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CELS > Progress Test (lectures 2-14) > Flashcards

Progress Test (lectures 2-14) Flashcards

1
Q

State the 8 characteristics of life

A 
Cellular organisation
Reproduction
Metabolism
Homeostasis
Heredity
Response to stimuli
Growth and development
Adaptation through evolution
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2
Q

How many micrometers in a metre?

A

1 million

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3
Q

Which take up most of the total distribution of organisms- plants or animals? How many Gt?

A

Plants- 450Gt

Humans- 0.7Gt

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4
Q

Natural selection

A

The process by which organisms better adapted to their environment survive and produce more offspring, leading to evolution of the species.

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5
Q

What is the process that allows for evolution?

A

Natural selection

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6
Q

Does natural selection act on biological molecules, or just animals and plants?

A

All

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7
Q

What does natural selection require? (4)

A

Variation
Inheritance
Selection
Time

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8
Q

Name of the diagram used to relate organisms to others through shared characteristics

A

Phylogenetic tree

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9
Q

Three domains of life

A

Archaea
Bacteria
Eukarya

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10
Q

Which domain can grow at very high temperatures?

A

Archaea- can grow at over 100 degrees Celsius

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11
Q

What term can be used to refer to both bacteria and archaea domains collectively?

A

Prokaryotes

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12
Q

Three main differences between prokaryotic and eukaryotic cells

A

Prokaryotic cells are smaller, have no nucleus and don’t contain organelles

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13
Q

Endosymbiosis

A

The theory which explains how eukaryotic cells may have evolved from prokaryotic cells.

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14
Q

Which organelles of plant and animal cells are derived from bacteria? What is the name of the theory that explains this?

A

Mitochondria and chloroplasts

Endosymbiosis

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15
Q

How much of a typical cell is water?

A

70%

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16
Q

Does DNA make up a large amount of the cell?

A

No- only 0.25%

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17
Q

What are the building blocks of the cell? (6)

A

Amino acids
Nucleobases
Simple carbohydrates
Glycerol, fatty acids, hydrocarbon rings

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18
Q

Macromolecules of the cell (5)

A 
Proteins
DNA
RNA
Complex carbohydrates
Lipids
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19
Q

Which building block makes up proteins?

A

Amino acids

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20
Q

Which building block makes up DNA and RNA?

A

Nucleobases

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21
Q

Which building block makes up complex carbohydrates?

A

Simple carbohydrates

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22
Q

Which building blocks make up lipids? (3)

A

Glycerol, fatty acids, hydrocarbon rings

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23
Q

What are the three supramolecular assemblies of the cell?

A

Membranes
Ribosomes
Chromatin

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24
Q

Name the organelles found in an animal cell (5)

A 
Nucleus
Golgi apparatus
Mitochondrion
Endoplasmic reticulum
Lysosomes
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25
Q

What organelle do plant cells contain that animal cells don’t?

A

Chloroplasts

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26
Q

Macromolecule

A

An organic biological molecule of large molecular mass which is necessary for life

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27
Q

Name the four levels of carbohydrate

A

Monosaccharides
Disaccharides
Oligosaccharides
Polysaccharides

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28
Q

Monosaccharides and disaccharides are what type of carbohydrate?

A

Simple

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29
Q

Oligosaccharides and polysaccharides are what type of carbohydrate?

A

Complex

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30
Q

How many sugars are in a monosaccharide?

A

One

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31
Q

Glucose is what type of carbohydrate?

A

Monosaccharide (simple)

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32
Q

Which monosaccharides are the building blocks of higher order carbohydrates?

A

Hexose monosaccharides

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33
Q

Which simple carbohydrates are usually part of larger molecules? Give an example of these molecules

A

Pentose monosaccharides, DNA

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34
Q

How are disaccharides made up?

A

By two monosaccharides joined together

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35
Q

How many monosaccharides join to form an oligosaccharide?

A

3-10

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36
Q

What is the name of the complex carbohydrate which is formed by joining over 10 monosaccharides?

A

Polysaccharides

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37
Q

Name two types of polysaccharides

A

Starch and cellulose

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38
Q

Describe starch

A

A plant carbohydrate made of long chains of glucose monomers linked to form a branch shape

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39
Q

Describe cellulose structure

A

A fibre- long chains of glucose stacked on top of each other

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40
Q

Functions of carbohydrates (3)

A

Recognition of other cells/ bacteria
Source of energy
Structure

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41
Q

What do nucleic acids do?

A

They are informational molecules- they tell the cell what to do and where and when to do it

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42
Q

Name the two types of nucleic acids

A

Ribonucleic acid RNA

Deoxyribonucleic acid DNA

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43
Q

What are the two structural differences between RNA and DNA?

A

DNA has a hydrogen atom whereas RNA has a hydroxyl group at the second carbon position

RNA has one polynucleotide, DNA has two

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44
Q

Name the three components of a nucleotide

A

Phosphate group
Ribose sugar
Base

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45
Q

Name the five bases in nucleic acids

A

Adenine
Guanine
Thymine/ uracil in RNA
Cytosine

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46
Q

What do bases A and G have in common?

A

They are both purines

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47
Q

Thymine, uracil and cytosine are all what type of base?

A

Pyrimidines

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48
Q

How do nucleotides join to form a polynucleotide?

A

They join by their phosphate groups

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49
Q

Transcription (cellular process)

A

Process by which DNA is copied to messenger RNA (mRNA)

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50
Q

Translation (cellular process)

A

Process by which mRNA is used to produce proteins

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51
Q

How do amino acids differ?

A

By their R group (side chain)

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52
Q

What base joins to cytosine?

A

Guanine

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53
Q

Which base joins to adenine?

A

Thymine

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54
Q

Which macromolecule is not a polymer?

A

Lipids

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55
Q

Name five common types of lipids

A 
Triacylglycerols TAG (fats)
Steroids
Phospholipids
Glycolipids
Fat soluble vitamins
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56
Q

Are lipids hydrophilic or hydrophobic?

A

Hydrophobic

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57
Q

Three functions of lipids

A

Forming cell membrane
Energy storage (in form of fat molecules TAG)
Regulate temperature

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58
Q

Five actions of the cell

A 
Manufacture cell materials
Obtain raw materials
Remove waste
Generate required energy
Control above actions
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59
Q

Why does the cell have separate organelles? (3)

A

To provide different conditions for specific processes

To allow substances to be concentrated, and therefore form concentration gradients

To package substances for transport

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60
Q

What is the name of the semi-permeable barrier at the boundary of the cell? What does this semi-permeability mean?

A

Plasma membrane

It controls what substances are let in and out

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61
Q

Which parts of a phospholipid bilayer are hydrophobic/phillic?

A

Hydrophobic head

Hydrophilic tails

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62
Q

What are the hydrophobic tails of phospholipids made of? What do they do?

A

Fatty acids, affect membrane fluidity.

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63
Q

Describe a more fluid phospholipid bilayer

A

The tails (fatty acids) are unsaturated, so they prevent packing. This is due to the kinks in the tails caused by double bonded carbons.

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64
Q

Describe a more viscous phospholipid bilayer

A

Saturated tails are packed tightly together.

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65
Q

What is the function of cholesterol in cell membranes? Which cells is it found in?

A

It fits between phospholipids and strengthens and stabilises the membrane. Found only in animal cells

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66
Q

Name the three types of transport across the cell membrane

A

Passive, active and co-

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67
Q

What is the difference between diffusion and facilitated diffusion?

A

Hydrophobic molecules are able to pass through the membrane- diffusion.

Hydrophilic (including charged) molecules are able to pass through the membrane using channels and carriers- facilitated diffusion.

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68
Q

Difference between passive and active transport

A

Molecules move down their concentration gradient in passive transport, and against it in active transport.

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69
Q

Aquaporins

A

Channel proteins which allow water molecules to move down their concentration (osmotic) gradients

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70
Q

Is active transport aiming for homeostasis?

A

No, it moves molecules against their concentration gradients.

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71
Q

What is needed for active transport to take place? (2)

A

Energy, usually in the form of ATP

Transport proteins to facilitate the movement

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72
Q

Contransport

A

A form of active transport that allows two or more types of molecules to cross the membrane against their concentration gradients.

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73
Q

Example of contransport

A

H+ ions are pumped out of cell by proton pump

They cross back into it passively, taking sucrose molecules with them

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74
Q

What causes diseases such as albinism II, Wilson’s disease and cystic fibrosis?

A

A lack of/ damage to transport mechanisms in the cell membrane

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75
Q

Name four roles of membrane proteins

A 
Signal transduction (relay messages into cell, to grow, divide etc.)
Cell recognition (of invading cells)
Intercellular joining (cell junctions)
Linking cytoskeleton and ECM
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76
Q

What is included in the endomembrane system? (7)

A 
Nuclear envelope
ER
Golgi apparatus
Vesicles
Lysosomes
Vacuoles
Plasma membrane
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77
Q

How is the endomembrane system connected?

A

By direct physical contact, and transfer by vesicles

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78
Q

What are the two regions of the ER?

A

Smooth and rough

sER and rER

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79
Q

Which region of the ER can be increased or decreased to meet the cell’s demands?

A

sER

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80
Q

Functions of sER (4)

A

Metabolises carbohydrates
Synthesises lipids for membranes
Detoxifies drugs/ poisons
Stores calcium ions

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81
Q

What is a main function of the smooth ER in liver cells?

A

Detoxifying drugs and poisons e.g. alcohol

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82
Q

Function of rER

A

Synthesising proteins

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83
Q

How does the rER process proteins?

A

They move into the lumen of the rER, are folded into shape, are processed then move to the Golgi complex.

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84
Q

Describe the structure of the Golgi apparatus

A

A complex made of flattened tubules with a cis face and a trans face.

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85
Q

Functions of Golgi apparatus

A

Organises, modifies and sorts proteins

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86
Q

Describe the travel of proteins through the Golgi apparatus

A

Arrive at cis face from the rER, leave at the trans face in vesicles

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87
Q

What is the name of the process that adds/ modifies carbohydrates to proteins in the Golgi apparatus?

A

Glycosylation

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88
Q

Which proteins is glycosylation important for?

A

Cell surface and secreted proteins

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89
Q

How does the Golgi apparatus direct proteins out into the cell?

A

Molecular markers are added to the proteins. They leave in vesicles which are also tagged with markers of short proteins. These act as barcodes

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90
Q

Where are proteins directed to from the Golgi apparatus?

A

Lysosomes, plasma membrane or secretion

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91
Q

Two categories of bulk transport

A

Exocytosis (out of the cell) and endocytosis (into the cell)

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92
Q

Two types of exocytosis

A

Constitutive exocytosis

Regulated exocytosis

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93
Q

Which process continuously releases ECM proteins?

A

Constitutive exocytosis

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94
Q

Bulk transport

A

Form of transport of glycoproteins across the plasma membrane

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95
Q

Describe regulated exocytosis

A

A signal is required to move vesicles in the cell which release hormones and neurotransmitters into the ECM

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96
Q

Phagocytosis

A

A pseudopodium stretches out of the cell, forming a phagocytic vacuole.

This vacuole traps particles (like food), then merged with a lysosome which digests the food particles.

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97
Q

What do lysosomes contain?

A

Hyrdolytic enzymes which break the bonds between particles

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98
Q

Macrophages

A

White blood cells

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99
Q

Which type of bulk transport occurs in macrophages?

A

Phagocytosis- it takes in bacteria to fight.

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100
Q

Pinocytosis

A

Form of bulk transport (endocytosis) which forms a vacuole in the cell wall.

The vacuole is lined with protein called coat protein. This helps direct the vacuole in the right direction.

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101
Q

Receptor-mediated endocytosis

A

A specialised form of pinocytosis which is selective about the solute captured into the vacuole.

Receptors sit on the cell membrane, and the vacuole forms once a bulk quantity of the required solute is captured.

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102
Q

What is the pH level hydrolytic enzymes require to function well?

A

Low pH (acidic)

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103
Q

What are lysosomes made by?

A

rER and Golgi apparatus

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104
Q

Lysosome functions (2)

A

To break down proteins, lipids, carbohydrates and nucleic acids

To recycle unwanted cellular materials

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105
Q

Autophagy

A

Process of cell eating itself/ breaking down. Performed in lysosomes.

Important for cell health and to facilitate cell death

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106
Q

What is Tay-Sachs disease caused by?

A

Hydrolytic enzymes in the lysosomes aren’t able to properly break down molecules, which build up in cells and damage the kidneys, eyes, brain.

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107
Q

Vacuoles

A

Large vesicles derived from the rER and Golgi. Unlike other vesicles, their membranes cannot fuse with others.

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108
Q

Function of cytoskeleton

A

Maintain cell shape and organelle positions

Allows change in cell shape by disassembling/ reassembling rapidly

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109
Q

Three components of the cytoskeleton

A

Microtubules
Intermediate filaments
Microfilaments

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110
Q

Which component of the cytoskeleton is the smallest?

A

Microfilaments

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111
Q

Microtubules

A

A component of the cytoskeleton. Made of tubular subunits.

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112
Q

Functions of microtubules (3)

A

Maintain cell shape by resisting compression

Provide cell motility

Provide organelle motility

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113
Q

What structures can microtubules make up to provide cell motility?

A

Flagella and cilia

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114
Q

Describe the movements of flagella and cilia

A

Flagella- few per cell- have a snake-like motion

Cilia- lots per cell- have a rowing-like motion (undulating)

These can move the cell itself, or move fluid past it.

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115
Q

How are microtubules organised?

A

They can radiate out from a centrosome, or can be arranged alongside each other

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116
Q

How do microtubules facilitate organelle motility?

A

ATP-powered motor proteins can ‘walk’ along the microtubules, transporting an attached vesicle/ organelle to a different part of the cell

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117
Q

Describe the structure of microfilaments

A

A double chain of actin subunits, which can form linear strands or 3D networks.

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118
Q

Function of microfilaments

A

To resist tension- e.g. the cortical network under plasma membrane helps maintain cell shape by making it less fluid

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119
Q

What happens when microfilaments (actin) and motor proteins interact?

A

Muscle contraction
Amoeboid movement
Cytoplasmic streaming (plants)

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120
Q

Intermediate filaments structure

A

Composed of various proteins e.g. keratins (hair), lamins (nucleus), neurofilaments (neurons)

They are supercoiled into cables.

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121
Q

Functions of intermediate filaments

A

Maintain cell shape- more long lasting than other components

Anchor organelles in place

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122
Q

Three types of cell junction

A

Tight junctions
Desmosomes
Gap junctions

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123
Q

How do tight junctions connect cells?

A

Press neighbouring cells tightly together by attaching the microfilaments networks beneath the plasma membrane (cortical network).

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124
Q

Function of tight junctions?

A

Prevents movement of fluid across cell layer

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125
Q

How do desmosomes connect cells?

A

Anchor them together via intermediate filaments.

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126
Q

A torn muscle is a torn _____?

A

Desmosome

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127
Q

Gap junction structure

A

Proteins, arranged with a pore in the middle, attach the two cells.

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128
Q

Function of gap junctions

A

Allows rapid communication between cells. Ions and small molecules can pass through quickly.

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129
Q

Do all cells make direct contact with each other?

A

No. Some lie with an ECM

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130
Q

What is the ECM composed of?

A

Material secreted by cells. Includes various proteins

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131
Q

Which glycoproteins is most abundant in the ECM?

A

Collagen

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132
Q

What do proteoglycans do in the ECM?

A

Trap water to help it keep shape

133
Q

Complex matrix proteoglycans

A

Proteins with extensive sugar additions

134
Q

Fibronectins

A

Glycoproteins that attach cells to the ECM

135
Q

Integrins

A

Proteins that connect the ECM to the cytoskeleton

136
Q

Protoplast (5)

A

The term used to describe inside the plant cell (so not including cell wall)

Nucleus
Golgi apparatus
Central vacuole
Mitochondrion
Chloroplast
137
Q

Two phases of the plant cell wall

A

Cellulose

Noncrystalline matrix

138
Q

Cellulose structure

A

Glucose polymer
Highly organised and strong

Cellulose molecules bond to form microfibrils

139
Q

What two polysaccharides are in the noncrystalline matrix?

A

Pectin and hemicellulose

140
Q

What is pectin and what is it’s function?

A

Branched, negatively charged polysaccharides

They bind water with their gel-like properties

141
Q

Hemicellulose and it’s structure

A

Heterogenous group of polysaccharides

A long chain of one sugar type with short side chains

Strengthen cell wall

142
Q

Extensin

A

A protein with dehydrated the cell wall by cross-linking with pectin

This reduces extensibility and increases strength if the cell wall

143
Q

Rosette

A

An enzyme complex at the cell wall which produces cellulose

144
Q

Three parts of primary cell wall synthesis. What type of transport is performed?

A

Cellulose microfibrils laid down at plasma membrane

Polysaccharides are transported in vesicles from Golgi to the cell wall

Cell wall proteins (e.g. extensins) are transported to the cell wall

Constitutive exocytosis

145
Q

What determines where the microfibrils are laid during primary cell wall synthesis?

A

Cortical microtubules. Rosettes start at one end and travel parallel to the cortical microtubules as they lay down the microfibrils.

146
Q

Middle lamella

A

In between the primary and secondary cell walls. Made up of pectin mostly

147
Q

Functions of cell wall

A

Influences cell morphology (it’s shape, size, form etc.)
Provides structural support
Prevents excessive water uptake

148
Q

What in the cell wall influences the cell’s morphology?

A

The orientation of microfibrils.

When arranged parallel to long axis- the cell will expand longitudinally

When arranged randomly, the cell will expand equally in all directions

149
Q

What will cause the cell to shrivel up?

A

Water loss

150
Q

How does the cell wall prevent excessive water uptake?

A

The cell wall pressure limits the volume of water it can take- it restricts the protoplast from expanding too far.

151
Q

How many membranes do vacuoles have?

A

One

152
Q

Hypotonic

A

Too much water

153
Q

Hypertonic

A

Not enough water

154
Q

Isotonic

A

Just right amount of water

155
Q

Do all plant cells have a secondary cell wall?

A

No

156
Q

Which cell wall is thicker?

A

Secondary

157
Q

Which layers make up the secondary cell wall?

A

S1, S2 and S3

158
Q

What makes the layers in the secondary cell wall different?

A

Different orientations of microfibrils- this adds strength

159
Q

Does the secondary cell wall have more or less cellulose, and more or less pectin?

A

More cellulose, less pectin

160
Q

Which macromolecule can be found in the secondary cell wall but not the primary one?

A

Lignin

161
Q

Describe lignin

A

Second most abundant organic macromolecule to cellulose

Complex polymer

Very strong and rigid. Excludes water

162
Q

Plasmodesmata

What do they allow?

A

Intercellular connections allowing cells to communicate. They are pores in the cell wall.

Allow free exchange of small molecules- organelles cannot pass through.

163
Q

Does the plasma membrane stop at plasmodesmata?

A

It is continuous with the plasma membrane of the other cell at the pore.

164
Q

What main reaction occurs in photosynthesis?

A

Light energy transferred into chemical energy in organic molecules

165
Q

By product of photosynthesis

A

O2

166
Q

Where does photosynthesis take place?

A

In the chloroplasts in plant cells

167
Q

ATP

A

Adenosine Triphosphate, an energy carrier

168
Q

What makes up ATP?

A

Adenine, ribose and a triphosphate group

169
Q

What has to happen for energy to be released from ATP?

A

One phosphate is removed, turning ATP into ADP adenosine diphosphate

170
Q

What does the cell require energy for?

A

Mechanical walk
Making new materials
Power active transport
Maintain order (fight entropy)

171
Q

Reaction occurring in mitochondria

A

C6H12O6 + 6O2 —> 6CO2 + 6H2O + energy

172
Q

How many mitochondria per cell? What does the number depend on?

A

1-1000’s

Depends on energy demand

173
Q

What does the mitochondrion contain?

A

Mitochondrial DNA and ribosomes

174
Q

Cristae

A

Folds in the inner membrane of the mitochondrion

175
Q

Three stages of cellular respiration

A

Glycolysis
Pyruvate oxidation + citric acid cycle
Oxidative phosphorylation

176
Q

Describe the glycolysis stage of cellular respiration

A

Glucose 6C molecule is split in half into two pyruvate 3C molecules.

2ATP released.

Electrons transferred to -NAD+ which becomes NADH

177
Q

NADH

A

A high energy electron carrier

178
Q

Describe the pyruvate oxidation and citric acid cycle stage of cellular respiration

A

Pyruvate 3C converted into Acetyl CoA

More electrons to NADH

Acetyl CoA enters the citric acid cycle

More electrons to NADH. Some higher energy electrons go to FADH2

2 ATP released

179
Q

Describe the oxidative phosphorylation stage of cellular respiration

A

1: proton gradient is generated

Protons pumped by electron carriers accumulate in inter membrane space. Energy for this comes from electrons

2: chemiosmosis

Proton gradient causes protons to move back into matrix. This powers ATP synthase

ADP + Pi —> ATP

180
Q

ATP synthase

A

Protein complex that synthesises ATP molecules from ADP and Pi

181
Q

What process is responsible for almost all of the planet’s energy resources?

A

Photosynthesis

182
Q

What are the two products of photosynthesis?

A

Organic molecules and O2

183
Q

What are the two products of cellular respiration?

A

CO2 and H2O

184
Q

What are the two parts of photosynthesis?

A

Light reactions and Calvin cycle

185
Q

Where in the plant cell does photosynthesis occur?

A

In the chloroplasts

186
Q

How many membranes do chloroplasts have?

A

Three

187
Q

What membrane-bound compartments make up the central membrane system of a chloroplast?

A

Thylakoids

188
Q

Granum

A

A stack of thylakoids

189
Q

Light reactions (photosynthesis)

A

Light is captured in the thylakoids and converted to chemical energy in the form of ADP and NADH

190
Q

Calvin cycle (photosynthesis)

A

ATP and NADPH drive the reactions to turn CO2 into carbohydrates (3 carbon sugars)

191
Q

Stroma

A

Fluid-filled space within the chloroplast, surrounding the grana

192
Q

What is the name of the system which moves electrons during photosynthesis?

A

Photosynthetic electron chain

193
Q

Photosystems

A

Protein complexes in the thylakoid membranes that work together to carry out photosynthesis.

194
Q

Which part of a photosystem is able to absorb light energy?

A

Chlorophyll

195
Q

How are the two photosystems in photosynthesis connected?

A

By the electron transport chain

196
Q

What happens after light energy is absorbed in photosystem II?

A

Electrons get excited, and enter the electron chain

197
Q

What are the electrons leaving photosystem II replaced by?

A

Electrons taken from H2O molecules

198
Q

How is O2 produced during the light reactions?

A

By stripping electrons from H2O molecules to replace excites electrons which have left the photosystems

199
Q

What does the energy from electrons go towards in the photosynthetic electron chain?

A

Pumping hydrogen ions from the stroma into the thylakoid

200
Q

What powers ATP synthase?

A

The high concentration of hydrogen ions inside the thylakoid

201
Q

How does NADPH function in the light reactions?

A

It captures excited electrons from photosystem I.

202
Q

What are the two energy products of the light reactions in photosynthesis?

A

ATP and NADPH

203
Q

Where does the Calvin cycle take place?

A

In the stroma of the chloroplast

204
Q

What is the reaction that takes place in ATP synthase?

A

ADP + phosphate group —> ATP

205
Q

Cytochrome complex

A

A complex used to pump protons through the thylakoid membrane by using energy from electrons from photosystem II

206
Q

List the three parts of the Calvin cycle

A

Fixation
Reduction
Regeneration

207
Q

Describe carbon fixation

A

Low energy CO2 is fixed into sugars.

Three CO2 molecules react with three 5-carbon molecules to produce six 3-carbon sugars.

3CO2 + 3(5C) —> 6(3C)

208
Q

Describe reduction in the Calvin cycle

A

The six 3-carbon sugars are converted into slightly different 3-carbon sugars.

This step requires energy from ATP and NADPH.

209
Q

How much ATP and NADPH is needed for reduction in the Calvin cycle?

A

One molecule of each per carbon sugar.

210
Q

Describe regeneration in the Calvin cycle.

A

One 3-carbon sugar has exited, and we are left with five 3-carbon sugars.

These five 3-carbon sugars are used to regenerate the starting molecules (three 5-carbons) required for the fixation step.

3ATP is needed for this (one per 5-carbon product)

211
Q

Inputs of photosynthesis (3)

A

Light
Water
Carbon dioxide

212
Q

Main difference in cellular respiration between plants and animals

A

Animals must source their glucose externally, while plants generate their own (Calvin cycle)

213
Q

Difference between electron transport chains in cellular respiration of plants and animals

A

It pumps H+ ions into inter-membrane space for animals, and thylakoid space for plants

214
Q

Describe the theory of endosymbiosis

A

An ancestral host cell engulfed a cyanobacterium. Instead of digesting it, the host cell kept it because it benefited the cell (photosynthesis). Eventually the genes of the bacterial cell merged with those of the host cell, and the cell reproduced.

Over generations, the engulfed cell became an organelle.

215
Q

How large is the nucleus?

A

5-10 micrometres

216
Q

Where are most of the cells genes found?

A

In the nucleus

217
Q

What makes red blood cells different to other animal cells?

A

They have no nucleus- takes up too much room in a cell whose job is to transport oxygen

218
Q

Where are genes found in the cell?

A

Nucleus, mitochondria and chloroplasts

219
Q

Functions of nucleus (2)

A

Protects genes

Controls cell

220
Q

Perinuclear space

A

The space between the two membranes of the nucleus

221
Q

Nuclear envelope

A

Two lipid bilayer membranes that surround the nucleus

222
Q

What is continuous with the perinuclear space?

A

Lumen of ER

223
Q

What is continuous with the outer membrane of the nucleus?

A

ER membrane

224
Q

Nuclear pore complex

A

Pores scattered on the surface of the nuclear outer membrane.

They control the movement of particles into/ out of the nucleus

225
Q

What travels out of the nucleus? (3)

A

mRNA
tRNA
Ribosomal subunits

226
Q

What is tRNA and it’s function?

A

Transfer RNA

Carries information from a gene

227
Q

What is mRNA and it’s function?

A

Messenger RNA

Needed to build ribosomal subunits

228
Q

What travels into the nucleus? (3)

A

Energy
Control signals
Building materials for RNA

229
Q

In what forms does energy enter the nucleus? (3)

A

Proteins
Carbohydrates
Lipids

230
Q

What is the process of moving particles into/ out of the nucleus called?

A

Nucleocytoplasmic exchange

231
Q

Nuclear lamina

A

Sheet of intermediate filaments that form a mesh work inside the nucleus

232
Q

Two functions of nuclear lamina

A

Maintains shape of nucleus

Organises packing of DNA

233
Q

How does a detective nuclear lamina effect the cell?

A

How it divides

It’s behaviour e.g. premature aging

234
Q

Nucleolus

A

Prominent structure within the nucleus of non-dividing cells

235
Q

Function of nucleolus

A

Produce ribosomal RNA

236
Q

What does ribosomal RNA produce in the cell? What does it combine with?

A

Ribosomes- by combining with proteins

237
Q

How much DNA does each cell contain? How does this compare to the size of the cell?

A

~2.5m

250 000 times the diameter of the nucleus

238
Q

How does DNA fit within the nucleus?

A

It is tightly packed into dense fibres (chromosomes when dividing)

239
Q

How large in diameter is a DNA double helix?

A

~2nm

240
Q

Histones

A

Proteins that serve as a spool for the DNA helix to wrap around almost twice

241
Q

How many histones are there and what are they called?

A

8

H2a (2)
H2b (2)
H3 (2)
H4 (2)

242
Q

What are the ‘beads’ called that are formed by DNA helix wrapping around a histone?

A

Nucleosomes

243
Q

How does DNA further condense after wrapping into nucleosomes?

A

Into a 10nm fibre
Then a 30nm fibre
Then a 300nm fibre
Then a metaphase chromosome (but only if undergoing cell division)

244
Q

List the packing steps of DNA

A

Double helix —> nucleosomes —> 10nm fibre —> 30nm fibre —> 300nm fibre —> metaphase chromosome (when dividing)

245
Q

Euchromatin

A

A less dense region in a chromosome which contains genes that are being used

246
Q

Heterochromatin

A

A more dense region in a chromosome containing genes not being used by the cell

247
Q

Which regions in a chromosome are darker?

A

Heterochromatin

248
Q

What do chromosomes consist of? (2)

A

Nucleic acid

Proteins

249
Q

DNA varies between species. What does this show?

A

That DNA is the genetic material differentiating species

250
Q

Chargaff’s two rules

A

Base pairing: A to T and G to C

The composition of DNA varies between species

251
Q

What makes up the Watson-Crick model of DNA structure? (5)

A

DNA has a double-stranded helix a structure

Sugar phosphate backbone on the outside

Based on the inside

Stabilised by hydrogen bonds

The two polynucleotide strands run anti parallel

252
Q

How are the nucleotides of nucleic acids joined together?

A

By phosphodiester bonds

253
Q

In which direction is the polynucleotide synthesised?

A

5’ end to 3’ end

254
Q

How many bonds join adenine to thymine?

A

Two hydrogen bonds

255
Q

How many bonds join guanine to cytosine?

A

Three hydrogen bonds

256
Q

What stabilises the DNA molecule?

A

Hydrogen bonds

257
Q

Which parts of the nucleotides do the phosphodiester bonds attach?

A

The 3’ hydroxyl group and the 5’ phosphate group.

258
Q

What kind of reaction occurs when a phosphodiester bond is formed? Why?

A

Condensation reaction, because an H2O molecule is formed.

OH from 3’ hydroxyl group, and H from 5’ phosphate group

259
Q

Where does DNA replication occur?

A

At origins of replication

260
Q

Why are there multiple origins of replication?

A

Because a single origin would take too long

261
Q

What is the point where a DNA strand is untwisting called?

A

Replication fork

262
Q

Helicase

A

Enzymes which pull the two parental strands of a DNA helix apart.

Pulls like a zipper- travels as it pulls

263
Q

Topoisomerase

A

Enzymes which release tension and unwind the strands ahead of the replication fork

264
Q

Primase

A

An enzyme containing a 3’ hydroxyl group, which it uses to synthesise an RNA primer, which ends in a phosphate group.

265
Q

DNA pol III

A

Synthesises DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand

266
Q

Single-strand binding proteins

A

Bonds to single strands of DNA to protect from other enzymes and keep the two parental strands apart

267
Q

DNA pol I

A

Enzyme which removes RNA primer nucleotides and replaces them with DNA nucleotides. It leaves fragments of DNA that aren’t linked by phosphodiester bonds.

268
Q

DNA ligase

A

Enzyme which forms a phosphodiester bond between two Ogazaki fragments.

e.g. joins lagging strand parts into one, as well as joining the strands of adjacent bubbles

269
Q

Why do lagging strands exist?

A

As the helicase unwinds more of the DNA helix, more of the 3’ end is exposed as single strands to replicate.

Since DNA pol III can only synthesise from 5’ to 3’, and the daughter strand must run antiparallel to the parent strand, only fragments of DNA can be synthesises at a time.

270
Q

Exonuclease

A

Enzyme (DNA pol III) which repairs errors in DNA by removing nucleotides from the end of the strand.

Occurs during replication

271
Q

Endonuclease

A

Enzyme (DNA pol III) which repairs errors in DNA by removing bases at any point of the strand.

Occurs after replication.

272
Q

How does DNA pol III perform exonuclease activity?

A

As it synthesises the strand, it detects an incorrect base, removes it, then continues synthesis.

273
Q

How does DNA pol III perform endonuclease activity? What other enzyme is involved?

A

After synthesis, it takes a chunk of bases out of the strand- one of which is the incorrect base. It replaces with the correct bases.

DNA ligase forms phosphodiester bonds to join the new nucleotides to the strand.

274
Q

What happens if an error in DNA is not corrected?

A

Incorrect bases is passed down to daughter cells, which leads to permanent DNA change or mutation.

275
Q

PCR

A

Polymerase chain reaction

It is used to make large quantities of DNA copies (in vitro replication)

276
Q

Why do we use in vitro replication?

A

When we want a large amount of material to work with- for example when examining a disease

277
Q

What are the three steps of PCR?

A

Denaturation
Annealing
Extension

278
Q

Denaturation (PCR)

A

DNA is heated to 94-98 degrees Celsius, strands separate

279
Q

Annealing (PCR)

A

DNA is cooked to 45-70 degrees Celsius, allowing primers to base pair to parental strand

280
Q

Extension (PCR)

A

72 degrees Celsius, polymerase extends primer to form a nascent DNA strand

281
Q

How many DNA copies do we get after 30 rounds of PCR?

A

Two billion

282
Q

Nascent DNA strand

A

A DNA strand which has just come into existence

283
Q

Karyotype

A

An ordered visual representation of chromosomes in a cell

284
Q

How do we make a karyotype? (3)

A

Take blood sample
Treat with mutagen, colchicine and stain
Organise pictures by pairing homologous chromosomes

285
Q

Each chromosome is made of two ___?

A

Chromatids

286
Q

Homologous pairs 1-22 are called ____?

A

Autosomes

287
Q

What are the differences between X and Y chromosomes?

A

Y is smaller and contains less genes

288
Q

Locus

A

Particular location on a chromosome where a particular gene is found

289
Q

Gene

A

Sequence of nucleotides in a chromosome that determine a specific trait

290
Q

Alleles

A

Different forms of a gene

291
Q

Homozygote

A

An individual who has two of the same allele

292
Q

Heterozygote

A

An individual who has two different alleles

293
Q

What does cell division allow? (3)

A

Development from a fertilised cell
Growth from foetus to adult
Repair of cells/ tissue

294
Q

Mitosis

A

Cell division that produces two genetically identical daughter cells

295
Q

Two main phases of cell cycle

A

Interphase

Mitotic phase

296
Q

How much of the cell cycle does interphase take up?

A

90%

297
Q

Three phases in interphase

A 
Growth 1 (G1)
Synthesis
Growth 2 (G2)
298
Q

Two phases within mitotic phase

A

Mitosis

Cytokinesis

299
Q

Five phases of mitosis

A 
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
300
Q

Describe prophase

A

Occurs after G2

Chromosomes condense and become visible as a sister chromatin pair

Early mitotic spindle develops

301
Q

What does the mitotic spindle develop from?

A

Disassembled cytoskeleton

302
Q

At what point are two sister chromatids connected?

A

Centromere

303
Q

What appear at the two ends of the mitotic spindle?

A

Centrosomes (clusters of microtubules)

304
Q

Describe prometaphase

A

Occurs after prophase

Nuclear envelope fragments

Microtubules extend from mitotic spindle and attach to kinetochores of sister chromatid pairs

305
Q

Kinetochore microtubules

A

Microtubules that attach to the kinetochores of sister chromatids

306
Q

Nonkinetochore microtubules

A

Microtubules that don’t attach to the kinetochores of sister chromatids

307
Q

Metaphase

A

Occurs after prometaphase

Kinetochore microtubules pull at each sister chromatid of a pair until they settle at the metaphase plate

308
Q

What is the imaginary equator of the cell called?

A

Metaphase plate

309
Q

Describe anaphase

A

Occurs after metaphase

Kinetochore microtubules shorten, which pulls sister chromatids apart, towards the piles of the cell

Nonkinetochore microtubules lengthen, pushing and widening the cell

310
Q

Describe telophase

A

Occurs after anaphase

Cleavage furrow forms in centre of cell, forming two connected cell shapes.

Nuclear envelopes form around the chromatids at each pole of the cell

311
Q

Cytokinesis

A

Splitting of the cell into two daughter cells (occurs during telophase)

312
Q

What causes the cleavage furrow?

A

A ring of actin filaments contracting around the parent cell

313
Q

Haploid cell

A

A cell with one set of chromosomes

314
Q

Diploid cell

A

A cell with two sets of chromosomes

315
Q

Meiosis

A

A process of cell division that halves the number of chromosomes going into gametes

316
Q

Explain the sexual life cycle

A

Meiosis of parent cell produces haploid gametes- eggs or sperm with a single set of chromosomes

Two gametes fuse (fertilisation) to form a diploid zygote with the original number of chromosomes is the same as the parent cell

317
Q

Three basic phases of meiosis

A

Interphase- Chromosomes duplicate

Meiosis I- Homologous chromosomes separate

Meiosis II- Sister chromatids separate

318
Q

Prophase I (meiosis)

A

Occurs after interphase

Homologous chromosome pairs align and synapse (two pairs join)

Crossing over occurs between non-sister chromatids at chiasmata

Mitotic spindle is forming and nuclear envelope fragments like mitosis

319
Q

What does crossing over result in?

A

Chromatids being a mix of pieces from each chromosome

320
Q

Describe metaphase I (meiosis)

A

The chiasmata of paired homologous chromosomes line up with the metaphase plate

321
Q

How many chromosome pairs are at the metaphase plate in meiosis I, compared to the number of chromosomes in mitosis?

A

Half as many chromosome pairs in meiosis I as chromosomes in mitosis

322
Q

Describe anaphase I (meiosis)

A

Recombined homologous chromosomes separate, but sister chromatids remain attached

323
Q

Describe telophase I (meiosis) (and cytokinesis)

A

Cleavage furrow causes haploid cells with duplicated chromosomes to form

324
Q

What is different about the two cells formed from meiosis I, and the two formed from mitosis?

A

The two cells formed from meiosis I are haploid cells- they only have half the genetic information in each cell. Their chromosomes are also duplicated (for division in meiosis II)

325
Q

Differences between mitosis and meiosis I (5)

A

In mitosis, chromosomes align independently. In meiosis, homologous chromosomes synapse.

Meiosis has chiasmata.

Mitosis has centromeres on metaphase plate, meiosis has chiasmata.

Chromatids disjoin during mitosis, while chromosomes disjoin during meiosis.

2n—>2n (diploid cell formed) for mitosis
2n—>n (haploid cells formed) for meiosis

326
Q

Advantage of asexual reproduction

A

Can produce a much larger number of offspring

327
Q

Advantage of sexual reproduction

A

Produces much more genetic diversity

328
Q

How does genetic diversity arise from sexual reproduction? (3)

A

Independent assortment of chromosomes (organised indecently during metaphase)

Crossing over between non-sister chromatids

Random fertilisation of gametes

329
Q

In what circumstances does genetic diversity allow for better survival? (3)

A

Spatially variable environments (climate, ecology etc)

Changing environments (parasites, seasons etc)

Sib-sib competition (different siblings will utilise resources differently)

CELS (3 decks)

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