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Why do cells need to be able to send and receive signals?
- For function, growth, communication
- To alter cell behavior
- Ion channel
- Send signals across the synapse
- Turn chemical into electrical
- Transported through the blood
- Made in the endocrine system
Signals are received by directly connecting with the receptor site of another cell
Signal molecules are transported through interstitial fluid and received by nearby cell receptors
What are the classes of signaling molecules?
- Direct Contact
- Paracine system
What are the three classes of membrane receptors?
- Ion- channel
- Enzyme linked channel
How does the ion-channel receptor work?
- Turns chemical into electrical
- When signaling molecule binds to the receptor, it opens the channel and the impulse goes inside along with sodium
How does the G-protein receptor work?
- Signaling molecule binds to receptor
- G-protein is activated
- G-protein drops GDP and gains GTP
- Starts releasing proteins to alter the cell
- When finished, phosphate group is dropped and becomes GDP again
How does the enzyme linked channel receptor work?
- Signalling molecule binds to receptor
- Activates enzymatic phosphorylation
- ATP becomes ADP
- Phosphate group binds to tyrosine kinase linked to the cell receptor
How does cAMP transduct signals?
- G-protein activates
- Binds to adenylyl cyclase
- Adenylyl cyclase turns ATP into cAMP
- cAMP becomes secondary messenger and amplifies original signal
How are G proteins activated and deactivated
Actiavted- releases GDP and gains GTP
Deactivated- Drops a phosphate group and becomes GDP again
What do G proteins activate?
Activate adenylyl cyclase or activated other proteins to stimulate change in the cell
What does cAMP activate?
Protein kinase enzymes that heighten signal transmission
How do intracellular signaling ligands and receptors differ from those on the cell surface?
They pass through the membrane and enter the nucleus to bind directly to the DNA and transcribe it. Normally the signal molecule binds to the receptor and changes the cell activity without touching the DNA
How are intracellular hormone receptors activated and how do they effect gene expression?
- Signaling molecule travels through the cell membrane and into the nucleus
- Binds to the receptor on the DNA and begins the transcription process
- Transcription decides if the gene is expressed or repressed
- mRNA carries out new change and begins to alter cell activity
How do mutations in the signal transduction lead to cancer?
- If a signal to stop is never received by the cell, it will keep sending out changes to the cell.
- G protein will never drop its phosphate group and the cells will begin to multiply
Why do cells need to be small?
So food can be carried in and waste carried out in a reasonable amount of time
What are four differences between eukaryotic and prokaryotic cells?
- Animal cells
- DNA in nucleus
- Usually large
- Usually multicellular
- Needs oxygen
- Membrane bound organelle
- DNA throughout
- Usually small
- Single celled
- May not need oxygen
- non-membrane bound organelles
Why do plant cells need chloroplasts, vacuoles and cell walls but animal cells do not?
Plants cannot move to get food and water so they must take it from the sun. Cell walls give the plant extra protection and structure that animal cells do not need. Animals can move on their own and plants cannot so they need to be able to make and store resources and energy.
How were Mitochondria made?
- Aerobic bacteria invaded a cell
- They chilled together and became mitochondria
- Still has its own membrane and circular DNA
How were chloroplasts made?
- Photosynthetic bacteria invaded the cell
- They chilled and eventually made the chloroplast
- Contains DNA
- Control center
- Contains enzymes to synthesize lipids and carbohydrates
- Synthesizes phospholipids
- Contains ribosomes
- Makes proteins
- Made of RNA and protein
- Reads RNA and makes instructions for protein construction
Carry things around the cell
- Packages things for the cell
- Modifies proteins and makes sure they were made right
Recycling center of the cell
- Site of metabolic reactions
- Breaks down things (like fatty acids)
- Found in plants
- Stores waste and water
- Maintains hydrostatic pressure
Maintains structure, mobility and shape of the cell
Cilia and Flagella
- Little tails to help organisms get around
- (like sperm cells)
- Gives structure and rigidity to the cell
- Maintains a certain shape
What is the importance of the nucleolus
Makes rRNA that is used by the ribosome
What are the differences between the rough ER and the smooth ER?
Smooth ER- synthesizes lipids and carbohydrates
- Rough ER- has ribosomes to form seal on ER and force proteins to enter
- Creates proteins which are then transported using vesicles
- Signal sequencing dictates which protein is meant to go where and how it should be made
What are the functions of the vesicle and the Golgi Complex?
- Vesicles bring proteins from the rough ER to the Golgi Complex
- The cis face of the golgi is the entrance where proteins are modified
- The trans face is the exit where the proteins are packaged for their trip to their destination
What is the function of lysosomes and peroxisomes?
- Lysosomes are the recycling center, they store and get rid of waste
- Peroxisomes perform metabolic reactions and breakdown things like long fatty chains
What is Pompe disease?
Over accumulation of glycogen due to a lack of enzyme meant to break it down
What is ALD
Deterioration of the myelin sheath due to an over accumulation of very long fatty chains because of an enzymatic defect
What is the purpose of the vacuole?
- Store water and waste
- Maintain hydrostatic pressure
What is the general function of the cytoskeleton?
- Maintains structure, shape and mobility of the cell
- Microtubules- cell framework
- Intermediate filaments- help with mechanical strength and cell shape
- Microfilaments- bundles of fibers for support of various cell structures
Movement of water through semi-permeable membrane from higher concentration to lower concentration
- Has a small amount of solute compared to the amount of water
- Water is moving into the cell
- A fluid that is equal concentration water and dissolved material (ex: salt water)
- Water molecules pass in and out of the cell at an equal rate
- There is a lot of solute compared to the amount of water
- Water is moving out of the cell
Substances pass in and out of the cell and move about the cell in random motion
Integral (transmembrane) protein
- Protein that is firmly bound to the membrane
- Transmembrane protein extends completely through the membrane
Not embedded in the membrane but is attached to the integral protein
Protein that has received sugar from the rough ER lumen
Lipid that has received sugar
What are the membrane protein functions?
Anchoring, passive and active transport, signal transduction, cell recognition, intercellular junction
What is the structure of the transmembrane proteins?
Cell shrinks when the solution it is in is hypertonic
Solution traveling from one concentration to another
When a plant cell shrinks and the plasma membrane separates from the cell wall
What is facilitated diffusion?
A specific protein makes the membrane permeable to a specific enzyme, which then becomes the one thing allowed into or out of the cell
How is facilitated diffusion different from passive diffusion?
Facilitated diffusion only allows a certain enzyme in or out while passive diffusion is random
What is active transport?
A substance is pumped from a lower concentration to a higher concentration using ATP
How is sodium and potassium transport related?
ATP pumps sodium out of the cell and potassium into the cell
How does active transport related to symports and antiports?
Symports and antiports use ATP indirectly (through sodium/potassium pump) while active transport uses ATP directly
2 substances traveling in the same direction
2 substances traveling in different directions
Substances are traveling into the membrane
Receptor- mediated endocytosis
Molecules combine with receptor proteins in the plasma membrane
Cell ejects waste or specific substances like hormones
Cell eats large food particles or bacteria
Cell drinks dissolved substances