Unit 2 AP Biology Key Concepts

How do ribosomes reflect the common ancestry of all known life?

All living cells contain a genome and ribosomes.

What is the structure and function of ribosomes?

Structure:

made of rRNA and proteins.

Function:

Synthesize proteins according to mRNA sequence.

What is the structure and function of the rough ER?

Structure:

Network of membrane tubes within the cytoplasm of eukaryotic cells

Function:

Associated with packaging newly synthesized proteins made by attached ribosomes for possible export from the cell.

What is the structure and function of the smooth ER?

Structure:

Network of membrane tubes within the cytoplasm of eukaryotic cells without ribosomes attached to the membrane.

Function:

Detoxification and lipid synthesis.

What is the structure and function of Golgi complex?

Structure:term-9

Flattened membrane-bound sacs found in eukaryotic cells.

Function:

Involved in the correct folding and chemical modification of newly synthesized proteins and packaging for protein export.

What role do vesicles play in the Golgi complex?

Membrane containers that help move materials from one part of the cell to the next.

What is the structure and function of mitochondria

Structure:

Outer membrane is smooth and inner member is highly convoluted. (double membrane)

Function:

Produces ATP energy that eukaryotes can use for cell work.

What is the structure and function of lysosomes?

Structure:

Membrane-enclosed sacs that contain hydrolytic enzymes.

Function:

Intracellular digestion, recycling of organic materials, apoptosis.

What is the structure and function of a vacuole?

Structure:

Membrane-bound sacs

Function:

Storing water and other macromolecules to the release of waste from a cell. In plants, they aid in retention of water for turgor pressure.

What is the structure and function of chloroplasts?

Structure:

Double outer membrane. Thylakoid.

Stroma.

Function:

Specialized for capturing energy from the sun and producing sugar for the organism.

How do the sub-cellular components of chloroplast interact and contribute to the function of the cell?

Thylakoid membranes contain chlorophyll pigments that comprise the photosystems. They host the light-dependent reactions. Stroma hosts carbon fixation reactions.

How do the sub-cellular components of mitochondria interact and contribute to the function of the cell?

The inner mitochondrial membrane hosts electron transport and ATP synthesis. The matrix hosts the Krebs cycle.

What are the structural features of a cell that allow organisms to capture, store, and use energy?

Double membrane provides compartments for different metabolic reactions. Increased folding of internal membranes, surface area, increases the efficiency and allows for more ATP to be made.

Why are cells typically small?

Being small gives the cell a larger surface area to volume ratio, and the smaller the cell, the more rapid information transfer will be between nucleus and cell membrane.

How is the surface area to volume ratio calculated?

Use equations on formula sheet.

What are some examples of structural modifications of cells that increase surface area?

Root hairs on the surface of plant roots increase the surface area of the root allowing for increased absorption of water and nutrients.

How does the surface area to volume ratio effect the rate of heat exchange with the environment?

Smaller surface area to volume ratios result in difficulty of releasing heat from their bodies. (lower rate of heat exchange)

How are specialized structures and strategies used by cells and organisms for the efficient exchange of molecules with the environment.

Cells and organisms use specialized exchange surfaces, such as stomatal openings of leaves, to obtain molecules from and release molecules into the surrounding environment.

How does the structure of a phospholipid establish and maintain the internal environment of the cell?

Phospholipids spontaneously form a bi-layer in an aqueous environment. They make it harder for large and polar molecules to penetrate the membrane and go into the cell.

What role do phospholipids have in maintaining the internal environment of the cell?

They provide a boundary between the interior of the cell and outside environment. They control the transport of materials in and out of the cell.

What role do proteins have in maintaining the internal environment of the cell?

1. Transport

2. Cell-cell recognition

3. Enzymatic activity

4. Signal transduction

5. Intercellular joining

6. Attachment for extracellular matrix or cytoskeleton

What is the structural framework of the Fluid Mosaic Model of cell membranes?

Mosaic of protein molecules in a fluid bilayer of phospholipids. Held together primarily by hydrophobic interactions (LDFs) which are weaker than covalent bonds. Its fluidity helps the cell membrane maintain its role as a barrier.

How does the structure of cell membranes result in selective permeability?

Small non-polar molecules pass freely across, while large polar molecules and ions cannot freely move across the membrane.

How do cell membranes separate the internal environment of the cell from the external environment of the cell?

By separating the cell membrane into polar and nonpolar regions and being selectively permeable.

What is the direct consequence of membrane structure, as described by the fluid mosaic model?

Selective permeability.

What type of substances move across the membrane through embedded channel and transport proteins?

Hydrophilic substances.

What molecules pass through the membrane in small amounts?

Small polar molecules such as H2O.

What type of boundaries do cell walls provide?

A structural boundary:

Protects and maintains the shape of the cell. Prevents against cellular rupture when high turgor pressure. Helps plants stand up against the force of gravity.

A permeable barrier:

Plasmodesmata - small holes between plant cells that allows the transfer of nutrients, waste, and ions.

What type of molecules are cell walls of plants, prokaryotes, and fungi composed of?

Plants - cellulose

Fungi - chitin

Prokaryotes - peptidoglycan

How does passive transport move molecules across the membrane?

Towards the concentration gradient, from high concentration to low concentrations. Requires no energy.

How does active transport move molecules across the membrane?

Against the concentration gradient, from low concentration to high concentrations. Requires energy.

How do concentration gradients form across membranes?

They are formed when a solute is more concentrated in one area than another.

How do large molecules move into the cell?

Endocytosis. Requires energy and vesicles to bring the molecule in.

How do large molecules move out of the cell?

Exocytosis. Requires energy and vesicles to fuse with the plasma membrane and secrete the molecules out.

Why are membrane proteins required for diffusion of certain molecules?

Large & small polar molecules, and charged ions cannot diffuse directly through the membrane.

How do large quantities of water move across the membrane?

Through aquaporins.

How do membranes become polarized?

Through the movement of ions which allows for the formation of electrochemical gradients.

What molecules are necessary for active transport to occur?

Carrier proteins called pumps. Metabolic energy.

When is metabolic energy needed for transport of molecules across the membrane?

During cotransport and active transport.

What is membrane potential?

Electrical charge difference (voltage) that occurs across the cell membrane

How does Na+/K+ ATPase contribute to membrane potential?

It pumps 3 sodiums against the concentration gradient and 2 potassiums toward the concentration gradient, creating a difference in charge, membrane potential.

What are the different ways to describe relative tonicity of environments?

Hypertonic (Greater salt/solute than water), Isotonic, Hypotonic (Less salt/solute than water)

How do differences in osmolarity impact the movement of water in a cell?

Water moves by osmosis into the area with a higher salt/solute concentration. Into the hypertonic environment. Water concentration and solute concentration are inversely related.

How does the constant movement of molecules across a membrane maintain growth and homeostasis?

If a cell is not at equilibrium, then the passing of molecules can correct its state.

What is osmoregulation?

The control of water balance.

How does osmoregulation contribute to the health and survival of organisms?

In plants, osmoregulation maintains water balance and allows control of internal solute composition.

How does water potential impact the movement of water?

Water moves from an area of high water potential to an area of low water potential. The more negative the water potential, the more likely water will move into the area.

How does solute potential impact the movement of water?

Solute potential causes lower water potential. This means that an area with higher solute potential will have more water come into it.

How do organisms maintain water balance?

Through osmoregulation.

What are some examples of membrane-bound organelles in eukaryotic cells that compartmentalize intracellular reactions?

Membranes in the lysosome minimize competing interactions. The inside of the lysosome can maintain an acidic pH, while the rest of the cytoplasm can remain neutral.

How do internal membranes facilitate cellular processes?

Convolutions/foldings in the inner membrane allow for increases in surface area, which leads to increased efficiency.

How might a change in the internal membranes or membrane-bound organelles effect the ability of eukaryotic cells to perform necessary functions?

Might slow them down as they will not be as efficient as they are now.

What are some similarities and/or differences in compartmentalization between prokaryotic and eukaryotic cells?

Similarities:

Plasma membrane that separates internal and external environments.

Differences:

Prokaryotes have a nucleoid region that contains its genetic material, while it is contained in the nucleus in eukaryotes.

Eukaryotes have more membranes and membrane-bound organelles.

How did mitochondria and chloroplasts evolve from previously free-living prokaryotic cells via endosymbiosis?

A free-living aerobic prokaryote was engulfed by an anaerobic cell through endocytosis. The engulfed prokaryotic cell did not get digested by the engulfing cell; this arrangement became mutually beneficial.

What is some evidence to support the claim that mitochondria and chloroplasts evolved through the process of endosymbiosis?

Both have double membranes, ribosomes, and their own circular DNA.

What is the role of a double membrane?

Regulate the passage of materials into and out of the cell. Maintain a stable internal environment.