BIo-111: Chapter 3 Exam

What is active transport?

the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.

What is the function of the cell cytoskeleton?

Providing the cell shape, providing scaffolding for the enzymes in certain areas of the cell, organizing the cell's activities and providing movement of molecules in the cell are the functions of cytoskeleton

What is passive transport? List the three types of passive transport.

The movement of substances (as by diffusion) across a cell membrane without the expenditure of energy — compare active transport. The three types of passive transport are: Osmosis: The movement of water across the plasma membrane from a region of high water concentration to the region of low water concentration is called Osmosis. Simple diffusion: The transport of metabolites across the membrane along the concentration gradient without the use of a carrier molecule is called Simple diffusion Facilitated diffusion: It is a type of passive transport similar to simple diffusion in the sense that it takes place along the concentration gradient and does not require energy. However, it requires a carrier molecule (i.e. proteins of low molecular weight) for transport across the membrane.

Identify the function of a tight junction, anchoring junction, and gap junction.

The purpose of tight junctions is to keep liquid from escaping between cells, allowing a layer of cells (for instance, those lining an organ) to act as an impermeable barrier. For example, the tight junctions between the epithelial cells lining your bladder prevent urine from leaking out into the extracellular space

Please indicate the direction of water movement (into or out of a cell) in an isotonic, hypertonic, and hypotonic solution. Explain why water moves in that particular direction for each solution.

Water molecules will move from the side of higher water concentration to the side of lower concentration until both solutions are isotonic. At this point, equilibrium is reached. An easy way to visualize this rule is simply that the net water movement is from an area of high water concentration (little dissolved solute) to an area of low water concentration (high levels of solute). A hypertonic solution has increased solute, and a net movement of water outside causing the cell to shrink. the hypotonic solution has a higher water potential than that of the cell, so water will enter the cell from a region of higher water potential to a lower water potential down a water potential gradient across a partially permeable membrane via osmosis.

Identify the function of the chloroplast and vacuole in a plant cell.

Plant cells have a cell wall, a large central vacuole, and plastids such as chloroplasts. ... The central vacuole maintains turgor pressure against the cell wall. Chloroplasts capture light energy from the sun and use it with water and carbon dioxide to produce sugars for food.

What are plasmodesmata? (in plant cells)

Plasmodesmata (Pd) are co-axial membranous channels that cross walls of adjacent plant cells, linking the cytoplasm, plasma membranes and endoplasmic reticulum (ER) of cells and allowing direct cytoplasmic cell-to-cell communication of both small molecules and macromolecules (proteins and RNA)

How is facilitated diffusion different from active transport?

Facilitated diffusion is the movement of a molecule from an area of high concentration to an area of lower concentration with the help of a protein channel or carrier. Active transport is the movement of molecules from areas of low concentration to areas where the molecule is found in higher concentration.

List three responses of cell signaling.

First, reception, whereby the signal molecule binds the receptor. Then, signal transduction, which is where the chemical signal results in a series of enzyme activations. Finally, the response, which is the resulting cellular responses

What happens to a plant cell in a hypertonic and hypotonic solution? Why?

If you place an animal or a plant cell in a hypertonic solution, the cell shrinks, because it loses water ( water moves from a higher concentration inside the cell to a lower concentration outside ). A single animal cell ( like a red blood cell) placed in a hypotonic solution will fill up with water and then burst.

How does an open system differ from a closed system?

In open system there is no exchange of energy and matter between the surroundings. In closed system there is no exchange of matter, but exchange of energy is possible.

Compare and contrast (How are they similar? How are they different?) microtubules, intermediate filaments, and microfilaments.

Microfilaments thicken the cortex around the inner edge of a cell; like rubber bands, they resist tension. Microtubules are found in the interior of the cell where they maintain cell shape by resisting compressive forces. Intermediate filaments are found throughout the cell and hold organelles in place.

How is osmosis different from diffusion?

Osmosis only allows solvent molecules to move freely, but diffusion allows both solvent and solute molecules to move freely. Osmosis happens when molecules move from higher to lower concentrations, but diffusion happens when it is reversed.

What is the difference between phagocytosis and pinocytosis?

Pinocytosis (cell drinking) describes the internalization of extracellular fluid and small macromolecules by means of small vesicles. Phagocytosis (cell eating) describes the ingestion of large particles such as cell debris and whole microorganisms by means of large vesicles.

What is plasmolysis? What is turgor pressure?

Plasmolysis is a typical response of plant cells exposed to hyperosmotic stress. The loss of turgor causes the violent detachment of the living protoplast from the cell wall. The plasmolytic process is mainly driven by the vacuole. Plasmolysis is reversible (deplasmolysis) and characteristic to living plant cells. Turgor pressure in plants plays a key role in processes such as growth, development, mechanical support, signalling, flowering and stress response. Turgor pressure is an ideal means in plant cells through which the energy content of water molecules (water potential) can be adjusted quickly, within seconds.

Give two locations where ribosomes are located in an animal cell.

Ribosomes are organelles located inside the animal, human cell, and plant cells. They are situated in the cytosol, some bound and free-floating to the membrane of the coarse endoplasmic reticulum.

What is signal transduction? What are some influences on signal transduction?

Signal transduction (also known as cell signaling) is the transmission of molecular signals from a cell's exterior to its interior. Signals received by cells must be transmitted effectively into the cell to ensure an appropriate response. This step is initiated by cell-surface receptors.

Identify the function of the nucleus, endoplasmic reticulum, lysosome, golgi bodies, and mitochondria in an animal cell.

The nucleus controls and regulates the activities of the cell (e.g., growth and metabolism) and carries the genes, structures that contain the hereditary information. The endoplasmic reticulum can either be smooth or rough, and in general its function is to produce proteins for the rest of the cell to function. The rough endoplasmic reticulum has on it ribosomes, which are small, round organelles whose function it is to make those proteins. A Golgi body, also known as a Golgi apparatus, is a cell organelle that helps process and package proteins and lipid molecules, especially proteins destined to be exported from the cell. View all Mitochondria are membrane-bound cell organelles (mitochondrion, singular) that generate most of the chemical energy needed to power the cell's biochemical reactions. Chemical energy produced by the mitochondria is stored in a small molecule called adenosine triphosphate (ATP).

Identify two differences between a plant cell vs. a bacterial cell, a plant cell vs. an animal cell, and an animal cell vs. a bacterial cell. (six differences total)

The plant cell is a eukaryotic cell whereas a bacterial cell is a prokaryotic cell. ... Bacterial cells lack membrane-bound organelles, and their genome is arranged into the nucleoid. The main difference between plant cell and bacterial cell is their structure and function. Major structural differences between a plant and an animal cell include: Plant cells have a cell wall, but animals cells do not. Cell walls provide support and give shape to plants. Plant cells have chloroplasts, but animal cells do not. Bacteria cells are very different from animal, plant or fungal cells. They don't have organelles such as nuclei, mitochondria or chloroplasts. Although they do have ribosomes and a cell wall, these are both different in structure to the ribosomes and cell walls in the cells above.

Identify the function and location of a transmembrane protein, peripherial protein, and integral protein.

Transmembrane proteins span the entire plasma membrane. Transmembrane proteins are found in all types of biological membranes. Integral monotopic proteins are permanently attached to the membrane from only one side. Unlike integral membrane proteins, peripheral proteins do not enter into the hydrophobic space within the cell membrane. They can be involved in moving substances within or outside of a cell, activate other proteins and enzymes, or be involved in cell to cell interactions Integral proteins are the proteins of the cell membrane which are completely embedded in the bilayer of phospholipids and have hydrophilic and hydrophobic regions. ... Their main function is to allow the polar and big molecules to pass across the membrane which are restricted by the phospholipid bilayer