Module 1 Flashcards
juxtacrine communication
Juxtacrine (direct) communication
Cells need to be in physical contact with each other
The communication is ensured by specific proteins
Gap junctions or gap junction channels connect the inside of the two adjacent cells. Gap junctions permit rapid transfer of various substances and electrical impulses between adjacent cells.
Examples – heart and gastrointestinal tract.
endocrine signaling
Endocrine signalling
the messenger molecule is called a hormone.
Produced by an endocrine gland.
Reaches target cells via bloodstream – may travel long distances.
Examples: thyroid (thyroud hormones, e.g. thyroxine), pancreas (insulin and glucagon), testes and ovaries (testosterone, progesterone, oestrogens).
paracrine signaling
Paracrine signalling
The messenger molecule is called a paracrine (hormone).
Produced by a paracrine cell or gland.
Does not enter the bloodstream but remains in the interstitial l space surrounding the paracrine cell and diffuses to cell nearby – this is how the effect of the paracrine is exerted.
This form of communication is much shorter reaching.
Examples: common in the gastrointestinal tract.
autocrine signaling
Autocrine signalling
The messenger molecule is called an autocrine (hormone)
Produced by autocrine cell
Does not enter blood stream
Remains in the interstitial fluid and acts on the same cell that produced it.
The cell changes its function
It is not cell to cell communication because it acts on itself.
Example: common in the immune system and ovaries.
neurotransmission
Neurotransmission
The messenger molecule is called a neurotransmitter
Produced by a neuron (nerve cell)
The neurotransmitters are released from the pre-synaptic neuron across the synaptic cleft where receptors on the post-synaptic neuron receive the neurotransmitters.
neurocrine communication
Neurocrine signalling/Neurosecretion
Messenger molecule is called neurohormone
Produced by a neuron
Reaches target cells via bloodstream
Examples: oxytocin, vasopressin produced by a specific region of the brain.
indirect and direct forms of commuinication
direct - juxtacrine
indirect
- neurocrine
- neurotransmission
- autocrine
- paracrine
- endocrine
describe how cell receptors work
Cell surface receptors
Most messenger molecules
Cannot pass through cell membrane
Bind to cell surface receptors
Most of the hormone and neurotransmitters work this way.
Process: messenger molecule binds to the surface receptor, the receptor molecule changes its shape, various changes are triggered in the cell, cellular function changes.
The main steps of neurotransmission
A nerve impulses reaches the presynaptic terminal.
Ca+ enters the presynaptic terminal.
Ca+ concentration increase in the presynaptic terminal.
Synaptic vesicles adhere to the presynaptic membrane - “docking”
Neurotransmitter is released into the synaptic cleft.
Neurotransmitter binds to its receptors on the other side.
Effect is ixerted.
what is the importance of ATP in living cells
`Transfers energy released from exergonic (catabolic) reactions to power endergonic (energy requiring) reactions.
Power activities – e.g. muscle contraction, chromosome movement during cell division, membrane pumps and anabolic reactions
3 x phosphate groups attached to adenosine (adenine plus ribose sugar)
ATPase hydrolyses (involving water molecule) ATP into ADP + phosphate group, releasing energy stores in the phosphate bond.
ATP synthase catalyses the addition of a phosphate group to ADP.
Energy is stored in the phosphate bond.
explain glucose catabolism and the cycles etc.
Glucose catabolism
Cellular respiration – oxidation of glucose (removal of electrons and H+ atoms) to produce ATP.
Four sets of reactions in cellular respiration:
Glycolysis in the cytosol
Formation of acetyl-coenzyme A – occurs in mitochondria
Krebs cycle (citric acid cycle) - occurs in mitochondria
Electron transport chain. - occurs in mitochondria
glycolysis
Glycolysis
Occurs in the cytosol
Glucose – two 3 carbon molecules (pyruvic acid)
Uses two ATP, produces four ATP (net gain 2 ATP).
When oxygen is available, pyruvic acid is converted to acetyl coenzyme A inside mitochondria (aerobic respiration).
When oxygen is not available, pyruvic acid is converted into lactic acid/lactate (anaerobic respiration).
krebbs cycle
Krebs cycle (or citric acid cycle)
Acetyl CoA enters Krebs cycle in matrix of mitochondria.
Releases carbon dioxide
Electrons are transferred to two energy carrying coenzymes, NAD+ and FAD.
For each turn of the Kreb cycle (it takes two turns of the Kreb cycle for every molecule of glucose).
3 NADPH
3 H+
1 FADH
1 ATP.
electron transport chain
Electron transport chain
On inner mitochondrial membrane, cristae increases SA – more electron transport chain, more ATP.
Integral membrane proteins that are electron carriers.
Electrons passed along the chain generating ATP by pumping of hydrogen ions (H+), known as chemiosmosis.
Final electron acceptor is oxygen.
what are the primary tissue types
Primary tissue types
Epithelial – cover all exposed surfaces, line internal passageways and chambers, form glands
Connective – fill internal spaces, provide structure and support for other tissues, store energy and transport materials in the body.
Muscle – contraction, forms muscle walls.
Neural (nerve) - carries info throughout body in form of electrical impulses in conjunction with hormones.
define tissue
Tissue – group of similar cells for a specific function
