Multicellularity and Signalling Flashcards

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1
Q

Advantages of size (multicellularity)

A

Mobility

Strength/power

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2
Q

Challenges of size (multicellularity)

A

Instability

Absorption and excretion more difficult

Greater energy and space needs

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3
Q

Advantages of multicellularity

A
  1. Size
  2. Specialization of cell/organ/tissue function: division of labor
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4
Q

Challenges of multicellularity

A
  1. Size
  2. Compartmentalization at organism’s level
  3. Organization of cells/organs/tissues
  4. Communication between cells/tissues
  5. Complex reproduction
  6. Generation times longer
  7. Slower adaptation/evolution
  8. CANCER
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5
Q

Aplysia

A

Famous model system for study of learning and memory

Exhibits learning behaviors similar to humans despite lack of brain

Evidence that learning and memory are , to some extent, mediated on a cellular level

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6
Q

Adaptations of multicellularity

A
  1. Stability and cellular organization (cell adhesion and extracellular matrix)
  2. Compartmentalization/protection from environment (mostly cell adhesion; ECM to some degree)
  3. Enhanced intercellular communication (mostly cell signaling)
  4. Mechanisms to absorb nutrients, H20, O2, etc. and to excrete waste (Physiology)
  5. Differentiation of cells (developmental biology)
  6. Reproduction (physiology and developmental biology)
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7
Q

Stability and cellular organization (multicellular adaptation)

A

Cell adhesion and extracellular matrix

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8
Q

Compartmentalization/protection from environment (multicellular adaptation)

A

Mostly cell adhesion; ECM to some degree

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9
Q

Enhanced intercellular communication (multicellular adaptation)

A

Mostly cell signaling

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10
Q

Cell adhesion molecule (CAM)

A

Integral membrane proteins

Bind to CAMs on adjacent cells

Stabilize the organism

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11
Q

Homophilic cell adhesion

A

CAMs bind to same molecule on adjacent cell

Helps cells of organs stay together in same place

All cells of one type express same CAM so they know to associate with each other

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12
Q

Epithelial cells

A

Polarized cells that form epithelia

Held together by tight junctions

Every point of contact made of tight junctions/CAMs

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13
Q

Epithelia

A

Boundary between organism and outside world

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14
Q

Tight junctions

A

Continuous intercellular barrier between epithelial cells

Made up of multitudes of cell adhesion molecules

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15
Q

Extracellular matrix (ECM)

A

Dense thicket of proteins that fill virtually all space between cells in animals

Lots of glycosylation

Anchors cells
Structural support/cusioning
Filtering of substances (eg kidney
Signaling and communication

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16
Q

Cell signaling

A

Cells must be able to respond to signals from both outside and inside the organism

Their response should benefit the organism or the population

17
Q

Dictyostelium (cell signaling example)

A

Stalk cells commit “suicide” after spore cells detach, providing nutrients to other cells

18
Q

Tadpole eye (cell signaling example)

A

Cell death benefits organism; in some cases if cell death is prevented organism could die

19
Q

Ligand

A

Signaling molecule

Produced (secreted) by “sender” cell and received by “recipient” cell (bind with high affinity to specific receptors on recipient cells)

20
Q

Autocrine signaling

A

Sender and recipient are the same cell or group of cells

Advantages: very specific responding population; FAST

Disadvantages: limited utility, very short range

(EXTREMELY RARE)

21
Q

Juxtacrine signaling

A

Sender and recipient are immediately adjacent; signal diffuses a very short distance or not at all

Advantages: precise; immediate

Disadvantages: adjacent cells only; very short range

22
Q

Practice signaling

A

Signaling molecule that can diffuse one or several diameters away to nearby recipient cells

Advantages: more recipient cells than juxtacrine; fairly fast

Disadvantages: not as precise as juxtacrine; still short-range

23
Q

Endocrine signaling

A

Signaling molecule (hormone) is secreted into the bloodstream, allowing it to diffuse throughout body

Advantaged: coordinates behavior of all tissues in the body

Disadvantages: very little specificity; relatively slow; may need lots of ligand

24
Q

Phosphorylase

A

Enzyme that catalyzes addition of a phosphate

25
Q

Second messenger

A

Soluble/diffusable molecule

Nonexistent in absence of ligand

Produced when ligand binds to receptor on cell membrane

Responsible for activating the cellular response

26
Q

Epinephrine (adrenaline)

A

Brain sends signal to nerves in spinal cord, which sends signal to adrenal medulla

Epinephrine secreted into bloodstream

Liver (stores glucose) in form of glycogen

Liver cells express receptors for epenephrine

Activates GLYCOGEN PHOSPHORYLASE, breaaking last glucose off of glycogen chain