3.2.1.1 Structure of Eukaryotic Cells

Question 1

Nucleoplasm

Answer 1

Bulk of the nucleus formed from a granular jelly

Question 2

Nucleoulus

Answer 2

Spherical region within the nucleus which manufactures RNA and assembles ribosomes

Question 3

Nuclear envelope

Answer 3

Double stranded, it controls what goes in and out of the cell, reactions take place here and they contain ribosomes

Question 4

Nuclear pores

Answer 4

These allow passage of large materials e.g., mRNA

Question 5

Chromatin in the nucleus

Answer 5

Linear DNA which is histone bound, this condenses to form visible chromosomes during nuclear division

Question 6

List the functions of the nucleus

Answer 6

Produces mRNA and RNA for protein synthesis

DNA replication

Contains genetic information for primary structure of polypeptides

Question 7

Double membrane (mitochondrion)

Answer 7

Controls entry and exit of substances in a cell and the inner of the 2 membranes fold to form cristae

Question 8

Cristae

Answer 8

Extensions forming folds of the inner membranes, these provide a large surface area for enzymes involved in aerobic respiration e.g., ATP synthase

Question 9

Matrix

Answer 9

Contains: proteins, lipids mitochondrial DNA and 70S ribosomes. By contains mitochondrial DNA, it allows mitochondria to produce its own proteins for respiration independent of a nucleus

Question 10

Rough endoplasmic reticulum

Answer 10

Found on certain parts of the outer membrane of the nucleus

Contains ribosomes

Provides a large surface area for the synthesis of proteins

Packages proteins into vesicles and transports these to the Golgi apparatus ready for modification

Question 11

Smooth endoplasmic reticulum

Answer 11

No ribsomes

Tube like appearance

Stores, transports and synthesis carbohydrates and lipids

Question 12

State the definition of a eukaryotic cell (1)

Answer 12

(A cell that contains a) nucleus AND membrane-bound organelles

Accept membrane bound organelles AND nucleus

Ignore any reference to prokaryotic cells

Ignore any reference to examples of organelles

Ignore any reference to diagrams

Question 13

Golgi apparatus

Answer 13

1. Lipids and proteins formed in the RER and SER are passed through the GA in a strict sequence
2. These are then modified by adding carbohydrates and lipids to them forming glycoproteins and glycolipids
3. These modified proteins are then packaged into vesicles which are regularly ‘pinched off’ from the Golgi cistarne
4. These vesicles then fuse or move towards the cell surface membrane where they release there contents during exocytosis

Question 14

Ribosomes

Answer 14

Formed of ribosomal RNA and protein subunits needed to synthesise proteins. They may be found in the cytoplasm or attached to the membrane of the RER. There are 2 types:
1. 70S which are smaller and found in prokaryotic cells
2. 80S which are larger and found in eukaryotic cells

Question 15

Cell surface membrane

Answer 15

• Controls passage of molecules in and out of the cell
• Made up of: carbohydrates, phospholipids and specific transport proteins arranged in ‘fluid mosaic model’
• All cell surface membranes have the same basic structure, however, the proportion of molecules varies depending on the function of the cell.

Question 16

Draw and label a nucleus

Answer 16

See notes

Question 17

Draw and label a mitochondrion

Answer 17

See notes

Question 18

Draw and label a lysosome

Answer 18

See notes

Question 19

Lysosomes are produced by which organelle?

Answer 19

Golgi apparatus

Question 20

An important structure of a eukaryotic cell is lysosomes.

Describe the general behaviour and structure of lysosomes

Answer 20

• Contains and releases hydrolytic enzymes
• Contains and releases lyzozomes (enzyme)
• It is single membrane and in a spherical shape
• They isolate the hydrolytic enzymes before release so that there is no unwanted breakdown of the cells ultrastructure

Question 21

List the functions of lysosomes

Answer 21

• Fuse with foreign materials ingested by phagocytic cells and release hydrolytic enzymes
• Release enzymes to the outside of the cell in exocytosis to break down molecules
• Breakdown damaged and worn out organelles so the useful molecules they’re built from can be restored
• Completely break down dead cells (autolysis)

Question 22

Describe the role of organelles in eukaryotic cells for the production, transport and release of proteins (6)

Answer 22

1. DNA in the nucleus codes for proteins
2. Ribosomes/RER produce proteins
   Allow synthesise proteins
3. Mitochondria produce ATP (for protein synthesis)
   Reject any reference to energy
4. Golgi apparatus modify and package proteins
5. Vesicles transport proteins
6. Vesicles fuse with cell (surface) membrane during exocytosis

Question 23

What do plant cells contain that animal cells do not?

Answer 23

• Large central vacuole containing cell sap
• Chloroplasts
• Cell wall

Question 24

What is the main storage difference between animal and plant cells?

Answer 24

• Animal cells store carbohydrates as glycogen
• Plant cells store carbohydrates as starch

Question 25

Draw out and label the structure of a chloroplast

Answer 25

Include:
- Inner membrane and outer membrane
- Granum
- Thylakoid
- Starch grain
- 70S ribosomes
- DNA
- Stoma

Question 26

Describe the structure of a chloroplast

Answer 26

1. Site of photosynthesis
2. The chloroplast envelope is a double membrane, it is highly selective and controls what goes in and out.
3. Inside, is the grana, these are stacks of (up to 100) disc shaped thylakoid which contain membranes
4. Thylakoid membranes contain the photosynthetic pigment chlorophyl, the first stage of photosynthesis takes place here
5. The stroma is a fluid filled matrix, which contains photosynthetic enzymes and starch grains. The second stage of photosynthesis takes place here

Question 27

Outline the functions of a chloroplast

Answer 27

• The thylakoid membrane has a large surface area so that lots of (the photosynthetic pigment) chlorophyll can be stored
• Chloroplasts contain their own circular DNA and ribosomes so that they can form there own proteins for photosynthesis

Question 28

Draw and label the structure of a cellulose cell wall

Answer 28

See notes

Question 29

Describe the structure and functions of a cellulose cell wall

Answer 29

• Straight chains of beta glucose are held together by many (weak) hydrogen bonds forming microfibril
• These provide strength, stability and rigidity
• They prevent the cell from bursting due to pressure of water entry by osmosis

Question 30

Draw and label the structure of a vacuole

Answer 30

See notes

Question 31

Outline the structure and functions of a vacuole

Answer 31

• Fluid containing sack bound by a single membrane called a tonoplast
• Contains: mineral salts, waste, amino acids, sugars, and sometimes pigment
• It provides support - keeps the cell turgid
• Pigment attracts pollinating insects

Question 32

State the differences a prokaryotic cell has compared to a eukaryotic cell (6)

Answer 32

• DNA is circular, not histone bound and contains no introns
• No true nucleus, DNA is found free in the cytoplasm
• Contains smaller 70S ribosomes
• Cell wall is made of glycoprotein meurin (plant cell walls are made of cellulose)
• No membrane-bound organelles
• Contains: capsule, one or more plasmids and one or more flagella

Question 33

One key function of lysosomes

Answer 33

• Fuse with vesicles
• Release hydrolytic enzymes
• Break down