Cell structure and function

How is a concentration gradient established and maintained?

A concentration gradient exists when a higher concentration of a solute is separated from a lower concentration, by a semipermeable membrane. Ion pump enzymes transport ionic solutes such as sodium, potassium, hydrogen ions, and calcium across the membrane.

What is the structure of the inner membrane (cristae) of the mitochondria? How does that contribute to the function of the inner membrane (cristae) of the mitochondria?

A fold in the inner membrane of a mitochondrion. It gives the inner membrane its characteristic wrinkled shape, providing a large amount of surface area for chemical reactions to occur on.

What is the function of an ATPase? How does the Na+/K+ ATPase maintain the membrane potential?

A group of enzymes that catalyze the hydrolysis of a phosphate bond in adenosine triphosphate (ATP) to form adenosine diphosphate (ADP). They harness the energy released from the breakdown of the phosphate bond and utilize it to perform other cellular reactions. The Na+ K+-ATPase pump maintains the gradient of a higher concentration of sodium extracellularly and a higher level of potassiumintracellularly.

Lysosome What is the structure and function of the lysosome? How does the structure of the lysosome aid in the function?

A lysosome is a membrane-bound cell organelle that contains digestive enzymes. They break down excess or worn-out cell parts. They may be used to destroy invading viruses and bacteria. Their external membrane is like a gateway that allows molecules inside of the lysosome without allowing the digestive enzymes to escape into the cell.

What is exocytosis? Identify an example of a material that would require exocytosis

A process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane. The secretion of proteins like enzymes

How does an increase of surface area affect the increase in volume? How can a cell increase surface area without increasing the volume? How can an increase in surface affect heat exchange?

As volume and surface area increase, the volume increases faster. Folds in the membrane. An object with a wider area has more surface particles working to conduct heat.

Chloroplast What is the structure and function of a chloroplast? How does the structure of the chloroplast aid in the function? How is the chloroplast organized?

Chloroplasts are a type of membrane-bound plastids that contain a network of membranes embedded into a liquid matrix and harbor the photosynthetic pigment called chlorophyll. It is this pigment that imparts a green color to plant parts and serves to capture light energy. Part of the photosynthesis reactions occur in an internal membrane within the organelle. The chloroplast contains many of these internal membranes, making photosynthesis very efficient. These internal membranes stack on top of each other, just like a stack of pancakes. In particular, their three membranes divide chloroplasts into three distinct internal compartments: (1) the intermembrane space between the two membranes of the chloroplast envelope; (2) the stroma, which lies inside the envelope but outside the thylakoid membrane; and (3) the thylakoid lumen.

Describe the process of passive transport. Describe the process of facilitated diffusion. Describe the process of active transport.

Does not require energy to move substances across cell membranes. Molecules diffuse across the plasma membrane with assistance from membrane proteins, such as channels and carriers. The movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.

What is endocytosis? Describe the three types of endocytosis. Identify an example of a material that would require endocytosis. How are the food materials brought in by endocytosis digested?

The taking in of matter by a living cell by invagination of its membrane to form a vacuole. Phagocytosis, pinocytosis and receptor-mediated endocytosis. White blood cells engulfing a virus and eliminating it. Lysosomes attach to the vacuole and release digestive enzymes to extract nutrients. The leftover waste products of digestion are carried to the plasma membrane by the vacuole and eliminated through the process of exocytosis.

Vacuoles What is the structure of the vacuole? What is the function of the food vacuole? What is the function of the central vacuole? What is the function of the contractile vacuole?

They are surrounded by a thin membrane and filled with fluid and any molecules they take in. Food vacuoles are membrane-bound sacs within a cell, which contain food matter to be digested. A central vacuole functions as a combination of reservoir, waste dump, storage region and even as a means of keeping the cell in shape. CV controls the intracellular water balance by accumulating and expelling excess water out of the cell, allowing cells to survive under hypotonic stress as in pond water.

How do ions move across the membrane?

Through ion channels that move down their concentration gradient and create a flow of electrical energy

How does the thylakoid aid in energy capturing? How does the thylakoid aid in energy storing?

Thylakoid membranes contain chlorophyll and other pigments arranged in antenna arrays to capture light energy.

Where do the light-dependent and light-independent reactions take place?

In photosynthesis, the light-dependent reactions take place on the thylakoid membranes. The inside of the thylakoid membrane is called the lumen, and outside the thylakoid membrane is the stroma, where the light-independent reactions take place.

Golgi Bodies/Apparatus/Complex Note: any of the names could appear on the exam so be knowledgeable about the different ways you might see this structure What is the structure and function of the Golgi? How does the structure of the Golgi aid in the function?

It helps process and package proteins and lipid molecules, especially proteins destined to be exported from the cell. It appears as a series of stacked membranes. The many sacs and folds of the Golgi apparatus allow for many reactions to take place at the same time

How does the phospholipid bilayer maintain the internal environment of a cell?

It is selectively permeable so it only allows certain things in and out of the cell. Things cannot enter or exit freely.

How does the lysosome aid in intracellular digestion? How does the lysosome aid in recycling the cell's organic materials? How does the lysosome aid in apoptosis (programmed cell death)?

Lysosomes assist in the intracellular digestion of worn-out cellular organelles and materials taken into the cell by endocytosis. Lysosomes break down cellular waste products, fats, carbohydrates, proteins, and other macromolecules into simple compounds, which are then transferred back into the cytoplasm as new cell-building materials. It is able to breakdown dead cell parts.

Mitochondria What is the structure and function of the mitochondria? Note: Mitochondria is the "powerhouse of the cell" is not an appropriate response on the AP exam How does the structure of the mitochondria aid in the function?

Mitochondria are membrane-bound cell organelles that generate most of the chemical energy needed to power the cell's biochemical reactions. Outer membrane - the outer membrane contains transport proteins that enable the shuttling of pyruvate from the cytosol. Inner membrane - contains the electron transport chain and ATP synthase

Where does the citric acid cycle (Krebs cycle) in cellular respiration take place? Where does the electron transport chain in cellular respiration take place? Where does the electron transport chain in photosynthesis take place? Where is ATP synthesized in cellular respiration? Don't get tricked... Where is ATP synthesized in photosynthesis?

Mitochondrial matrix Inner mitochondrial membrane. Thylakoid membrane. Cytoplasm. Thylakoid membrane.

Identify and describe two examples of specialized surfaces for exchanging materials with the surrounding environment. Identify and describe two examples of strategies that organisms use to obtain nutrients and eliminate wastes.

Photosynthesis and consuming food. Exhaling and urination.

How does the vacuole assist in storage of macromolecules? How does the vacuole provide turgor pressure?

Proton pumps also maintain high concentrations of protons in the vacuole interior. These high concentrations cause the entry, via osmosis, of water into the vacuole, which in turn expands the vacuole and generates a hydrostatic pressure, called turgor, that presses the cell membrane against the cell wall.

Which "cell" from question #5 would be the most efficient? Justify.

Reference problem on guide. Cell with highest surface area to volume ratio.

Ribosome What is the structure and function of the ribosome? How does the structure of the ribosome aid in the function? What are the three types of RNA involved in the structure or function of the ribosome? How does the ribosome demonstrate a common ancestry of all known life?

Ribosomes are made of proteins and ribonucleic acid (abbreviated as RNA), in almost equal amounts. It comprises of two sections, known as subunits. The tinier subunit is the place the mRNA binds and it decodes, whereas the bigger subunit is the place the amino acids are included. Messenger RNA (mRNA) molecules carry the coding sequences for protein synthesis and are called transcripts; ribosomal RNA (rRNA) molecules form the core of a cell's ribosomes (the structures in which protein synthesis takes place); and transfer RNA (tRNA) molecules carry amino acids to the ribosomes during protein synthesis. Ribosomes, in all species use mRNA as a blueprint for building all the proteins and enzymes essential to life.

How does the endoplasmic reticulum provide mechanical support? How does the endoplasmic reticulum aid in protein synthesis? How does the endoplasmic reticulum aid in intracellular transport?

So that its shape is maintained. Proteins that get sent to the ER, are sorted according to their destinations, then forwarded to the appropriate cellular compartment.

What does it mean if a solution is hypotonic? What does it mean if a solution is hypertonic? What does it mean if a solution is isotonic?

Solute concentration inside the cell is higher an water moved into the cell. Solute concentration is lower inside the cell and water moves out. Solute concentration is equal inside and outside the cell and water moved in and out of the cell at an equal rate.

How does surface area to volume ratio affect the size of the cell? What type of surface area to volume ratio is most favorable for cells?

Surface area to the volume ratio gets smaller as the cell gets larger. More surface area, less volume.

Endoplasmic Reticulum What is the structure and function of the rough ER? How does the structure of the rough ER aid in the function? What is the structure and function of the smooth ER? How does the structure of the smooth ER aid in the function? What is the relationship between the ribosome and the rough ER?

The ER consists of the nuclear envelope and the peripheral ER, which includes smooth tubules and rough sheets. While the ER is defined as an interconnected network with a continuous membrane. It performs a variety of essential cellular functions, including protein synthesis and processing, lipid synthesis, and calcium (Ca2+) storage and release. Smooth: It synthesizes lipids, phospholipids as in plasma membranes, and steroids.

What is homeostasis?

The ability to maintain a relatively stable internal environment in an ever-changing outside world.

What are the components of the cell membrane? How do each of the above components function in the cell membrane? Describe the orientation of the components for the structure of the phospholipid.

The cell membrane consists of two adjacent layers of phospholipids, which form a bilayer. Composed of a glycerol backbone carrying a hydrophilic polar head group and two hydrophobic fatty acyl tails.

Define the fluid mosaic model.

The fluid mosaic model states that a cell membrane consists of a phospholipid bilayer with proteins embedded throughout.