1
Q
What is an Organism?
A
a level in the hierarchy of the living world; can consist of a single cell or multiple cells & all of its component parts work together to promote the organism’s survival
2
Q
The major divisions of the living world are defined by ______________________________.
A
cell characteristics
3
Q
Name the three domains of life
A
Bacteria, Archaea, Eukarya
4
Q
____________ networks support plasma membrane and organelles within cytoplasm
A
protein fibre
5
Q
The cytoskeleton allows movement of ________________________ within the cell and maintenance of their spatial relationships.
A
organelles
6
Q
Cytoskeleton allows cells to control their ____________ and to ________________.
A
shape; move
7
Q
Microtubules
A
- cytoskeleton
- hollow tube formed from tubulin dimers
8
Q
Intermediate filaments
A
- cytoskeleton
- strong fiber composed of intermediate filament proteins
9
Q
Microfilaments
A
- cytoskeleton
- double helix of actin monomers
- important for movement and intracellular transport
10
Q
Cytoskeletal elements that allow cells to move or create currents:
A
cilia and flagella
11
Q
There is usually a difference in _________________ & ______________ between cilia and flagella
A
length (flagella>cilia) and number (fewer flagella than cilia)
12
Q
Eukaryote Endomembrane System’s function is to
A
- efficient way of folding up large SA in a small volume, allowing for greater activity
13
Q
The EES is a collective term for the ________________, _________, _____________, _____________, ________________.
A
nuclear envelope
lysosomes
Golgi apparatus
vacuoles
endoplasmic reticulum
14
Q
EES has series of flattened sacs and tubes formed of ___________________________ membranes, which are directly interconnected by moving ____________. Their general functions are to:
A
lipid bilayer
vesicles
- compartmentalize the interior of the cell, isolating incompatible biochemical processes and transferring products between the compartments to increase SA
15
Q
Prokaryote genome a single loop of DNA, which is good for ___________________. A requirement for this is that ______________________.
A
rapid replication;
gene regulation must be simple as everything is on the same structure
16
Q
Eukaryote genome is divided between a number of ________________________
A
linear chromsomes
17
Q
Eukaryotic genome allows for
A
gene regulation
cell differentiation
prodiction of different tissue types
chromosome replication to take place in parallel
18
Q
Eukaryotic gene ___ prokaryotic gene
A
>
19
Q
Mitochondria
A
not found in prokaryote cells but some engage in oxidative phosphorylation
- site of oxidative phosphorylation in eukaryotic cells
- increase SA for these processes when compared to prokaryotes
20
Q
Chloroplast
A
not found in prokaryote cells but some engage in photosynthesis
- site of photosynthesis in eukaryotic cells
- increase SA for these processes when compared to prokaryotes
21
Q
Sexual production
The fusion of two haploid gametes from two parents form new individual genetically different from either parent; what is this process called?
A
vertical transmission (inheritance)
- generates genetic diversity through independent assortment and recombination
22
Q
Evidence for endosymbiotic origins (__________________)
A
(lateral transfer)
- circular DNA with highly reduced functional genes
- independent fission - remove mitochon. or plastids from eukaryotic cell and it cannot produce new ones
- size = 1-10 microns (bacteria size)
- double membrane
- certain proteins specific to bacteria cell membrane are also found in mito/chloro membranes
- 70s ribosomes - different size than eukaryotic 80s ribosome
23
Q
Primary Endosymbiosis Hypothesis P1
A
heterotrophic eukaryotes evolved first through the union of ancestral archaeon with aerobic a-proteobacterium –> which became mitochondrion
24
Q
Primary endosymbiotic hypothesis P2
A
autotrophic eukaryotes evolved from heterotropihc eukaryotes through union with photosynthetic cyanobacterium which became chloroplasts
25
# Endosymbiotic origins of mito/plastids
The aquisition of mitochondria and plastics by primary endosymbiosis is a form of __________________
lateral transfer
| diagram on page 32
26
What are the two alternative scenarios for evolution of final form of eukaryote cell?
**ancestral archaeon** first evolved endomembrane system, then entered *symbiosis* with **a-proteobacterium** --> becoming *mitochondrion*
OR
**ancestral archaeon** entered *symbiosis* with **a**-**proteobacterium**, which became *mitochondrion* - endomembrane system then evolved subsequently
27
# Page 35 - Endosymbiotic origins of mito/plastids
Prokaryote genes transferred to eukaryote _________.
## Footnote
What is this an example of?
nucleus
- this is a form of lateral transfer
28
What are the different forms/examples of lateral transfer
- bacteria swapping DNA
- endosymbiosis
- chloroplast genome --> nuclear genome
- lateral transfer through endoviruses
29
# Modern Endosymbiosis - Aquisition of New Organelles
Braarudosphaera bigelowii
- modern marine unicellular eukaryote alga
- nitrogen-fixing organelle shown to originate from symbiotic nitrogen-fixing bacterium
- they became organelle long time ago (100 My)
| Host cell was already eukaryote and was able to engage in phagocytosis
30
Secondary Endosymbiosis
- major eukaryote taxa arose as a result of *symbiosis of heterotrophic eukaryote cell *within an **auxotropic eukaryote cell**
- 3 independent occurances
| Page 37
31
_______________ was an important route for the acquisition of evolutionary novelties
lateral transfer
32
SA-V Relationships - Cells
SA and V of a solid do not increase linearly with an increase in linear dimensions
- SA is proportional to length^2
- V is proportional to legnth^3
SA=V^2/3
- the large cell and cluster of small cells have the same volume but the cluster of small cells has total SA of 162 units^2
CHECK slide 42
33
# Constraining Relationship
Exchange across membranes around or within a cell is by _____________ or ______________
| When do both work effectively?
diffusion or active transport
- both only work effectively over very short distances and rates are dependent on SA
34
Cube-Square Relationship
critical limiting relationship - this is why cells are small
- rates at which all materials *enter or exit* cell is a function of the **SA**
there must be a balance between SA and V in cells
- rates at which *gasses and nutrients* are used and *wastes produced* are a function of the **V**
35
Based on the Cube-Square Relationship, what type of cells can exchange materials more effectively with their environment?
small cells as the V increases more rapidly than the SA (check graph on page 44)
36
# SA/V Relationships in Eukaryotic Cells
What is the importance of SA/V in eukaryotic cells?
the *endomembrane system* and increased internal SA of *chloroplasts and mitochondria* involve elaborate folding of **extensive membranes**
- allows for more scope for** membrane-associated processes**
- allows eukaryotic cells to produce **more energy** and have **greater synthetic scope**
- they can be BIGGER and MORE ENERGETIC than prokaryotes
37
Types of Multicellularity
simple multicellularity
complex multicellularity
38
Bulk Flow
movement of fluids or gasses through channels, rather than cell-to-cell
39
Simple Multicellularity
- cell adhesion
- cell-cell communication but little less structurally simple
- no bulk flow
- most cells in direct contact with environment
- related, simpler forms have fewer cells, little specialization
- each stage has advantages
40
Volvox
simple multicellularity example
- constituent cells specialized as flagellated photosynthesizers or reproductive cells
| review figure 1.26 on slide 48
41
Complex Multicellularity
cells adhere
communicate
differentiate
specialize
- formation of tissues
42
Slime Molds
example of simple multicellularity
- they spend part of the life cycle as unicellular amoebas, congregate and produce mutlicellular structures under conditions of environmental stress
43
Three Theories of Origins of Multicellular Life
symbiotic theory
syncytial theory
colonial theory
44
Symbiotic theory
different species coming together
-
45
Syncytial theory
undergoes mitosis - more copies of mucleus but do not split
undergoes cytokinesis with cells specializing
46
Colonial theory
same species coming together
47
6 times complex multicellularity arose independently in history of life
- many unicellular eukaryotes have capacities needed for multicellularity (adhesion and communication)
- plantae
- amoebozoans
- stramenopiles
- alveolates
- rhizarians, opisthokonts
- discobids, metamonads
48
What are the capacities needed for multicellularity
adhesion, communication
49
Evolution of Multicellularity
1. Cyanobacteria - The Great Oxygenation Event
actually prolonged period in history - happened over the years
- rise in environmental oxygen levels due to **photosynthesis** gave *selective advantag*e to possesion of **mitochondria and aerobic respiration** = permitted multicellularity
50
When does simple multicellularity appear? complex?
end of Great Oxygenation Event; complex appears with subsequent rise in environmental O2 levels
51
ancestral holozoan
group that includes animals and their close relatives
- a recently found fossil shows evidence of cell-cell adhesion and cell differentiation
52
Most evolutionary models begin with what? They required ___________, which affected?
flagellated unicellular organisms (choanoflagellates in case of animals)
They required:
- cells be able to adhere to each other
- cells to divide up tasks and specialize
- cells to learn to communicate with each other
This affected:
- each others behaviour
- influence each others development
- coordinate complex actions
| Diagram on 56
53
Which groups exhibit complex multicellularity?
brown algae (stramenopiles)
red, green algae (plantae)
land plants (archaeoplastids)
fungi
animals
54
Why multicellularity?
- unicellular organisms must carry out all functions of metabolism, homeostasis, reproduction, repair, etc. with the resources of a **single cell**
- single isolated cells must deal directly with their **environment**
- unicellular organism can't get very big because the **cube-square relationship** keeps them small
55
Selective advantages of multicellularity
divisions of labour and economy of scale
increased size
56
What do the advantages of multicellularity allow?
avoid predation/eat larger things
exploid new environment
storage
increased feeding mechanisms/opp
protected internal environent that can be regulated (homeostasis)
specialization since internal env. is regulated
new metabolic functions
enhanced mobility
increased traction in currect/wind
share information with other cells
57
Consequences of multicellularity
complexity
- predator/prey and host/parasite interactions
- increased opportunity for diversity in form/function an niches
58
Challenges for being multicellular and large
**intercellular communication** - cells must be able to communicate with one another
- diffusion - can be use to communicate in short range
- gap junctions/plasmodesmata (equiv. of plants)
- bulk flow
- nerrves
- signalling molecules
**Cell Adhesion **- cells in the multicellular boy must stick together
**Cube-Square Relationship**
- volume increases as a function of the cube of linear dimensions with increasing size
- SA increases as a function of the square of the linear dimensions with increasing size
**Structure and Support**
- physical laws set absolute limits on animal size and performance
- morphology reflects accommoation with these limits
- challenges vary over animal boy size range
**Homeostasis**
- defend cells against hostile environment
- maintain stable internal environment for internal cells
- lot of exchange between intracelullar fluid and extracellular fluid - so composition and volume of extracllular flouid must be kept **STABLE**
**Reproduction and Growth**
- multicellular body must be able to produce new multicellular bodies
- development and differentiation require complex and flexible control systems
59
As an organism gets larger, its SA becomes ___________ relative to its volume
smaller
60
Metabolic rate in mammals is effectively measure by _____________________________________
organism's O2 consumption (mLO2/hr)
- O2 consumption increases with body size
61
Basal metabolic rate is much _____________ for an elephant than a mouse because?
lower; because constraint of SA/V ratio is much lower for an elephant than a mouse
check graph on page 68
62
An elephant has proportionately much less __________________ for dissipation of heat than a rabbit; hence with greater _________, ______________ must decrease
SA; body size; mass-specific metabolic rate
63
Adaptions for increasing SA
Gas Exchange
- gills bear lamellae, composed of flattened epithelial cells
- highly folded to pack greater SA into smaller V
Nutrient Absorption
- villi of small intestine epithelial cells increase SA for absorption within a small V
Filtration
- body's combine capillary beds provide extremely large **cummulative SA** for exchange between blood and tissues
64
# SA/V Relationships
multicellular bodies therefore consist of very large areas of [blank] utlilzing [blank] to move materials across
## Footnote
this requires?
cell membranes; short-range transport molecules
- requires extensive folding to fit all this within a reasonable volume
65
# SA/V Relationships
larger boies must have what to ensure that materials reach every square unit of the total membrane SA for effective exchange across total membrane surface?
long-range transport systems
- bulk flow
66
Most anatomical and physiological features of multicellular organisms are the result of accomodating what?
SA/V relationships - folding extensive membrane area into magageable volume, plumbing systems (bulk flow) to service this
67
# Example of homeostasis on page 74 as a challenge of being multicellular:
water content of a multicellular organism can be divided into two major compartments:
- extracellular fluid compartment
- intracellular fluid
68
# Example of homeostasis on page 74 as a challenge of being multicellular
What is intracellular fluid
## Footnote
water content of a multicellular organism can be divided into two major compartments:
all of the body's water found within cells - liquid portion of cytoplasm
69
# Example of homeostasis on page 74 as a challenge of being multicellular
Extracellular fluid compartment
## Footnote
water content of a multicellular organism can be divided into two major compartments:
all the body's water NOT FOUND *within* cell plasma membranes (this forms cell's immediate environment)
70
Why must the extracellular fluid's compositon and volume be kept stable for homeostasis?
| 75
composition and volume of extracllular flouid must be kept **STABLE** because there is lots of exchange between intracellular and extracellular fluids and the amount of work cells must do to maintain their own individual homeostasis can be minimized this way.
71
# Cell Adhesion 78
Cells in multicellular bodies must be attached to one another or to a acellular matrix. What are the three types of junctions in animals:
**tight junctions** - penetrate cell membranes of adjacent cells, fix cells in place, prevent movement of liquids between cells
**anchoring junctions** - of adjacent cells link to each other and microfilaments or intermediate fibres of cyotskeleton
**gap junctions** - of adjacent cells form channels penetrating cell membranes of both cells
- signalling molecules and water can be passed directly from cell to cell
- hence they can communicate with each other
72
How are cells able to communicate with each otehr?
gap junctions
73
Tissue
group of similar cells and extracellular substances working together to carry out specific function for the organism
- requires cells to attach to each other and communicate
- both plants and animals are organized in tissue level
74
Tissue in Animals: 4 types of tissues in triploblasts are? What do they arise from?
- epithelia
- connective tissues
- muscle tissue
- neural tissue
embryonic germ layers
75
# Extracellular Matrix and Cells
Characteristic of animals' extracellular matrix and cells
basic matrix is acellular (not alive but have to manage water)
- penetrated by network of collagen fibres
- varies greatly among diff organisms and types of connective tissues
76
Collagen
extracellular fibrous protein found in connective tissues
- only in animals
- like rubber (strong but flexible)
BIOL371
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