Tour of the Cell

Question 1

Prokaryotic cells

Answer 1

Prokaryotic cells are simple, single-celled organisms lacking a nucleus and other membrane-bound organelles. Examples include bacteria and archaea.

Question 2

Eukaryotic cells

Answer 2

Eukaryotic cells are complex cells with a nucleus and membrane-bound organelles, found in organisms like animals, plants, fungi, and protists.

Question 3

Plasma membrane

Answer 3

Semi-permeable barrier that surrounds the cell, separating its interior from the external environment. It is composed of a lipid bilayer embedded with proteins. The hydrophobic tails are faced inwards (lipid bilayer) and the hydrophilic head is faced outwards (phospholipid).
The plasma membrane regulates the passage of substances in and out of the cell, controlling the movement of ions, molecules, and nutrients. It also plays a crucial role in cell signaling and communication with neighboring cells.

Question 4

Nucleus

Answer 4

Cell core that works as a control center where the master plans are stored, orders are given, changes are made in response to external signals.

Question 5

Nuclear envelope

Answer 5

The nucleus is seperated from the cytoplasm by a double membrane. The membrane is a phospholipid bilayer with associated proteins. Pores between the nucleus and the surrounding cytoplasm allow certain materials to pass.

Question 6

Nucleolus

Answer 6

Core of the nucleus where ribosomes are produced.

Question 7

Chromatin

Answer 7

Long DNA-molecules associated with proteins form fibers. Each long chromatin fiber constitutes part of a chromosome.

Question 8

Ribosomes

Answer 8

Ribosomes are resposible for protein synthesis. They are made in the nucleus and then transported through the nuclear envelope to the cytoplasm. Ribosomes make proteins either freely in the fluid of the cell or attached to the endoplasmic reticulum.

Question 9

How does DNA direct protein production?

Answer 9

(1) DNA transfers its coded information to messenger DNA (mRNA). The mRNA carries the order to “build this type of protein”.

(2) The mRNA travels through the pores of the nuclear envelope and travels to the cytoplasm where it binds to a ribosome.

(3) The ribosome the mRNA, translating the genetic message into a protein with a specific amino acid sequence.

Question 10

Endoplasmic reticulum (ER)

Answer 10

Main manufacturing facilities within a cell connected to the nuclear envelope. It’s involved in synthesizing, modifying, and transporting proteins and lipids within the cell.

Question 11

Rough ER

Answer 11

The rough endoplasmic reticulum (RER) is a region of the endoplasmic reticulum (ER) characterized by the presence of ribosomes attached to its surface. It’s involved in protein synthesis, modification, and folding within the cell.

Question 12

How rough ER manufactures and packages secretory proteins.

Answer 12

(1) A ribosome links amino acids into a polypeptide which threads through the membrane into the interior of the ER.

(2) Proteins often get modified in the ER.

(3) Proteins to be get packaged into transport vesicles.

(4) Dispatched to other locations in the cell.

Question 13

Smooth ER

Answer 13

The smooth endoplasmic reticulum (SER) is a region of the endoplasmic reticulum (ER) that lacks ribosomes on its surface. It is involved in lipid synthesis, detoxification of harmful substances, and regulation of calcium levels in the cell.

Question 14

Golgi apparatus

Answer 14

Organelle that consists of flattened membrane-bound sacs called cisternae.
Is involved in modifying, sorting, and packaging proteins and lipids synthesized in the endoplasmic reticulum (ER). It acts as a distribution center where these molecules are processed and directed to their final destinations within or outside the cell.

Question 15

Lysosomes

Answer 15

Membrane-enclosed sac of digestive enzymes.
They contain enzymes that break down waste materials, cellular debris, and foreign particles through hydrolysis. Lysosomes play a crucial role in cellular digestion, recycling of cellular components, and defense against pathogens. They are often referred to as the “digestive system” of the cell.

Question 16

Vacuoles

Answer 16

Membrane-bound organelles found in the cells of plants, fungi, protists, and some animals. They are essentially storage compartments within the cell and can contain various substances such as water, nutrients, ions, and waste products. Maintains cell turgor pressure, storing nutrients and metabolites, facilitating cellular digestion, and helps to maintain cell structure and shape. In plant cells, the central vacuole is particularly prominent and contributes significantly to the rigidity of the cell and the overall structure of the plant.

Question 17

Chloroplasts

Answer 17

Photosynthetic organelles of plants and algae. Divided into compartment by a membrane. The inner compartment holds a thick fluid called stroma which contains DNA, ribosomes and enzymes. A network of sacs called thylacoids are suspended in the stroma. The sacs are stacked = granum. The grana are solar power packs, coverting light energy to chemical energy.

Question 18

Mitochondria

Answer 18

Mitochondria are double-membrane-bound organelles found in eukaryotic cells. They are often referred to as the “powerhouses” of the cell because they generate most of the cell’s supply of adenosine triphosphate (ATP), which is used as a source of chemical energy. Mitochondria contain inner membrane structures called cristae, which increase the surface area available for the chemical reactions involved in ATP production. The inner membrane is highly folded, forming cristae, while the outer membrane is smooth. Additionally, mitochondria play roles in regulating cell metabolism, apoptosis (programmed cell death), and calcium signaling.

Question 19

Cytoskeleton

Answer 19

The cytoskeleton is a network of protein filaments found in the cytoplasm of eukaryotic cells. It provides structural support, maintains cell shape, and facilitates cell movement. The cytoskeleton is composed of three main types of filaments: microfilaments (made of actin), intermediate filaments (made of various proteins), and microtubules (made of tubulin). These filaments work together to organize the cell’s interior, transport organelles, and facilitate processes such as cell division and cell signaling.

Question 20

Flagella and Cilia

Answer 20

Flagella and cilia are cellular appendages found in many types of cells, primarily in single-celled organisms and specialized cells in multicellular organisms.

Flagella are long, whip-like structures that protrude from the cell surface and are used primarily for locomotion. They move in a wave-like motion, propelling the cell through its environment. Flagella are typically fewer in number and longer than cilia.

Cilia, on the other hand, are shorter, hair-like structures that also extend from the cell surface. They can be found in large numbers on the cell surface and are involved in various functions, including movement, sensing the environment, and moving substances along the cell surface. Cilia often have a coordinated beating motion that helps move fluid or particles along the cell surface or propel the cell itself.

Both flagella and cilia are composed of microtubules and are anchored to the cell by a basal body, which is structurally similar to a centriole.