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Human Biosciences > Cells > Flashcards

Cells Flashcards

1
Q

5 kingdom classifications of life?

A 
Plantae
Fungi
Animalia
Protista
Prokaryotae

Classification mainly based on morphology

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2
Q

3 domain classifications of life?

A

Bacteria
Archaea
Eukaryota

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3
Q

What are eukaryotic cells and what are prokaryote?

A 
Eukaryote:
Plants
Animals 
Fungi
Protoctisa

Prokaryote:
Bacteria and Archaea (both are monera)

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4
Q

Organisation of a bacterium?

A 
Pilli
Cell wall
Plasma membrane
Cytoplasm
Nucleoid (DNA) (so no nucleus)
Ribosomes
Flagellum
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5
Q

Organisation of a eukaryotic cells?

A 
Plasma membrane
Golgi apparatus
Peoxisome
Mitochondrium
Lysosome
Enoplasmic reticulum
Nuclear membrane
Nucleus
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6
Q

Only cell that doesn’t have cell wall?

A

Animals

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7
Q

What extra do plants have?

A

Vacuole
Cell wall
Chloroplast

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8
Q

What extra do fungi have?

A

Cell wall

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9
Q

What is larger pro or eukaryote?

A

Eukaryote by far, also more complicated so theory that they developed after prokaryotes

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10
Q

A catalytic RNA molecule is called a?

A

Riboenzyme

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11
Q

Evidence RNA earlier than proteins?

A

RNA makes protein

RNA fundamental part of ribosome, whereas protein have just been added

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12
Q

How were the building blocks or RNA generated?

A

Random early earth conditions (eg lightening)

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13
Q

What could ribonucleotides bind together to form?

A

Replicase ribozymes which could make new replicases after polymerising on a clay surface

So can duplicate, due to temperature changes

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14
Q

How was a the lipid bi-layer in a cell made?

A

In Geysers, minerals catalyse the formation of fatty acids from hydrogen and carbon monoxide

Which have one end which hydrophilic (outside) and one is hydrophobic (inside) in a droplet known as micelles

Vesicle formation triggered by acidic pH or clay surfaces

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15
Q

What then occurs within the vesicle to from a protocell?

A

Flipping of fatty acids could bring in molecules, so they accumulate within the vesicle

The RNA replicase uses ribonucleotides to make a copy of another RNA replicase

Micelles fuse with the vesicle and enlarge it until it becomes unstable and divides

Random mistakes could lead to better replicases which could make protocol grow and divide faster

Protocell competes for resources driving evolution

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16
Q

What is the optical resolution limit and what does it rely on?

A

Minumum distance that allows recognition of object details

The optical resolution depends on the wave length of the light/beam used (smaller wave length = better resolution)

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17
Q

Features of light microscope?

A

Visible light ( wave length 390-700nm)

Glass lenses focus light

Resolution limit is 200 nm

Advantage is cells alive

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18
Q

Features of electron microscopy?

A

Electron beam ( wave length 0.0025 nm)

Electromagnetic lenses focus beam

Resolution limit 0.05 nm

Advantage is high resolution

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19
Q

Difference between scanning electron microscopy (SEM) and Transmission electron microscopy (TEM)?

A

SEM:
Electron beam scans over surface of sample
Can produce 3d images
Image shown on monitor

TEM:
Electron pass through THIN sample
Samples specially prepared
2D image shown on fluorescent screen

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20
Q

What is freeze fracture electron microscopy?

A

Freeze cell in resin, cut in half and analysis

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21
Q

What is averaging in microscopy?

A

Averaging many images together allowing reconstruction of the ultra-structure

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22
Q

What is fluorescence?

A

The emission of light by a substance that has absorbed light

The emission will be at a higher wavelength than excitation (the initial light), energy is lost before light is emitted

Allows visualisation of single molecules

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23
Q

What is GFP?

A

A reporter to analyse proteins in the living cell

It fuses to the DNA which will make the protein - which are normally still functional

These proteins are transcribed

They are exposed to blue light and will appear green

Different colours discovered so can observe interactions between different proteins

Also quantitive information as brightness represents how many there are

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24
Q

Advanced use of fluorescent proteins

A

FRAP (fluorescent recovery after photobleaching):
High energy sent in, which photobleaches the gfp molecules so can’t reflect light, if molecules are moving they will move into it and it will light up again, if not then nothing is moving

FLIP Fluorescent loss in photobleaching:
Used to see if one protein moves to another, so photo bleach, and then see if this photo bleach area appears in the place we think it will move

Photoactivation (photo-activatble GFP):
400nmlaser light induces a chemical reaction

About 100 fold increase in fluorescence after photo-activation

So allows you to identify the proteins you want to, as they will give lots of light off as their gfp has been activated

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25
Q

Features of plasma membranes?

A

Contains specific proteins, lipids and sugars

Surrounds the cell

Phospholipids are amphiphatic (hydrohphillic and hydrophobic) and assemble into bio-membranes in the presence of water

Fatty acid tails are hydrophobic, phosphate groups are hydrophilic

Cholesterol reduces membrane fluidity at moderate temperature and avoids solidification at low temperature (Temperature buffer)

Cholesterol also serves as a hormone

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26
Q

What’s a lipid raft protein?

A

Membrane regions that assemble specialised lipids and proteins to perform a certain task (Normally show reduced fluidity)

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27
Q

Types of protein in plasma membrane?

A

Transporters

Enzymes

Receptors

Cell-cell recognition

Intracellular joining

Attachment to the extracellular matrix and intracellular cytoskeleton

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28
Q

What does bio-membranes being semipermeable lead to?

A

Uncharged and hydrophobic molecules can pass through the membrane

However charged or polar cannot pass, so require a mechanism to get in and out

Such as protein channels, which can be open or gated

Also can go through via facilitated diffusion (protein changes shape not let molecule through, it can’t go back and no ATP needed

Pumps can pump molecules through requires ATP

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29
Q

4 types of gated channels?

A

Voltage
Mechanically
Temperature
Ligand

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30
Q

What charge is in the inside of the membrane normally and how is it created?

A

-50 to -70mV

SOPI pumps, and leakage channels

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31
Q

Example of non excitable and an excited cell?

A

Epithelial

Muscle cells and neurones

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32
Q

What do cells in an epithelium establish?

A

Tight lateral and basal contact to withstand friction

Tight junctions are formed hold membranes of the cells together, functions as a diffusion barrier, and consists of plasma membrane proteins that interact

There are also here’s junctions, consists of cadherin and catenin, cadherins bridge between the cells, catenins link to the actin cytoskeleton, they both control actin organisation

Gap junctions allow diffusion from cytoplasm of one epithelial cell to another, made up of connexins

There are desmosomes, contain specialised Catherine proteins that interact with each other and with intermediate filaments, they resist shear force in epithelia

They are hemidesmosomes which contain man proteins that interact with the extracellular membrane, they anchor the epithelia cell to the basal lamina ( extracellular matrix underneath the epithelium, probably also used in signalling

Extracellular matrix is fibres of secreted proteins, and they hold tissue together, provides strength and directing cell migration

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33
Q

Describe a simple intracellular signalling pathway?

A

Extracellular signal molecule

Receptor protein, on plasma membrane of target cell

Intracellular signalling molecules released, either will be via phosphorylation of proteins by protein kinases and phosphatases, or signalling by GTP-binding proteins

Effector proteins:
Metabolic enzymes - altered metabolism
Gene regulatory protein - altered gene expression
Cytoskeleton - altered cell shape or movement

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34
Q

Describe signalling via GTP-binding proteins?

A

G-proteins are molecular switches

They are activated by a Guanine nucleotide exchange factor (GEF), and inactivated via a GTPase-activating protein(GAP)

Small monomeric G-proteins receive signals from many receptors

Large trimeric G-proteins interact with G-protein coupled receptors

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35
Q

What’s a kinase?

A

An enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific substrates

Process is known as phosphorylation

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36
Q

What are phosphatases?

A

An enzyme that removes a phosphate group from a protein, a process called dephosphorylation

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37
Q

What can occur to protein kinases for the signal to be amplified and spread to other pathways?

A

Get phosphorylated themselves

Creates signalling cascade

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38
Q

Function of Cdk kinase?

A

Control of cell cycle progression

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39
Q

Function of Src-type kinase?

A

Control or regulate various biological functions

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40
Q

What do the particles and molecules undergo in cytoplasm?

A

Brownian motion - flickering movement due to collisions

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41
Q

What does diffusion in cytoplasm depend on?

A

Size of the molecule/organelle

Smaller they are the more they move

Diffusion is very limited to larger objects as it’s too crowded

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42
Q

Features of ribosomes?

A

Consist of 2 subunits (small and large) made from ribosomal RNA and proteins

Prokaryotes have 70 S (smaller)

Eukaryotes have 80 S (larger)

S (Svedbery value) stands for sedimentation rate of a particle - depends on mass density and shape

Translate information from mRNA into proteins

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43
Q

Basic steps of protein translation?

A

Matching tRNA to mRNA codon
Release of elongation factor
Formation of peptide bond
Elongation factor G triggers a forward movement of ribosome

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44
Q

What is a polysome?

A

Numerous ribosomes operating along a single mRNA molecule

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45
Q

What is the nucleus linked to?

A

The endoplasmic reticulum

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46
Q

Parts of the nucleus?

A

Euchromatin
Heterochromatin
Lamina
Nuclear pore

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47
Q

Features of nuclear pores?

A

have 8 fold symmetry

Made up of numerous proteins and control nuclear transport

Made up of nuclearporins

Gated, control what goes in and out

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48
Q

What goes in and out of the nucleus through the nuclear pores?

A

In (import):
Proteins

Out (export):
Proteins
RNAs
Ribosomal subunits

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49
Q

What happens to the nucleus during mitosis?

A

It releases its content so has to re-import it’s nuclear proteins

Also the nuclear envelope and the nuclear lamina disassemble:

Phosphorylation of lamins - breakdown

Dephosphorylation of lamina

Fusion of nuclear envelope fragments

Fusion of enveloped chromosomes

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50
Q

What’s the nuclear lamina and it’s functions?

A

Forms a network at the inner nuclear membrane

Consists of intermediate filaments (cytoskeleton)

It organises chromosomes and supports transcription of genes

Also anchors nuclear pores and prevents clustering

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51
Q

What does the nucleolus do?

A

Forms ribosomes

Contains granular components which is the ribosome assembly site

Contains fibrillar centres where rRNA transcription occurs

Ribosomal proteins are imported into the nucleolus, the assembled ribosomes are then exported into the cytoplasm

It’s not membrane bound just a gathering of material

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52
Q

DNA associates with proteins into?

A

Chromatin

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53
Q

Features of DNA in the nucleus?

A

Heterochromatin:

  • Remains packed after mitosis
  • Transcriptionally less active
  • 8% of DNA
  • 2 types

Consecutive Heterochromatin - Always packed, non-coding DNA near centromere and telomers)

Faculative heterochromatin - Variable between cell type and development stages

Then there is euchromatin which is 92% of DNA and transcriptionally active

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54
Q

When is all the DNA tightly packed?

A

Mitosis, makes it easier to transport

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55
Q

What does packing DNA require?

A

Being wrapped around positively charged proteins called histones

Organised into nucleosomes - which loosen during transcription

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56
Q

What does RNA polymerase 1 form?

A

rRNA

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57
Q

What does RNA polymerase 11 form?

A

mRNA

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58
Q

What does RNA polymerase 111 form?

A

tRNA

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59
Q

What does RNA polymerase in plants form?

A

siRNAS required for heterochromatin formation

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60
Q

Basic Principle of transcription?

A

Numerous transcription factors bind to the TATA box in the promoter (upstream of the gene)

RNA polymerase binds to the template strand and synthesises an exact copy of the coding strand (except thymines are replaced with uracil)

RNA is released, further processed and the released from the nucleus bound to RNA binding proteins

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61
Q

Do prokaryotes have a nucleus, and how does this make them different to Eukaryotes?

A

NO, so transcription and translation occur in the compartment, and many genes on one mRNA

Whereas in eukaryote transcription and translation are compartmentalised and, one mRNA per gene

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62
Q

What does the endomembrane system contain?

A 
Nucleus
Endoplasmic Reticulum
Golgi apparatus
Lysosome/vacoule
Endosomal compartment
Transport vesicles

All the compartments of the endomembrane system are connected by transport vesicles that serve material exchange

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63
Q

What do molecular motors do?

A

Transport vesicles and organelles within the cell, this is called membrane trafficking

They are enzymes that use ATP to walk along the cytoskeleton

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64
Q

What happens at membrane with transport vesicles?

A

Exocytosis or endocytosis

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65
Q

What is secretory pathway?

A

Going out of cell

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66
Q

What is the endocytic pathway?

A

Outside to a vesicle inside

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67
Q

2 types of endoplasmic reticulum?

A

Smooth (no ribosomes)

Rough (studded with ribosomes)

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68
Q

Function of smooth ER?

A

Calcium storage for signalling
Lipid synthesis
Detoxification of poisons
Metabolism of carbohydrates

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69
Q

What is the Golgi apparatus?

A

Disc shaped stack of membranes

Has Cis end which receives transport vesicles from ER

Trans end releases the secretory vesicles

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70
Q

What do oliogosacchardides do (sugar chains on membrane) and where are they processed?

A

Provide protection against pathogens

Serves in cell-cell recognition and signalling

Marks progression of protein

Helps folding and interaction with other proteins

Made in the golgi apparatus

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71
Q

2 ways oligosaccharides can be linked to proteins?

A

Asparagine (N-linked)

Threonine (O-linked)

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72
Q

3 types of endosomes which are involved in processing endocytose material?

A

Early endosome
Recycling endosome
Late endoscope

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73
Q

Describe endocytosis?

A

Formation of a vesicle at the plasma membrane

Fusion of vesicle with early endosome

Decision - degradation or recycling

If recycling - pH drop removes ligand, and the rest is taking out

Or Maturation of early endoscope to late endosome - which can send material to Golgi

Or Lare endosome could turn into a lysosome - this is degradation

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74
Q

Describe lysosomes ( can also be called vacuoles in certain circumstances)?

A

Serves as a disposal container

pH far lower in lysosomes due to acid hydrolyses such as proteases, and lipases creating small building blocks

pH is low due to H+ pumps, which requires ATP

75
Q

3 pathways to degradation in lysosomes?

A

Bacterium taken up via phagocytosis, then broken down in the lysosome

Pinocytosis and receptor mediated endocytosis, small particles go to lysosome and are broken down

Autophagy, lysosomes break down own cytosol , eg if starved

76
Q

What are peroxisomes?

A

Single membrane bound organelles that contain many enzymes

Major site of oxygen utilisation

Detoxification produces Hydrogen peroxide which is degraded by catalase

Play important role in lipid metabolism

77
Q

What are lipid droplets?

A

Fat storage droplets

Vary in size and are enclosed by a monolayer

Associated proteins regulate the metabolism of the fat droplets

Created at the endoplasmic reticulum

78
Q

What is a nucleomorph?

A

When algae have a DNA containing relict of an engulfed eukaryote

79
Q

What does Fat-acid-binding protein (FABP) do?

A

Makes fatty acids water soluble

80
Q

Features of transport vesicles?

A

Carry cargo

50 types of integral proteins

Membrane speciality is provided by SNARE receptors

Most common vesicle is v-SNARE

81
Q

Steps of fusion of a vesicle with a target membrane?

A

Therthering:
Rab-GTP on vesicle binds to Rab-binding tethering factor on membrane

Docking:
V-snare from vesicle forms complex with tT-snare on membrane

Fusion:
Cargo is unloaded into membrane

82
Q

Features of vesicles having a coat?

A

Clathrin coat
COP1 coat
COP11 coat

Different coats are specific for particular places in endocytic and exocytic pathways

Coat concentrates specific proteins in patches

83
Q

Features of extracellular vesicles?

A

Transport vesicles released from cells

Found in body fluids

Contain RNAs and proteins provided by the donor cell

Deliver their contact to recipient cells

84
Q

Features of micro vesicles?

A

500-1000nm diameter

Formation at donors plasma membrane

Transfer proteins mRNASs and miRNAs that control protein expression

Uptake via fusion with plasma memrbrane

85
Q

Features of exosomes?

A

40-100nm diameter
Formed at early endosome, released from late endoscopes

Transfer proteins, mRNAS and miRNAS that control protein expression

Uptake via endocytosis or fusion with recipients plasma membrane

86
Q

Functions of exosomes and micro vesicles?

A

In immunology
In blood
In CNS
In bone

Also can spread cancer

87
Q

What provides tracks that link the regions of the cell?

A

Cytoskeleton

88
Q

Definition of the cytoskeleton?

A

Consists of filamentous bio-polymers ( microtubules, F-actin and intermediate filaments) and of associated proteins that are modulating the activity, dynamics, or organisation of the cytoskeleton

89
Q

Why is the cytoskeleton called this?

A

Connects all of parts of the cell

Supports motility

Helps spatial organisation

90
Q

3 filaments that make up the cytoskeleton?

A

F-Actin - Short range transport, cell migration, 7-9nm

Microtubuli - Long-range transport, Chromosome inheritance (mitosis and meiosis), 25nm

Intermediate filaments - mechanical strength, 10nm

91
Q

Types of actin?

A 
Filamentous actin (F-actin)
Actin bundles (stress fibres)
Actin monomers (G=Actin pool)
92
Q

Where do you find Microtubules?

A

Coming from the centrosome - microtubule organising centre, near the nucleus

93
Q

Where do you find F-actin?

A

Gathered on One side of the cell

94
Q

Where do you find intermediate filaments?

A

Everywhere in cell

95
Q

Describe the structure of F-actin?

A

G-actin Protein subunits that forms 2 Protofilaments wrapped around each other

96
Q

Structure of microtubules?

A

Have dimers which are made of Beta tubulin and alpha tubulin, which forms protofilaments which form microtubulus

97
Q

Describe polymerisation of a microtubule?

A

GTP-bound tubulin dimers get added to the positively charged end (polymerisation)

A cap of GTP tubulin stabilises the growing microtubule

98
Q

Describe pausing of a microtubule and what can occur after?

A

Stops growing as GTP-Tubulin cap has all been hydrolysed by tubulin behind forming GDP-tubulin + phosphate

Then a rapid depolymerisation will occur:
The microtubule becomes unstable, this moment is known as a catastrophe

However then polymerisation can occur again, GTP-tubulin can bind creating a new cap, this is known as a rescue attempt

The switch between growth and shrinking is known as dynamic instability

99
Q

Why is dynamic instability useful?

A

Allows the microtubule to reorganise

100
Q

How has speckle microscopy proven dynamic instability?

A

If label some tubulin with GFP then will appear in patches on microtubule

101
Q

What do plus-end binding proteins do?

A

Control the dynamics of microtubules and participate in intracellular motility

102
Q

What do animal centrosomes contain, and what do they do?

A

They contain centrioles and the PCM

Centrioles consist mainly of microtubule
Become the basal body of flagella and cilia
They organise the pericentriolar material (PCM) and ensure it’s inheritance

Fungi and plants do not have centrioles

103
Q

Do centrioles replicate during the cell cycle?

A

Yes

104
Q

What does PCM contain?

A

Gamma tubulin which nucleates (making) the microtubules

105
Q

General function of intermediate filaments?

A

Providing mechanical strength and in organising cytoplasmic architecture

Interact with microtubules and F-actin

106
Q

Structure of intermediate filaments?

A

Made up of protein subunits which form a coiled coil made up of alpha helices

alpha helices are often amphipathic (charged at one side) which serves protein interaction

107
Q

Extra facts on intermediate filaments?

A

Only found in animal cells

Do not require ATP or GTP for assembly, but rather self assemble into an apolar filament (2 bind to each other due to being amphipathic

They can disassemble into subunits to allow cell movement

Have different types of sun units

108
Q

What forms the nuclear lamina and what does it do?

A

Intermediate filaments

Lamina provides stability and organises the nucleus

109
Q

Example of an intermediate filament?

A

Keratin - makes nails

Some intermediate filaments also determine the optical properties of the eye lens

110
Q

What drives cell motility and examples?

A

Molecular motors which are mechanical enzymes (protein complexes that utilise ATP to walk along the cytoskeleton)

Microtubule associated:
Kinesin
Dynein

Actin associated:
Myosin

111
Q

How do molecular motors move across cytoskeleton?

A

They walk

112
Q

Antony van Leeuwenhoek is famous for?

A

the discovery of microbes using a simple microscope

113
Q

According to the “RNA World Hypothesis, the protocell had the following features?

A

It was surrounded by a lipid-bilayer (a bio-membrane)

It contained ribozymes and RNA

114
Q

Which of the following structures confer resistance against shear forces and thereby ”strengthen” epithelial tissues?

A

Desmosomes
Hemidesmosomes
Tight junctions

115
Q

What does the nucleus contain?

A

Heterochromatin

Euchromatin

A nucleolus

116
Q

Organelles of the endomembrane system communicate with each other by?

A

Transporting vesicles

117
Q

What does the endosomal compartment consist of?

A

early endosomes

recycling endosomes

late endosomes

118
Q

Lipid droplets are fat storage compartments that are generated at the?

A

Smooth ER

119
Q

Fusion of transport vesicles with a target membrane involves?

A

tethering of the vesicle to factors in the target membrane

docking of the vesicle to the target membrane

120
Q

What do motors take through the cell?

A

Vesicles and organelles

121
Q

Principle how a motor works?

A

Weak binding

Tight binding due to ATP-binding

Hydrolysis and power stroke

Release of ADP and Pi

122
Q

Which molecular motors walk towards the plus end, and which walk towards the minus end?

A

Plus:
Kinesin
Myosin

Minus:
Dynein

123
Q

How are motors recycled?

A

For example Kinesin and dynein would bind to the same cargo on either side of it

Then Kinesin would take it to plus end, when it reaches there will flip over to other side and dynein can take it back

124
Q

How are collisions between Kinesin and Dynein avoided?

A

Dynein can move to avoid the Kinesin, as can move to another protofilament on the track

Kinesin just moves forward

125
Q

What is the motility in neurones known as?

A

Axonal transport - Dynein and Kinesin working together

126
Q

What does skeletal muscle mainly consist of?

A

Myosin, and F-actin in sarcomers

127
Q

What do thick filaments consist of?

A

Myosin 11

128
Q

What do thin filament consist of?

A

F-actin (sandwich the thick filaments)

129
Q

How is muscle contraction controlled?

A

Stimulus from neutron spreads over the plasma membrane of the muscle cell

Depolarisation of membrane releases calcium from the sarcoplasmic reticulum into the cytoplasm

Binding of calcium to the troponin complex releases the bloke of the myosin binding site on actin

Myosin binds actin and walks towards the Z-disk

Calcium is removed by calcium pumps and myosin releases the actin filament = relaxation of muscle

130
Q

Features of cardiac muscle?

A

Spontaneous contractions

Same principle of skeletal just less ordered

131
Q

Difference between flagella and cilia?

A

Flagella come in smaller numbers and move the cell, propellar like motion

Cillia are in larger numbers and have function in fluid and particle transport, back and forth movement

132
Q

Describe the structure of a cilliim/flagella?

A

Axoneme - The core, made from microtubules

Basal body anchors them to the cell - formed from centrioles

133
Q

What support the formation and function of the cilium?

A

Intraflagellar transport along the axoneme:
Kinesin-2 moves building material up
Dynein bring moves material back down

134
Q

Ultrastructure of cilium and flagellum?

A

9 pairs of microtubules around edge but on is half attached

1 microtubule pair in the middle

Dynein (slides microtubules against each other- they have protein bridges so results in bending):
Radial spokes (like a bike)
Outer arm dynein
Inner arm dynein

135
Q

What leads motility in cells?

A

Actin in treadmilling, so led by the actin side

Steps:

Extension of plasma membrane pushing it forward due to actin polymerisation

Adhesion so doesn’t spread out

Translocation of the body forward

De-adhesion

Process that heals wounds

136
Q

What occurs in prophase?

A

Chromosomes condense

Nuclear envelope disrupts

Spindle is formed

137
Q

What occurs in metaphase?

A

Microtubules make contact with chromosomes

Chromatids are positioned in one plane

138
Q

What occurs in anaphase?

A

Microtubules and motifs pull on chromosomes

Chromatids move to the poles

Rapid elongation of the spindle

Formation of a contractile ring

139
Q

What occurs in telophase?

A

Cell middle contracts and separates (cytokinesis)

The chromosomes decondense

The nuclear envelope is formed

140
Q

3 types of microtubules in the organisation of the mitotic spindle?

A

Astral microtubules
Polar microtubules
Kinetochor microtubules

141
Q

How can you test that microtubules are required for mitosis?

A

Use Nocodazole which is anti microtubule, and see that mitosis can no longer occur

142
Q

2 mechanisms that microtubules provide the force for chromosome segregation by creating a polar ejection force?

A

1-
de/polymerization of microtubules
Exerts force on attached chromosome

2-
Molecular motors that act on the microtubules

143
Q

What’s checked at different checkpoints?

A

G2 (entering M) - is all DNA replicated, is environment favourable

Metaphase (end of M) - Are all chromosomes attached to the spindle

G1 (entering S) - is environment favourable

144
Q

How does cytokinesis occur?

A

A contractile ring localises the area of constriction, near the cortex at the end of anaphase

composed of actin, myosin 11, regulators and actin binding proteins

145
Q

Main features of mitochondria?

A

Have a double membrane with inner membrane folds (Cristae) and their own mitochondrial genome

Use sugars fats and oxygen to produce ATP (power house of the cell)

146
Q

Steps of energy generation in mitochondria?

A

Uptake of food molecules from the cytosol into the mitchondrial matrix

Oxidation of Acetyl-CoA into carbon dioxide (Citric acid cycle = Krebs cycle); Production of the electron shuttle molecule NADH

NADH transfers the electrons to the respiration chain at the inner membrane; electron flux is used to build up a proton gradient

Back-flow of protons drives ATP synthesis

147
Q

Do mitochondria and chloroplasts have their own genome?

A

Yes

148
Q

What is apoptosis?

A

Programmed cell death

Occurs in multi cellular organisms

Blocks are recycled after death

It’s triggered by cell damage, apoptotic proteins cause damage to the mitochondria, which release factors that activate the apoptotic enzymes

149
Q

Features of viruses?

A

DNA or RNA that is protected by a protein coat (capsid)

1000 x smaller than a human cell

Extracellular form known as a vision

Intracellular form = replication of DNA/RNA to assemble virus

Infecting fungi = mycophaves

Infect bacteria = bacteriophage

They are not alive

They self assemble

150
Q

What’s a naked virus?

A

Protein coat (capsid)

Nucleic acid (RNA or DNA)

Enzymes (not always)

151
Q

What’s an enveloped virus?

A

Protein coat (capsid)

Nucleic acid (RNA or DNA)

Enzymes (not always)

Biomembrane (lipids from host cell)

Enveloped proteins (from the virus)

152
Q

What’s a complex virus?

A

Protein coat (capsid)

Nucleic acid (RNA or DNA)

Enzymes (not always)

Complex protein tail

153
Q

3 distinct ways viruses enter the host cell?

A

Endocytosis - enters as a Trojan horse

Membrane fusion

Injection - inject genetic information and leave rest of virus particle behind

154
Q

Lifecycle of a complex virus?

A

Virus attaches to surface receptors

The tail contracts, enzymes break the cell wall, and the core needle pinches the cell

The content of the head (proteins, DNA/RNA) is released into the cell

The bacterial metabolism is disrupted and the genomic DNA degraded

Viral DNA is transcribed into mRNA

Viral DNA is replicated

mRNA is translated into viral proteins

Complex virus particle self assembles (50-100)

Cell lysis and release

155
Q

Lifecycle of an enveloped virus

A

Entry into the host cell by endocytosis or membrane fusion

Release of DNA into cytoplasm, motors (dynein) can also bind directly to the viral capsid so virus is making use of the intracellular transport machinery

DNA made and translation of proteins occurs, new viruses made

Budding occurs, virus leaves cell taking membrane to form it’s envelope

156
Q

What are magnetotatics?

A

Bacteria that navigate along magnetic fields by detecting it

They contain crystals of an iron material called magnetosomes, they use them for magnetotaxis (a compass)

Gram negative

157
Q

Main actin like proteins in prokaryotes?

A

MreB - cell shape

ParM - DNA partitioning

MamK- forms filaments

158
Q

Modes of motility of bacteria and archaea and how they move ?

A

Swimming
Swarming - on surfaces
Gliding
Twitching

Flagella rotating due to protons generating ATP

Have directly motility for food

Pili retract and grow to allow twitching (creates colonies) or slow gliding

159
Q

How do bacteria enter mammalian cells?

A

They force the host cell to take them up

A protein ring assembles into a needle

The needle injects proteins into the human cost cell to manipulate the actin cytoskeleton, thereby forcing uptake

Type 3 or type 6 secretion systems inject the proteins

160
Q

2 major growth forms of fungi?

A

Yeast:
Uniceullar and often rounded
Grow by budding

Hyphal:
Usually multi-cellular and elongated
Extend by polarized growth

161
Q

What does fungal growth rely on?

A

Delivery of vesicles to the growth region (bud or hyphal tip) via the cytoskeleton and the fungal motors on them

Dynein to negative end, kinesis to positive end

162
Q

What’s the spitzenkorper?

A

The apical body involved in hyphal growth

It’s a vesicle cluster at the tip, it serves as a vesicle supply centre

Contains secretory and recycling vesicles

Hyphal growth relies on this structure

163
Q

Describe hyphal growth?

A

Transport along the cytoskeleton

Storage of vesicles in the spitzenkorper

Release and fusion with plasma membrane

164
Q

Function of Woronin bodies?

A

Prevent if one cell dies in fungal chain the cytoplasm leaking out of all of them

Blocks the gaps between the cell bodies by plugging

They are specialised peroxisomes

Contain hexagonal crystals of the protein Hex1

165
Q

Why do mushrooms release spores?

A

For reproduction

166
Q

What actually is a mushroom?

A

The organisation of basidiomycete fruiting body

167
Q

Mechanism of spore discharge in basidiomycetes?

A

Two water drop are formed Due to secretion of secretion of mannitol and other hygroscopic sugars
on the surface of the spore

The Adaxial drop and the Buller’s drop

Buller’s drop increases in size due to recruitment of atmospheric water

Sudden change of centre of gravity
by fusion of both drops create a propulsive force

168
Q

How do ascomycetes release spores?

A

Turgur pressure built up within the ascus and a sudden burst

169
Q

What are chloroplasts?

A

Use light, carbon dioxide, and water to produce glucose and oxygen = photosynthesis

Surrounded by a double membrane

Have inner membrane system

Have their own genome

170
Q

What’s the thylakoid?

A

membrane compartment; the thylakoid membrane surrounds the thylakoid lumen

171
Q

What’s a granum?

A

A stack of thylakoids

Contains light capturing system and ATP synthase

172
Q

What’s the storm?

A

Matrix of the chloroplast

Contains fixation enzymes, chloroplast DNA, Ribosomes

173
Q

Why are plants green?

A

Doesn’t absorb green light

So they don’t use the visible spectrum very efficiently

But if they did (say there were black) too much heat would be generated

Mainly absorbs blue and red light.

174
Q

Why do leaves turn from green to yellow to red in autumn?

A

Sense of reduced photosynthesis

Degradation and recycling of cellular components is induced

Chloroplasts turn into gerontoplasts

Breakdown products get stored in the plant vacuole

Formation of anthocyanin that protect against too much light and oxidative stress (turns them red)

Finally the cells get killed and the recycled cellular components released from the vacuole and delivered to the plant

175
Q

Are chloroplasts motile? Why?

A

yes

To avoid photo damage from light

3 steps:
Photoperception - Plant blue - light photoreceptors perceive the light
Signal transduction - Calcium signalling
Chloroplast movement - Motor dependent

176
Q

What is cytoplasmic streaming?

A

Occurs independently of chloroplast movement

Depends on energy and requires F-actin

There is a nonmoving cytoplasm (Exoplasm) and a streaming cytoplasm around the vacuole (endoplasm) it’s moving due to sliding theory (so basically just motors moving everything which drags the cytoplasm)

177
Q

Features of plant cell wall?

A

Primary wall is flexible and unorganised,

The secondary wall is formed in fully developed cells far more rigid. Contains Lignin (wood)

Both contain cellulose

Cellulose synthase complex forms a rosette in the plant plasma membrane in which a nascent 36 gluten chains are extruded into the wall. These organise the walls

178
Q

What control expansion of the cell?

A

Plant vacuole

Generates outward pressure (turgor) that is counter balanced by the cell wall

Variation in cell wall rigidity due to orientation of the cellulose fibres directs cell expansion

179
Q

What is plasmolysis?

A

The reversible shrinkage of the plant cell, due to reduced turgor pressure in the vacuole

Reveals cell-cell contacts

180
Q

What connects plant cells?

A

Cytoplasmic bridges called plasmodesmata

They allow free passage of small molecules

Can be plugged by formation of callose if one cell is infected

181
Q

How do plant cells divide?

A

Microtubules form a plant-specific array called the phragmoplast in the middle

Vesicles then transported to here to form the cell plate by fusing

Endoplasmic reticulum crosses the cell plate (helps form plasmodesmata)

Cell wall in interior fuses with plasma membrane

182
Q

What is cellular endosymbiosis?

A

Is when a single cell organism lives in a host cell

183
Q

What is endosymbiosis theory?

A

Three fundamental organelles, mitochondria, chloroplasts and basal bodies of flagella were once themselves free-living cells

With the mechanisms of:
Phagocytosis of a prokaryote
Host cell and endosymbiont reproduce
Development of an interdependence

184
Q

Arguments for endosymbiosis theory?

A

Mitochondria and Chloroplasts have their own circular genomes

Mitochondria and Chloroplasts have 70S ribosomes which is the same as prokaryotes

Chloroplasts and cyanobacteria (prokaryote) ave thylakoid membranes

Chloroplasts and mitochondria both have a double membrane - derived from incomplete phagocytosis

Human Biosciences (69 decks)

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