AP Bio Unit 2 Flashcards
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113 Terms
What is the structure of a ribosome?
Made of mRNA and proteins; no membrane; free in the cytosol or attached to the rough ER.
What is the main function of a ribosome?
Synthesizes proteins through translation.
Where are ribosomes found?
All cells, including prokaryotes and eukaryotes.
What is the structure of the rough ER?
A membrane network studded with ribosomes.
What is the main function of the rough ER?
Makes proteins for secretion, membranes, and lysosomes; compartmentalizes the cell.
Where is the rough ER found?
Eukaryotic cells.
What is the structure of the smooth ER?
A membrane network without ribosomes.
What is the main function of the smooth ER?
Lipid synthesis, detoxification, and Ca²⁺ storage.
Where is the smooth ER found?
Eukaryotic cells.
What is the structure of the Golgi complex?
Stacks of flattened membrane sacs called cisternae.
What is the main function of the Golgi complex?
Modifies, sorts, and packages proteins into vesicles.
Where is the Golgi complex found?
Eukaryotic cells.
What is the structure of a mitochondrion?
Double membrane with a folded inner membrane called cristae and an inner matrix.
What is the main function of a mitochondrion?
Cellular respiration and ATP production.
Where are mitochondria found?
Nearly all eukaryotic cells.
What is the structure of a lysosome?
A membrane-bound sac containing hydrolytic enzymes.
What is the main function of a lysosome?
Intracellular digestion, recycling old organelles, and involvement in apoptosis (programmed cell death).
Where are lysosomes mainly found?
Animal cells.
What is the structure of a vacuole?
A membrane-bound sac; plants often have a large central vacuole.
What is the main function of a vacuole?
Stores water, macromolecules, and waste; maintains turgor pressure in plants.
Where are vacuoles found?
Eukaryotic cells, including plant and animal cells.
What is the structure of a chloroplast?
Double membrane; thylakoids stacked into grana; fluid stroma.
What is the main function of a chloroplast?
Photosynthesis.
Where are chloroplasts found?
Plant cells and photosynthetic algae.
Cells need a high ______ to ________ ratio, to exchange materials efficiently
Surface area to volume
In a cell, surface area and volume effect….
Heat exchange
The phospholipid bilayer is also referred to as the?
Plama Membrane
Which proteins span the membrane?
Integral proteins.
Which proteins sit on the surface of the membrane?
Peripheral proteins.
What is the job of Chloestrol?
Regulates fluidity, and keeps the membrane from becoming too fluid when warm or too stiff when cold.
What are glycoproteins and glycolipids made from?
Carbohydrates on the outer surface.
What do glycoproteins and glycolipids act in?
Cell recognition and signaling.
Membranes are _________ permeable
Selectively.
What types of molecules are small and nonpolar?
O₂, CO₂, N₂, and steroid hormones.
Can small nonpolar molecules cross the phospholipid bilayer directly?
Yes, freely.
What are examples of small polar, uncharged molecules?
H₂O and glycerol.
Can small polar, uncharged molecules cross the phospholipid bilayer directly?
Yes, in small amounts. Water moves much faster through aquaporins.
What are examples of large polar molecules?
Glucose and sucrose.
Can large polar molecules cross the phospholipid bilayer directly?
No. They require transport proteins.
What are examples of ions that cross cell membranes?
Na⁺, K⁺, Cl⁻, H⁺, and Ca²⁺.
Can ions cross the phospholipid bilayer directly?
No. They require channel or carrier proteins.
What is passive transport?
Movement of molecules down their concentration gradient (high → low) without metabolic energy.
What are three examples of passive transport?
Simple diffusion, facilitated diffusion, and osmosis.
In which direction do molecules move during passive transport?
From high concentration to low concentration, down the concentration gradient.
What is active transport?
Movement of molecules against their concentration gradient, requiring energy, usually ATP.
In which direction do molecules move during active transport?
From low concentration to high concentration, against the concentration gradient.
Does active transport require energy?
Yes, usually ATP.
What is bulk transport?
Movement of large molecules or many particles using membrane-bound vesicles; requires energy.
What are the two main types of bulk transport?
Exocytosis and endocytosis.
What happens during exocytosis?
Vesicles fuse with the cell membrane and release their contents outside the cell.
What are examples of substances released by exocytosis?
Insulin and neurotransmitters.
What happens during endocytosis?
The cell membrane folds inward to bring materials into the cell in vesicles.
What are the three types of endocytosis?
Phagocytosis, pinocytosis, and receptor-mediated endocytosis.
What is phagocytosis?
“Cell eating” — the cell takes in large particles or other solid material.
What is pinocytosis?
“Cell drinking” — the cell takes in extracellular fluid and dissolved substances.
What is receptor-mediated endocytosis?
Specific molecules bind to membrane receptors before the cell brings them inside in vesicles.
What is facilitated diffusion?
Passive transport in which transport proteins help large polar molecules or charged particles move down their concentration gradient.
Does facilitated diffusion require metabolic energy?
No. It is passive transport and does not require ATP.
In which direction do molecules move during facilitated diffusion?
From high concentration to low concentration, down their concentration gradient.
What do channel proteins do?
Form pores in the membrane that allow specific substances to cross.
What are two examples of channel proteins?
Ion channels and aquaporins.
What do aquaporins transport?
Water molecules across the cell membrane.
How do carrier proteins transport molecules?
They bind to a specific molecule and change shape to move it across the membrane.
What is an example of a carrier protein?
GLUT glucose transporters, which help glucose cross the membrane.
What limits the rate of facilitated diffusion?
The number of available transport proteins.
What happens when all transport proteins are in use?
The transport rate levels off because all available proteins are occupied. This is called saturation.
What is membrane potential?
The electrical charge difference across a cell membrane.
How can ion movement create membrane potential?
Unequal movement or distribution of charged ions across the membrane creates a difference in electrical charge.
What is osmosis?
The diffusion of water across a selectively permeable membrane from high water potential (low solute concentration) to low water potential (high solute concentration).
In which direction does water move during osmosis?
Water moves toward the side with the higher solute concentration, assuming the solutes cannot cross the membrane.
What is a hypotonic solution compared to a cell, and how does it affect water movement?
It has a lower solute concentration than the cell, so water moves into the cell.
What happens to an animal cell in a hypotonic solution?
The cell swells and may lyse (burst).
What happens to a plant cell in a hypotonic solution?
The cell becomes turgid, meaning firm, as water enters the central vacuole and creates turgor pressure.
What is an isotonic solution compared to a cell, and how does it affect water movement?
It has an equal solute concentration, so water moves in both directions at equal rates, resulting in no net water movement.
What happens to an animal cell in an isotonic solution?
The cell remains at its normal size.
What happens to a plant cell in an isotonic solution?
The cell becomes flaccid, meaning limp, because it lacks sufficient turgor pressure.
What is a hypertonic solution compared to a cell, and how does it affect water movement?
It has a higher solute concentration than the cell, so water moves out of the cell.
What happens to an animal cell in a hypertonic solution?
The cell shrivels, a process called crenation.
What happens to a plant cell in a hypertonic solution?
The cell becomes plasmolyzed as water leaves and the cell membrane pulls away from the cell wall.
What is crenation?
The shrinking of an animal cell due to water loss in a hypertonic solution.
What is plasmolysis?
The process in which a plant cell loses water, causing its cell membrane to pull away from the cell wall.
What is osmoregulation?
The regulation of water and solute concentrations to maintain balance within an organism or cell.
What is the function of contractile vacuoles in freshwater protists?
They collect and pump excess water out of the cell to prevent it from taking in too much water.
How does the central vacuole help plant cells maintain water balance?
It stores water and helps maintain turgor pressure, which keeps the plant cell firm.
How does the plant cell wall help with osmoregulation?
It resists expansion as water enters the cell, helping prevent the cell from bursting and supporting turgor pressure.
What is turgor pressure, and why is it important for plants?
The pressure of the cell's contents against the cell wall as water enters. It helps keep plant cells firm and supports the plant.
Why do plant cells generally resist bursting in hypotonic solutions better than animal cells?
Plant cells have a rigid cell wall that resists expansion, while animal cells lack a cell wall and may lyse.
What is the sodium-potassium pump?
A membrane transport protein that uses ATP to move sodium and potassium ions against their concentration gradients.
How many sodium and potassium ions does the sodium-potassium pump move per ATP molecule?
It uses 1 ATP to move 3 Na⁺ out of the cell and 2 K⁺ into the cell.
Why is the sodium-potassium pump important for nerve and muscle cells?
It maintains ion concentration differences across the membrane, helping establish the membrane potential needed for nerve signaling and muscle contraction.
What is primary active transport?
Transport in which a protein uses energy directly from ATP to move substances against their concentration gradients.
What are two examples of primary active transport?
The sodium-potassium pump and proton pumps.
Where does primary active transport get its energy?
Directly from ATP.
What is secondary active transport?
Transport in which the energy stored in an ion gradient drives the movement of another substance across a membrane.
Does secondary active transport directly use ATP to move the cotransported molecule?
No. It uses energy stored in an ion gradient that was typically created by primary active transport.
How can hydrogen ions help transport sucrose into plant cells?
Hydrogen ions (H⁺) move down their concentration gradient through a cotransporter, providing energy to carry sucrose into the cell.
What is a cotransporter?
A membrane protein that moves two substances together, using the movement of one substance down its gradient to help transport the other.
What is a concentration gradient?
A difference in the concentration of a substance between two regions.
How does a concentration gradient store potential energy?
A difference in concentration stores energy that can be used when substances move down the gradient, similar to water flowing from behind a dam.
How are concentration gradients related to secondary active transport?
Primary active transport establishes an ion gradient, and secondary active transport uses the stored energy in that gradient to move another substance.