Biology - Section 1 - Notes

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Section 1

1.1:Studying the Structure of Cells

1. Cell: the smallest unit that can perform the functions of life2.

Microscopy: the science of using microscopes to view samples or objectsi) In the 1860s and 70s, compound microscopes were used in the discovery of

disease-causing germs

ii) As a result, people understood the importance of:a) Clean drinking waterb) Disposing of sewage properlyc) Sterilizing surgical instrumentsbetween operationsd) Washing hands regularly

iii) Advanced our understanding of cells3. In 1665, English scientist Robert Hookebecame the first person to study cells4. First cell structure to be seen with early microscopes was the nucleus (looked like a dark

spot)

i) Nucleus: the organelle that controls the cells activitiesii) Organelle: a specialized structure in a cell

5. Micrograph: aphotograph taken with a microscope6. The cell theory was developed in the mid-1800s and is one of the most important

developments in biology

i) Three main ideas:a) All living organisms are made of one or more cellsb) The cell is the basic organizational unit of lifec) All cells come from pre-existing cells

7. Cytosol: the fluid materialbetween the cell membrane and the nucleus8. Cytoplasm: the cytosol and organellescontained by the cell membrane9. Numerous organelles are involved in theproduction, storage, ortransport of proteins

i) Proteins are essential nutrients for the growth and repair of body tissues10.Some types of organelles are found in only plant or only in animal cells; some are found

in both

i) Chloroplastsplant cellsii) Mitochondriaplant and animal cells; its function is to release energy from

glucose11.Cellular respiration:

i) Theprocess of cellular respiration:a) C6H12O6 + 6 O2 are broken downb) Glucose isbroken down in a series of chemical reactions to gradually

release energy

c) Final products are ATP (adenosine triphosphate) + 6 CO2 + 6 H2O


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1.2: Genes Questions and Answers

1. The nucleus contains the master set of instructions, carried in chromosomesi) Chromosome:in a cell nucleus, a thread-like structure made mostly of DNA

a) Every organism has a specific number of chromosomes in the nucleus ofeach cell

b) Typically come in pairsone of each pair comes from either parentupon fertilization

c) Humans normally have 46 chromosomesper cell nucleusd) Made up ofdeoxyribonucleic acid (DNA)

i. DNA: material found in the cell nucleus that contains geneticinformation

e) Each chromosome consists ofa single molecule of DNA, which isdivided into segments called genes

i. Gene: a segment of DNA that controls protein productionI)Genes control the cells activities and much of its

structure by controlling what proteins are made and when

f) 1953: James Watson and Francis Crickcreated a DNA model based onprevious scientific models (termed double helix)

g) Three types of building-blockmolecules called nucleotides:phosphate, deoxyribose sugar, nitrogenous base

i. Fourtypes of nitrogenous bases: adenine, thymine, cytosine,guanine

2. DNA controls many of yourphysical features and how your body digests different foods3.

DNA is in charge of protein production and role distribution through genes, such as:

i) Building parts of the bodyii) Courierscarrying materials around the body

iii) Pick-up/Transfer signals from one body part to anotheriv) Enzymes speed up various chemical reactions

4. DNA/Genetic screening: theprocess of testing individuals to determine whether theyhave the gene or genes associated with certain genetic disorders

i) Down syndromea) Amniocentesis: a technique used to detect Down syndrome in the fetusb) Karyotype: a micrograph that shows if a person has too many/few

chromosomes or any broken onesc) Look forthree chromosomes on Strand 21

ii) PKUa) Detected by obtaining ablood sample

i. Examined for an enzyme needed to digest certain proteins;otherwise, phenylalanine builds up

iii) Huntington disease: a genetic disorder that affects nerve cells


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a) Symptoms: loss of muscle control and brain functionb) Symptoms worsen for 15 years before the victim diesc) If one parent has it, the child will have a 50 per cent chance of having

the gene

iv) Arguments againstgenetic screening:a) Causes emotional pain for parentsb) Testing is expensive and doesnt save lives

v) Arguments forgenetic screening:a) Reduces uncertaintyb) May changemany of a persons life decisions

vi) Other conditions that can be identified include:a) Certain genes associated with breast cancerfor womenb) Cystic fibrosisc) Spina bifida

5.

Drug companies research the cures for many diseasesi) Expensive

ii) Time-consumingiii) Might notbe as successful outside of the labiv) Trial data may bepresented as more positive than it really isv) If they found an effective, but costly, cure: sell to profit or to fulfill ethical

obligation?

6. Genetic code is universal so genes can be modifiedi) GMO/Transgenic organism: an organism whose genetic information has been

altered with the insertion of genes from another species

ii) Some people question genetic modification becomes evolution occurs naturallyover an extremely long period of time

iii) Uses of some GMOs:a) Bacteria: have a simple cell structuretherefore, the first type of

organism to be modifiedand used formedical treatments (less likely to

cause allergic reactions or diseases)

b) Bacteria/other plant genes: inserted into crop chromosomes (resist pests,have higher nutritional value,better withstand harsh weather)

c) Growth hormones: injected into animals (increase human food supplies,lower price of meat)

7. Cloning: the process ofcreating identical genetic copies of an organismi) Gardeners have done this for centuries by taking cuttings from a plant and rooting

them, resulting in copies of the parent plant

ii) Steps in cloning a plant:a) Take pieces of the rootb) Separate individual cells and grow them in a nutrient solution


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c) Becomes a plant embryod) Grows into a plantlete) Finally, a mature plant

iii) Steps in cloning a mammal:a) Scientists remove the cell nucleus of an egg from the femaleb) A cell from an adult is removed; it and the egg cell areplaced beside

each other in a bath of chemicals

c) Electrical jolt causes them to fused) The fused cell begins dividing to form an embryoe) The embryo is inserted in the uterus to complete its development. The

offspring is a clone of the mammal that donated the adult cell.

8. Mutation: a change in the DNA of an organismi) Affects how well a protein does its job

a) Sickle cell anemia: a disease in which the gene that codes forhemoglobin is less effective

ii) Mutagen: a substance or factorthat can cause a mutation in DNAa) Electromagnetic radiation, such as X-rays and UV raysb) Chemicals, such as mercury and cigarette tar

iii) Some occur in only one or a few cellsiv) Some are inheritedv) Mutations that occur on a non-genetic part of DNA are notharmful

vi) Some allow foradaptationvii) As of now, mostpeople who participate in trials of gene therapy treatment

become sickerordie

viii) Other concerns for gene therapy treatments:a) Arent people with hereditary diseases able to lead happy, successful

lives?

b) Who gets access to treatments and who pays?c) Who funds research and who holds control over the resulting product or

technology?

d) How far should society go in using treatments?


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1.3: Cells from Cells

1. Cell reproduction: theprocess by which new cells are formedi) In single-celledorganisms:

a) Only one parentb) One cell divides to produce two new cells

i. Daughter cellsii. Genetically identical to each otherand to their parent cell

ii) Inmulticellularorganisms:a) Two parents mateb) Offspring receive half of their genes from each parent

i. Offspring share genetic material and may look alike, but they arenot identical to the parents

2. Cell division: theprocess by which a parent cell divides into two daughter cellsi) Single-celled organisms reproduce this way

ii) Formulticellular organisms:a) The process by which a fertilized egg (a single cell) eventually becomes

an adult with millions of cells

b) The process that replaces lost or damaged cells3. Cells also divide when they grow too large to efficiently perform the functions necessary

for their survival

i) Cell membrane is important in this instancea) Food and oxygen molecules must cross the membrane to get inside all of

the cells

b)

Waste materials cross the membrane to exit the celli. Diffusion: the movement of molecules from areas of higher

concentrations to areas of lower concentrations until equilibrium is

reached

c) Selectively permeable:i. Not all materials can cross it

ii. Some kept out and others in4. Cells are surrounded by solutions that contain water and dissolved nutrients and gases5. Cells use nutrients, produce more organelles and cytosol; get bigger and increase in

volume

6. Cells need enough surface area to service its volume (more surface area = more nutrients+ easier to get rid of wastes)

7. Cells only use 10 per cent of their genes to produce the proteins they need to do theirparticular job, as a result ofcell specialization


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1.4: The Cell Cycle

1. Skin cells and cells that line the stomach have short lifespans2. Muscle cells have long lifespans (15 years)3. Cell cycle: a continuous sequence of cell growth and division, including the stages of

interphase, mitosis, and cytokinesis;i) Controlled by protein molecules

ii) Stages of the cell cycle:a) Interphase:periods of growth in the life of a cell

i. Longest stage of the three (90 per cent of the cell cycle)ii. Consists oftwo growth stages and a stage of DNA replication

a. DNA replication: theprocess by which DNA is copied,creating sister chromatids joined at the centromere

I) Prepares the cell for cell divisionb. Growth in size and in organelles before and afterDNA

replication

iii. Cells do whatever activities they are designed to do, as well asnecessary cell activities

a. i.e., absorbing oxygen and glucose, cellular respiration,waste removal

b) Mitosis: theprocess by which the duplicated contents of the cellsnucleus divide into two equal parts

i. Centrosome: an organelle that helps to organize the tubules thatmake up the cells cytoskeleton

ii.

Theprocess of mitosis:a. Prophase: thephase of mitosis in which sister chromatids

condense and coil, allowing the chromosomes tobecome

visible

I)Nucleolus and the nuclear membrane disappearII)Spindle fibres form from thread-like tubules extending

from the two centrosomes towards the centromeres

III)Two centrosomes head towards opposite cell polesb. Metaphase: the longest phase of mitosis in which the

chromosomes are aligned across the centre of the cell

I)Each centromere is attached to two spindle fibresoneat each end of the cell

c. Anaphase: the shortest phase in mitosis in which thecentromere splits apart and the chromatids are pulled to

opposite sides of the cellby the spindle fibres

I)Spindle fibres retract, each pulling a chromatid towardsone end of the cell (separate and become chromosomes)


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I) The cell has twice as many chromosomes asusual

d. Telophase: thephase of mitosis in which two daughternuclei are formed

I)Form separate membranes (around each set ofchromosomes) and nucleoli (appears within each new

nucleus)

I) Chromosomes become harder to seeiii. Mitosis is a continuous process without breaks between phases

c) Cytokinesis: following mitosis, the third stage in cell division thatinvolves the separation of the two nuclei and cell contents into two

daughter cells

i. The cytosol and the organelles divideii. In animalcells:

a.

A ring of specialized proteins in the middle of the cellcontracts

b. The contraction pinches the cell membrane until the parentcell divides into two

c. Each daughter cell has a complete set of chromosomes inits nucleus and its own share of cytosol and organelles

iii. In plantcells:a. The Golgi body produces small vesicles, carrying the

materials needed to form a new cell wall

b. The vesicles line up between the two new nucleiI)Cell plate: a structure that helps to form the cell wall in

the process of plant cell cytokinesis

c. The cell plate grows out, joining the old cell walld. New cell walls are secreted on each side of the cell plate,

dividing the cytoplasm into two

e. New cell membranes form inside the cell walls4. Cell cycle checkpoints: apoint in the life of a cell when proteins determine whether cell

division should or should not occur

i) Cell division doesnt occurunder three conditions:a) Insufficient nutrients to support cell growth (during interphase)

i. For many cells, this checkpoint seems to be the most importanta. More cells of that type are not needed

b) The DNA has not replicated (during interphase, before mitosis)c) The DNA is damaged (during mitosis)

i. e.g. Chromosomes have not attached in metaphase, chromosomeshave not moved to poles in anaphase


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ii) Cells that leave the cycle enter a non-dividing stagea) Most of the bodys cells are in this stage

i. e.g., muscle cells, nerve cells5. Cells die when they are damaged beyond repairbyphysical force orexposure to toxic

materials

i) The cells contents leak out, causing swelling and redness in that body region6. Some cells are known assuicide genes

i) Pre-programmed into the cellii) The genes code for proteins responsible for killing cells undercertain conditions

a) Normal finger and toe development in human embryosb) There is a threat to the organism

i. e.g., a cell is infected with a virus7. Cancer: cells with abnormal genetic material that are dividing uncontrollably and can

spread to other body parts

i)

Tumour: an abnormal clump or group of mutated cells that have dividedrepeatedly and excessively

ii) Cell division inhealthytissue:a) Carefully controlled by chemical messages that pass from cell to cellb) When cells mature and die, other cells are stimulated to divide and

replace the dead cells

c) Rate of cell division = rate of cell deathiii) Abnormalcell division:

a) Cells divide much more often and the cycle continues with their cellsand their cells cells

b) Forms a tumourand further changes to the clump can result in cancerc) Cancer cellsbreak away, move into the circulatory system, and spread to

a new location in the body

8. Cells must be attached to a surface when they divide9. Most normal cells undergo 20 to 30 rounds of cell division

i) More may result in a greater chance ofcell mutationii) After this, cells carry outprogrammed suicide

a) Cancer cells make an enzyme called telomerase which allows them tokeep dividing

i. May also disable cells to produce or recognize suicide-causingproteins

10.Cancer cells must have several mutations before cell division control is completely losti) Mutations occurbecause of:

a) Chanceb) Inherited geneticsc) Contact with mutagens


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i. Carcinogens:mutagens that lead to cancera. e.g., asbestos, tobacco smoke, human papilloma virus

(HPV)

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Biology - Section 1 - Notes