Studied by 2 peopleEndocrine
Long distance signaling in the circulatory system
Autocrine
Self signaling
Juxtracrine
Signals affect only adjacent cells
Paracrine
Short distance signaling between cells
When a response occurs in a cell, what is needed to stop it?
Ligand needs to detach or amount of ligand needs to decreases
What are gap junctions?
Small tunnels that connect cells, facilitating the movement of small molecules and ions between animal cells.
What are plasmodesmata?
Small tunnels that connect cells, facilitating the movement of small molecules and ions between plant cells.
What are local regulators?
Messenger molecules that travel only short distances
What is synaptic signaling?
A signal moves along a nerve cell which triggers the secretion of neurotransmitter molecules
In what type of signaling are hormones used?
Long distance (endocrine)
What is another name for endocrine signaling?
Hormonal signaling
What occurs in hormonal signaling?
Specialized cells release hormone molecules that travel via the circulatory system
Who discovered how the hormone epinephrine acts on cells?
Earl W. Sutherland
What are the three processes in cell signaling Sutherland suggests?
Reception, detection of the signal
Transduction, conversion of the signal to a cellular response, via a signal transduction pathway
Response, a cellular activity in response to the signal
What is a ligand?
A signaling molecule
What type of bond do the ligand and receptor create?
A highly specific bond
Ligand binding generally causes what to happen to the receptor?
Shape change occurs
What are most receptors activated by?
The shape change in its structure initiated by a ligand
What type of proteins are most signal receptors?
Plasma membrane proteins
What are the two main type of membrane receptors?
G protein-coupled receptors (GPCRs) and ligand-gated ion channels
What protein works with GPCRs?
G protein
What molecule does G protein bind to?
GTP
How do ligand gated ion channels act?
As a "gate" for ions when the receptor changes shape
What may get triggered by the diffusion of ions through open channels?
An electric signal
Where are intracellular receptor proteins found?
The cytoplasm or nucleus of target cells
What type of molecules can readily cross the membrane and activate receptors?
Small or hydrophobic chemical messengers
Name examples of hydrophobic messengers
Steroid and thyroid hormones of animals and nitric oxide (N O) in both plants and animals
What is phosphorylation?
Transfer of a phosphate group to ATP using protein kinase
What is a phosphorylation cascade?
A type of signal transduction pathway where phosphorylation occurs, then protein phosphatases remove the phosphates, in a continuous pattern adding a phosphate and then taking it off.
What changes the form of a protein from inactive to active?
The addition of phosphate groups
What do protein phosphates do?
Remove the phosphates from proteins
What is dephosphorylation?
Removal of phosphates from proteins, initiated by protein phosphatases
What do protein phosphatases provide a mechanism for?
Turning off a signal transduction pathway
What is a pathways "first messenger"?
The ligand
What are second messengers?
Small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion
What are two common second messengers?
Cyclic AMP (cAMP) and calcium ions (CA2+)
What converts ATP to cAMP?
Adenylyl cyclase
What is the immediate effect of cAMP?
The activation of protein kinase A, which then phosphorylates a variety of other protiens
Where may the response occur?
In the cytoplasm or nucleus
Describe positive feedback pathways
Cell communication: Endocrine
Example of use: Breastfeeding
Explanation: Effector makes initiation event stronger
Describe negative feedback pathways
Cell communication: Paracrine
Example of use: Insulin production to lower blood sugar
Explanation: Stimulus is reduced by the effector
Describe humoral immune response
Cell communication: Autocrine
Example of use: When foreign material (antigens) are detected in the body
Explanation: Signal (antigen) is digested into cytokinesis and T-cell creates antibodies
Describe cell mediated immune response
Cell communication: Cell to cell endocrine
Example of use: When body is infected with a virus or bacterium
Explanation: Infected cells get killed by multiplying killer T-cells
Describe neurotransmitters
Cell communication: Paracrine
Example of use: To help you move your limbs, feel sensations, and keep your heart beating
Explanation: Calcium reaches vesicles to release neurotransmitters then neurotransmitters are sent to the nucleus of nerve cells through the axon
Describe plant responses (hormones, tropisms)
Cell communication: Paracrine
Example of use: To sense the change of season
Explanation: Regular process (ligand to receptor to response) and regulates growth
Describe morphogens, embryonic development
Cell communication: Long-distance signaling (paracrine)
Example of use: To regulate cell fate specification and tissue patterning during embryonic development
Explanation: Morphogen binds to transmembrane receptor, then signal transduction allows message to enter the nucleus
What is a genome?
All the DNA in one cell of an organism
What are DNA molecules packaged into?
Chromosomes
What is chromatin?
A complex of DNA and protein
What are somatic cells and how many chromosomes do they have?
Non-sex cells, 46
What are gametes and how many chromosomes do they have?
Sex cells, 23
What do chromosomes look like when a cell is not dividing?
Long, thin chromatin fiber
What happens in preparation for cell division?
DNA is replicated and the chromosomes condense
What is a sister chromatid?
One half of a duplicated chromosome
What is a centromere?
The point on a chromosome where the chromatids are most closely attached
What are the stages of cell division and what occurs in them?
Mitosis: the division of the genetic material in the nucleus
Cytokinesis: the division of the cytoplasm
How are gametes produced?
Meiosis
What is the result of meiosis?
4 haploid daughter cells
What are the five phases of the cell cycle in order?
Interphase, prophase, metaphase, anaphase, telophase
In what process does cytokinesis occur in animal cells?
Cleavage which forms a cleavage furrow, a shallow groove in the cell surface
What forms during cytokinesis in plant cells?
Cell plate
What is binary fission?
A form of asexual reproduction in which the parent divides into two approximately equal parts
What occurs during binary fission in bacteria?
The single chromosome replicates beginning at the origin of replication. The two daughter chromosomes actively move apart as the cell elongates, and the plasma membrane pinches inward, dividing the cell into two
What did mitosis evolve from?
Binary fission
Certain protists exhibit what type of cell division?
Some sort of intermediate between mitosis and binary fission
What is the cell cycle driven by?
Specific signaling molecules present in the cytoplasm
What directs the sequential events of the cell cycle?
The cell cycle control system
What is the cell cycle control system regulated by?
Internal and external controls
What occurs in a cell if the cell cycle control system does not give cell division the go ahead after G1?
Cell goes into non-dividing state called G0
What is a reason anaphase would not begin?
If any kinetochores remain unattached to spindle microtubules
What does attachment of all kinetochores activate?
A regulatory complex
What are growth factors?
Proteins released by certain cells that stimulate other cells to divide
What is density-dependent inhibition?
When crowded cells stop dividing
What is anchorage dependence?
The need for cells to be in contact with a solid surface to divide
Cells in culture that can divide indefinitely are said to have undergone what process?
Transformation
What do malignant tumors undergo?
Metastasis, exporting cancer cells to other parts of the body where they may form additional tumors
What are the 3 stages of interphase?
G1, S, G2
What are mitosis and cytokinesis considered?
Mitosis phase
What occurs in G1?
Cell performs normal functions, gets bigger, protein synthesis and respiration occur, cell grows by producing more proteins and organelles
What occurs in S phase?
DNA replication
What occurs in G2 phase?
Chromosomes start to condense, organelles duplicate, centrioles form, cell prepares to divide with the division of centrosomes
What occurs in prophase?
Centrioles move to opposite poles forming spindle fibers, nuclear envelope begins to break
What occurs in prometaphase?
Sister chromatically have joined to spindle fibers
What occurs in metaphase?
Chromosomes line up in the middle of the cell
What occurs in anaphase?
Spindle fibers pull sister chromatids apart
What occurs in telophase?
Cell begins to reform (nucleolus and nuclear envelope), spindle fibers break down
What occurs in cytokinesis?
Cleavage forms cleavage furrow in animal cells, cell plate forms in plant cells
What is nondisjunction?
Chromosomes don't separate properly during cell division
What is apoptosis?
Programmed cell death
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