different types of cells.
Most animal cells differentiate at an early stage.
Most tulips of plant cells retain the ability to differentiate through life.
In mature animals, cell division is mainly restricted to repair and replacement. As a cell differentiates it acquires
different subcellular structures to enable it to carry out a certain function, becoming a specialized cell.
Structural differences enable different types of cells to perform specific functions within the organism. It's important as
a cell changes to become specialized.
4.1.2.1 chromosomes
The nucleus of a cell contains chromosomes made of DNA molecules. Each chromosome carries a large number of
genes.
In body cells the chromosomes are normally found in pairs. One from each pair is inherited from the mother and the
other from the father. Humans have 46 chromosomes found in 23 pairs. Different species have different numbers of
chromosomes. Before a cell divides the genetic material needs or doubles which results in the X characteristic
shaped chromosomes we see in diagrams.
4.1.2.2 mitosis and the cell cycle
Cells divide in a series of stages called the cell cycle.
During the cell cycle the genetic material is doubled and then divided into two identical cells. Before it divides it needs
to grow and increase the number of subcellular structures such as ribosomes and mitochondria. The DNA replicates
to form two copies of each chromosome.
In mitosis, one set of chromosomes is pulled at each end of the cell and the nucleus divides. Finally, the cytoplasm
and cell membrane divide to form two new identical cells.
Cell division by mitosis is important in the growth and development of multicellular organisms.
1. Growth phase : the chromosomes are doubled, two copies of each chromosome are made which remain
attached to each other then will eventually be divided between the two genetically identical daughter cells.
The number of subcellular structures increases.
2. Mitosis: one chromosome from each set is pulled to each cell and a new nucleus forms around each group
of chromosomes.
3. Cytokinesis :the cytoplasm and cell membranes divide which result in the formation of two genetically
identical daughter cells.
