Unit 3: The Working Cell Flashcards
Why is the cell membrane called a fluid mosaic model?
The membrane is mosaic because it has diverse protein molecules embedded in a framework of phospholipids. It is fluid because most of the molecules can drift around the membrane
What makes the membrane fluid (why is good for the membrane) and what makes it mosaic?
Double bonds in the unsaturated fatty acid tails kid the phospholipids make kinks that prevent the phospholipids from packing tightly together, making it fluid this is good for the membrane because it stabilizes the membrane at warm temperatures and keeps it fluid a low temperatures.
The position of proteins in the phospholipid bilayer and their varied functions make it mosaic
What are the two main components of the cell membrane
Phospholipids and proteins
What is the role of cholesterol in the cell membrane?
Helps stabilize membranes at warm temperatures and keeps them fluid at low temperatures
Glycoproteins
Involved in cell to cell recognition
Integrins
Span the membrane, attach to the cytoskeleton and give the membrane a stronger framework
Enzymes
Work as a team to carry out reactions
Receptors
Has a shape that fits a specific messenger
Transport proteins
Helps certain molecules enter and exit the cell
Plasma membrane proteins
Form junctions between cells
What types of molecules can pass through the semi permeable membrane? Which types can’t?
Small, nonpolar molecules can pass
Large, polar molecules can’t
Diffusion
The tendency of particles to spread out evenly in spaces, moving from highly concentrated areas to low concentrated areas
Passive transport
The diffusion of a substance across a biological membrane
How does diffusion work in our lungs?
Diffusion down a concentration gradient is how oxygen enters red blood cells and carbon dioxide passes out of them
Why are oxygen and carbon dioxide able to easily diffuse across the membrane?
They are both nonpolar
What kind of molecules can not leave by diffusion? What helps them?
Ions and polar molecules. They can enter and leave if they are moving down their concentration gradients and have transport proteins
Osmosis
Diffusion of water molecules across a selectively permeable membrane
Solute
Substance being dissolved
Tonicity
What does it depend on?
The ability of a solution to cause a cell to gain or lose water
Depends on it’s concentration if solutes that can not across the plasma membrane relative to the concentrations of solutes in the cell
Facilitated diffusion
Does it require energy? What is the driving force?
When a protein helps move a substance down its concentration gradient
Does not require energy, the driving force is the concentration gradient
How does the number of transport proteins in a cell affect the rate of diffusion?
The greater number of transport proteins, the faster its rate of diffusion across the membrane
What types of substances need to use facilitated diffusion?
Sugars, amino acids, ions, water
What are aquaporins?
Transport proteins that make it possible to diffuse water in and out of certain cells quickly
Active transport
What molecule supplies energy for active transport?
Active transport expands energy in order to move a solute against its concentration gradient
ATP
Steps of active transport
- Solute binds to transport protein
- ATP transfers one of its phosphate groups to the transport proteins
- Protein changes shape so the solute is released in the other side of the membrane
- Phosphate group detaches and protein returns to its original shape
What does active transport allow cells to maintain?
Allows them to maintain concentrations of small molecules that are different from concentrations of its surroundings
Why is the sodium potassium pump important for nerve signaling?
Nerve signals depend on the concentration differences between potassium ions and sodium ions (higher K concentration inside cell and lower Na concentration ) the sodium potassium pump helps cells maintain the steep gradients by moving Na and K across the membrane against their concentration gradients
Kinetic energy
Energy of motion
Potential energy
Stored energy
Chemical energy
Potential energy for a chemical reaction
Thermodynamics
Study of energy transformations that occur in a collection of matter
First and second law of thermodynamics
- The energy in the universe is constant
2. Energy conversions increase the entropy (disorder) of the universe
Entropy
Measure of disorder
Exergonic reaction
Chemical reaction that releases energy
Endergonic reaction
Creates products rich in potential energy
ATP
Adenosine triphosphate-powers nearly all forms of cellular work
ADP
Adenine diphosphate-when bonds connecting phosphate groups become broken by hydrolysis and energy is released
Phosphorylation
The hydrolysis of ATP releases energy by transferring the third phosphate group from ATP to another molecule
Cofactors
Non protein helpers for enzymes
Coenzymes
A cofactor that is an organic molecule
Factors affecting fluidity
- liquids ability to shift
- temperature (hot=more fluid)
- cholesterol
- length of fatty acid (long=more immobile)
- degree of saturation (unsaturated=more fluid)
Glycoalyx
Layer of carbohydrates on extra cellular side
Glycolipids
Attached to lipids
Glycoprotein
Sugar attached to protein r
Proteoglycons
Long sugars attached to proteins
Isotonic
When the solute concentration of a cell and its environment are equal, so the cell gains and loses water at the same rate
Hypotonic
A solution with a solute concentration lower than the concentration of the cell
Hypertonic
A solution with a higher solute concentration
What happens to an animal cell when it’s placed in a HYPOTONIC solution?
The cell gains water and lyses (bursts)
What happens to an animal cell when it’s placed in a HYPERTONIC solution?
The cell shrivels and can die from water loss-crenation
Why are water balance issues different in plant, prokaryote, and fungi cell?
Because they have a cell wall
What happens when a plant cell is placed in an ISOTONIC solution?
It will be flaccid (limp)
What happens when a plant cell is placed in a HYPOTONIC solution?
It becomes turgid (very firm) when water flows in
What happens when a plant cell is placed in a HYPERTONIC solution?
The cell loses water and shrivels, the plasma membrane pulls away from the cell wall, a process called plasmolysis
Importance of contractile vacuole in freshwater protists
Freshwater protists live in hypotonic environments and there is a constant net osmosis of water into the cell.The contractile vacuoles expel excess water, preventing the cell from bursting.
Channel proteins
Molecules use these as a tunnel through the membrane
Carrier proteins
Binds to its passenger, changes shape and releases its passenger on the other side
Bulk transport
Transporting many substances in a vesicle at once
Phagocytosis
“Cellular eating” takes in large molecules of cells
Pinocytosis
“Cellular drinking” takes in dissolved solutes
Receptor-mediated endocytosis
Receptor proteins for specific molecules are embedded in regions of the membrane that are lined by a layer of cost proteins
