Chapter 2.2: Cell Structure

Question 1

Cell

Answer 1

The basic structural and functional units of all living organisms.

Question 2

Organelle

Answer 2

A structure within the cell, usually membrane-bound, which carries out a specific purpose.

Question 3

Cell membrane

Answer 3

• Outer boundary of the cell which separates the cell contents from the environment outside the cell and from neighbouring cells.
• ROLE: Encloses the contents of the cell and controls what is able to enter and leave.
• Acts as a physical barrier
• Regulates the passage of materials
• Sensitive to changes (in extracellular environment)
• Helps support the cell

Question 4

Mitochondria

Answer 4

• ROLE The site of some of the chemical reactions of cellular respiration which provides energy.
• Folding of inner membrane provides a large surface area for chemical reactions.

Question 5

Ribosome

Answer 5

• ROLE: Site at which amino acids are joined together to make proteins.
• Can either be free in the cytoplasm or attached to the (rough) endoplasmic reticulum.

Question 6

Golgi apparatus/body

Answer 6

• ROLE: To modify and package proteins to be released from the cell.
• A series of flattened membranes stacked one upon the other. Usually positioned near the nucleus

Question 7

Nucleus

Answer 7

• Contains DNA which contains genetic information.
• The DNA controls the structure of the cell and the way it functions. The nucleus contains DNA, therefore it controls all cell activities.
• Nuclear membrane has pores through which mRNA can leave the nucleus.

Question 8

Nucleolus

Answer 8

• Plays a part in protein synthesis (nucleolus produces ribosomes)

Question 9

Lysosome

Answer 9

• Contain digestive enzymes that break down large molecules.
• When particles, or liquids are taken in into a cell, they form vesicles in the cytoplasm. Lysosomes can join with these vesicles, and the digestive enzymes break down the material in the vesicle.
• Lysosomes also digest worn-out organelles.
• ROLE: Contain digestive enzymes which break down cell debris (and worn-out organelles.)

Question 10

Endoplasmic reticulum

Answer 10

• Pairs of parallel membranes throughout the cytoplasm, from the cell membrane to the nuclear membrane.
• Membranes provide a large surface area for chemical reactions.
• Channels are for storing or transporting molecules.

Question 11

Rough ER

Answer 11

• Ribosomes are attached to the outside of some membranes.
• ROLE: It holds the ribosomes in place while they carry out protein synthesis.

Question 12

Smooth ER

Answer 12

No ribosomes attached to the outside of membranes.

Question 13

Cytoplasm

Answer 13

• Everything in the cell excluding the nucleus.
• Consists of cytosol and organelles.

Question 14

Cytosol

Answer 14

• Jellylike/watery fluid. (The liquid part of the cytoplasm)
• ROLE: It is where most of the metabolic reactions occur. It also plays a role in controlling the osmotic pressure of the cell and the flow of chemicals into and out of the cell.
• 75-90% water and contains:
• Salts (dissolved)
• Carbohydrates (dissolved)
• Proteins (suspended)
• Fats (suspended)

Question 15

What makes up the cell membrane?

Answer 15

The phospholipid bilayer: a membrane made up made up of phospholipids that consist of a hydrophilic head and hydrophobic tails, which are assembled into two layers with the hydrophobic tails facing the center of the bilayer and the heads facing the cytoplasm and the outside of the cell.

Question 16

Why are the phospholipid molecules arranged with their heads (hydrophilic) on the outside, and their tails (hydrophobic) on the inside?

Answer 16

The human body is 70% water, so the outside of cells must be hydrophilic, because if they were hydrophobic, it would “hate” the extracellular fluid, and your body wouldn’t stay together.