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Biomedical Science Y1 (Sem 1) > Cell Structure > Flashcards

Cell Structure Flashcards

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1
Q

Examples of Prokaryotic cells:

A

Bacterium

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2
Q

Examples of Eukaryotic cells:

A

Animal, plant, fungi and protists (algae)

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3
Q

An example of a non eukaryotic/prokaryotic cell

A

Virus

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4
Q

Organelles within a (prokaryote) bacterium:

A
  • Nucleoid
  • Flagellum
  • 70s ribosomes
  • Chromosomal DNA (plasmids)
  • Cell wall
  • Cell membrane
  • Capsule (peptidoglycan)
  • Pili
  • Cytoplasm
  • Food granule
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5
Q

Organelles within an (eukaryote) animal:

A
  • Nucleus
  • Nucleolus
  • Nuclear pore
  • Nuclear envelope
  • Cytoplasm
  • Cell membrane
  • 80s ribosomes
  • Lysosome
  • Small multiple vacuoles
  • Microtubules
  • Golgi apparatus
  • Golgi vesicles
  • RER
  • Smooth ER
  • Chromatin
  • Centrioles
  • Secretory vesicle
  • Mitochondria
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6
Q

Organelles within an (eukaryote) plant:

A
  • Nucleus
  • Nucleolus
  • Nuclear pore
  • Nuclear envelope
  • Cytoplasm
  • Cell membrane
  • Cell wall
  • 80s ribosomes
  • Lysosome
  • Large central vacuole
  • Vacuole membrane
  • Microtubules
  • Golgi apparatus
  • Golgi vesicles
  • RER
  • Smooth ER
  • Chromatin
  • Secretory vesicle
  • Mitochondria
  • Chlorplast
  • Amyloplast (starch grains)
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7
Q

Organelles that only plant cells have and animal cells don’t

A

Cell wall and chloroplasts

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8
Q

Organelle only animal cells have:

A

Centrioles

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9
Q

Size (diameter) and DNA arrangement of prokaryotes

A

1-5um and circular

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10
Q

Size (diameter) and DNA arrangement of eukaryotes

A

10-100um and linear

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11
Q

Components of the cytoskeleton

A

Microtubules, intermediate filaments and actin filaments

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12
Q

What is locomotion in a cell?

A

The ability of cells or organisms to move and propel itself from place to place.

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13
Q

What is the purpose of a cytoskeleton in eukaryotic cells?

A

Maintains the cell’s shape, and is responsible for the locomotion of the cell itself and the movement of the various organelles

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14
Q

Which part of the cell is responsible for breaking down

used organelles and essentially “digesting” substances?

A

Lysosomes

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15
Q

What part of the cell allows materials to enter and exit

the cell?

A

Plasma membrane

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16
Q

When biologists wish to study the internal ultrastructure of cells, they most likely would use…

A

Transmission electronic microscope

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17
Q

The advantage of light microscopy over electron microscopy is that…

A

Light microscopy allows one to view dynamic processes in living cells

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18
Q

What is the primary objective of cell fractionation?

A

To separate the major organelles so that their particular functions can be determined

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19
Q

Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?

A

Proteins

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20
Q

Which type of organelle is primarily involved in the synthesis of oils, phospholipids, and steroids?

A

Smooth endoplasmic reticulum

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21
Q

Which of organelle contains its own DNA and ribosomes?

A

Mitochondria

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22
Q

Grana, thylakoids, and stroma are all components found in?

A

Chloroplast

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23
Q

Organelles other than the nucleus that contain DNA include:

A

Mitochondria and chloroplast

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24
Q

The mitochondrion, like the nucleus, has two or more membrane layers. How is the innermost of these layers
different from that of the nucleus?

A

The inner mitochondrial membrane is highly folded

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25
Q

Components of a chloroplast

A
  • Envelope (outer membrane)
  • Inter-membrane space
  • Inner membrane
  • Stroma
  • Thylakoid system
  • Grana
  • Peripheral reticulum
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26
Q

Components of a mitochondrion

A
  • Inner membrane
  • Outer membrane
  • Transmembrane space
  • Cristae
  • Matrix
  • DNA
  • Ribosomes
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27
Q

How does chloroplast replicate/reproduce?

A

Binary fission

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28
Q

How does mitochondria replicate/reproduce?

A

Simple fission (mitochondrial fission)

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29
Q

Which cell structure would most likely be visible with a light microscope?

A

Mitochondrion

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30
Q

Which cell would be best for studying lysosomes?

A

Phagocytic white blood cell

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31
Q

Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through

A

Gap junctions

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32
Q

What is protoplasm made up of?

A

Cytoplasm + nucleus + cell membrane

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33
Q

What are cells considered to be?

A
  • the basic units of life

- the building block of all living things

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34
Q

What is the aqueous solution found in the cytoplasm?

A

Cytosol (approx. 70% of cell volume)

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35
Q

Current cell theory:

A
  1. Cells are structural and organizational unit of life
  2. All living organisms are composed of cells
  3. All cells come from pre-existing cells
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36
Q

Where are nucleoproteins synthesised?

A

Cytoplasm

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37
Q

Where are microtubules not found in?

A

Mitochondria

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38
Q

What are lysosomes rich in?

A

Hydrolytic enzymes

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39
Q

Polyribosomes are aggregates of?

A

rRNA

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40
Q

Who was the cell discovered by?

A

Robert Hooke

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41
Q

Which part of the cell is responsible for breaking down used organelles and essentially “digesting” substances?

A

Lysosomes

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42
Q

All cells come from pre-existing cells (1858)

A

Virchow R

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43
Q

All animals are made of cells (1839)

A

Schwann T

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44
Q

All plants are made of cells (1838)

A

Schleiden M

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45
Q

First person to observe bacteria (1676) and the sperm cell (1677)

A

Van Leeuwenhoek A

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46
Q

What is microbiome?

A

Gut influencing the brain

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47
Q

Ratio of non human cells to human cells

A

3:1

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48
Q

Describe the DNA of prokaryotes

A

Naked, circular and usually no introns

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49
Q

Describe the DNA of eukaryotes

A

Bound to proteins, linear and has introns

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50
Q

Reproduction of prokaryotes and eukaryotes:

A
  • Binary fission

- Mitosis and meiosis

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51
Q

Animal cell and plant cell shape:

A
  • Round or irregular

- Rectangular or cubic

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52
Q

Animal cell size

A

10-30um

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53
Q

Plant cell size

A

10-100um

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54
Q

Types of animal cell tissue

A
  • Muscle tissue
  • Nervous tissue
  • Epithelial tissue
  • Connective tissue
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55
Q

Types of muscle cells:

A
  • Skeletal
  • Cardiac
  • Smooth
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56
Q

Types of neural cells:

A
  • Dentrites

- Axon

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57
Q

Types of epithelial cells:

A
  • Squamous
  • Cuboidal
  • Columnar

> Simple
Stratified

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58
Q

Visible limits

A
  • Naked eye (10-4m)
  • Light microscope (10-7m)
  • Electron microscope (10-10m)
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59
Q

Types of microscopy

A
  • Light microscopy (brightfield (visible light) and fluorescent microscopy)
  • Electron microscopy (EM)
  • Scanning electron microscopy (SEM)
  • Transmission electron microscopy (TEM)
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60
Q

Brightfield (visible light)

A 
Essential for cell culture and histology 
Pros:
- Inexpensive 
- Living cells
Cons:
- Lack of contrast
- Resolution 0.2um
- Staining is time consuming
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61
Q

Fluorescence microscopy

A 
Essential for cell biology 
Pros:
- Living cells
- Greater contrast
- Always improving 
- 3D

Cons:

  • Resolution 0.2um
  • Staining is time consuming
  • Fairly expensive
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62
Q

Fluorescent markers:

A
  • DAPI (adenine/thymine of DNA, fixed) = blue
  • Hoechst 33342 (dsDNA, live and fixed) = blue
  • Propidium iodide (PI) = red

Cytoskeleton:
Phalloidin (actin filaments, fixed) - red

63
Q

Fluorescent proteins:

A
  • Green fluorescent protein (GFP) isolated from jellyfish ‘aqueorea victoria’
  • Gene encoding GFP can be fused to any other gene
  • When protein is expressed it will be tagged with GFP
  • Living cells
64
Q

Electron Microscopy

A

> Scanning EM

  • Reveals surface topography of sample
  • Sample must be coated with an e- absorbent material such as gold

Pros:

  • Highest resolution of all - almost atomic level
  • Magnification
  • Still improving

Cons:

  • Very expensive and time consuming
  • Specialist knowledge
  • 2D (3D very hard)
  • Fixed specimens only
  • Sensitive to vibration and electromagnetic field (isolated room)
65
Q

What is cell centrifugation?

A

Applies strong rotational force, effectively increases the gravitational force on the sample and separates out materials according to their masses

66
Q

Name the 2 types pf cell culture

A

Primary cultures and cell lines

67
Q

Primary cultures

A

Derived from tissues eg. animals and tissue samples

Pros:
- Real cells = more accurate experiments
Cons:
- Costly: animal use: limited cell numbers

68
Q

Cell lines

A

Immortalised cell lineages, can be propagated indefinitely in the lab

Pros:
- Cheap; easy to manipulate; a lot of cells
Cons:
- A model system; may not give true results

69
Q

How thick is the cell membrane?

A

8nm thick

70
Q

Function of the cell membrane

A
  • Selective permeability
  • Maintenance of cell integrity
  • Transport and cell signalling
71
Q

Component of the cell membrane:

A
  1. Phospholipid bilayer
  2. Cholesterol
  3. Carbohydrates
  4. Proteins
72
Q

Phospholipid bilayer

A

Phospholipid bilayers form between aqueous internal and external environments

  • Hydrophobic core (tails)
  • hydrophilic surface (head)
73
Q

Cholesterol

A
  • Sterols are present in eukaryotic membranes
  • Cholesterol = major sterol in mammalian membrane
  • Cholesterol os amphipathic
74
Q

Fluidity of bilayer: Cholesterol

A
  • Makes lipid bilayer less deformable
  • Decreases its permeability to small water soluble molecules
  • Prevents phase shifts
  • Stops phospholipids packing too tightly at low temp (more fluid)
  • Holds phospholipids together at high temp (less fluid)
75
Q

Membrane carbohydrates

A
  • Generally short and branching
  • <15 sugar units
  • Covalently bound to lipids (glycolipids) or commonly to proteins (glycoproteins)
  • Vary among species, individuals and cell types
  • Play a role in cell-cell recognition
  • Identification markers
76
Q

Membrane proteins

A
  • A membrane is a collage of different proteins embedded in the fluid matrix of the lipid bilayer
77
Q

Types of membrane proteins

A
  • Integrals (transmembrane and partially embedded)

- Peripheral (associated with PL head groups or other integral proteins)

78
Q

Membrane permeability

A
  • Hydrophobic molecules = eg hydrocarbons, CO2 AND O2 can dissolve in lipid bilayer and pass through the membrane
  • Ions, polar molecules (eg. water) and larger molecules (eg. glucose) do not cross the membrane easily. Can be transported across membrane by the aid of membrane proteins
79
Q

Membrane transporter

A
  • Gradient (internal conc vs external conc)

- Uniporter/antiporter/symporter

80
Q

What is the cytoskeleton?

A

Eukaryotic cells are criss-crossed by long filamentous proteins
- Mix of polymers and proteins

81
Q

Function of the cytoskeleton

A
  • Provide structure = shape, support and organization

- Plays an essential role in cell movement, endocytosis/exocytosis and cell division

82
Q

Where is the cytoskeleton present?

A
  • Cell cortex
  • Cytosol
  • Nucleoplasm
83
Q

What are the components of the cytoskeleton?

A
  1. Intermediate filaments
  2. Actin filaments
  3. Microtubules
84
Q

Intermediate filaments:

A
  • Stable, rope like
  • Approx 10nm diameter
  • High tensile strength
  • Strengthen nuclear lamina
  • Extend throughput the cytoplasm and nucleus
  • Anchored to cell-cell junctions (desmosomes) and cell matrix junctions (hemidesmosomes)
85
Q

Microtubules:

A
  • Long, hollow tubes
  • Relatively stiff
  • Extend from the centrosome (near nucleus)
  • Cellular scaffols
  • Form long tracks throughout the cell
86
Q

Function of microtubules

A
  • Migration of chromosomes
  • Cell movement (flagella/cilia)
  • Organelles structure
  • Exo/Endocytosis
87
Q

Structure of microtubules:

A
  • Alpha and beta tubulin dimers
  • Dimers stack to form protofilaments
  • 13 parallel protofilaments form to hollo microtubules
  • 25nm diameter
88
Q

Centrosome

A
  • The main microtubule organising centre (MTOC)
  • Provides anchoring for the microtubule network
  • Enriched in y-tubulin rings
  • Nucleation site
  • Microtubules enxtend from here
  • Plus end is away from MTOC
89
Q

Actin filaments:

A
  • Thin and flexible (helical)
  • 5-9nm diameter (7nm)
  • Stabilised by actin binding proteins
  • Can form permanent structures ( microvilli)
  • Polymerisation of globular actin to a chain
  • Two chains arranged in a double helix
90
Q

Motor protein (actin filaments)

A

Myosin

91
Q

Extracellular matrix

A

Part of support tissue for almost all organs and nutrition role

92
Q

What is the extracellular matrix composed of?

A

Macroproteins and polysaccharides:

  • collagen
  • elastin
  • proteoglycan
  • glycoaminoglycans
  • glycoproteins
  • growth factors

connective cells/also epithelial cells

93
Q

Types of cell junctions (epithelial cells)

A
  • Tight junctions
  • Adherens junctions
  • Gap junctions
94
Q

Tight junctions

A
  • Ensure cell-cell cohesion at the apical membrane

- Prevent protein diffusion between basal and apical side

95
Q

Adherens junctions

A
  • Attachment via cytoplasmic plaque (cell belt)
  • Maintaining cell shape
  • Desmosomes (stud like structures)
96
Q

Gap junctions

A
  • Juxtapositions of channels for the cell-cell communication
  • Channel opening: pH and calcium dependent
97
Q

What is the endomembrane?

A
  • Series of membrane bound organelles evolved from plasma membrane by invagination
  • As cells increased in size, maintains membrane surface area to volume ratio
98
Q

What is the secretory pathway?

A

The part of the endomembrane system involved in the synthesis, modification and sorting of secreted proteins and transmembrane protein

99
Q

What is the secretory made up of?

A
  • Endoplasmic reticulum
  • Golgi apparatus
  • Secretory and transport vesicles
  • Membrane bound organelles
100
Q

The ER

A
  • A series of hollow tubes, vesicles and sacs (cisternae)
  • Extends throughout cell
  • Continuous lumen
  • Up to 50% of cell’s membrane content
101
Q

Structure of the endoplasmic reticulum:

A
  • Phospholipid bilayer
  • Dense cisternae towards towards cell centre
  • Tubules towards periphery
  • Extends throughout cell
  • Continuous with nuclear envelope
102
Q

The Rough ER

A
  • Cytoplasmic surface studded with ribosomes

- Site for protein synthesis

103
Q

Protein translocation

A

Proteins made by ribosomes on RER are translocated into the ER

104
Q

Protein translocation process:

A
  • Signal sequence of nascent protein recognised
  • Threaded into translocon
  • Soluble proteins released in ER lumen
  • Transmembrane proteins released sideways into membrane
105
Q

The Smooth ER

A
  • No ribosomes
  • Generally tubular
  • Periphery of the cell
106
Q

Function of the Smooth ER:

A
  • Synthesis of lipids (FA’s) and steroids
  • Calcium homeostasis
  • Detoxification (liver)
107
Q

Sarcoplasmic reticulum

A
  • Specialised form of sER
  • Found in muscle cells
  • Stores and releases CA2+ to trigger contraction
108
Q

ER exit

A
  • Proteins leave the ER via cop-coated vesicles

- Vesicles moved to the golgi apparatus along microtubules

109
Q

The golgi apparatus

A

Series of flattened sacs (cisternae)

  • ER side = cis golgi
  • Middle = medial golgi
  • Cell membrane side = trans golgi
110
Q

Function of Golgi apparatus:

A
  • Post translational modifications, modification of carbohydrates and addition of new carbohydrates
  • Sorting into vesicles for transport
  • Plasma membrane endosomes/lysosomes
111
Q

Secretion via exocytosis

A

Two forms:

  • Constitutive secretion
  • Regulated secretion
112
Q

Constitutive secretion

A
  • Continuous secretion
  • Uncontrolled secretion
    Examples:
  • Serum proteins, eg albumin from hepatocytes
  • Extracellular matrix proteins, eg collagen from fibroblasts
113
Q

Regulated secretion

A
  • Proteins are packaged into dense secretory granules
  • Granules stored in the cytoplasm
  • Released only upon stimulation (hormones and depolarisation)
  • Eg, mucus, insulin and neurotransmitters
114
Q

What is the endocytic pathway?

A

Part of the endomembrane involved in the internalisation, recycling, and degradation of transmembrane proteins proteins and extracellular materials

115
Q

What is the endocytic pathway made up of:

A
  • Endocytic vesicles
  • Endosomes
  • Lysosomes
  • Membrane bound compartments
116
Q

Features of endocytosis:

A
  • Cell membrane is hydrophobic

- Large, polar molecules cannot pass through

117
Q

Process of endocytosis:

A
  1. Pit formation
  2. Inward budding
  3. Neck closure
  4. Vesicle formation
118
Q

Endosomes

A

Vesicles move to endosomes
There are 2 major types:
Early endosomes = just beneath the PM
Late endosomes = closer to the nucleus

119
Q

Early Endosomes (EE)

A
  • Tubulo vesicular
  • Protein sorting site
  • Returns useful cargo to PM or golgi tubule
  • Concentrates cargo for destruction at lysosome (body)
120
Q

Late Endosomes (LE)

A
  • EE steadily pulled towards the centre
  • Once all recyclable cargo is removed, EE matures into late endosome (LE)
  • Able to sude with lysosome
  • Mediates final sorting and preparation for cargo destruction
121
Q

Endosomal pH

A

Endosomes and lysosomes are acidic vesicles (H+ pumps in membrane)

  • Sorting of cargo is pH dependent
  • Gradient exists through endosomal pathway
  • EE pH = 6.0
  • LE pH = 5.5
  • Lysosome pH = 4.8
122
Q

Lysosome features:

A
  • Very low pH = 4.8
  • Hydrolytic enzymes
  • 40 different types
  • Includes nucleases, proteases, lipases, glycosidases…
123
Q

Function of lysosomes:

A
  • Late endosomes fuse with lysosome = degration of contents
  • Useful molecules are transported out of lysosome to cytosol
  • Lysosome resident TM proteins are highly glycosylated
124
Q

What are the other forms of endocytosis?

A
  • Receptor mediated endocytosis

- Autophagy

125
Q

Receptor mediated endocytosis

A
  • Concentrating mechanisms for internalisation
  • Via clathrin coated vesicles
  • Increased efficiency of uptake (without large EC fluid intake)

Obtaining nutrients:

  • Cholesterol, iron
  • Terminate signalling
126
Q

Clathrin

A
  • Vesicle coat protein

- Forms special shape called triskelion (3 heavy chains, 1 or 2 light chains associated with each heavy chain

127
Q

Autophagy

A
  • Method by which cell’s own contents and organelles are degraded
128
Q

Endosymbiosis

A

Primary endosymbiosis refers to the original internalization of prokaryotes by an ancestral eukaryotic cell, resulting in the formation of the mitochondria and chloroplasts

129
Q

Mitochondria

A

Found in virtually all eukaryotic cells:

  • Animal
  • Plants
  • Most eukaryotic microorganisms

Specialised site for oxidative phosphorylation

130
Q

Liver cell’s mitochondria

A

1000-2000 mitochondria to provide energy to drive chemical reactions

131
Q

Sperm mitochondria

A

Many mitochondria wrapped around flagellum to provide energy for movement

132
Q

Aspects of mitochondria

A

Contains own circular DNA

  • Mitochondrial disease (Leigh syndrome)
  • Maternal inheritance

RNA and transcription/translation machinery can make some of their own proteins

133
Q

Features of the mitochondrion

A 
Contains two membranes:
 - Outer 
- Inner 
Confers 4 distinct compartments:
- Matrix
- Intermembrane space
134
Q

Matrix

A
  • Approx 1um wide

Contains highly conc mixture of enzymes

135
Q

Inner membrane

A

Folded into numerous cristae

136
Q

Outer membrane

A

Contains a large channel-forming protein, porin, the outer membrane is permeable to all molecules of 5000 daltons or less

137
Q

Inner and Outer membranes

A

Outer:

  • Many transmembrane channel proteins called porins
  • Very porus = intermembrane space similar to cytosol

Inner:

  • Folded into cristae
  • Not porus
  • Site of electron transport chain
  • ATP synthase embedded in membrane (matrix side)
138
Q

Mitochondrial matrix

A
  • Concentrated mix 100s of enzymes
  • Involved in aerobic respiration which supplies the cell with energy in the form of ATP
  • Also concerned with the oxidation of fatty acid molecule
  • Site of the citric acid cycle
  • The matrix also contains the circular DNA molecules and components for protein synthesis
139
Q

Features of mitochondria:

A
  • 1um wide
  • Two membranes
  • Makes ATP
    Use of oxygen
  • Shape varies
  • Can form chains
  • Own DNA
  • Own proteins
  • Ribosomes not like eukaryotes
  • Binary fission
140
Q

Features of chloroplasts:

A
  • Double membrane encased organelle
  • Found only in plants, algae and some protists
  • Site of photosynthesis
  • Fixes CO2 to make sugars
  • Releases oxygen
  • Site of FA synthesis in plants
141
Q

Thylakoids

A

Harness light energy to produce ATP and NADPH to power the production of sugars from oxygen

142
Q

Stromal matrix

A

House the enzymes necessary to trap CO2 in the form of sugar

143
Q

Summary of chloroplasts:

A
  • Approx 2um and 1um thick
  • Two membranes
  • Contains chlorophyll
  • Make ATP and sugars (photosynthesis)
  • Fix CO2 liberate O2
  • Shape varies
  • Can form chains
  • Own proteins
  • Ribosomes not like in eukaryotes
  • Binary fission
144
Q

The nucleus

A

Two critical functions:

  • contains and protects DNA
  • coordinates cellular activity
Nucleoplasm
- 8-10% total cell volume
(inhibition of nuclear export up to 50%)
- approx diameter = 5um 
- absent in red blood cell
145
Q

In H&E staining what colour is the nuclei?

A

Purple

146
Q

The nuclear envelope

A 
2 concentric membranes 
Inner:
- binding of chromosomes 
- anchors for nuclear lamina
Outer:
- continuous with ER

Perinuclear space

  • Import and export of molecules accomplished via nuclear pore complexes
147
Q

Nuclear pore complexes (NPC’s)

A
  • large structures - 30 different nucleoporins
  • 400-2000 per cell
  • Central water filled channel
  • Diameter pore = 10nm (uto 25nm)
  • Roughly octagonal
  • 8 filaments projects into cytoplasm
  • 8 filaments project into nucleoplasm = joined to form nuclear basket
148
Q

Nucleoplasmic transport

A

Passive transport

  • bidirectional
  • Can pass freely = water, ions, metabolites (nucleotides) and proteins

Active transport

  • Signal sequences
  • Nuclear localisation signal (NLS) recognised by importin
  • Nuclear export signal (NES) recognised by exportin
149
Q

Functional units of the nucleus

A
  • Chromatin = DNA and specialised packaging proteins known as histones
  • Visible as chromosomes during cell division

Nucleolus

  • Non membranous ‘organelle’ within the nucleus
  • Contains genes encoding for ribosomal RNA
  • Place for synthesis of rRNA and assembly of ribosomes
150
Q

Ribosomes

A
  • Not strictly a true organelle
  • Not membrane bound
  • Decode mRNA message into proteins (translation)
  • Typical cell has millions of ribosomes
151
Q

Ribosome function:

A

Small unit = matches the tRNAs to the mRNA codon
Large unit = catalyses the formation of peptide bonds

Prokaryotic = 50s+30s = 70s
Eukaryotic = 60s+40s = 80s
152
Q

Proteasome

A
  • Not a ‘true’ organelle
  • Not membrane bound
  • A large macromolecular complex (approx. 50 protein subunits)
  • Functions to degrade unwanted protein in the cytosol
153
Q

Peroxisome

A
  • Membrane bound
  • Roughly spherical
  • 0.2-1um in diameter
  • Rich in enzymes
154
Q

Peroxisome functions:

A
  • Oxidative break down FAs AA and toxins such as uric acid
  • Yield hydrogen peroxide (H2O2)
  • contains catalase to breakdown H2O2 to water and oxygen
  • Site for synthesis of cholesterol and other metabolites for biosynthetic pathways
  • In liver cells = bile acids produced

Biomedical Science Y1 (Sem 1) (7 decks)

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