topic 1: cells. 1.1 cell theory 1.1.1 discuss the theory that living organisms are composed of...

Topic 1: CellsTopic 1: Cells

1.1 Cell Theory1.1 Cell Theory

1.1.11.1.1Discuss the theory that living Discuss the theory that living

organisms are composed of cells. (3)organisms are composed of cells. (3)

Skeletal muscle and some fungal Skeletal muscle and some fungal hyphae are not divided into cells but hyphae are not divided into cells but have a multinucleate have a multinucleate cytoplasm. Some biologists consider cytoplasm. Some biologists consider unicellular organisms to be acellular.unicellular organisms to be acellular.


1.1.2 1.1.2

State that a virus State that a virus is a non-cellular is a non-cellular structure structure consisting of consisting of DNA or RNA DNA or RNA surrounded by a surrounded by a protein coat.protein coat. (1)(1)


1.1.3 1.1.3

State that all cells are formed from State that all cells are formed from other cells. (1)other cells. (1)

xref . 1.5- Mitosis, 8.1- Meiosisxref . 1.5- Mitosis, 8.1- Meiosis


1.1.41.1.4

Explain three advantages of using light Explain three advantages of using light microscopes. (3)microscopes. (3)

Advantages include:Advantages include: colour images instead of monochrome, colour images instead of monochrome, a larger field of view,a larger field of view, easily prepared sample material, easily prepared sample material, the possibility of examining living the possibility of examining living

material and observing movement.material and observing movement.


1.1.51.1.5Outline the advantages of using electron Outline the advantages of using electron

microscopes.microscopes. (2)(2)Greater:Greater:Resolution – the ability to distinguish Resolution – the ability to distinguish

between two points on an image. Like between two points on an image. Like pixels in a digital camera.pixels in a digital camera.

Magnification – how much bigger a sample Magnification – how much bigger a sample appears to be under the microscope than appears to be under the microscope than it is in real life.it is in real life.


Transmission electron microscopes Transmission electron microscopes pass a beam of electrons through the pass a beam of electrons through the specimen. The electrons that pass specimen. The electrons that pass through the specimen are detected on a through the specimen are detected on a fluorescent screen on which the image fluorescent screen on which the image is displayed.is displayed.

Thin sections of specimen are needed for Thin sections of specimen are needed for transmission electron microscopy as transmission electron microscopy as the electrons have to pass through the the electrons have to pass through the specimen for the image to be produced.specimen for the image to be produced.

1.1 Cell Theory1.1 Cell Theory Scanning electron microscopes Scanning electron microscopes pass a beam of pass a beam of

electrons over the surface of the specimen in the form electrons over the surface of the specimen in the form of a ‘scanning’ beam.of a ‘scanning’ beam.

Electrons are reflected off the surface of the specimen Electrons are reflected off the surface of the specimen as it has been previously coated in heavy metals.as it has been previously coated in heavy metals.

It is these reflected electron beams that are focused It is these reflected electron beams that are focused on the fluorescent screen in order to make up the on the fluorescent screen in order to make up the image.image.

Larger, thicker structures can thus be seen under the Larger, thicker structures can thus be seen under the scanning electron microscope as the electrons do not scanning electron microscope as the electrons do not have to pass through the sample in order to form the have to pass through the sample in order to form the image.image.

However the resolution of the scanning electron However the resolution of the scanning electron microscope is lower than that of the transmission microscope is lower than that of the transmission electron microscope.electron microscope.

1.1 Cell Theory1.1 Cell TheoryLight Light ElectronElectronCheap to purchase (£100 Cheap to purchase (£100 – 500)– 500)

Expensive to buy (over Expensive to buy (over £1,000,000)£1,000,000)

Cheap to operateCheap to operate Expensive to produce Expensive to produce electron beamselectron beams

Small and portableSmall and portable Large and requires Large and requires special roomsspecial rooms

Simple and easy Simple and easy preparationspreparations

Lengthy and complex Lengthy and complex preparationspreparations

Material rarely distorted Material rarely distorted by preparationby preparation

Preparation distorts Preparation distorts materialmaterial

Vacuum is not requiredVacuum is not required Vacuum is requiredVacuum is required

Natural color maintainedNatural color maintained All images in black and All images in black and whitewhite

Magnifies objects only up Magnifies objects only up to 2000 timesto 2000 times

Magnifies over 500,000 Magnifies over 500,000 timestimes


1.1.61.1.6

Define organelle. (1)Define organelle. (1) Literally ‘little organ’Literally ‘little organ’ An organelle is a discrete structure An organelle is a discrete structure

within a cell, and has a specific within a cell, and has a specific function.function.

i.e. – nucleus, cell membrane, i.e. – nucleus, cell membrane, mitochondriamitochondria


1.1.7 1.1.7 Compare the relative sizes of molecules, cell Compare the relative sizes of molecules, cell

membrane thickness, viruses, bacteria, membrane thickness, viruses, bacteria, organelles and cells, using appropriate SI units organelles and cells, using appropriate SI units (2)(2)

Appreciation of relative size is required,Appreciation of relative size is required, molecules (1 nm), molecules (1 nm), thickness of membranes (10 nm), xref. 1.4thickness of membranes (10 nm), xref. 1.4 viruses (100 nm), viruses (100 nm), bacteria (1 µm), xref. 1.33bacteria (1 µm), xref. 1.33 organelles (up to 10 µm), xref. 6.4.2, 7.1.3, 7.2.1organelles (up to 10 µm), xref. 6.4.2, 7.1.3, 7.2.1 most cells (up to 100 µm). most cells (up to 100 µm). Don’t forget: all of these structures are in 3D spaceDon’t forget: all of these structures are in 3D space


1 nm = 1/1,000,000,000 of a meter, or . . . 1 nm = 1/1,000,000,000 of a meter, or . . . 0.000000001m, or . . .0.000000001m, or . . . 1 billionth of a meter 1 billionth of a meter 1 1 µm = 1/1,000,000 of a meter, or . . .µm = 1/1,000,000 of a meter, or . . . 0.000001m, or . . .0.000001m, or . . . 1 millionth of a meter1 millionth of a meter

1 nm = 1/1,000 of a µm, or1 nm = 1/1,000 of a µm, or1 µm = 1,000 nanometers1 µm = 1,000 nanometers

Therefore. . . Therefore. . .


A 100 µm cell A 100 µm cell 10x larger than 10x larger than a. . .a. . .

A 10 µm organelleA 10 µm organelle 10x larger than 10x larger than a. . .a. . .

A 1 µm bacteriaA 1 µm bacteria 10x larger than a. . .10x larger than a. . .

A 100 nm virusA 100 nm virus 10x larger than a. . .10x larger than a. . .

A 10 nm membrane A 10 nm membrane 10x larger than a. . .10x larger than a. . .

A 1 nm moleculeA 1 nm molecule


1.1.81.1.8

Calculate linear magnification of Calculate linear magnification of drawings. (2)drawings. (2)

Drawings should show cells and cell Drawings should show cells and cell ultra-structure with scale barsultra-structure with scale bars

Magnification could also be stated, eg Magnification could also be stated, eg x250. x250.


1.1.91.1.9Explain the importance of the surface area to Explain the importance of the surface area to

volume ratio as a factor limiting cell size. (3)volume ratio as a factor limiting cell size. (3)The rate of metabolism of a cell is a function of The rate of metabolism of a cell is a function of

its mass:volume ratio, its mass:volume ratio, Whereas the rate of exchange of materials and Whereas the rate of exchange of materials and

energy (heat) is a function of its surface area. energy (heat) is a function of its surface area. Simple mathematical models involving cubes Simple mathematical models involving cubes

and the changes in the ratio that occur as the and the changes in the ratio that occur as the sides increase by one unit could be compared.sides increase by one unit could be compared.

12

3

1 cm 10 cm 100 cm

Assume we have 3 cubes:

With sizes:

What will happen to ratio between V and S.A. as their size increases?

Ratio of V:S.A.Ratio of V:S.A.

CubeCube Side Side LengtLengthh

Volume Volume (x(x33))

S.A. (6xS.A. (6x22)) Ratio Ratio (S.A./V)(S.A./V)

11 1 cm1 cm

22 10 cm10 cm

33 100 100 cmcm

1 cm3

1 000 cm3

1 000 000 cm3

6 cm2

600 cm2

60 000 cm2

6

0.6

0.06


1.1.101.1.10

State that unicellular organisms carry out State that unicellular organisms carry out all the functions of life. (1)all the functions of life. (1)

MOVEMENT – Intracellular and/or extracellularMOVEMENT – Intracellular and/or extracellular

RESPIRATION – Gas exchange. Not always ORESPIRATION – Gas exchange. Not always O22 and CO and CO22

NUTRITION – Need raw materials, i.e.- food, water, NUTRITION – Need raw materials, i.e.- food, water, mineralsminerals

EXCRETION – Get rid of waste materialsEXCRETION – Get rid of waste materialsREPRODUCTION – Ability to produce like organismsREPRODUCTION – Ability to produce like organismsIRRATIBILITY – Respond to external stimuli IRRATIBILITY – Respond to external stimuli GROWTH – Cells grow larger . . . and don’t forget . . .GROWTH – Cells grow larger . . . and don’t forget . . .

‘‘MR. NERIG’ also carries out the functions of life!MR. NERIG’ also carries out the functions of life!


1.1.111.1.11

Explain that cells in multicellular Explain that cells in multicellular organisms differentiate to carry out organisms differentiate to carry out specialized functions by expressing specialized functions by expressing some of their genes but not others. some of their genes but not others. (3)(3)


1.1.121.1.12

Define: (1)Define: (1)

Tissue – A group of Tissue – A group of cellscells working together working together to perform a common functionto perform a common function

Organ – A group of Organ – A group of tissuestissues working working together to perform a common functiontogether to perform a common function

Organ System – A group of Organ System – A group of organsorgans working working together to perform a common functiontogether to perform a common function

1.2 Prokaryotic Cells1.2 Prokaryotic Cells

1.2.11.2.1Draw a generalized prokaryotic cell as Draw a generalized prokaryotic cell as

seen in electron micrographs. (1)seen in electron micrographs. (1) Use images of bacteria as seen in Use images of bacteria as seen in

electron micrographs to show the electron micrographs to show the structure. structure.

The diagram should show the cell The diagram should show the cell wall, plasma membrane, mesosome, wall, plasma membrane, mesosome, cytoplasm, ribosomes and nucleoid cytoplasm, ribosomes and nucleoid (region containing naked DNA).(region containing naked DNA).


1.2.21.2.2State one function for each of the State one function for each of the

following: (1)following: (1) cell wall – forms a protective outer cell wall – forms a protective outer

layer that prevents damage from layer that prevents damage from outside and bursting if internal outside and bursting if internal pressure is too highpressure is too high

plasma membrane – controls entry plasma membrane – controls entry and exit of substances, pumping some and exit of substances, pumping some of them in by active transportof them in by active transport


mesosome – increases the area of mesosome – increases the area of membrane for ATP production. May membrane for ATP production. May move the DNA to the poles during move the DNA to the poles during cell divisioncell division

cytoplasm – contains enzymes that cytoplasm – contains enzymes that catalyse the chemical reactions of catalyse the chemical reactions of meabolism and DNA in a region call meabolism and DNA in a region call the nucleoidthe nucleoid


ribosomes – synthesize proteins by ribosomes – synthesize proteins by translating messenger RNA. Some translating messenger RNA. Some proteins stay in the cell and others proteins stay in the cell and others are secretedare secreted

naked DNA – stores the genetic naked DNA – stores the genetic information that controls the cell information that controls the cell and is passed on to daughter cellsand is passed on to daughter cells


1.2.31.2.3

State that prokaryotes show a wide State that prokaryotes show a wide range of metabolic activity including range of metabolic activity including fermentation, fermentation, photosynthesis and nitrogen fixation.photosynthesis and nitrogen fixation.

(1) (1)

1.3 Eukaryotic Cells1.3 Eukaryotic Cells

1.3.11.3.1

Draw a diagram to show the Draw a diagram to show the ultrastructure of a generalized ultrastructure of a generalized animal cell as seen in electron animal cell as seen in electron micrographs.micrographs. (1) (1)

The diagram should show ribosomes, The diagram should show ribosomes, rough endoplasmic reticulum (rER), rough endoplasmic reticulum (rER), lysosome, Golgi apparatus, lysosome, Golgi apparatus, mitochondrion and nucleus.mitochondrion and nucleus.

Insert electron micrograph Insert electron micrograph and diagram of eukaryotic and diagram of eukaryotic

cellscells


1.3.21.3.2State one function of each of these State one function of each of these

organelles: (1)organelles: (1)

ribosomes – protein synthesisribosomes – protein synthesisrough endoplasmic reticulum (rER) – rough endoplasmic reticulum (rER) –

synthesis of proteins to be secretedsynthesis of proteins to be secretedlysosome – holds digestive enzymeslysosome – holds digestive enzymesGolgi apparatus – for processing of proteins Golgi apparatus – for processing of proteins mitochondrion – for aerobic respirationmitochondrion – for aerobic respirationnucleus – holds the chromosomesnucleus – holds the chromosomes

1.3 Eukaryotic Cells1.3 Eukaryotic Cells1.3.31.3.3 Compare prokaryotic and eukaryotic cells: Compare prokaryotic and eukaryotic cells:

(2)(2)Differences should include:Differences should include: naked DNA in a loop versus DNA associated with naked DNA in a loop versus DNA associated with

protein in strands, protein in strands, DNA in cytoplasm versus DNA enclosed in a nuclear DNA in cytoplasm versus DNA enclosed in a nuclear

envelope, envelope, no mitochondria versus mitochondria, no mitochondria versus mitochondria, 70S versus 80S ribosomes.70S versus 80S ribosomes.Similarities include:Similarities include: Both types have cell membranes, cytoplasm, DNA Both types have cell membranes, cytoplasm, DNA

and ribosomes (although slightly different)and ribosomes (although slightly different)

1.3 Eukaryotic Cells1.3 Eukaryotic Cells1.3.41.3.4

Describe three differences between plant and animal Describe three differences between plant and animal cells.cells. (2)(2)

Carbohydrates Carbohydrates stored as stored as starch.starch.

Carbohydrates Carbohydrates stored as stored as glycogen.glycogen.

Stores large amounts of liquid (juice). Larger size of cell.

Central Central VacuoleVacuole

XDoes not store large amounts of liquid. Smaller size of cell.

Rigid, cannot easily change shape.

Cell WallCell WallXFlexible, can easily change shape.

Can produce its own food.

ChloroplastChloroplastXCannot produce its own food

Plant CellsPlant CellsStructureStructureAnimal CellsAnimal Cells


1.3.51.3.5

State the composition and function of State the composition and function of the plant cell wall. (1)the plant cell wall. (1)

The composition of the plant cell The composition of the plant cell wall should be considered only in wall should be considered only in terms of cellulose microfibrils.terms of cellulose microfibrils.

1.4 Membranes1.4 Membranes

1.4.11.4.1Draw a diagram to show the fluid mosaic model of Draw a diagram to show the fluid mosaic model of

a biological membrane. a biological membrane. (1)(1) The diagram should show the phospholipid The diagram should show the phospholipid

bilayer, cholesterol, glycoproteins and integral bilayer, cholesterol, glycoproteins and integral and peripheral proteins. and peripheral proteins.

Use the term plasma membrane not cell surface Use the term plasma membrane not cell surface membrane for the membrane surrounding the membrane for the membrane surrounding the cytoplasm. cytoplasm.

Integral proteins are embedded in the Integral proteins are embedded in the phospholipid of the membrane whereas phospholipid of the membrane whereas peripheral proteins are attached to its surface. peripheral proteins are attached to its surface.


1.4.21.4.2

Explain how the hydrophobic and Explain how the hydrophobic and hydrophilic properties of phospholipids hydrophilic properties of phospholipids help to maintain the structure of cell help to maintain the structure of cell membranes. (3)membranes. (3)

Hydrophobic – ‘afraid of water’Hydrophobic – ‘afraid of water’

Hydrophilic – ‘loves water’Hydrophilic – ‘loves water’


Plasma Membranes


1.4.31.4.3List the functions of membrane List the functions of membrane

proteins including proteins including (1)(1) hormone binding siteshormone binding sites enzymes enzymes electron carrierselectron carriers channels for passive transport channels for passive transport pumps for active transport.pumps for active transport.


1.4.41.4.4Define diffusionDefine diffusion (1) (1)Diffusion is the passive movement of particles from Diffusion is the passive movement of particles from

a region of high concentration to a region of a region of high concentration to a region of low concentration (down a concentration low concentration (down a concentration gradient), until there is an equal distribution.gradient), until there is an equal distribution.

Define osmosisDefine osmosis Osmosis is the passive movement of water Osmosis is the passive movement of water

molecules, across a partially permeable molecules, across a partially permeable membrane, from a region of lower solute membrane, from a region of lower solute concentration (high water concentration) to a concentration (high water concentration) to a region of higher solute concentration (low region of higher solute concentration (low water concentration).water concentration).


High Concentration

Low Concentration

Diffusion moves down the concentration gradient just like a ball rolling down a hill. It cannot roll uphill without energy.


1.4.51.4.5

Explain passive transport across membranes Explain passive transport across membranes in terms of diffusion.in terms of diffusion. (3)(3)

Requires no energyRequires no energy

Moves from down the concentration gradientMoves from down the concentration gradient

Some molecules pass through the membraneSome molecules pass through the membrane

Some molecules use channels for facilitated Some molecules use channels for facilitated diffusiondiffusion


1.4.61.4.6Explain the role of protein pumps and ATP in Explain the role of protein pumps and ATP in

active transport across membranes.active transport across membranes. (3)(3)

Requires energy, in the form of ATP, or Requires energy, in the form of ATP, or adenosine triphosphateadenosine triphosphate

Molecules are ‘pumped’ across the membrane Molecules are ‘pumped’ across the membrane UP the concentration gradientUP the concentration gradient

Pumps fit specific moleculesPumps fit specific moleculesThe pump changes shape when ATP activates The pump changes shape when ATP activates

it, this moves the molecule across the it, this moves the molecule across the membranemembrane

Active TransportActive Transport


1.4.71.4.7

Explain how vesicles are used to transport Explain how vesicles are used to transport materials within a cell between the rough materials within a cell between the rough endoplasmic reticulum, Golgi apparatus endoplasmic reticulum, Golgi apparatus and plasma membrane. (3)and plasma membrane. (3)

1.4.81.4.8 Describe how the fluidity of the Describe how the fluidity of the membrane allows it to change shape, membrane allows it to change shape, break and reform during endocytosis and break and reform during endocytosis and exocytosis. (2)exocytosis. (2)


Endocytosis – the mass movement INTO the cell Endocytosis – the mass movement INTO the cell by the membrane ‘pinching’ into a vacuoleby the membrane ‘pinching’ into a vacuole

Exocytosis – the mass movement OUT of the cell Exocytosis – the mass movement OUT of the cell by the fusion of a vacuole and the membraneby the fusion of a vacuole and the membrane

This is possible because the of the fluid This is possible because the of the fluid properties of the membrane (able to break properties of the membrane (able to break and reform easily, phospholipids not attached and reform easily, phospholipids not attached just attracted)just attracted)

ExocytosisExocytosis

EndocytosisEndocytosisendo- and exo-

-cytosis

1.5 Cell Division1.5 Cell Division

1.5.11.5.1

State that the cell-State that the cell-division cycle division cycle involves involves interphase, interphase, mitosis, and mitosis, and cytokinesis.cytokinesis. (1) (1) Interphase

Mitosis

Cytokinesis


1.5.21.5.2

State that interphase State that interphase is an active period is an active period in the life of a cell in the life of a cell when many when many biochemical biochemical reactions occur, as reactions occur, as well as DNA well as DNA transcription and transcription and DNA replication.DNA replication.

(1) (1)


1.5.31.5.3

Describe the events that occur in the four Describe the events that occur in the four phases of mitosis phases of mitosis (2)(2)


PROPHASE - PROPHASE - breakage of breakage of nuclear nuclear membranes membranes and and supercoiling supercoiling of DNA to of DNA to form visible form visible chromosomeschromosomes


METAPHASE - METAPHASE - chromosomes chromosomes line up along line up along equatorial equatorial region of cell, region of cell, attachment of attachment of spindle spindle microtubules microtubules to to centromerescentromeres


ANAPHASE - ANAPHASE - splitting of splitting of centromeres, centromeres, movement of movement of sister sister chromosomes to chromosomes to opposite poles opposite poles as spindle as spindle microtubules microtubules shortenshorten


TELOPHASE - TELOPHASE - uncoiling of uncoiling of chromosomes and chromosomes and reformation of reformation of nuclear nuclear membranesmembranes


P rophase

M etaphase

A naphase

T elophase

P-MAT

Drosophilia Embryo Division

Mitosis Video


1.5.41.5.4 Explain how mitosis produces Explain how mitosis produces two genetically identical nuclei.two genetically identical nuclei. (3)(3)

Synthesis of identical chromosomes in Synthesis of identical chromosomes in interphaseinterphase

Lining up during mitosis ensures that Lining up during mitosis ensures that each new cell gets a copy of each each new cell gets a copy of each chromosomechromosome


1.5.51.5.5

Outline the differences in mitosis and Outline the differences in mitosis and cytokinesis between animal and cytokinesis between animal and plant cells.plant cells. (2)(2)

No centrioles in plant cellsNo centrioles in plant cells

Cell plate formed in plants, membrane Cell plate formed in plants, membrane ‘pinching’ in animal cells‘pinching’ in animal cellsCytokinesis


1.5.61.5.6

State that growth, tissue repair and State that growth, tissue repair and asexual reproduction involve mitosis.asexual reproduction involve mitosis.(1)(1)

1.5.71.5.7

State that tumours (cancers) are the result State that tumours (cancers) are the result of uncontrolled cell division and that of uncontrolled cell division and that these can occur in any organ.these can occur in any organ. (1) (1)

topic 1: cells. 1.1 cell theory 1.1.1 discuss the theory that living organisms are composed of...

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