Question

unit 1

1. describe the function of each of the following cell organelles:

a. cell wall:
b. cell membrane:
c. golgi body:
d. mitochondria:
e. chloroplast:

1. define the term homeostasis:
2. describe the main difference between active and passive transport.

hint: think about energy use

1. label the diagram with phosphate head, fatty acid tails, hydrophobic,

and hydrophilic.
which part touches the cytoplasm?
which part faces the center of the
membrane bilayer?

Explanation:

1. a. Cell Wall: Provides structural support and protection to plant cells, bacteria, fungi, etc. It also helps maintain cell shape and prevents excessive water uptake.

b. Cell Membrane: Regulates the movement of substances in and out of the cell (selective permeability), acts as a barrier between the cell and its environment, and is involved in cell signaling and recognition.
c. Golgi Body: Modifies, sorts, and packages proteins and lipids received from the endoplasmic reticulum. It also transports these molecules to their final destinations (inside or outside the cell).
d. Mitochondria: Known as the "powerhouse of the cell," it is the site of cellular respiration, where energy (ATP) is produced by breaking down glucose and other nutrients.
e. Chloroplast: (In plant cells and some protists) Site of photosynthesis, where light energy is converted into chemical energy (glucose) using carbon dioxide and water.

1. Homeostasis: The ability of an organism or a cell to maintain a stable internal environment despite changes in the external environment. This involves regulating factors like temperature, pH, and nutrient levels within a narrow range to ensure proper cellular function.
2. Active vs. Passive Transport: Passive transport (e.g., diffusion, osmosis, facilitated diffusion) does not require energy (ATP) as substances move down their concentration gradient (from high to low concentration). Active transport requires energy (ATP) because substances are moved against their concentration gradient (from low to high concentration), often with the help of transport proteins.
3. Diagram Labeling: The phosphate head is hydrophilic (water - attracting) and the fatty acid tails are hydrophobic (water - repelling). The phosphate head (hydrophilic part) touches the cytoplasm (aqueous environment) and the extracellular fluid. The fatty acid tails (hydrophobic part) face the center of the membrane bilayer, away from water.

Answer:

1. a. Provides support, protection, maintains cell shape.

b. Regulates substance movement, cell - environment barrier.
c. Modifies, sorts, packages proteins/lipids.
d. Produces ATP (cellular respiration site).
e. Photosynthesis site (plant cells).

1. Maintains stable internal environment.
2. Active needs ATP (against gradient), passive doesn't (with gradient).
3. Phosphate head: hydrophilic, touches cytoplasm. Fatty acid tails: hydrophobic, face membrane center.