Chapter 3: Cells Flashcards
Define Cell
are the basic structural and functional units of living organisms.
They vary in size, shape, and function.
3 main parts of a cell
Plasma (cell) membrane
Cytoplasm
Nucleus
Plasma Membrane
• Forms the boundaries of the cell → separates intracellular from extracellular fluid.
• Structure is described by “fluid mosaic model”
• Phospholipid molecules are arranged in 2 layers (bilayer).
> polar heads (hydrophilic)
> nonpolar tails (hydrophobic)
> heads facing both sides of the membrane and their tails pointing toward each other.
Function: selectively permeable barrier that regulates the flow of materials into and out of cells.
Component of the plasma membrane
98% Lipids
- 76% phospholipids
- 20% cholestorol
- 5% glycolipids
2% Proteins
What is a glycolipid?
- is a phospholipid that has a sugar lipid attached to it
- Glycoproteins are used as biologic markers. Everycell type has a dif pattern of sugars and we can use that as recognition markers
Two types of Membrane Proteins
1) Integral (transmembrane) proteins
2) Peripheral membrane proteins:
Many membrane proteins are glycoproteins with branching sugar groups facing the extracellular fluid.
Integral (transmembrane) proteins
extend through the phospholipid bilayer.
Peripheral membrane proteins:
are associated loosely with only one side of the membrane.
List 5 Functions of Membrane Proteins
1) Transporters → as channels or carriers.
2) Receptors for chemical messengers.
3) Enzymes that catalyze reactions.
4) Markers in cell recognition.
5) Anchors to cell’s cytoskeleton. (Some proteins anchor cells to each other or provide structural stability)
Membrane Permeability
- What’s it mean?
- What can pass through?
- Is there any exceptions?
- A membrane is permeable to substances that can pass through it and impermeable to substances that can’t.
- Cell membranes are selectively permeable – allow some things to pass more easily than others.
- Usually permeable to nonpolar, uncharged and small molecules (exception: water).
- Usually impermeable to ions, charged or polar molecules.
- Water despite being a polar molecule can still clip through the membrane (major exection), but normally things that have a charge can’t get through the memebrane withownt help
2 Types of transport of subrange across the membrane
Passive Processes:
-substances move down their concentration gradients (from [high] to [low]) with no energy required from the cell.
Active Processes:
-energy is required to move substances against their concentration gradients (from [low] to [high]) or for substances otherwise unable to pass.
List 2 types of Passive Transport
-Difusion
>Simple
>Facilitated
- Channel-mediated
- Carrier-mediated
-OsmosisDiffusion
- Define
- How it the rate effected?
- List 2 types
• Net movement of molecules from an area of [high] to an area of [low] until equilibrium is reached. • Rate is affected by: - temperature - particle size* - [ ] gradient - surface area** - distance***
There are two types of diffusion:
i) Simple
ii) Facilitated
- Smaller the particles, the faster they move
- *The more surface areas the more space to move across the membrane the higher the rate
- **If the memb is thicker/a farther distance it’ll slow down the date
Simple Diffusion
nonpolar and lipid soluble substances diffuse directly through the lipid bilayer.
eg. CO2, O2, fat-soluble vitamins (A, D, E, K)
Facilitated Diffusion
- What is it?
- 2 types
polar & charged molecules require transmembrane proteins as carriers, or use ion channels to move through the lipid bilayer.
eg. glucose, amino acids, ions
Carrier-mediated facilitated diffusion : gluc binds to protein, the protein changes shape and releases on the other side
Channel-mediated facilitated diffusion : K+ ion can’t get through so it passes through the channel protein, some have a gate, some are constantly open with no gate
NO ENERGY REQUIRED: they flow through their [ ] gradient but they can’t make it through the memb on their own (too big, charged, etc.)
Osmosis
• Net movement of water from an area of high [water] to an area of low [water] through a semipermeable membrane, until equilibrium is reached.
Osmotic pressure:
• the ability of a solution to attract or draw in water.
• the greater the # of solute particles in a solution, the greater the osmotic pressure.
• the greater the tendency to draw in water.
3 Types of Active Transport
1) Primary active transport
2) Secondary active trasport
3) Vesicle trasport
- Exocytosis
- Endocytosis
Primary active transport
energy from ATP hydrolysis changes the shape of a transporter protein and it “pumps” a substance across the membrane.
eg. Na+/K+ pump transports Na+ out of cells and K+ in. NRG from breaking up ATP changes the shape and it pumps a substance across the memb
Secondary active trasport
coupled transport of 2 molecules using energy supplied by an ion gradient, maintained by a primary active transport pump.
eg. Na+ is co-transported with glucose
- Energy stored in a Na+ or H+ concentration gradient is used to drive other substances into the cell.
- They indirectly use energy from ATP.
- Prim is pumping ions across memb so that they’ll continute to flow down memb passively. Second allows another molecule to hitch a ride when this happens
Vesicle trasport
- Define
- 2 types
• used for large particles, macromolecules, and fluid.
Exocytosis:
- Moves a packaged vesicle out of the cell by fusing with the cell membrane & releasing its contents (eg. hormones, neurotransmitters.)
- exo = exit
Endocytosis:
-Moves materials into the cell by forming a vesicle.
An example of endocytosis is phagocytosis.
Phagocytosis
- Phagocytosis = cell eating.
- Cell engulfs a large particle
- This example shows a white blood cell engulfing a yeast cell.
- Protein receptors on outside of cell, binding triggers cytoplasmic extensions called pseudopods which eventually meet up forming a vesicle called a phasgosome. Then a lysosome will merge with the phagosome and then breaks down the molecule which can then be rejected from the cell
Cytoplasm:
- Define
- 2 major elements
• Cellular material b/t the plasma membrane & nucleus.
Has 2 major elements:
1) Cytosol:
2) Organelles: specialized structures that have specific functions necessary for the life of the cell.
- most organelles are membrane-bound
Cytosol
- fluid surrounding the organelles.
- is 75-90% water with dissolved and suspended components.
- is the site of many chemical reactions required for a cell’s existence.
Organelles
- specialized structures that have specific functions necessary for the life of the cell.
- most organelles are membrane-bound
