Lesson 3 - Eukaryotic cell structure

Question 1

Prokaryotic structure

Answer 1

Single-celled organisms with a simple structure of just a single undivided internal area called the cytoplasm.

Question 2

What makes up Cytoplasm?

Answer 2

Cortosyl. This is made up of water, salts and organic molecules

Question 3

Eukaryotic cells

Answer 3

Make up multicellular organisms such as plants, animals and fungi.
Have a more complicated internal structure, containing a membrane bound nucleus (nucleoplasm) and cytoplasm, which contains many membrane bound cellular components.

Question 4

Simply, what does metabolism involve?

Answer 4

Synthesis (building up) and breaking down of molecules

Question 5

What are the smallest things an electron microscope can see?

Answer 5

Water molecules / 0.1nm

Question 6

What is the minimum resolvable image by light microscope?

Answer 6

1000nm (1 micrometer)
Red blood cell / Bacterium

Question 7

Width of human hair?

Answer 7

100 micrometer

Question 8

Size of ribosome?

Answer 8

10nm

Question 9

Size of double helix?

Answer 9

10 nm

Question 10

What is required for a chemical reaction in cells?

Answer 10

Enzymes and specific reaction conditions

Question 11

Cell membranes?

Answer 11

Selectively permeable and control movement of substances into and out of the cell and organelles. Membranes are effective barriers in controlling which substances enter and exit cells. They are fragile.

Question 12

Organelles in eukaryotic cells?

Answer 12

• Nucleus
• Nucleolus
• Vesicles
• Microtubule network
• Golgi apparatus
• Mitochondria
• Secretory vesicles
• Cytoskeleton
• Smooth endoplasmic reticulum
• Rough endoplasmic reticulum
• Centriole
• Ribosome
• Cytosol
• Cell-surface membrane

Question 13

Nucleus:

Answer 13

The nucleus contains coded genetic information in the form of DNA molecules.
Biggest organelle in the cell.

Question 14

What is the purpose of DNA?

Answer 14

Directs the synthesis of all proteins required by the cell (although protein synthesis occurs outside of the nucleus in the ribosomes).
DNA controls the metabolic activities of the cell, as many of these are proteins are the enzymes necessary for metabolism to take place.

Question 15

Where is DNA contained?

Answer 15

Nuclear envelope to protect it from damage in the cytoplasm. The nuclear envelope contains nuclear pores that allow molecules to move into and out of the nucleus. DNA itself is too large to leave the nucleus to the site of protein synthesis in the cytoplasm. So instead it is transcribed into smaller RNA molecules, which are exported via the nuclear pores.

Question 16

Chromosomes?

Answer 16

DNA associates with proteins called histones to form a complex called chromatin. Chromatin coils and condenses to form structures known as chromosomes. These only become visible when the cells are preparing to divide.

Question 17

Nucleolus?

Answer 17

An area within the nucleus that is responsible for producing ribosomes. Composed of proteins and RNA. RNA is used to produce ribosomal RNA (rRNA) which is then combined with proteins to form the ribosomes necessary for protein synthesis.

Question 18

Mitochondria

Answer 18

Essential organelles in almost every eukaryotic cell. Site of the final stages of cellular respiration.

Question 19

How does aerobic respiration happen?

Answer 19

Energy stored in the bonds of the complex, organic molecules is made available for the cell to use by the production of the molecule ATP.

The number of mitochondria in a cell is generally a reflection of the amount of energy it uses, so very active cells usually have a lot of mitochondria.

Question 20

Structure of mitochondria?

Answer 20

Have double membrane. Inner membrane is highly folded to form structures called cristae and the fluid interior called the matrix.
The membrane forming cristae contains the enzymes used in aerobic respiration.

Question 21

Reproduction of mitochondria?

Answer 21

Mitochondria also contain small amount of DNA, called mitochondrial DNA. Mitochondria can produce their own enzymes and reproduce themselves.

Question 22

Vesicles

Answer 22

Vesicles are membranous sacs that have storage and transport roles.
The consist simply of a single membrane with fluid inside. Vesicles are used to transport materials inside the cell

Question 23

Lysosomes

Answer 23

Specialised forms of vesicles:
- Contain hydrolytic enzymes. They are responsible for breaking down waste material in cells, including old organelles.
- Important role in immune system as they are responsible for breaking down pathogens ingested by phagocytic cells. They also play an important role in programmed cell death or apoptosis.

Question 24

Cytoskeleton:

Answer 24

Cytoskeleton is present throughout the cytoplasm of all eukaryotic cells. Network of fibres necessary for the shape and stability of a cell. Organelles are held in place by cytoskeleton and it controls cell movement and the movement of organelles within the cell.

Question 25

3 components of cytoskeleton:

Answer 25

Microfilaments:

Microtubules:

Intermediate fibres:

Question 26

Microfilaments: in cytoskeleton

Answer 26

Contractile fibres formed from the protein actin.
These are responsible for cell movement and also cell contraction during cytokinesis (the process in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells.

Question 27

Microtubules:

Answer 27

Globular tubulin proteins polymerise to form tubes that are used to form a scaffold-like structure that determines the shape of a cell.
They also act as tracks for the movement of organelles, including vesicles, around the cell. Spindle fibres, which have a role in the physical segregation of chromosomes in cell division, are composed of microtubules.

Question 28

Intermediate fibres:

Answer 28

These fibres give mechanical strength to cells and help maintain their integrity.