Bio - Cells Flashcards
What six things make up a living organism?
- Need energy
- Produce waste
- Respond and adapt to environment
- Reproduce
- Grow
- Made up of cells
Explain cell theory
- All organisms are composed of 1 or more cells
- Cell is the smallest functional unit of life
- All cells are produced from other cells
What is abiogenesis? How long was this theory accepted for?
Abiogenesis is the theory that life could arise from non-living matter. It was widely accepted for over 2000 years.
What is biogenesis?
Biogenesis is the theory that life could arise only from other living organisms.
Describe the composition of the cell membrane
- Composed of a double layer of phospholipids
- Proteins, lipids, and carbohydrates are embedded between the layers
What are the two main functions of a cell membrane?
- Biological barrier to prevent some substances from entering the cell in any way and surround each organelle to prevent unwanted chemical reactions.
- Selective filter to allow some, but not all, materials to cross.
What properties does a cell membrane have?
- All material entering & exiting the cell must cross the cell membrane
- Can change according to the cell’s needs
- Fluid and flexible, “fluid-mosaic” model
What is the phospholipid bilayer? What is it made out of?
Phospholipids:
- Each molecule has a head and a tail-
Heads are hydrophilic (water loving), dissolves in water, polar
Tails are hydrophobic (water fearing), H2O molecules push away tail, not polar
- Heads face out, tails are sandwiched between
- Two layers (bilayer)
What does Brownian motion state?
“In liquid or air, particles are in a constant, random motion.”
What is a concentration gradient? Which way are you moving if molecules go from a high concentration to a low concentration? How about a low conecntration to a high concentration?
Concentration Gradient:
Difference in concentration
High concentration to low concentration moving down
Low concentration to high concentration moving up
What is equilibrium? What 3(ish) things happen?
Equilibrium:
- Molecules are evenly distributed on either side of cell membrane
- Overall (net) flow does not change
- Do not stop moving after reaching balance
What are three ways molecules can be transported across the cell membrane in order to reach equilibrium?
- Passive transport (Diffusion, osmosis, facilitated diffusion)
- Active Transport
- Endo- and exocytosis
What is passive transport? What is it used for? What types are there?
- Does not require energy to move across membrane
- Used for molecules too large to pass through membrane or charged particles
Types:
- Diffusion - movement of particles from high to low
- Osmosis - movement of water molecules from high to low // Less solute, more water. More solute, less water //
- Facilitated diffusion -
- Carrier proteins - change shape to allow certain molecules (ie. sugar) to pass
- Channel proteins - charged ions in and out of cell (ie. Na+), must be opened
What is active transport? What is it used for?
- Requires energy (ATP) from cell to move particles from low concentration to high concentration
(against concentration gradient)
- Transport proteins bind to materials & change shape to move across membrane
Used by:
- Plant root cells to take in minerals from soil
- Remove waste in cells
What is endocytosis? When is it used? What direction does it go? What types are there?
- Membrane folds in, forms a pocket that turns into vesicle for transport
- Used when molecules cannot be moved by passive or active transport
- Into the cell
Types:
- Phagocytosis: “cell-eating”, ingest food/other solid materials
- Pinocytosis: “cell-drinking” ingest droplets of water/other fluids
- Receptor-mediated endocytosis: take in molecules (ie cholosterol), receptor on cell identies item and binds it to trigger endoycytosis
What is exocytosis? What is it used for? What direction does it go?
- Allows materials stored in vesicles/vacuoles to exit cell
- Used to release waste
- Out of the cell
What happens when the size of a cell increases?
Size increases, surface area to volume ratio decrease.