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IB Biology > 1. Cell Biology > Flashcards

1. Cell Biology Flashcards

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1
Q

Cell Theory

A
  1. All living organisms are composed of cells
    1. The cell is the smallest unit of life
      1. Cells only arise from pre-existing cells
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2
Q

The functions of life (carried out by unicellular organisms)

Ex: Paramecium, chlorophyll

A

MRHGERN
- Metabolism: essential chemical reactions
- Reproduction: sexually or asexually
- Homeostasis: maintain a stable internal environment
- Growth: can move and change size/shape
- Excretion: exhibit the removal of waste
- Response: to internal and external stimuli
- Nutrition: either by synthesis or absorption of organic matter
Ex: Paramecium (cilia for movement)

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3
Q

Importance of large SA:V ratio

A
  • As cell grows, volume increases faster than surface area, leading to a decreased SA:V ratio
    • If metabolic rate > exchange rate of vital materials, cell eventually dies
    • Thus cell divides to maintain smaller size again
      Ex: villi and microvilli
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4
Q

Emergent properties (for multicellular organisms)

A

The whole is more than the sum of its parts- a complex system possesses properties that its constituent parts do not have
Thus multicellular organisms capable of performing functions unicellular organisms cannot

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5
Q

Cell differentiation

A

The process by which unspecialised cells changes and carries out a specific function in the body

  • caused by activation of different genes
  • expression of some genes and not others
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6
Q

Stem Cells

A

Able to continuously divide, replicate, and differentiate into any specialized cell

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7
Q

Difference between totipotent and pluripotent

A

Both can differentiate into any cell, but totipotent includes placental cells and pluripotent cannot differentiate into a whole organism i.e. blastocyst

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8
Q

Multipotent

A

Can differentiate into a few closely related types of body cell i.e. umbilical cord

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9
Q

Unipotent

A

Cannot differentiate, only capable of self-renewal

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10
Q

Stem Cell therapy

A
  1. trigger differentiation
  2. surgical implantation of cells
  3. suppression of host immune system
  4. monitor for cancerous growth
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11
Q

Stargardt’s Disease

A

Juvenile macular degeneration –> progressive loss of central vision
Replacing dead cells in the retina with functioning ones derived from stem cells

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12
Q

Leukemia

A

Cancer of the blood or bone marrow (abnormal white blood cells)
Hematopoietic stem cells (HSC) taken from bone marrow, patient undergoes chemotherapy
HSCs are transplanted back into bone marrow and differentiate into new healthy white blood cells

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13
Q

Ethical issues of stem cell therapy

A

For:
- Eliminates serious diseases in population
- Donating organs risks another human’s life
- Stem cells harvested from embryo at an early
stage
Against:
- Destruction of potential living organism
- May cause tumour
- Religious or moral objections

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14
Q

Embryos vs adult tissue stem cells

A

Check folder notes

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15
Q

Prokaryote structure

A 
Cytoplasm
Nucleoid- contains naked DNA
Plasmids- transferable circular DNA
70S ribosomes
Cell membrane
Cell wall
Pilli- helps in cell adhesion and transferring DNA
Flagella- locomotion, propels cell
Slime capsule- protection
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16
Q

Explain binary fission

A

Asexual reproduction

1. Circular DNA is replicated semi-conservatively 
2. The two copies of the DNA loop move to opposite ends of the cell
3. Cell elongates and pinches off (cytokinesis), forming two identical daughter cells
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17
Q

Four kingdoms of Eukaryotes

A
  • Protista
  • Fungi
  • Plantae
  • Animalia
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18
Q

Compartmentalisation (eukaryotes only)

A

Greater efficiency of metabolisms
Optimal internal conditions
Isolation of toxic substance
Flexibility of changing number and position of organelles

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19
Q

Features of both plant and animal cells (9)

A 
Plasma membrane- controls entry/exit
Cytoplasm- internal structure & enzymes
Mitochondria- cell respiration
80S ribosomes- protein synthesis
Nucleus- genetic info
Endoplasmic Reticulum- smooth and rough 
Golgi Apparatus- processes and packages
Vesicle- transports
Vacuole- osmotic balance
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20
Q

Plant cells only

A

Cell Wall- protection and shape

Chloroplasts- photosynthesis

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21
Q

Animal cells only

A

Lysosomes- hydrolytic enzymes, breaks down molecules

Centrioles- role in nuclear division

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22
Q

Electron Microscopy vs light microscopy

A

higher range of magnification and high resolution but not in colour

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23
Q

The Fluid Mosaic Model + who proposed it?

A

Biological membranes consist of phospholipid bilayers with proteins embedded in the bilayer
Singer and Nicholson

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24
Q

Why do phospholipids form bilayers in water?

A

Due to amphipathic properties of phospholipid molecules

  • hydrophilic phosphate heads
  • hydrophobic fatty acid tails
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25
Cholesterol function
Improves stability and reduces fluidity - membrane less permeable - prevents crystallization
26
Difference in property of integral and peripheral proteins
Integral- amphipathic | Peripheral- polar
27
Membrane protein functions
CCRRE Channels: passive transport Carriers: use energy to change shape (protein pump) Recognition: differentiates between self and non-self cells Receptors: relay information (transmembrane) Enzymes: enhance rate of reaction
28
The Davson-Danielli model
3 layers | lipo-protein sandwich- 2 layers of protein with central phospholipid bilayer
29
Assumptions of Davson-Danielli model
All membranes would be the same Symmetrical surfaces No Permeability
30
Falsification evidence (of Davson-Danielli model)
Proteins are amphipathic and varied in size Fluorescent antibody tagging shows that membrane proteins move and are not static Freeze fracturing reveals irregular rough surfaces inside membrane- transmembrane proteins present
31
Passive Transport
Along concentration gradient | Does not require ATP
32
Factors affecting rate of diffusion
- Temperature - Surface area - Size of particles - Concentration gradient of diffusing particles
33
Facilitated diffusion (potassium channels in axon)
The K+ channels only allow the movement of K+ (inside to outside of axon for repolarisation) Channels are voltage-gated to control neuron firing
34
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
35
Hypertonic
High solute concentration- gains water Plant cell in hypertonic solution --> plasmolyzed Animal cell in hypertonic solution --> shriveled
36
Hypotonic
Low solute concentration- loses water Plant cell in hypotonic solution--> turgid Animal cell in hypotonic solution --> lysed
37
Application of osmolarity to medical procedures
Tissues and organs are bathed in a solution of same osmolarity as cytoplasm to prevent osmosis
38
Active Transport
Against concentration gradient Uses ATP Uses a carrier protein
39
Explain the sodium-potassium pump
1. 3 sodium ions bind to intracellular sites on the sodium-potassium pump 2. Phosphate group transferred to the pump via hydrolysis of ATP 3. Pump undergoes conformational change, translocating sodium across membrane 4. Conformational change exposes 2 potassium binding sites on extracellular surface of pump 5. Phosphate group is released, pump returns to original conformation 6. This translocate potassium ions across membrane
40
Vesicular transport
Proteins produced by ribosomes enter Rough ER - Vesicles bud off from RER & carry proteins to Golgi apparatus - Vesicle fuses with Golgi apparatus, where proteins are modified and packaged - Vesicles bud off from Golgi apparatus & carry proteins to the membrane - Vesicles fuse with membrane and spill contents out of cell
41
Endocytosis
Phagocytosis: absorption of solids Pinocytosis: ingestion of liquids
42
Exocytosis
Excretion: not useful materials Secretion: vesicular transport
43
What allows for bulk transport (exo and endo cytosis)
The fluidity of the plasma membrane
44
Biogenesis (principle)
Principle that living organisms only arise from other living things by reproduction (not spontaneous generation) 'Cells can only arise from pre-existing cells'
45
Louis Pasteur's experiment
Broth in swan neck flasks boiled to sterilise | Growth only occurred if flask was broken or contents exposed to contaminants stuck in neck
46
Miller-Urey's experiment's recreated conditions of pre-biotic earth (to prove non-living synthesis)
High temperatures A reducing atmosphere (no oxygen) High radiation levels and electrical storms Simple amino acids and hydrocarbons were synthesised
47
Conditions for emergence of life
1. Simple organic molecules must be formed 2. Larger organic molecules must be assembled from simpler organic molecules 3. Organisms reproduce, replication of nuclei must be possible 4. Biochemical reactions require optimal conditions (pH) --> membranes
48
The endosymbiosis theory
Mitochondria and chloroplasts were prokaryotes taken in by larger prokaryotes by endocytosis - These cells remained undigested inside host cells and contribute new functionality to engulfing cell - Prokaryote and larger evolved to have a mutualistic relationship- prokaryote provide energy, larger cell provide nutrients
49
Evidence supporting the endosymbiosis theory
Double membranes- taken in by endocytosis Singular naked DNA 70S ribosomes Divide by binary fission
50
Mitosis
The division of the nucleus into two genetically identical daughter nuclei
51
Explain the 3 phases of interphase
G1: cell grows and preps for DNA replication, organelles duplicated S: DNA is replicated G2: cell finishes growing and preps for divison
52
Chromatin vs Chromosome
Chromatin: DNA loosely packed within nucleus, accessible for transcription/translation Chromosome: DNA tightly wound around histones and condensed via supercoiling, inaccessible
53
When do DNA condense
in mitosis- only visible then
54
Explain prophase
``` DNA supercoils and chromosome condense --> sister chromatids Nucleolus disappears Nuclear membrane disintegrates Microtubule spindle fibres form Centrioles move to opposite poles ```
55
Explain metaphase
Spindle fibres bind to centromere of sister chromatids and cause their movement towards the equatorial plate Sister chromatids align at equatorial plate (centre of cell)
56
Explain anaphase
Sister chromatids are separated (chromosomes) and pulled to opposite poles by spindle fibres
57
Explain telophase
Chromosomes have reached poles Nuclear membrane starts to reform at each pole Nucleolus appears in each new nucleus Spindle fibres disintegrate Cell elongates in prep for cytokinesis (which actually occurs concurrently, splitting cell in 2)
58
Mitotic index
Ratio of the number of cells in a population undergoing mitosis to the total number of visible cells
59
Cytokinesis in animal cell
- Microtubule filaments located immediately beneath plasma membrane at the equator pulls plasma membrane inwards - Inward pull on plasma membrane forms a cleavage furrow - When cleavage furrow reaches centre of cell, cell is completely pinched off, two daughter cells are produced - Centripetal: moves from outside towards centre
60
Cytokinesis in plant cell
- Golgi apparatus forms vesicles carrying material to form new cell wall - Vesicles merge and form the cell plate - Cell plate grows and divides into two daughter cells - Centrifugal: central and moves laterally
61
Cyclins
Cyclins bind to enzymes - cyclin-dependent kinases (CDKs) and activate them - forms a complex Activated CDKs (the complex) attach phosphate groups to other (specific) proteins in the cell Attachment of phosphate will trigger the target protein to carry out some specific event within the cell cycle (i.e. DNA replication) Cyclin levels will peak when their target protein is required for function and remain at a lower levels other times
62
Benign tumour
localised, does not spread to other parts of the body
63
Malignant tumour
cancerous growth that is often resistant to treatment- may spread to other parts of the body, may recur after removal
64
How can a tumour occur
When events of a cell cycle are disrupted due to a mutation in a cyclin or CDK, or an associated protein Cell may have lost ability to enter G1, mutation is passed on to daughter cells and a clump of cells form
65
Mutagens
Agents that cause gene mutations i.e. carcinogens, X-rays
66
Proto-oncogenes
gene codes for proteins that stimulate cell cycle etc. --> mutation causes it to become cancer-causing oncogene
67
Tumour suppressor genes
gene codes for proteins that repress cell cycle progression --> mutation stops its normal function of preventing tumour formation
68
Metastasis
Cancerous cells detach from the primary tumour Some cancerous cells penetrates wall of lymph or blood vessels and so circulate the body Circulating cancerous cells invade tissues at different locations and develop, by uncontrolled cell division, into secondary tumours
69
Smoking and cancer
Correlation and not necessarily causation

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