Topic 2 (CELLS) IB Biology SL
Topic 2 (CELLS) IB Biology SL
Topic 2 (CELLS) IB Biology SL
2.1.1 Outline the Cell Theory
- Cells are the building blocks of structure in living things
- Cells are the smallest unit of life
- Cells are derived from pre-existing cells by division
2.1.2 Discuss the evidence of the Cell Theory
- Living things are made of cells
- observations by microscoptists of uni- and multicellular organisms, especially structure of tissue and organs
- Cells are the smallest unit of life
- discovery of viruses, which can only exist with a host cell
- biochemical investigations of organelles, only functioning for a limited amount of time outside of the cell
- Cells come from pre-existing cells
- Pasteurs Obseravtion
- Observations of the beahviour of cells at division
2.1.3 State the unicellular organisma carry out all functions of life
Unicellular organisms are the smallest organisms capable of human life
M ovement
R eprodcution
S ensitivity
G rowth
R espiration
E xcretion
N utrition
2.1.4 Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropiate SI unit
A molecule: 1nm
Cell membrane thickness: 7.5nm
Virus: 100nm (range: 20-200nm)
Bacteria: 1-5nm
Organelles: +10um
Eukaryotic Cells: +100um
2.1.6 Explain the importance of the surface area to volume ratio as a factor limiting cell size
- The rate of metabolism of a cells is a function of its mass/volume
- The rate of material exchange in and out of a cell is a functions of its surface area
- As the cell grows, volume increases faster than surface area
- If metabolic rate is greater than the rate of exchange of vital materials and waste, the cell will die
- Cell must consequently divide in order to restore viable surface to volume ratio to survive
- Cells and tissues specialized for gas or material exchange (ei.elveoli) will increase surface area to optimize the transfer of materials
2.1.7 State that multicellular organisms show emergent properties
- Cells may group together to form tissues
- Organs are then formed from the functional grouping of multiple tissues
- Organs that interact may form organ systems capable of carrying out specific body functions
- Organ systems carry out the life functions required by an organism
2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized fucntions by expressing some of their genes but not others
- When a cell changes its structure in order to perform a specific function, it's called a differentiated cell
- When differentiated cells perform specific functions they are termed specialized
- All cells carry the same genetic information
- Depending on the position of a cell in the body and the needs of the body, it becomes specialized in order to perform certain functions
- This is done by switching on the relevant genes so that only certain proteins required dor the cell to function are produced
- The other genes stay switched off
2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized fucntions by expressing some of their genes but not others
- When a cell changes its structure in order to perform a specific function, it's called a differentiated cell
- When differentiated cells perform specific functions they are termed specialized
- All cells carry the same genetic information
- Depending on the position of a cell in the body and the needs of the body, it becomes specialized in order to perform certain functions
- This is done by switching on the relevant genes so that only certain proteins required dor the cell to function are produced
- The other genes stay switched off
2.1.9 State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways
Self rewenewal: They can continously divide and replicate
Potency: They have the capacity to differentiate into specialized cell types
2.1.10 outline the therapeutic use of stem cells
Leukaemia - bone transplant is done in leukaemia patients. Large numbers of white blood cells uncontrollably produced that can not function
- chemiotherapy used to destroy white blood cells and stem cells in the patient
- a donor with the same tissue match will donate bone marrow (contains large numbers of stem cells)
- this is transplanted into the patient
- the immune system has to be supressed, to prevent the rejection of the bone marrow, through immune supressend drugs
- healthy stem cells will start dividing and differentiating and producing healthy white blood cells
2.2.1 Draw and laberl a diagram of the ultrastructure of Eschterchia Coli as an example of a prokaryote
Bild:
2.2.2 Annote the diagram from 2.2.1 with funstions of each named structure
Cell wall: Protects cell / Keeps shape / prevents cell from bursting
Plasma Membrane: Controls entry and exist of substances
Pili: Allows plasmids to be transported
Ribosomes: Synthesizes proteins
Cytoplasm: Site for chemical reactions
Nucleoid: Contains genteic information, hence controls metabolism
Flagella: Used for movement
Plasmid: Smaller rings od DNA consisting of genetic information
Capsule: Prevents dehydration
2.2.3 Identify strucutres from 2.2.1 in electron micrographs of E.coli
Bild:
2.2.4 State that prokaryotic cells divide by binary fission
Binary fission is a form of asexual reproduction and cell division used by prokaryotic organisms
It is not the same as mitosis
-The circular DNA is copied in response to a replication signal
-The two DNA loops attach to the membrane
-The membrane elongates and pinches off (cytokinesis) forming two seperate cells
2.3.1 Draw and label a diagram of the ultrastructure of a lovel cell as an example of an animal cell
Bild:
2.3.2 Annote the diagram of 2.3.1 with the function of each named structure
Polysomes: Produces specialized proteins used with the cell as such as enzymes (ribosomes that are detached from endoplasmic reticulum)
Plasma membrane: Controls incoming and existing substances
Mitochondria: Produces ATP by aerobic cell respiration; fat is digested here
Endoplasmic Reticulum: Synthesizes proteins made by ribosomes
Cytoplasm: Site for chemical reaction
Microvilli: Increasing surface area to volume ratio
Nucleus: Stores genetic information
Centrosome: for mitosis
Lysosome: Killing bacteria
Vessicles: Transport protein
Ribosomes: produce protein
Polysomes: produce protein
2.3.3 Identify structures from 2.3.1 in electron micrograph of liver cells
Bild:
2.3.4 Compare prokaryotic and eukaryotic cells
Prokaryotic / Eukaryotic
Cell wall present / Cell wall only present in plants/fungi
A naked loop of dna / Strands of DNA (4+ chromosomes present)
DNA in nucleoid and cytoplasm / DNA in nucleus
Mitochondria not present / Mitochondria always present
Flagella solid / Flagella flexible
Ribosomes: 70s / 80s
Fewer/none internal membranes present / Many internal membranes present
pili/plasmis present / absent
Both:
functional cells performing metabolic actions; have cell membrance, cytoplasm, genetic material
2.3.5 State the difference between plants and animal cells
Plants / Animals
Cell wall and plasma membrane present / No cell wall, only plasma membrane
Chloroplasts present in cells that photosynthesize / Chloroplasts not present
Starch is used as storing compound / Glycogen is used as storing compound
Vacuole often present (filled with water) / Vacuole not usually present, if they are small and specialized
Fixed shape / Able to change shape
Centrosome absent / Centrosome present
2.3.6 Outline the roles of extracellular components
- The plant wass maintains shape, prevents excess water uptake, and holds the whole plant up agains the force of gravity
- Animal cells secrete glycoproteins that form extracellular matrix (ECM). This function is for support, adhesion and movement
2.4.1 Draw and label a diagram to show the structure of a membrane
Bild:
2.4.2 Explain how phospholipid properties help to maintain membrane structure
Structure of Phospholipids
- Consist of a polar head (hydrophilic) made from glycerol and phosphate
- Consist of two non-polar fatty acid tails (hydrophobic)
Arrangement in Membrane
- Phospholipids spontaneously arrange in a bilayer
- Hydrophobic tail regions face inwards and are shielded from the surrounding polar fluid while the two hydrophilic head regions associate with the cytosolic and extracellular environments respectively
Structural Properties of Phospholipid Bilayer
- Phospholipids are held together in a bilayer by hydrophobic interactions (weak associations)
- Hydrophilic / hydrophobic layers restrict entry and exit of substances
- Phospholipids allow for membrane fluidity / flexibility (important for functionality)
- Phospholipids with short or unsaturated fatty acids are more fluid
- Phospholipids can move horizontally or occasionally laterally to increase fluidity
- Fluidity allows for the breaking / remaking of membranes (exocytosis / endocytosis)
2.4.3 List the funstions of membrance proteins
Antigen Protein: Cell to cell recognition; antibody reaction
Channel Protein: allows, by facillitated diffusion, one specific substance to pass
Pump Protein: for active transport across membranes
Carrier Protein: Involves ATP; carries ions
Electron Carrier Protein: Chain of peripheral and integral proteins that allow electrons to pass through membrance
Active Site: the substrate molecule fits here and the reaction then occurs
Glycoprotein: for attachment of specific hormone; responsible for cell to cell binding and recognition
Enzymes: Catalysing reaction in or outside cell
Receptive Protein: Responsible for recieving chemical stimuli
2.4.4 Define Diffusion and Osmosis
Diffusion:
The net movement of particles from a region of high concentration to a region of low concentration (along the gradient) until equilibrium
Osmosis:
The net movement of water molecules across a semi-permeable membrane from a region of low solute concentration to a region of high solute concentration until equilibrium is reached
2.4.5 Explain the passive transport in terms of simple facilitated diffusion
The plasma membrane is semi-permeable and selective in what can cross
Substances that move along the concentration gradient (high to low) undergo passive transport and do not require the expenditure of energy (ATP)
Simple diffusion:
- Small, non-polar (lipophilic) molecules can freely diffuse across the membrane
Facilitated diffusion:
- Larger, polar substances (ions, macromolecules) cannot freely diffuse and require the assistance of transport proteins (carrier proteins and channel proteins) to facilitate their movement (facilitated diffusion)
2.4.6 Explain the role of protein pumps ant ATP in active transport across membrane
- Particle is large and moves against gradient - requires ATP
- Carrier Protein is needed, when carrier protein works together with ATP it becomes a Protein Pump
- Proteins only carry a specific molecule and the process is highly selective. Takes in molecule through protein and ATP synthesase. ATP is used to change structure of the protein so that molecule can be transported and moved to otherside of membrane
2.4.7 Explain how vessicles are used to transport materials within a cell between the rough endoplasmic reticulum , golgi apparatus and plasma membrane
Ribosomes make proteins, which reacg the rough endoplasmic reticulum. In the endoplasmic reticulum the protein can be stored or transported. If transported the ER breaks up into the golgi body, which becomes vessicles. The vessicles diffuse with plasma membrane and release proteins
- Ribosome make proteins and they are transferred to ER
- Protein is already synthesized and present in the rER
- Protein is moved through the rER and modified
- A spherical vessicle us formed from the end of the rER with the protein inside
2.4.8 Describe how the fluidity of the membrane allows it to change shape, break and re-form during endocytosis and exocytosis.
The membrane is principally held together by the relatively weak hydrophobic associations between phospholipids
This association allows for membrane fluidity and flexibility, as the phospholipids (and to a lesser extent the proteins) can move about to some extent
This allows for the breaking and remaking of membranes, allowing larger substances access into and out of the cell (this is an active process)
Endocytosis
- The process by which large substances (or bulk amounts of smaller substances) enter the cell without travelling across the plasma membrane
- An invagination of the membrane forms a flask-like depression which envelopes the material; the invagination is then sealed off forming a vesicle
- There are two main types of endocytosis:
1. Phagocytosis
- The process by which solid substances (e.g. food particles, foreign pathogens) are ingested (usually to be transported to the lysosome for break down)
2. Pinocytosis
- The process by which liquids / solutions (e.g. dissolved substances) are ingested by the cell (allows quick entry for large amounts of substance)
Exocytosis
- The process by which large substances exit the cell without travelling across the plasma membrane
- Vesicles (usually derived from the golgi) fuse with the plasma membrane expelling their contents into the extracellular environment
2.5.1 Outline the stages in the cell cycle, including interphase (G1, S, G2), mitosis and cytokinesis
G1 - major phase in interphase. All metabolic reactions are taking place in G1 phase. Including formation of new organelles (also growing)
S - When the genetic material gets duplicated (replication of DNA)
G2 - Preparation for division
Mitosis
- Karyokinesis (nucleus division)
- Cytokinesis (cytoplams division)
2.5.2 State that tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue
Cell Division is a controlled process. Due to certain chemicals or radiations, which cause changes in genetic make up of a cell (mutation), the cell may undergo uncontrolled cell division. This can result in a tumor which may be harmless (benign) or harmful (malignant). The agent causing uncontrolled cell division is called carcinogen.
2.5.3 State that interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/ or chloroplasts
The cell cycle can be divided into interphase and mitosis. The major part of the cell cycle comproses the Interphase. The stage is divided into G1, S and G2 phases. During G1 all metabolic reactions are taking place, including formation of new organelles and growth. During S phase genetic material gets duplicated. During G2 preparation of division is taking place. Inter phase is and active phase un the cell during which many mnetabolic activities take place including cellular respiration, gaseous exchange and protein synthesis.
2.5.4 Decribe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telephase)
Prophase:
- Nuclear membrane disintigrates
- Genetic information coils to form chromosomes
- Centrioles move to opposite sides of cells and spindle fibres conecz with centromere
Metaphase:
- Spindle fibres move chromosomes into one row
Anaphase:
- Centromere breaks
- Sister chromatides seperate by bein pulled to opposite ends
Telophase:
- Chromatids are pulled to opposite poles
- Formation of nuclear membrance
- Spindle fibres break down
- Chromosomes uncoild and are no longer individually visible
Cytokinesis:
- Membrane grows inwards and divides with cytoplasm
- Division may not be equal
2.5.5 Explain how mitosis produces two genetically identical nuclei
In the S phase of Interphase the DNA of chromosomes gets replicated, so ther are two identical copies. When they coil they become chromatids. These split and are pulled to opposite end of poles to form two new nuclei, with identical genetic information, because it is made of the same information of chromosomes.
2.5.6 State that growth, embryonic development, tissue repair and asexual reproduction involve mitosis
Growth: Multicellular organisms increase their size by increasing their number of cells through mitosis
Asexual reproduction: Certain eukaryotic organisms may reproduce asexually by mitosis (e.g. vegetative reproduction)
Tissue Repair: Damaged tissue can recover by replacing dead or damaged cells
Embryonic development: A fertilised egg (zygote) will undergo mitosis and differentiation in order to develop into an embryo
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Lernkarten
2.1.1 Outline the Cell Theory
- Cells are the building blocks of structure in living things
- Cells are the smallest unit of life
- Cells are derived from pre-existing cells by division
2.1.2 Discuss the evidence of the Cell Theory
- Living things are made of cells
- observations by microscoptists of uni- and multicellular organisms, especially structure of tissue and organs
- Cells are the smallest unit of life
- discovery of viruses, which can only exist with a host cell
- biochemical investigations of organelles, only functioning for a limited amount of time outside of the cell
- Cells come from pre-existing cells
- Pasteurs Obseravtion
- Observations of the beahviour of cells at division
2.1.3 State the unicellular organisma carry out all functions of life
Unicellular organisms are the smallest organisms capable of human life
M ovement
R eprodcution
S ensitivity
G rowth
R espiration
E xcretion
N utrition
2.1.4 Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropiate SI unit
A molecule: 1nm
Cell membrane thickness: 7.5nm
Virus: 100nm (range: 20-200nm)
Bacteria: 1-5nm
Organelles: +10um
Eukaryotic Cells: +100um
2.1.6 Explain the importance of the surface area to volume ratio as a factor limiting cell size
- The rate of metabolism of a cells is a function of its mass/volume
- The rate of material exchange in and out of a cell is a functions of its surface area
- As the cell grows, volume increases faster than surface area
- If metabolic rate is greater than the rate of exchange of vital materials and waste, the cell will die
- Cell must consequently divide in order to restore viable surface to volume ratio to survive
- Cells and tissues specialized for gas or material exchange (ei.elveoli) will increase surface area to optimize the transfer of materials
2.1.7 State that multicellular organisms show emergent properties
- Cells may group together to form tissues
- Organs are then formed from the functional grouping of multiple tissues
- Organs that interact may form organ systems capable of carrying out specific body functions
- Organ systems carry out the life functions required by an organism
2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized fucntions by expressing some of their genes but not others
- When a cell changes its structure in order to perform a specific function, it's called a differentiated cell
- When differentiated cells perform specific functions they are termed specialized
- All cells carry the same genetic information
- Depending on the position of a cell in the body and the needs of the body, it becomes specialized in order to perform certain functions
- This is done by switching on the relevant genes so that only certain proteins required dor the cell to function are produced
- The other genes stay switched off
2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized fucntions by expressing some of their genes but not others
- When a cell changes its structure in order to perform a specific function, it's called a differentiated cell
- When differentiated cells perform specific functions they are termed specialized
- All cells carry the same genetic information
- Depending on the position of a cell in the body and the needs of the body, it becomes specialized in order to perform certain functions
- This is done by switching on the relevant genes so that only certain proteins required dor the cell to function are produced
- The other genes stay switched off
2.1.9 State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways
Self rewenewal: They can continously divide and replicate
Potency: They have the capacity to differentiate into specialized cell types
2.1.10 outline the therapeutic use of stem cells
Leukaemia - bone transplant is done in leukaemia patients. Large numbers of white blood cells uncontrollably produced that can not function
- chemiotherapy used to destroy white blood cells and stem cells in the patient
- a donor with the same tissue match will donate bone marrow (contains large numbers of stem cells)
- this is transplanted into the patient
- the immune system has to be supressed, to prevent the rejection of the bone marrow, through immune supressend drugs
- healthy stem cells will start dividing and differentiating and producing healthy white blood cells
2.2.1 Draw and laberl a diagram of the ultrastructure of Eschterchia Coli as an example of a prokaryote
Bild:
2.2.2 Annote the diagram from 2.2.1 with funstions of each named structure
Cell wall: Protects cell / Keeps shape / prevents cell from bursting
Plasma Membrane: Controls entry and exist of substances
Pili: Allows plasmids to be transported
Ribosomes: Synthesizes proteins
Cytoplasm: Site for chemical reactions
Nucleoid: Contains genteic information, hence controls metabolism
Flagella: Used for movement
Plasmid: Smaller rings od DNA consisting of genetic information
Capsule: Prevents dehydration
2.2.3 Identify strucutres from 2.2.1 in electron micrographs of E.coli
Bild:
2.2.4 State that prokaryotic cells divide by binary fission
Binary fission is a form of asexual reproduction and cell division used by prokaryotic organisms
It is not the same as mitosis
-The circular DNA is copied in response to a replication signal
-The two DNA loops attach to the membrane
-The membrane elongates and pinches off (cytokinesis) forming two seperate cells
2.3.1 Draw and label a diagram of the ultrastructure of a lovel cell as an example of an animal cell
Bild:
2.3.2 Annote the diagram of 2.3.1 with the function of each named structure
Polysomes: Produces specialized proteins used with the cell as such as enzymes (ribosomes that are detached from endoplasmic reticulum)
Plasma membrane: Controls incoming and existing substances
Mitochondria: Produces ATP by aerobic cell respiration; fat is digested here
Endoplasmic Reticulum: Synthesizes proteins made by ribosomes
Cytoplasm: Site for chemical reaction
Microvilli: Increasing surface area to volume ratio
Nucleus: Stores genetic information
Centrosome: for mitosis
Lysosome: Killing bacteria
Vessicles: Transport protein
Ribosomes: produce protein
Polysomes: produce protein
2.3.3 Identify structures from 2.3.1 in electron micrograph of liver cells
Bild:
2.3.4 Compare prokaryotic and eukaryotic cells
Prokaryotic / Eukaryotic
Cell wall present / Cell wall only present in plants/fungi
A naked loop of dna / Strands of DNA (4+ chromosomes present)
DNA in nucleoid and cytoplasm / DNA in nucleus
Mitochondria not present / Mitochondria always present
Flagella solid / Flagella flexible
Ribosomes: 70s / 80s
Fewer/none internal membranes present / Many internal membranes present
pili/plasmis present / absent
Both:
functional cells performing metabolic actions; have cell membrance, cytoplasm, genetic material
2.3.5 State the difference between plants and animal cells
Plants / Animals
Cell wall and plasma membrane present / No cell wall, only plasma membrane
Chloroplasts present in cells that photosynthesize / Chloroplasts not present
Starch is used as storing compound / Glycogen is used as storing compound
Vacuole often present (filled with water) / Vacuole not usually present, if they are small and specialized
Fixed shape / Able to change shape
Centrosome absent / Centrosome present
2.3.6 Outline the roles of extracellular components
- The plant wass maintains shape, prevents excess water uptake, and holds the whole plant up agains the force of gravity
- Animal cells secrete glycoproteins that form extracellular matrix (ECM). This function is for support, adhesion and movement
2.4.1 Draw and label a diagram to show the structure of a membrane
Bild:
2.4.2 Explain how phospholipid properties help to maintain membrane structure
Structure of Phospholipids
- Consist of a polar head (hydrophilic) made from glycerol and phosphate
- Consist of two non-polar fatty acid tails (hydrophobic)
Arrangement in Membrane
- Phospholipids spontaneously arrange in a bilayer
- Hydrophobic tail regions face inwards and are shielded from the surrounding polar fluid while the two hydrophilic head regions associate with the cytosolic and extracellular environments respectively
Structural Properties of Phospholipid Bilayer
- Phospholipids are held together in a bilayer by hydrophobic interactions (weak associations)
- Hydrophilic / hydrophobic layers restrict entry and exit of substances
- Phospholipids allow for membrane fluidity / flexibility (important for functionality)
- Phospholipids with short or unsaturated fatty acids are more fluid
- Phospholipids can move horizontally or occasionally laterally to increase fluidity
- Fluidity allows for the breaking / remaking of membranes (exocytosis / endocytosis)
2.4.3 List the funstions of membrance proteins
Antigen Protein: Cell to cell recognition; antibody reaction
Channel Protein: allows, by facillitated diffusion, one specific substance to pass
Pump Protein: for active transport across membranes
Carrier Protein: Involves ATP; carries ions
Electron Carrier Protein: Chain of peripheral and integral proteins that allow electrons to pass through membrance
Active Site: the substrate molecule fits here and the reaction then occurs
Glycoprotein: for attachment of specific hormone; responsible for cell to cell binding and recognition
Enzymes: Catalysing reaction in or outside cell
Receptive Protein: Responsible for recieving chemical stimuli
2.4.4 Define Diffusion and Osmosis
Diffusion:
The net movement of particles from a region of high concentration to a region of low concentration (along the gradient) until equilibrium
Osmosis:
The net movement of water molecules across a semi-permeable membrane from a region of low solute concentration to a region of high solute concentration until equilibrium is reached
2.4.5 Explain the passive transport in terms of simple facilitated diffusion
The plasma membrane is semi-permeable and selective in what can cross
Substances that move along the concentration gradient (high to low) undergo passive transport and do not require the expenditure of energy (ATP)
Simple diffusion:
- Small, non-polar (lipophilic) molecules can freely diffuse across the membrane
Facilitated diffusion:
- Larger, polar substances (ions, macromolecules) cannot freely diffuse and require the assistance of transport proteins (carrier proteins and channel proteins) to facilitate their movement (facilitated diffusion)
2.4.6 Explain the role of protein pumps ant ATP in active transport across membrane
- Particle is large and moves against gradient - requires ATP
- Carrier Protein is needed, when carrier protein works together with ATP it becomes a Protein Pump
- Proteins only carry a specific molecule and the process is highly selective. Takes in molecule through protein and ATP synthesase. ATP is used to change structure of the protein so that molecule can be transported and moved to otherside of membrane
2.4.7 Explain how vessicles are used to transport materials within a cell between the rough endoplasmic reticulum , golgi apparatus and plasma membrane
Ribosomes make proteins, which reacg the rough endoplasmic reticulum. In the endoplasmic reticulum the protein can be stored or transported. If transported the ER breaks up into the golgi body, which becomes vessicles. The vessicles diffuse with plasma membrane and release proteins
- Ribosome make proteins and they are transferred to ER
- Protein is already synthesized and present in the rER
- Protein is moved through the rER and modified
- A spherical vessicle us formed from the end of the rER with the protein inside
2.4.8 Describe how the fluidity of the membrane allows it to change shape, break and re-form during endocytosis and exocytosis.
The membrane is principally held together by the relatively weak hydrophobic associations between phospholipids
This association allows for membrane fluidity and flexibility, as the phospholipids (and to a lesser extent the proteins) can move about to some extent
This allows for the breaking and remaking of membranes, allowing larger substances access into and out of the cell (this is an active process)
Endocytosis
- The process by which large substances (or bulk amounts of smaller substances) enter the cell without travelling across the plasma membrane
- An invagination of the membrane forms a flask-like depression which envelopes the material; the invagination is then sealed off forming a vesicle
- There are two main types of endocytosis:
1. Phagocytosis
- The process by which solid substances (e.g. food particles, foreign pathogens) are ingested (usually to be transported to the lysosome for break down)
2. Pinocytosis
- The process by which liquids / solutions (e.g. dissolved substances) are ingested by the cell (allows quick entry for large amounts of substance)
Exocytosis
- The process by which large substances exit the cell without travelling across the plasma membrane
- Vesicles (usually derived from the golgi) fuse with the plasma membrane expelling their contents into the extracellular environment
2.5.1 Outline the stages in the cell cycle, including interphase (G1, S, G2), mitosis and cytokinesis
G1 - major phase in interphase. All metabolic reactions are taking place in G1 phase. Including formation of new organelles (also growing)
S - When the genetic material gets duplicated (replication of DNA)
G2 - Preparation for division
Mitosis
- Karyokinesis (nucleus division)
- Cytokinesis (cytoplams division)
2.5.2 State that tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue
Cell Division is a controlled process. Due to certain chemicals or radiations, which cause changes in genetic make up of a cell (mutation), the cell may undergo uncontrolled cell division. This can result in a tumor which may be harmless (benign) or harmful (malignant). The agent causing uncontrolled cell division is called carcinogen.
2.5.3 State that interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/ or chloroplasts
The cell cycle can be divided into interphase and mitosis. The major part of the cell cycle comproses the Interphase. The stage is divided into G1, S and G2 phases. During G1 all metabolic reactions are taking place, including formation of new organelles and growth. During S phase genetic material gets duplicated. During G2 preparation of division is taking place. Inter phase is and active phase un the cell during which many mnetabolic activities take place including cellular respiration, gaseous exchange and protein synthesis.
2.5.4 Decribe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telephase)
Prophase:
- Nuclear membrane disintigrates
- Genetic information coils to form chromosomes
- Centrioles move to opposite sides of cells and spindle fibres conecz with centromere
Metaphase:
- Spindle fibres move chromosomes into one row
Anaphase:
- Centromere breaks
- Sister chromatides seperate by bein pulled to opposite ends
Telophase:
- Chromatids are pulled to opposite poles
- Formation of nuclear membrance
- Spindle fibres break down
- Chromosomes uncoild and are no longer individually visible
Cytokinesis:
- Membrane grows inwards and divides with cytoplasm
- Division may not be equal
2.5.5 Explain how mitosis produces two genetically identical nuclei
In the S phase of Interphase the DNA of chromosomes gets replicated, so ther are two identical copies. When they coil they become chromatids. These split and are pulled to opposite end of poles to form two new nuclei, with identical genetic information, because it is made of the same information of chromosomes.
2.5.6 State that growth, embryonic development, tissue repair and asexual reproduction involve mitosis
Growth: Multicellular organisms increase their size by increasing their number of cells through mitosis
Asexual reproduction: Certain eukaryotic organisms may reproduce asexually by mitosis (e.g. vegetative reproduction)
Tissue Repair: Damaged tissue can recover by replacing dead or damaged cells
Embryonic development: A fertilised egg (zygote) will undergo mitosis and differentiation in order to develop into an embryo
