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 is required for a chemical reaction in cells?

Answer 5

Enzymes and specific reaction conditions

Question 6

Cell membranes?

Answer 6

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 7

Organelles in eukaryotic cells?

Answer 7

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

Question 8

Nucleus:

Answer 8

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

Question 9

What is the purpose of DNA?

Answer 9

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 10

Where is DNA contained?

Answer 10

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 11

Chromosomes?

Answer 11

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 12

Nucleolus?

Answer 12

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 13

Mitochondria

Answer 13

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

Question 14

How does aerobic respiration happen?

Answer 14

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 15

Structure of mitochondria?

Answer 15

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 16

Reproduction of mitochondria?

Answer 16

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

Question 17

Vesicles

Answer 17

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 18

Lysosomes

Answer 18

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 19

Cytoskeleton:

Answer 19

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 20

3 components of cytoskeleton:

Answer 20

Microfilaments:

Microtubules:

Intermediate fibres:

Question 21

Microfilaments: in cytoskeleton

Answer 21

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 22

Microtubules:

Answer 22

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 23

Intermediate fibres:

Answer 23

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

Question 24

When does mRNA travel to free ribosomes?

Answer 24

If protein stays in the cytoplasm

Question 25

When do mRNA travel to RER?

Answer 25

If protein is secreted from cell

Question 26

Nucleoplasm

Answer 26

Contains enzymes and nucleotides needed for synthesis of DNA and RNA

Question 27

Nuclear envelope is made up of

Answer 27

phospholipid bilayers

Question 28

Dark material in Nucleus

Answer 28

Chromatin

Question 29

How are chromosomes formed?

Answer 29

DNA tightly wrapped around proteins called histones to form chromatin

Question 30

Fungi cell wall made up of?

Answer 30

Chitin Polysaccharide

Question 31

Cilia:

Answer 31

Hair like projections out of cells:
Can be mobile or stationary.

Mobile help move substances in a sweeping motion.

Sensory organs like nose

Question 32

Centrioles

Answer 32

Made of microtubles in pairs to form centrosome. Involved in the production of spindle fibres and organisation of chromosomes in cell division.

Question 33

Name of folded membranes on RER and SER?

Answer 33

Cisternae

Question 34

Functions of lysosome?

Answer 34

• Hydrolyse phagocytic cells
• Completely break down dead cells
• Exocytosis (release enzymes outside of the cell to destroy material)
• Digest worn out cells for reuse of materials

Question 35

Chloroplasts:

Answer 35

• Surrounded by double membrane
• Contains thykaloids (folded membranes imbedded with pigments)
• Fluid filled stroma contains enzymes for photosynthesis

Question 36

Cell wall:

Answer 36

• Middle lamella
• Primary cell wall
• Plasma membrane

Question 37

Cell membrane

Answer 37

Phospholipid bilayer
- molecules embedded within and attached to outside.

Question 38

What do plant cell walls contain that allow them to connect to neighbouring cells?

Answer 38

plasmodesmata

Question 39

Purpose of the vacuole:

Answer 39

1. Keeps cell turgid
2. Stores food reserves
3. Maintains pressure within the cell
4. Stores waste products