Cell Structure & Function

Question 1

Give a brief introduction about cells.

Answer 1

• Cells are the most basic units of life.
• It has a cell membrane that protects the cell.
• Inside the cell membrane is the cytoplasm [ includes the cytosol, liquid surrounding the organelles, and the organelles]
• In eukaryotic cells, there are membrane bound nucleus and other membrane bound organelles.
• All cells have genetic information, DNA, that helps produce proteins in the Ribosomes.

Question 2

Enumerate some organelles inside eukaryotic cells.

Answer 2

• There is a cell membrane which is composed of phospholipid bilayer.
• DNA inside the nuclear membrane of the cell.
• Nucleus that is connected to the Endoplasmic reticulum where some ribosomes are found.
• Rough ER has ribosomes attached to its outer surface while Smooth ER don’t.
• Ribosomes is where the information is transported and where the proteins are made.
• Golgi Bodies are like ERs but it is detached in the nuclear membrane.
• Mitochondria is where ATP is produced and it might have been independent cells because they have their own DNA.
• Chloroplasts are for the process of photosynthesis for plants and algae.
• Vacuoles are storage sites for water and enzymes, in plants they are very visible.
• Lysosomes do lysing or the breaking down of waste products.

Question 3

Elaborate the process of transporting proteins from the nucleus of a cell to the cell membrane or outside the cell.

Answer 3

• The replication and transcription of the genetic information happens inside the Nucleus of a cell.
• The mRNA travels through nuclear pores to some free ribosomes or the ribosomes attached to the Endoplasmic reticulum.
• The membrane of the Endoplasmic reticulum is the extension of the outer membrane of the nucleus.
• The space between the two lipid bilayers of the nucleus is called peri nuclear membrane.
• The ER is key for starting to produce & package proteins for the cell membrane or outside the cell.
• After the proteins go inside the ribosome, it will get inside the ER and after some time goes to the Transitional ER where proteins are budded of and turn into a vesicle which transports the protein to the Golgi body.
• There are also enzymes in the Golgi bodies.
• In the Golgi body, the proteins undergo maturation process to be able to go at the cell membrane or outside the cell.

Question 4

What is the endomembrane system?

Answer 4

• It is the system of membranes that interacts with one another inside a cell.
• All membrane are composed of phospholipid bilayers.
• The outer membrane of the nucleus extends to the membrane of the ER

Question 5

Define mitochondria.

Answer 5

• It is the ATP factories for cells.
• Its outer membrane is composed of phospholipid bilayers and has “porins” or tunnel where things pass through in it.
• The inner membrane is where the process of electron transport chain happens.
• A fold of the inner membrane is called Crista, Cristae in plural.
• The space between the outer and inner membrane is called intermembrane space.
• Matrix is the viscous liquid where the Krebs cycle occurs
• Mitochondrial DNA is believed to be from the mother’s side.

Question 6

Explain the relative scale of cells.

Answer 6

• A water molecule is ~0.275 nanometer (nm) or 0.275 billionth of a meter or 0.275 millionth of a millimeter
• Hemoglobin is ~5 nm
• HIV Virus is ~120 nm
• T-Cell and Red Blood Cell are ~6-8 micrometer (μm) or 6-8 millionth of a meter or 6-8 thousandth of a millimeter

Question 7

Describe the common cell sizes.

Answer 7

• A certain type of bacterial cell has a width of ~1 μm and a length of ~5 μm.
• Red Blood Cells have a diameter of ~7 μm.
• Egg cells have a diameter of ~100 μm.
• The smallest discovered cells are around the size of 100 nm.
• The volume and the surface area of the cell matters.

Question 8

What are cilia, flagella, & pseudopodia?

Answer 8

• All of them helps the cell move
• Pseudopod means “false foot”
• Cilia are hair-like structure of about 30 μm.
• Flagella are tail-like structure of about 1/4 μm.

Question 9

Explain the surface area to volume ratio of cells.

Answer 9

• Resources need to make their way through the outer membrane of the cell membrane of the cell so it can be used inside that cell machinery.
• Cells also generate waste products that need to be replaced across the membrane.
• There is also thermal energy going in and out of the cell.
• If the cell becomes larger the surface area to volume ratio decrease that makes the exchanges of resources, waste products, and energy harder.

Question 10

Explain the Fluid Mosaic Model of cell membranes.

Answer 10

• The cell membrane is made up of Phospholipid bilayers, proteins, sugars/carbohydrates, and cholesterol.
• A phospholipid is amphipathic which means it has both a hydrophobic and hydrophilic ends.
• There are two layers of phospholipids, the hydrophilic ends face outward and inward the cell and the hydrophobic ones are in between the hydrophilic ends.
• The sugars can attach to the lipids and protein for cell-cell recognition
• The cholesterol are for the maintenance of the fluidity of the membrane.
• The whole membrane is fluid-like though enough to keep the insides of the cell where they are.