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Biology of Cells 1 > An Introduction to the Structure of Cells > Flashcards

An Introduction to the Structure of Cells Flashcards

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1
Q

What do all cells have in common?

A

DNA

Cytoplasm

Plasma membrane surrounding the cell

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2
Q

Where is DNA stored in prokaryotic cells

A

Nucleoid

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3
Q

Where is DNA stored in eukaryotic cells

A

Nucleus

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4
Q

Cytoplasm

A

Semi-fluid matrix

Contains sugars, amino acids, proteins etc In a cytosol

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5
Q

How big are prokaryotes

A

1-10µm

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6
Q

How big are eukaryotes

A

10-100µm

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7
Q

Why aren’t cells bigger?

A

Would make diffusion less efficient

Surface area : volume ratio would be worse

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8
Q

Why is the surface area : volume ratio important in cells

A

Communication and interaction with internal environment happens through the surface of the cell

If the volume in the ratio was too large it wouldn’t be able to keep up

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9
Q

2 types of cell

A

Prokaryotes

Eurkaryotes

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10
Q

Types of prokaryotes

A

Bacteria

Archaea

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11
Q

Archaea

A

Ancient prokaryotes

Often adapted to extreme conditions

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12
Q

Extreme conditions arachaea

A

Methanogens

Extreme halophiles

Extreme thermophiles

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13
Q

Methanogens

A

Archaea

Metabolic activities produce methane

Poisoned by oxygen

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14
Q

Extreme halophiles

A

Archaea

Salt lovers

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15
Q

Extreme thermophiles

A

Archaea

Heat lovers

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16
Q

Structure of a prokaryotic cell

A

Nucleoid

Ribosomes

Cytoplasm

Pili

Plasma membrane

Cell wall

Flagellum (sometimes)

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17
Q

Prokaryote cell wall

A

Outside plasma membrane

Quite porous

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18
Q

Function of prokaryote cell wall

A

Protection

Maintains shape

Helps prevent excessive water uptake

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19
Q

Gram positive bacteria

A

Thick, single layered cell wall

Retains dye

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20
Q

Gram negative bacteria

A

More complex then gram positive

Many layers

Doesn’t retain dye

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21
Q

How do antibiotics often work

A

By disrupting cell walls

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22
Q

Bacteria

What is the cell wall often covered by What does it do

A

Capsule Is slimy, prevents it drying out and helps attachment

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23
Q

Ways prokaryotic cells move about

A

Flagellum

Pili

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24
Q

Interior organisation of prokaryotes

A

Simple

No internal compartmentalisation

No membrane bound organelles

No nucleus Cytoplasm with internal support structure

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25
Q

Types of Eukaryotes

A

Protists

Fungi

Plants

Animals

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26
Q

Structure of eukaryote cell

A

Compartmentalised

Plasma membrane

Cytoplasm

Organelles

Nuclear envelope

Nucleus

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27
Q

Which eukaryote cells have a cell wall

A

Plants

Fungi

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28
Q

What does the cell wall do

A

Provides mechanical support

Protects against infection

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29
Q

Eukaryote meaning

A

True nucleus

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30
Q

Prokaryote meaning

A

Before nucleus

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31
Q

Plant cell wall

A

Composed of fibres of cellulose embedded in polysaccharides and proteins

Interconnected by plasmadesmata

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32
Q

Plasmadesmata

A

Physical passageway in cell wall

Allows communication and movement of molecules between cells that the cell wall would stop

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33
Q

Central vacuole

A

Large membrane bound sac in plant cells

Stores proteins, pigments and waste

Presses against cell wall giving tugor pressure

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34
Q

How much of the cell does the central vacuole take up

A

Up to 80%

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35
Q

Contractile vacuole

A

Found in some protist cells

Stores water coming in by osmosis then expels the water

Stops the cell bursting from excess water

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36
Q

Types of vacuoles

A

Central (plant)

Contractile (protists)

Phagocytic

Food

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37
Q

Cytosol

A

Region of eukaryotic cells that is inside the plasma membrane and outside the organeles

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38
Q

Cytoplasm =

A

Cytosol + Organelles

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39
Q

Cytoplasm is the site of…

A

Metabolism

Catabalism

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40
Q

Metabolism

A

Utilisation of energy for synthesis of materials

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41
Q

Catabalism

A

Breakdown of materials to utilize energy and generate building blocks for construction macromolecules

Each step catalysed by an enzyme

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42
Q

Nucleus

A

Contains DNA

Spherical

Surrounded by nuclear envelope

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43
Q

What amount of cell volume is the nucleus

A

10-20%

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44
Q

Nucleolus

A

Inside nucleus

Site of intense ribosomal RNA synthesis

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45
Q

Nuclear envelope

A

Double membrane

Has nuclear pores to allow passage of substance

Interior filled with fluid containing chromosomes

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46
Q

What is eukaryotic DNA divided into?

A

Chromosomes

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47
Q

Chromosomal territory

A

Distinct

Non-overlapping

Where each chromosome is located within the cell nucleus of eurkaryotic cells

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48
Q

Chromosome

A

Unit of genetic material

Composed of DNA and proteins

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49
Q

Types of histone proteins

A

Central histone

Spacer histone

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50
Q

Nucleosomes

A

Formed by DNA coiled around clusters of histones

Looks like beads on a string

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51
Q

Chromotins around surrounded by…

A

Nucleoplasm

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52
Q

Nuclear lamina

A

Made of intermediate filaments

Lines the inner nuclear membrane

Attaches to chromatins which helps maintain nuclear shape and keep chromosomes in their territories

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53
Q

Ribosomes

A

Site of protein synthesis

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54
Q

Structure of ribosomes

A

Ribosomal Ribonuceic acid (rRNA) bound with several dozen types of protein 2 subunits, 1 large and 1 small

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55
Q

When are ribosomes functional and why

A

Only when attached to messenger RNA (mRNA)

mRNA contains the code required to make the protein

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56
Q

Free ribosomes

A

Make proteins that function in the cytoplasm

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57
Q

Proteins that function in membranes or for transport are made by…

A

Ribosomes on the rough endoplasmic reticulum

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58
Q

RER stands for

A

Rough endoplasmic reticulum

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59
Q

Why do cells in the same organism, with the same DNA, look and function differently

A

They share the same genome

But the proteome is different

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60
Q

Genome

A

Complete genetic composition of a species

61
Q

Proteome

A

The proteins that a cell can make

62
Q

Different cells may produce…

A

Different proteins

Different proportions of the same protein

Slightly different variants of proteins

Modifications of proteins

63
Q

Endoplasmic reticulum

A

Smooth and rough

Folded inner membranes (cisternae) give it an enormous surface area

64
Q

Rough endoplasmic reticulum

A

Site of protein synthesis

Covered with ribosomes

Proteins may be chemically modified there

65
Q

In what ways are proteins chemically modified in the RER

A

Glycosylated to become glycoproteins

Have “address label” signal sequences added

66
Q

Glycoprotein

A

A protein that has carbohydrate attached to it

67
Q

Glycosylation

A

The attachment of carbohydrate to a protein or lipid

Produces a glycoprotein or glycolipid

68
Q

Proteins leaving the RER may be….

A

Exported

Sent to the lysosomes or vacuoles

Become part of the plasma membrane

69
Q

When leaving the RER, what determines a proteins destination

A

The signal sequences attached

70
Q

Steps of protein synthesis in the RER

A

Free ribosomes produced in cytosol

If mRNA contains an ER signal sequence the ribosome attaches to the ER

ER signal sequence recognised by signal recognition particle (SRP)

SRP docks ribosome over channel protein in ER

Channel protein opens

Translation resumes and the growing polypeptide is threaded through the channel

The ER signal sequence is removed

Protein either released into ER lumen or embeds in ER membrane

71
Q

Why is the rough endoplasmic reticulum rough

A

Has ribsomes attached

72
Q

Contraslational sorting

A

Occurs during protein synthesis

First step of the sorting process happens during translation

Ribosome attaches to ER if mRNA contains an RE signal sequence

73
Q

Smooth ER (SER)

A

Diverse functions

Few ribsosomes

74
Q

Functions of the SER

A

Chemically modifies small molecules like drugs and alcohol

Hydrolyses glycogen

Synthesises and modifies lipids and steroids

Accumulates calcium ions

75
Q

What happens to proteins leaving the RER

A

Cargo (maybe protein molecules) binds to receptors on ER membrane

Cargo loaded into forming vesicle

Vesicle pinches off the membrane and is released

Coat proteins are shed V-snares bind to T-snares on target membrane

Vesicle fuses with target membrane to deliver cargo

76
Q

Coat proteins

A

Facilitate the formation of vesicles in transporting cargo from the ER

77
Q

Golgi apparatus function

A

Receives proteins from ER and modifies them

Concentrates, packages and sorts proteins

Sends them on to other destinations in secretory vesicles

Synthesises polysaccharides in plant cells

78
Q

Amount of golgi apparatus in: Simple cells Animal cells Plant cells

A

Simple - 1 or few

Animal - About 20

Plant - 100s

79
Q

How proteins are delivered to the nucleus, peroxisomes, mitochondria and chloroplasts using mitochondria as the example

A

Chaperone keeps protein unfolded

Sorting signal sequence binds to receptor on mitochonrion membrane

Chaperone released, protein transferred into channel

New chaperones bind to protein as it enters matrix

Sorting signal sequence cleaved off

Protein completely enters matrix

Chaperone released and protein folds into final 3D structure

80
Q

Why are chaperones needed in delivery of protons to the necleus, peroxsomes, mitochondria and chloroplasts

A

To prevent the protein from folding early and not fitting through the protein channels

81
Q

What are the chaperones

A

Proteins

82
Q

Lysosomes are features of

A

Animal cells

83
Q

How man lysosomes do you have

A

Maybe dozens per cell

84
Q

How are lysosomes formed

A

By budding from the endomembrane system

85
Q

Functions of lysosomes

A

Digestion of molecules taken up from outside the cell by endocytosis

Recycling cellular molecules

86
Q

Lysosomes internal pH and how maintained

A

pH4.8

Maintained by H+ ion pumps

87
Q

What stops a massive issue if a lysosome mebrane was damaged

A

Has a very acidic pH

Because of this the enzymes inside work optimally at a pH of around 4.8

The pH of the cytosol is 7 (neutral)

Therefor the enzymes would not be able to work very effectively outside the lysosme

88
Q

How does the lysosome break things down if the enzymes stay inside it

A

Engulfs the thing it digests

89
Q

Acid hydrolases

A

Used by lysosomes

Hydrolitic enzymes

Use a molecule of water to break a covalent bond

Work at an acidic pH

90
Q

What stage of cellular respiration happens in mitochondria In what part of the mitochodria

A

Oxidative phosphorylation

On the inner membrane

91
Q

What cells may require more mitochondria than usual

A

Liver

Heart

Muscle

92
Q

What about mitochondria’s shape makes it effecient

A

Much folded inner membrane to form cristae

Gives it a large surface area

93
Q

Role of mitochondria

A

Converts energy stored in organic molecules into ATP

Synthesis, modification and breakdown of other molecules like hormones

94
Q

What does the internal matrix of mitochondria contain

A

Enzymes

Ribosomes

95
Q

Describe mitochondria’s membranes

A

Outer -

Smooth and permeable

Inner -

Much folded, selectively permeable, embedded with protein complexs

96
Q

Site of photosynthesis in plant cells

A

Chloroplasts

97
Q

Semi-autonomous organelles

A

Have their own DNA and can stimulate it’s own replication

But depend on other parts of the cell for internal components

98
Q

What organelles are semi-automonous

A

Mitochondria

Chloroplasts

99
Q

Internal compartment of chloroplasts contains…

A

Hundreds of granum surrounded by stroma

100
Q

Grana

A

Inside chloroplasts

Stacked

Membranous

Contains several compartments called thylakoids

101
Q

Stroma

A

Fluid inside chloroplasts

Contains enzymes, ribosomes and DNA

102
Q

Thylakoids

A

Light capturing pigments on surface

Often connected to make a complex membranous system

103
Q

Peroxisomes

A

Hundreds per cell, especially in the liver

Collect toxic hydrogen peroxide and breaks it down to harmless water and oxygen using catalase

104
Q

Catalase

A

Enzyme

Used by peroxides to break hydrogen peroxide into water and oxygen

105
Q

Microbodies

A

In plant, animal, fungi and simple eukaryotic cells

Formed by budding from the ER

Grow by incorporating proteins and lipids and then divide

106
Q

Endosymbiosis

A

Describes a symbiotic relationship where the smaller species lives inside the larger one

107
Q

What makes mitochondria and chloroplasts weird organelles

A

They have their own DNA

108
Q

How mitochondria are believed to have come around

A

Descended from bacteria that existed inside eukaryotic cells in endosybiotic relationship

Over time (about 2 billion years) adapted to living in the cell and changed to mitochondria we see today

109
Q

Why would endosybiosis with purple bacterium have been benificial

A

Eukaryotic cell able to synthesise greater amounts of ATP

Purple cell may have benefited from stable environment and nutrients provided by cytosol (we don’t really know)

110
Q

What do we think mitochondria used to be?

A

Purple bacterium

111
Q

Evidence for endosymbiosis of mitochondria

A

Double layered outer membrane

Same size as prokaryotes

Some prokaryotes have folded membranes resembling cristae

Prokaryotes have similar sized and structured ribosomes

Have circular DNA molecules like prokaryotes

Share similar genes to prokayrotes

Divide by binary fission

Have own DNA

112
Q

Why does mitochondria having a double membrane support endosymbioisis

A

Inner membrane from original engulfed cell

Outer membrane from invaginated plasma membrane of host cell

113
Q

Mitochondria DNA

A

Have their own that codes for proteins needed for some functions

Some DNA moved to nucleus during evolution to help cell control mitochondria

114
Q

3 types of structural components in cytoskeleton

A

Intermediate filament

Microtubule

Actin filament (microfilament)

115
Q

Cytoskeleton

A

Network of 3 different types of protein filaments

Found primarily in the cytosol and in the nucleus along the inner nuclear membrane

116
Q

Actin filaments

A

Two protein strands made of actin subunits twirled together

Formed spontaneously

Have + and - ends

117
Q

Which end does actin filaments grow at

A

The positive (+) end

118
Q

Where do you often find actin filaments and why

A

Lie near plasma membrane

aSupports and allows quick changes in cell shape

119
Q

Actin filaments are responsible for….

A

Cell movement

Crawling

Pinching in cell division

Formation of cellular extensions

Supporting microvilli in intestine

120
Q

Intermediate filaments

A

Most durable cytoskelatal element

Stable, don’t break down

Like cables on suspension bridge

Intermediate in size between actin and microtubules

121
Q

Intermediate filaments roles

A

Stop cells stretching out of shape

Bears tension

122
Q

Structure of intermediate filaments

A

Tough, fibrous proteins twined in overlapping arrangement

123
Q

Microtubules

A

Hollow cylinders

Ring of 13 protofilaments

+ end faces away from nucleation centre, - towards

Rapidly polymerise and depolymerise to rapidly change in length

124
Q

Functions of micotubules

A

Rigid framework in cells Involved in organising cell wall (plant cells)

Distributes chromosomes during cell division (mitotic spindle)

Move materials within the cell

Anchor organelles in place

125
Q

Structure of microtubules

A

Have a + and -end

Hollow cylinders

Ring of 13 protofilaments

Globular proteins made of dimers of alpah- and beta- tubulin polymerise to form microtubule

126
Q

Where do microtubules form

A

From centrosome or microtubule organising centre

Radiates out

127
Q

Motor proteins

A

Consists of a head, tail and hinge

ATP hydrolysed at head

Hinge bends from hydrolysis of ATP

Tail region attached to other components

128
Q

How crawling cells move

A

At leading edge actin filaments polymerise pulling it forwards

Microtubules polymerise to stabilise this region

Myosin motors along actin filaments contract pulling cell towards newly extended front edge

129
Q

How do crawling cells know which way to go

A

Receptors on cell surface respond to chemical signals

130
Q

What do swimming cells use to move

A

Flagella or cilia

131
Q

Are flagella the same in prokayrotes and uekaryotes

A

No

Very different

132
Q

Structure of flagella and cilia

A

Same but cilia shorter and more numerous

Main part made up of axoneme

Anchored to basal body that sits just within the cell boundry

Linker protein nexin joins pairs of mircotubules

133
Q

Flagella/cilia axoneme

A

2 central microtubules

Surrounded by 9 microtubule doublets

Each of 9 pairs joined by the linker protein nexin

134
Q

Flagella/cilia basal body

A

Sits just within cell boundry

Has 9 triplet microtubules

135
Q

How does the flagella/cilia move

A

Dynein is activated to walk towards the - end of microtubules

Linking proteins hold dynein and microtubules in place

This tops dynein just walking up microtubules

Instead causes it to exert a force that bends the microtubules

This causes movement to start at the base of the flagella/cilia and progress with the same sequence towards the tip

136
Q

Prokaryotic cells flagellum

A

Made of flagellin helix and rotated by a protein motor secured in the plasma

One or more may be present

Rotated like motar

137
Q

Prokaryotic cells pili

A

Shorter but similar in structure to flagelli

Project from cell surface

Also allow attachment and exchange of genetic material

138
Q

Structure of flagellum/cilia diagram

A
139
Q

Structure of motor protein - diagram

A
140
Q

Movement of motor protein along cytoskeletal filament

A
141
Q

Structural components of cytoskeleton - diagram

A
142
Q

Rough endoplasmic reticulum protein synthesis diagram

A
143
Q

Ribosomes image

A
144
Q

DNA diagram

A
145
Q

Protein transport diagram

A
146
Q

Nucleus image

A
147
Q

Bacteria cell image

A
148
Q

Mitochondria image

A

Biology of Cells 1 (6 decks)

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