Unit 2 - Cells Flashcards
Mitochondria Structure + Function
Structure:
- Two layers of membrane
- Inner membrane is folded to maximize the amount of chemical reactions occuring and the membrane can hold more enzymes
- More surface area = more ATP being made!
- cristae - Folds of the inner membrane
- matrix - The innermost area of the mitochondria
- Matrix stores enzymes, proteins, ribosomes, and mitochondrial DNA
Function:
- Produces the energy molecule ATP through aerobic respiration
- Uses glucose to generate ATP
- proteins in the mitochondria help with production of ATP and other things
Chloroplast Structure + Function
Structure:
- Contains the pigment chlorophyll (which gives plants/protists green coloration).
- Thylakoids - Flat green pancakes that store chlorophyll and collect sun energy for the first part of photosynthesis
- Grana - Stacks of thylakoids - increase surface area
- Stroma - Fluid that surrounds the thylakoids. Site where the second half of photosynthesis occurs. Also contains ribosomes and chloroplast DNA
- Chloroplasts are considered plastids- which are organelles that contain pigments surrounded by a membrane. - Plastids have their own DNA and ribosomes
Function:
- Performs photosynthesis in plants and algae
- Chlorophyll captures energy from the sun and carbon from CO2 in the air to turn into glucose
Vesicles Function
- Small membranous sacs that store materials or transport/secrete materials around/out of cells
- Secretory vesicles: Fuse with the cell membrane to deliver membrane proteins or to release secretory proteins. This is done by exocytosis. Active transport because it uses energy.
Vacuoles - Type of Vesicle Structure + Function
Structure:
- membrane-bound sacs
Function:
- Larger vesicles that function as storage for food, water, or waste
- Large Central Vacuoles - found in plant cells
- Stores water and exerts an outward force (turgor pressure) on the cell wall to provide rigidity and structure to plants
- When plants wilt, they need water to replenish their large central vacuoles!
Contractile Vesicles - Type of Vesicle Function
- Used to dispel excess water in unicellular eukaryotes
- Prevents the single-celled organism from absorbing too much water from its environment
- Organisms that live in saltwater don’t have these because organisms that are in water are passively losing water so they don’t want to actively lose it as well.
Prokaryotic vs Eukaryotic Cells
Similarities:
Both have ribosomes
Both have plasma membranes
Both have DNA somewhere in the cell
Differences:
Prokaryote has no nucleus and no membrane bound organelles
Eukaryote has a nucleus and membrane bound organelles
Prokaryote has cell wall, eukaryotes only have cells walls if they are plant cells
DNA is in nucleus in eukaryotes
DNA is in a nucleoid in prokaryotes
Prokaryotes:
Plasma membrane
cytosol/cytoplasm
Genetic material (chromosomes)
Ribosomes
Eukaryotes:
Have internal membranes that: compartmentalize their functions (organelles), isolate specialized environments (pH, molecules), increase internal surface area for reactions.
Nucleus with DNA inside
Mitochondria vs Chloroplasts
Similarities:
Both have DNA, intermembrane space, inner membrane, ribosomes
Both are the same size, around 1um
Inner folds and space between folds to increase surface area for more efficient cellular processes
Differences:
Mitochondria used to make ATP
Chloroplasts used to make food
Lysosomes and Peroxisomes - Type of Vesicle Function
- Lysosomes: the cell’s recycling centers, use acid hydrolases to break down waste into reusable parts through autophagy and crinophagy. Release enzymes into cytoplasm to perform apoptosis.
- Peroxisomes: protect cells by isolating and breaking down harmful hydrogen peroxide into water and oxygen.
Endosymbiotic theory
Certain organelles, like mitochondria and chloroplasts, originated as free-living bacteria that were engulfed by prokaryotic cells, forming a symbiotic relationship. A prokaryotic cell folded its plasma membrane and engulfed organelles to form eukaryotic cells.
How do mitochondria and chloroplasts show evidence of the endosymbiotic theory?
Mitochondria and chloroplasts contain their own DNA, which resembles prokaryotic DNA rather than eukaryotic nuclear DNA. They have similar shape and size to bacteria. The folding of the cell membrane eventually led to the development of the endomembrane system and the nucleus. Mitochondria and some prokaryotes share similar metabolic reactions that produce
ATP.
Plant vs Animal Cells
Similarities:
Nucleus
ER
Golgi Body
Mitochondria
Cytoskeleton
Vesicles/Vacuoles
Peroxisomes
Nuclear Envelope (also called the nuclear membrane is a double membrane that encloses the nucleus of eukaryotic cells)
Nucleolus
Differences:
Plant cells: Chloroplast, Large Central Vacuole, cell wall
Animal cells: small vacuole, Centrioles, Gap Junctions, Tight Junctions, Lysosomes, Cilia, Microvilli, Flagella
all cells have which organelles/structures?
Cell membrane
Ribosomes
Cytoplasm
DNA/RNA
Prokaryotes vs Plant/Animal Cells
Differences:
- Nucleoid (an unevenly shaped region that stores genetic material)
- Pili (a hair-like structure associated with bacterial adhesion)
- Capsule (an outer protective covering found in the bacterial cells)
- Plasmids (small circular DNA molecule found in bacteria, physically separate from chromosomal DNA)
Similarities:
- has cell wall like plant cell
- has flagella like animal cell
- has everything else all cells have (refer to other flashcard)
Endomembrane System
The genetic material in the nucleus codes the instructions to synthesize proteins. The ribosomes in the rough ER get the instructions from the nucleus by mRNA and then synthesize the proteins. The proteins then travel from the rough ER to the golgi apparatus in vesicles, where new vesicles capture the proteins and carrying them to the cell membrane to get shipped out of the cell. Exocytosis.
Extracellular Matrix
- Animal cells have an extracellular matrix (ECM), networks of connective proteins (like collagen) outside the cell membrane
- Think of the ECM as an external support scaffold and how cells can adhere together better
- Ex: Collagen defects cause tissues to “tear” very easily
Cell Junctions
Cell junctions are multiprotein complexes that provide contact or adhesion between neighboring cells or between a cell and the extracellular matrix.
Animal Cells have a few types of junctions:
- Tight junctions: Fasten together plasma membranes of adjacent cells, like gluing them together. This helps prevent substances leaking through a membrane layer. For example, your stomach does not leak because the tight junctions seal up the stomach lining. Leaking stomach acid would be terrible!!! Ulcers result when the tight junctions are broken by bacteria or by diet.
- Adhering junctions: Fasten cells to one another. These make tissues strong, they actually connect to the cytoskeletons inside cells, like sewing cells together. Heart tissues and the skin have a lot of these, as they are subject to stretching and abrasion due to movement.
- Gap junctions: Closable channels/tubes that connect the cytoplasm of adjoining animal cells. They let water, ions, and SMALL molecules to pass from cell to cell through the cytoplasm. These channels let whole regions of cells respond to one stimulus. Heart muscles and nerve cells have a lot of these, to do coordinated actions.
Plant cells:
- plasmodesmata: passageways in the cell walls, connecting the cytoplasms of adjacent cells to allow communication
Cytoskeleton Function
- Network of structural protein filaments extending throughout the cytoplasm
- Reinforce, organize, and move cell structures, or can even move the whole cell
Cell Wall Function + what plant, fungi, bacteria cell walls are made of
Cross-linked networks of structural polysaccharides (carbohydrates)
Plant cell walls are made of cellulose
Fungi cell walls are made of chitin
Bacterial cell walls are made of peptidoglycan
Endoplasmic Reticulum (Rough and Smooth) Function
Rough:
- has ribosomes
- Proteins are packaged into vesicles and sent to the Golgi apparatus for further processing or to their final destinations
- site where protein synthesis occurs (ER does not synthesize the proteins though)
Smooth
- has no ribosomes
- responsible for synthesizing lipids, including phospholipids and cholesterol
Golgi Apparatus Function
- After proteins are synthesized in the Rough ER, they are transported to the Golgi apparatus, where they are modified
- These modifications help proteins fold correctly, become functional, and get directed to their appropriate destinations
- The Golgi apparatus also modifies lipids
- The Golgi apparatus sorts proteins and lipids, packaging them into vesicles
Ribosomes Function
- Ribosomes translate the genetic code from messenger RNA (mRNA) into a specific sequence of amino acids, forming proteins. This process is called translation.
- can be free ribosomes in the cytoplasm or ribosomes in the rough ER
Selective permeability
The ability of a cell membrane to control which substances and how much enter or leave the cell. Allows the cell to maintain a difference between its internal environment and extracellular fluid. Supplies the cell with nutrients, removes wastes, and maintains volume and pH
order that molecules can pass through cell membrane
Small nonpolar can pass through most easily, then small polar, then large polar, then ions cannot pass through at all (without help)
Passive transport
High concentration to low concentration, doesn’t require energy
Simple diffusion
type of passive transport, small, uncharged molecules pass through phospholipids
Facilitated diffusion
type of passive transport, proteins are necessary, large or charged molecules pass through membrane proteins
Glucose Transport
Glucose uses a carrier protein called GLUT for facilitated diffusion across the membrane. Protein changes conformation to allow glucose to enter; reverts back when diffusion is complete
Sodium/Potassium Ion Channels
Allow charged molecules like sodium and potassium to go through the cell membrane. In most neurons, potassium is present at higher concentrations inside the cell than outside. In contrast, sodium is usually present at higher concentrations outside the cell. Ion channels allow equilibrium to be reached. This is passive transport.
Which factors does rate of diffusion depend on?
- Size of molecules involved (larger molecules will diffuse slower)
- Temperature (diffusion happens faster with higher temperatures)
- Steepness of the concentration gradient (more concentrated areas will diffuse out faster)
- Charge of molecules involved
- Environment it is diffusing in (think water vs. oil),
- Pressure (higher pressure higher rate, lower pressure lower rate, this is because higher pressure leads to more collision of molecules)
Osmosis
Diffusion of water into the cell
Water does BOTH types of passive transport. Osmosis is the diffusion of water through phospholipid membrane (slowly) via simple diffusion. Osmosis can also occur through channel proteins called aquaporins via facilitated diffusion at a much faster rate. Water moves from the side of the membrane with lower osmolarity to the side with higher osmolarity. Osmolarity is the concentration of solute in a solution.
Why and which way does water move in liquids with a solute + water?
Water will diffuse via osmosis to the side of the membrane with the highest solute concentration until dynamic equilibrium is reached. Water moves from high concentration to low concentration, because the other solute CAN’T cross the semipermeable membrane, but water CAN.
Tonicity
the ability of a solution to affect the movement of water across a cell membrane
Isotonic
the cell with the same solute concentration on either side. Water moves into and out of the cell at equal rates. Happy cells!
isotonic -> i so happy
Hypotonic
the cell with the solution with a lower solute concentration outside the cell, so water will move INTO the cell to dilute the solutes there. Cells can swell, lyse (burst), and die.
Hypertonic
the cell with the solution with a higher solute concentration outside the cell, so water moves OUT of the cell in an attempt to dilute the solutes there. Cells become shriveled, dehydrated, and can die.
Water potential
ψ (psi)
The measure of the ability of water molecules to move freely in a solution
How can the direction of osmosis be determined using water potential?
- By determining the water potential inside a cell and outside a cell, the direction of osmosis can be determined.
- In pure water, where there is no solute, water potential is HIGH because all of the water molecules are free to move
- When a solute is dissolved in water, water potential decreases because there are less “free” water molecules to diffuse
- The more free water molecules, the higher the water potential
- 0 is the highest water potential
equation for water potential
Ψ = ψp + ψs
ψp = pressure potential
Ψs = solute potential
In an open container, the pressure potential of water is 0
How does water move in the context of water potential?
From high water potential to low water potential
In other words, from LOWER solute to HIGHER solute
Explain what contributes to the different polarities within a phospholipid
Lipids with double bonds between carbons makes the molecules unsaturated. The many carbons and hydrogens make the tails a lipid and also nonpolar (not in 1:2:1 ratio). The head is in 1:2:1 ratio making it a carb and also polar. The atoms involved in the hydrophilic head (typically oxygen and nitrogen) have higher electronegativities compared to carbon and hydrogen found in the tails. This difference in electronegativity leads to the formation of polar bonds in the head region and non-polar bonds in the tails.
How do phospholipid molecules lead to compartmentalization of a cell?
Separating and isolating reactions, makes it happen at proper, rate, proper ph, proper concentration
Explain why the flexibility (fluidity) of a membrane increases when more of the phospholipids in the layers contain double bonds
Because of the kinks created by double bonds, phospholipids with unsaturated fatty acids cannot align as closely as those with saturated tails.
Peripheral Proteins
Peripheral membrane protein is a protein that is found temporarily attached to the cell membrane. Peripheral membrane proteins attach to the membrane but are not embedded in it. Helps with support, communication, enzymes, and molecule transfer in the cell. Because they do not interact with the hydrophobic core of the membrane, peripheral proteins are generally soluble in aqueous solutions and can be removed from the membrane without disrupting the lipid bilayer.
Transmembrane Proteins
Transmembrane proteins are integral membrane proteins that go through the entire lipid bilayer of cell membranes.
- hydrophobic R groups interact with the lipid tails
- hydrophilic R groups exposed to the aqueous environment inside and outside the cell
- the amino acid interactions (hydrogen bonding and other forces) allows them to be anchors into the membrane
- Many transmembrane proteins function as channels or transporters, facilitating the movement of ions, small molecules, or larger substrates across the membrane. Examples include ion channels (e.g., sodium and potassium channels) and glucose transporters.
Cholesterol
- type of lipid molecule
- helps to maintain membrane fluidity and stability, allowing cells to remain flexible and functional
- embedded in cell membrane towards phospholipid tails
- forms weak attractive forces with multiple phospholipids in the bilayer
Fluid Mosaic Model
- Describes the organization of cell membranes
- Phospholipids drift and move like a fluid- they can flip sides or travel to different locations within the membrane
- Mosaic: Made of many proteins, glycoproteins, steroids, and cholesterol molecules embedded in the phospholipids.
Explain how cholesterol relates to the flexibility of the membrane in different temperatures
Cholesterol molecules embedded within the bilayer help to maintain membrane fluidity over a range of temperatures.
In higher temperatures (like our body temperature), cholesterol sticks to phospholipids and “packs” them together (decreases fluidity). This makes the membrane slightly more rigid and less permeable to small molecules. This helps the cell membrane from falling apart and the cells from losing too much water/other molecules.
In colder temperatures, cholesterol will prevent phospholipids from packing together too closely (increases fluidity)
Carrier protein
- transport of specific substances across cell membranes
- Unlike channel proteins, which provide a passageway for molecules to flow through, carrier proteins change shape to allow molecules to enter; reverts back when diffusion is complete
- passive transport/facilitated diffusion
Ion channel
- allow charged molecules like sodium and potassium to go through cell membrane
- In most neurons, potassium is present at higher concentrations inside the cell than outside. In contrast, sodium is usually present at higher concentrations outside the cell. Ion channels allow equilibrium to be reached
- passive transport/facilitated diffusion
Signal proteins
- include hormones, neurotransmitters, cytokines, and growth factors
- When a signaling protein (like a hormone or neurotransmitter) is released, it binds to specific receptors on the target cell, which then triggers a response within that cell.
Aquaporins
- channels to allow water molecules to pass in and out of cells
- allow water to pass through at a faster rate than just going through phospholipids because more water can go through the channel
- type of transmembrane protein
Glycoproteins
- proteins that have carbohydrate (sugar) attached to them
- immune responses, hormone signaling, and cell communication
- used for cell recognition and communication.
- helps your cells recognize other cells that belong to YOU along with glycolipids. This is why organ donors need to be “matched” and even then, organ donor recipients need to take immunosuppressant medication to prevent organ rejection (not recognizing the new organ and trying to attack it)
Glycolipids
- lipid with carbohydrate attached
- used for recognition, signaling, and stability
- helps your cells recognize other cells that belong to YOU along with glycoproteins. This is why organ donors need to be “matched” and even then, organ donor recipients need to take immunosuppressant medication to prevent organ rejection (not recognizing the new organ and trying to attack it)
Protein Pumps
- Protein pumps are activated when they are phosphorylated (take a phosphate from ATP)
- This causes a change in the protein’s shape
- Think of phosphorylation as an on/off switch
- Will know if its a protein pump because the picture will have ATP on it or it will say pump
- active transport
Sodium Potassium Pump (Na+/K+ pump)
- The Na+/K+ pump maintains high concentrations of sodium outside of neurons and high concentrations of potassium inside neurons
- This moves sodium and potassium against their concentration gradients
- active transport
Proton Pumps & Polarization of a Membrane
- Proton (H+) pumps create an electrochemical gradient across a membrane, known as a membrane protein, by pumping protons out of the cell
- The inside of the cell is negatively charged; positively charged ions are attracted to the negative charges on the inside
- Think of it as creating potential energy to be used later
- Active transport
Bulk Transport
- Cells can ingest (endocytosis ) or secrete (exocytosis) large particles
- Requires energy to move vesicles out and to “engulf” and create vesicles when taking in materials
- Active transport
Phagocytosis/Pinocytosis
- Phagocytosis: ingesting food
- Pinocytosis: ingesting liquid
- type of endocytosis
Receptor Mediated Endocytosis
- Receptor proteins on the cell surface are used to capture a specific target molecule
- The receptors, which are transmembrane proteins, cluster in regions of the plasma membrane known as coated pits
- When the receptors bind to their specific target molecule, endocytosis is triggered, and the receptors and their attached molecules are taken into the cell in a vesicle
