Cells and Organelles Lectures 5/6 Flashcards
Cells
the building blocks of life, come from preexisting cells, smallest form, and maintain cellular homeostasis
Cells are microscopic and characteristics relate to function
Cytology
study of cells
sex cells
haploid 23 chromosomal cells that are each unique and come from parents. (oocytes and spermatoza)
somatic cells
dipole 46 chromosome cells, each are idenifcal to mother cell and ensure cells are repaired and replaced
Cell Theory
- All organisms have one or more cells
- Cells come from the division of other cells
- cells carry out functions of the basic units of life ( cells determine function) Principle of Com. Structure function
cell components
cell membrane
cytoplasm ( cytosol, organelles)
Cell/Plasma Membrane
Contains receptors to detect changes. A fluid mosaic model made of phospholipids bilayer and cholesterol.
1. barrier: separates the ECF from the ICF
2. Control: controls entry of ions, nutrients and releases waste
3. First part of the cell to contact changes (stimulus)
4. connection between plasma membrane and inside
4 Main Functions Membrane
- Physical Barrier: excloses the cell separates the cytoplasm from the ECF
- Selective Permeable: determines what enters and exists
- Communication to inside cell: plasma proteins interact with chemical receptors inside the cell
- Cell recognition: surface carbs can recognize other cells with glycocalyx
Membrane Lipids
Two main membrane types:
Phospholipids: form the membranes bilayer, hydrophilic head of the phosphate head and a hydrophobic fatty acid tail.
Cholesterol : steroid that provides structure
Cell Membrane Diagram
Contains a phospholipid bilayer arrangement with polar heads and non polar tails
Has peripheral and intergal proteins
Cholesterol provides structure to the membrane
Intergral and Peripheral Proteins (plasma proteins)
Intergral (channel carriers) go through the membrane
Peripheral (enzymes) on the surface and can leave
Functional Proteins
Anchoring proteins: attach to cell to cell in ECF or they bind membrane to other organelles in cytoskeleton.
Recognition protein: immune cells, identify other cells in body normal/abnormal ,glycoproteins
Enzymes: catalyze reactions ( integral and peripheral) in cytosol or ECF.
Receptor: sensitive to ligands extraceullar mol. which trigger a response in the cell. Such as insulin, when it binds it prepares cell for uptake.
Carrier: (passive and active transport) Bind solutes and transport through membrane. Integreal proteins.
Channel: Allow to pass through membrane always intergral proteins.
Membrane Carbohydrates
Glycocalyx coats the outer surface of the membrane and does the following:
- protects/lubircate/ outer surface
-anchoring and locomotion
-specificty in bonding
-recognition
Membrane Transport
Active and Passive Transport
Active Transport
Transport that requires ATP
Passive Transport
No energy required
- diffusion
-facilaited diffisuion
-osmosis
Permability
Property of a plasma membrane that certain things can pass acorss the membrane.
Impermable: nothing passess
Freely: everything
Selective: certain things are allowed some are not , depends on solubility, size etc.
Diffusion
where molecules move from areas of higher concentration to area of lower concentration. Kinetic energy of molecules impacting.
Dynamic equilibrium: where the rate of diffusion in equals the rate of diffusion out. Goes down its concentration gradient.
Factors Affect Rate of Diffusion
- Distance: how far it has to diffuse, more distance is slower
- Molecule size: size, larger the slower
- temperature: increase in temperature= increase in KE so diffsuion
- Gradient Size: larger concentration gradient from high to low.
- Electrochemical forces: opposite charges are attracted
Simple Diffusion and Facilitated Diffusion
Simple Diffusion (lipid soluble) molecules diffuse through the membrane easily .
Facilitated Diffusion use carrier proteins to move in to the cell. Carrier and channel mediated are the two different types. Move down con. graident.
Carrier mediated facilitated diffusion
Intergral proteins bind specific ions/molecules across membrane.
Specificity ( specific to substances)
Saturation Limits ( availability limits rate of transport)
Regulation (cofactors affect carrier proteins)
Channel Mediated
Integral proteins (ions) move down through facilitated diffusion. Size and charge.
Co transport / counter transport
Cotransport – carrier transports two substances in the same direction across the cell membrane
Countertransport – One molecule moves into the cell while another moves out of the cell
Sodium-potassium pump
Through active transport, pumps 3 Na out for every 2 K+ in. This intergral protein uses ATP to pump them from low to high ( against) concentration gradient. ATP is hydrolised and loses one phosphate releasing energy.
Membrane potential is created from the [Na] positive being greater outside and the [k] negative greater inside. Electrochemical gradient created -70MV
1. There is a high con. of Na+ outside and K+ inside. Three Na+ bind to the pump causing the hydrolysis of ATP , this energy phosphyrolyates the pump
2. This phosphorylation causes the pump to have a low afinity for Na+, releasing them.
3. Pump then binds two K+ causing it to become dephopshoralated and will release a phosphate resuming it to its original concentration.
4. Pump binds ATP releases K+ inside Na+ is ready to bind again.
Receptor mediated
Uses receptors on the protein enabling the cell to ingest the vesicle . They may be released or digested by lyososme in the cell. Receptor Mediated brings specific ligands into the cell in higher concentrations. Specific to particle size.
