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IB Biology HL > 1 Cell Biology > Flashcards

1 Cell Biology Flashcards

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1
Q

What are the three points of cell theory?

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

How do striated muscle fibres not conform to cell theory?

A

The muscle cells fuse to become very long and thus have multiple nuclei with only one plasma membrane

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3
Q

What part of cell theory do striated muscle fibres challenge?

A

That cells always function as autonomous units

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4
Q

How do aseptate fungal hyphae not conform to cell theory?

A

They do not have hyphae separating cells.

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5
Q

What part of cell theory do aseptate fungal hyphae challenge?

A

That cells are composed on discrete cells

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6
Q

How do giant algae not conform to cell theory?

A

They grow extremely large (7cm)

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7
Q

What part of cell theory do giant algae challenge?

A

That larger organisms are made up of many microscopic cells

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8
Q

What are the 7 basic functions integral to life?

A 
Metabolism
Reproduction
Sensitivity
Homeostasis
Excretion
Nutrition
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9
Q

How does paramecium fulfil the basic function of responsiveness?

A

They are surrounded by cilia which help them move

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10
Q

How does paramecium fulfil the basic function of nutrition?

A

They engulf food via a feeding groves called cytostome

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11
Q

How does paramecium fulfil the basic function of metabolism?

A

Food particles are enclosed within small vacuoles that contain enzymes for digestion

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12
Q

How does paramecium fulfil the basic function of excretion?

A

Solid wastes are removed via contractile vacuoles

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13
Q

How does paramecium fulfil the basic function of homeostasis?

A

Essential gasses enter and exit via diffusion

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14
Q

How does paramecium fulfil the basic function of reproduction?

A

They divide asexually but horizontal gene transfer can occur via conjugation

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15
Q

How do you calculate rate of metabolism?

A

Mass/Volume

Larger cells need more energy to sustain essential functions

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16
Q

What does a large surface area mean in terms of rate of material exchange?

A

More material movement

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17
Q

Equation for magnification

A

Magnification = (image size/ actual size)

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18
Q

What 3 things should be included in a good diagram of microscopic structires?

A

Title
Scale/ Magnification
Clear labels of only what was visible

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19
Q

Define a tissue

A

Collection of similar cells

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20
Q

Define an organ

A

Tissues working together to complete a function

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21
Q

Define organ system

A

Organs working together to complete a vital part of life

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22
Q

Define an organism

A

Group of organ systems and tissues working together to form one living unit

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23
Q

Define differentiation

A

The process during development whereby newly formed cells become more specialised

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24
Q

What happens genetically when cells are specialised?

A

Different parts of the genome are activated

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25
Q

How is DNA present in a eukaryotic cell?

A

In the nucleus and packed with proteins to form chromatin

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26
Q

Define and describe euchromatin

A

Where the active genes are usually packaged in an expanded way so that they can be easily read

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27
Q

Define and describe heterochromatin

A

Where the inactive genes are usually packaged in a condensed way (this saves space as they are not transcribed)

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28
Q

What are the two key qualities of stem cells?

A

Self Renewal

Potency

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29
Q

Define a Totipotent cell

A

Can form any cell as well as extra-embryonic (placental) tissue (e.g.: zygotes)

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30
Q

Define a unipotent cell

A

Can not differentiate but are capable of self-renewal

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31
Q

Define a multipotent cell

A

Can differentiate into a number of closely related cells

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32
Q

Define a pluripotent cell

A

Can form (almost) any cell type

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33
Q

What does the process of using stem cells require?

A

Biochemical solutions to trigger differentiation
Surgical implantation
Suppression of host immune system
Careful monitoring to ensure they do not become cancerous

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34
Q

What is Stargardt’s disease?

A

A disease caused by a gene mutation which leads to blindness

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35
Q

How can we treat Stargardt’s Disease?

A

Replacing dead retinal cells with functioning ones derived from stem cells

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36
Q

What is Parkinson’s Disease?

A

A disorder which effects dopamine-secreting nerve cells meaning a patient can no longer control smooth, purposeful movements

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37
Q

How can we treat Parkinson’s Disease?

A

Replacing dead nerve cells with functioning ones derived from stem cells

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38
Q

How can we treat Leukaemia?

A

Produce bone marrow from stem cells

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39
Q

How can we treat Paraplegia?

A

Repair damage caused by spinal injuries to enable paralysed victims to regain movement (by using tissue derived from stem cells)

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40
Q

How can we treat Diabetes?

A

Replace non-functioning islet cells with those able to produce insulin (derived from stem cells)

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41
Q

How can we treat burn victims?

A

Graft new skin to replace the damage using stem cells

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42
Q

What are the three sources to find animal stem cells?

A

Embryos
Umbilical cord blood or placenta of a new-born baby
Certain adult tissues (such as bone marrow - not pluripotent)

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43
Q

What are the two techniques for artificial stem cells?

A

SCNT (Somatic cell nuclear transfer)

Nuclear reprogramming

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44
Q

Describe somatic cell nuclear transfer (SCNT)

A

Involves the creation of embryonic clones by fusing a diploid nucleus with an egg cell (therapeutic cloning)

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45
Q

Describe nuclear reprogramming

A

Inducing a change in gene expression to transdifferentiate a cell

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46
Q

What is one of the negative side effects of nuclear reprogramming?

A

Involves the use of oncogenic retroviruses and transgenes increasing health risks

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47
Q

Which kingdom do prokaryotic cells fall into?

A

Monera

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48
Q

What are the two domains within monera?

A

Archaebacteria (such as extremophiles)

Eubacteria

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49
Q

Name the 10 cellular components of prokaryotic cells

A 
Cytoplasm
Nucleoid region
Plasmids
Ribosomes (70S)
Cytoskeleton
Cell membrane
Cell wall
Slime capsule
Flagella
Pili
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50
Q

What is the function of the slime capsule?

A

A thick polysaccharide layer used for protection against desiccation (drying out) and phagocytosis

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51
Q

What is the function of pili?

A

Adherence to surfaces or to mediate bacterial conjugation (sex)

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52
Q

What is the cell wall of a prokaryotic cell made of?

A

Peptidoglycan

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53
Q

Describe the process of binary fission

A

DNA replicates
Two DNA loops attach to the membrane
The membrane elongates and pinches off (cytokinesis)

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54
Q

Into which kingdoms can eukaryotes be divided?

A

Protista
Fungi
Plantae
Animalia

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55
Q

What are protista?

A

Unicellular or multicellular organisms without specialised tissues

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56
Q

What is the difference between 70S and 80S ribosomes and where can they be found?

A

70S is smaller than 80S
70S can be found in prokaryotes and mitochondria
80S can be found in eukaryotic cells

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57
Q

Describe the smooth endoplasmic reticulum

A

A bare membrane network with the function of lipid synthesis

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58
Q

Describe the rough endoplasmic reticulum

A

A membrane network studded with ribosomes with the function of protein synthesis of dangerous proteins

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59
Q

Describe the Golgi apparatus

A

An assembly of folded vesicles and membranes involved in sorting, storing, modifying and exporting of secretory products

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60
Q

Describe mitochondrion

A

Double membrane structure, site of aerobic respiration

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61
Q

Describe peroxisomes

A

Membranous sac containing enzymes, catalyses breakdown of toxic substances

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62
Q

Describe centrosomes

A

Microtubule organising centre, radiating microtubules from spindle fibres to contribute to cell division (paired in animal but not plant cells)

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63
Q

Describe chloroplasts

A

[PLANT]

Double membrane structure with internal stacks of membranous discs, site of photosynthesis

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64
Q

Describe the vacuole

A

[PLANT]

Fluid-filled cavity surrounded by membrane, maintain hydrostatic pressure

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65
Q

Describe the cell wall of eukaryotic cells

A

[PLANT]

External outer covering made of cellulose, provides support and prevents excess water uptake

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66
Q

Describe lysosomes

A

[ANIMAL]

Membranous sacs filled with hydrolytic enzymes, breakdown/ hydrolysis of macromolecules

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67
Q

What is the function of a transmission electron microscope (TEM)?

A

Generating high-resolution cross-sections of objects

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68
Q

What is the function of a scanning electron microscope (SEM)?

A

Display enhanced depth to map the surface of object in 3D

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69
Q

Disadvantage of electron microscopes

A

Cannot display living specimens in natural colours

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70
Q

Advantages of electron microscopes

A

Higher range of magnification

Higher resolution

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71
Q

Define a micrograph

A

A photo or digital image taken through a microscope

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72
Q

Why do phospholipids form bilayers in water?

A

Due to the amphipathic properties of their molecules

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73
Q

Define amphipathic

A

Having both hydrophilic and hydrophobic parts

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74
Q

Which part of the phospholipid is hydrophobic?

A

The two non-polar lipid tails

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75
Q

Which part of the phospholipid is hydrophilic?

A

The polar glycerol and phosphate head

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76
Q

How is the phospholipid bilayer flexible?

A

Individual phospholipids can move around within it

77
Q

Why is fluidity important for the membrane?

A

Allows for spontaneous breaking and reforming of membranes (endo/exocytosis)

78
Q

What types of proteins can be found within the phospholipid bilayer?

A

Integral proteins

Peripheral proteins

79
Q

Describe integral proteins

A

Proteins which are permanently attached to the membrane and are typically transmembrane (span across the bilayer)

80
Q

Describe peripheral proteins

A

Proteins temporarily attached by non-covalent interactions and associate with one surface of the membrane

81
Q

Describe a channel protein

A

The non-polar (hydrophobic) amino acids associate directly with the lipid bilayer and the polar amino acids are located internally and face aqueous solutions

82
Q

What tertiary structures do transmembrane proteins most commonly form?

A

Single helices
Helical bundles
Beta barrels

83
Q

Which tertiary structure is most common amongst channel proteins?

A

Beta barrels

84
Q

Describe an α-helix tertiary structure

A

Single helix

A single protein goes straight through the membrane, perpendicular to it

85
Q

What are usually the functions of proteins in an α-helix structure?

A

Recognition

Receptors

86
Q

Describe a helical bundle tertiary structure

A

Many proteins which cross straight through the membrane, perpendicular to it and are all connected

87
Q

What are usually the functions of proteins in an helical bundle structure?

A

Enzymes
Transporters
Receptors

88
Q

Describe a β-barrel tertiary structure

A

A tandem repeats that twists and coils through the membrane so that the first strand is bonded to the last

89
Q

What are usually the functions of proteins in a β-barrel structure?

A

Transporters (channel proteins)

90
Q

What are the functions of membrane proteins?

A 
Junction
Enzymes
Transport
Recognition
Anchorage 
Transduction (receptors for peptide hormones)
[Mnemonic JETRAT]
91
Q

What is the function of cholesterol within animal cell membranes?

A

Maintaining integrity and stability

92
Q

Why do plant cells not require cholesterol?

A

They already have a rigid cell wall

93
Q

Describe cholesterol and it’s polarity

A

cholesterol is amphipathic
The cholesterol’s hydroxyl (-OH) groups is hydrophilic, the remainder, a steroid ring and hydrocarbon tail, is hydrophobic

94
Q

How do the cholesterol molecules align within the membrane?

A

The hydrophilic hydroxyl (-OH) group aligns with the phospholipid heads, and the hydrophobic steroid ring and hydrocarbons align with the phospholipid tails

95
Q

What are the main differences between the Davson-Danielli and the Singer-Nicolson Model?

A

There are transmembrane proteins in the Singer-Nicolson model
The membrane proteins moved and were not static in the Singer-Nicolson model

96
Q

What is the widely accepted membrane model?

A

Fluid-Mosaic model

97
Q

What were the assumptions and inaccuracies the Davson-Danielli model made?

A

All membranes were of uniform thickness
All membranes had symmetrical internal and external faces
Did not account for permeability
The temperatures at which the membranes solidified did not correlate

98
Q

How were modifications made to the pervious model to change it to the fluid-mosaic model?

A

Fluorescent antibody tagging showed that proteins were mobile
Freeze fracturing found a rough surface providing proof for transmembrane proteins

99
Q

Describe the permeability of a cellular membrane

A

(Selectively) semi-permeable

100
Q

What are the three forms of passive transport?

A

Simple diffusion
Osmosis
Facilitated diffusion

101
Q

Describe simple diffusion

A

Movement of small or lipophilic molecules down the concentration gradient

102
Q

Describe osmosis

A

Movement of water molecules down the concentration gradient (from low to high concentration of sugars)

103
Q

Describe facilitated diffusion

A

Movement of large or charged molecules via membrane proteins

104
Q

How does active transport occur?

A

Through the hydrolysis of ATP into ADP and a phosphate group, the phosphate group then binds to a protein which will change shape to accommodate active transport

105
Q

What are the two types of active transport?

A

Primary (direct) active transport

Secondary (indirect) active transport

106
Q

Describe direct active trasnsport

A

Involves direct use of metabolic energy, can be split into uniport and cotransport. This is pump-mediated

107
Q

Describe indirect active transport

A

Involves coupling the molecule with another along an electrochemical gradient, can be split into antiport and symport. This is carrier-mediated

108
Q

Describe uniport (active transport)

A

When one molecule moves from low to high concentration

109
Q

Describe cotransport (active transport)

A

When two molecules move across the membrane from low to high concentration simultaneously

110
Q

Describe antiport (active transport)

A

When two molecules move in opposite directions across the gradient but the high and low concentrations for each are on the same side (therefore one is going with and another against the concentration gradient)

111
Q

Describe symport (active transport)

A

When two molecules move together across the membrane in the same direction but one moves with and one against the gradient

112
Q

When does simple diffusion stop?

A

When an equilibrium is reached

113
Q

Which factors effecting rate of diffusion?

A

Temperature
Molecular size
Steepness of gradient

114
Q

Describe a hypertonic solution

A

One with a high solute concentration

115
Q

Describe a hypotonic solution

A

One with a low solute concentration

116
Q

Describe an isotonic solution

A

Same solute concentration

117
Q

What do we call a plant cell in a hypertonic solutions?

A

Shrivelled

118
Q

What do we call a plant cell in a hypotonic solutions?

A

Lysed

119
Q

What do we call a plant cell in an isotonic solutions?

A

Normal

120
Q

What do we call an animal cell in a hypertonic solutions?

A

Plasmolysed

121
Q

What do we call an animal cell in a hypotonic solutions?

A

Turgid

122
Q

What do we call an animal cell in an isotonic solutions?

A

Flaccid

123
Q

Which two types of proteins are involved in facllitated diffusion?

A

Carrier and channel proteins

124
Q

Describe carrier proteins

A

Integral glycoproteins

125
Q

How do carrier proteins work?

A

They bind to a solute and undergo a conformational change (they are also used in active transport)

126
Q

What is the rate of transport of carrier proteins?

A

~1000 molecules/sec

127
Q

Describe channel proteins

A

Integral lipoproteins which contain a pore via which ions may cross from one side of the membrane to the other

128
Q

How do channel proteins work?

A

They use ions to regulate the passage of ions

129
Q

How does the rate of transfer of channel proteins vary from that of carrier proteins?

A

Channel proteins have a much faster rate of transport than carrier proteins

130
Q

What does a sodium-potassium pump do at rest?

A

Expels sodium ions from the nerve cell while potassium ions accumulate within

131
Q

What happens in a sodium-potassium pump when the neuron fires?

A

The ions swap locations via facilitated diffusion via sodium and potassium channels

132
Q

Define abiogenesis

A

The theory that living cells arose from non-living matter

133
Q

What were the 4 stages of abiogenesis?

A

There was non-living synthesis of simple organic molecules
These molecules became more complex polymers
Some formed the ability to self-replicate
These were packaged into membranes

134
Q

Which experiment demonstrated the theory of abiogenesis?

A

Miller-Urey

135
Q

Describe the Miller-Urey experiment

A

A reducing atmosphere similar to that of early Earth was created
The mixture was then exposed to electrical discharge and left to cool for a week
This was then found to contain trace of simple organic molecules

136
Q

To whom is the law of biogenesis attributed?

A

Louis Pasteur

137
Q

Describe biogenesis

A

The principle that all living things arise form other living things by reproduction

138
Q

How did Pasteur prove biogenesis?

A

Swan neck experiment

139
Q

Describe the swan neck experiment

A

Two nutrient broths were sterilised. One had a swan neck the other was simply open.
After a week, microorganisms were only present in the open flask and not the swan neck flask, disproving miasma.

140
Q

Define endosymbiont

A

A cell which lives inside another with mutual benefits

141
Q

How did eukaryotes evolve?

A

From prokaryotic cells that were engulfed by phagocytosis and remained undigested as they contributed new functionality to the cell

142
Q

Name two organelles believed to have formed from endosymbiosis

A

Mitochondria

Chloroplasts

143
Q

Give evidence for endosymbiosis

A 
Membranes (double membrane bound)
Antibiotics (susceptibility)
Division (mode of replication)
DNA (presence and structure)
Ribosome (size)
[MNEOMONIC MAD DR]
144
Q

Which are the two main phases of the cell cycle?

A

Interphase and the M phase

145
Q

What are the stages of interphase?

A

G1, S and G2

146
Q

What happens during G1 (interphase)?

A

Cell grows and prepares for DNA replication

147
Q

What happens during S (interphase)?

A

Synthesis of DNA (DNA is replicated)

148
Q

What happens during G2 (interphase)?

A

Cell finishes growing and prepares for cell division

149
Q

What is interphase?

A

The part of the cell cycle where metabolism and growth occur.
(Consists of G1, S and G2 phases)

150
Q

What is M phase?

A

The period in the cell cycle in which the cell divides into two daughter cells.
(Consists of mitosis and cytokinesis)

151
Q

What are the stages of mitosis, in order?

A 
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
152
Q

Which are the key processes in mitosis?

A 
DNA replication
Organelle duplication
Cell growth
Transcription (key proteins and enzymes are synthesised)
Obtain nutrients
Respiration
[MNEMONIC DOCTOR]
153
Q

How is DNA found in the nucleus?

A

Usually loosely packed, unravelled chromatin

154
Q

What is a chromosome?

A

The tightly wound and condensed form of DNA found prior to division

155
Q

What is the difference between chromatin and chromosomes?

A

Chromatin is the loose DNA found during interphase which then undergoes supercoiling into a chromosome for cell division

156
Q

What is either half of a chromosome calles?

A

Chromatids

157
Q

What do we call the region where the chromatids are joined?

A

Centromere

158
Q

What do we call replicated chromatids?

A

Sister chromatids

159
Q

What do we call chromatids after division?

A

Daughter chromatids

160
Q

Describe mitosis

A

The process of nuclear division whereby duplicated DNA molecules are arranged into two separate nuclei

161
Q

Describe a cell just before mitosis

A

DNA is present as uncondensed chromatin (not visible under a microscope)
It is confined within a clearly defined nucleus
The cell is enlarged and ready to divide

162
Q

Describe prophase

A

DNA supercoils and condenses
Paired centrosomes move to the opposite poles of the cell and form microtubule spindle fibres
Nuclear membrane breaks down and dissolves

163
Q

Describe metaphase

A

Microtubule spindle fibres from both centrosomes connect to the cell centromeres
These contract aligning the chromosomes on the equatorial plate.

164
Q

How do spindle fibres contract?

A

Depolymerisation

165
Q

Describe anaphase

A

The contracting spindle fibres pull the chromatids to either pole (they are now chromosomes in their own right)

166
Q

Describe telophase

A

The spindle fibres dissolve and chromosomes decondense

A new nuclear envelope forms

167
Q

Describe cytokinesis in animal cells

A

The microtubules form concentric rings around the centre of the cell after anaphase
These constrict to form a cleavage furrow
When the furrow meets in the middle the cells pinch off

168
Q

How is cytokinesis in animal cells described?

A

Centripetal - it occurs from the outside in

169
Q

Describe cytokinesis in plant cells

A

After anaphase vesicles rich in carbohydrates form a row at the centre of the cell and fuse forming an early cell plate
This extends outwards to fuse with the cell wall forming two identical daughter cells

170
Q

How is cytokinesis in plant cells described?

A

centrifugal - it originates at the centre and moves laterally

171
Q

Define mitotic index

A

A measure of the status of a cell population (in terms of which cells are undergoing mitosis)

172
Q

How do you calculate the mitotic index?

A

Ratio between number of cells in mitosis and total number of cells

173
Q

How is the cell cycle controlled?

A

By cyclins (regulatory proteins)

174
Q

Define phosphorylation

A

The attachment of a phosphoryl group

175
Q

How do cyclins control the cell cycle?

A

Through the activation of CDKs which control the processes through phosphorylation
When a cyclin and CDK bond, they bind to a target protein and modify it via phosphorylation

176
Q

What happens to the cyclin and CDK after phosphorylation?

A

The cyclin is degraded

The CDK is rendered inactive again

177
Q

What does CDK stand for?

A

Cyclin dependant kinases

178
Q

Define tumour

A

Abnormal cell growth resulting in uncontrolled cell division

179
Q

What is a cancer?

A

A disease caused by the growth of tumours

180
Q

Define mutagen

A

An agent that changes the genetic material of an organism

181
Q

What are the three types of mutagens?

A

Physical (e.g.: radiation)
Chemical (e.g.: arsenic)
Biological (e.g.: bacteria)

182
Q

Define oncogenes

A

A gene with the potential to cause cancer

183
Q

Mutations to which two genes are most likely to cause cancer?

A

Proto-oncogenes (stimulate the cell-cycle)

Tumour suppressor genes (repress the cell-cycle)

184
Q

Define mestastasis

A

When a cancer spreads from a primary location to a secondary location (becoming malignant)

185
Q

What do we call a cancer that does not metastasis?

A

Benign

186
Q

How many chemicals are there in cigarettes and how many ae carinogenic?

A

60 of 4,000 are carcinogenic

187
Q

What percentage of lung cancer is attributed to smoking?

A

~90%

188
Q

Define Mesosome

A

The part of a prokaryotic cell wall which folds inwards

IB Biology HL (35 decks)

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