Eukaryotic Cells

Question 1

What is the function of the cell surface membrane?

Answer 1

• Partially permeable
• Formed from a phospholipid bilayer of phospholipids spanning a diameter of around 10nm

Question 2

What are the features of the cell surface membrane?

Answer 2

• Surrounds cells + controls the exchange of materials between the internal cell environment and the external environment

Question 3

What is the function of the cell wall?

Answer 3

• formed outside of cell membrane + gives structural support to the cell
• support is provided by the polysaccharide cellulose in plants + peptidoglycan in most bacterial cells

Question 4

What are the features of the cell wall?

Answer 4

• found in plant cells, not animal
• narrow threads of cytoplasm (surrounded by cell membrane) called plasmodesmata connect the cytoplasm of neighbouring plant cells

Question 5

What is the function of the nucleus?

Answer 5

• controls all cell activity
• where genetic code is stored, replicated and transcribed into RNA
• attached to the rough ER so mRNA can easily access ribosomes

Question 6

What are the features of the nucleus?

Answer 6

-present in all eukaryotic cells (except red blood cells)
- relatively large + separated from cytoplasm by a double membrane (nuclear envelope) which contains pores
- nucleus contains chromatin (material from which chromosomes are made)

Question 7

What are the features and the function of the nuclear pores?

Answer 7

-allows for small molecules to enter and leave the nucleus
- nuclear pores are important channels for the mRNA + ribosomes to travel out of the nucleus, as well as allowing enzymes (e.g. DNA polymerase) + signalling molecules to travel in.

Question 8

What are the features and the function of nucleolus?

Answer 8

• composed of RNA and proteins
• usually one or more darkly stained regions can be observed - the sites of ribosome production

Question 9

What are the features and the function of the nuclear envelope?

Answer 9

• double membrane which encompasses the nucleus and prevents damage. Protects the DNA

Question 10

What is chromatin?

Answer 10

• A complex of DNA and histone proteins
• Sections of linear DNA tightly wound around proteins called histones
• contains the genetic code and controls the activity of the cell

Question 11

What is the function of mitochondria?

Answer 11

the site of aerobic respiration within all eukaryotic cells

Question 12

What are the features of mitochondria?

Answer 12

• surrounded by double membrane within the inner membrane folded to form cristae
• matrix formed by cristae contains enzymes needed for aerobic respiration, producing ATP
• small circular pieces of DNA (mitochondrial DNA) and ribosomes are also found in the matrix (needed for replication)

Question 13

What is the function of chloroplasts?

Answer 13

• site of photosynthesis:
  light dependent stage takes place in thylakoids.
  light independent stage (Calvin cycle) takes place in stroma.
• contains small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis.

Question 14

What are the features of chloroplasts?

Answer 14

• found in plant cells
• larger than mitochondria, surrounded by double membrane
  -contains thykloids (membrane bound compartments containing chlorophyll) stack to form grana
• grana is joined together by lamellae (thin and flat thylakoid structures)

Question 15

What is the function of ribosomes?

Answer 15

Site of protein synthesis by assembling amino acids into proteins in chains using RNA.

Question 16

What are the features of ribosomes?

Answer 16

• found in all cells
• found freely in the cytoplasm of all cells / part of the rough ER (endoplasmic reticulum)
• each ribosomes is a complex of ribosomal RNA (rRNA) and proteins
  -80S and 70S ribosomes

Question 17

What is the differences between 80S and 70S ribosomes?

Answer 17

80S - composed of 60S +40S subunits - found in eukaryotic cells
70S - composed of 50S and 30S subunits - in prokaryotes, mitochondria, and chloroplasts

Question 18

What is the function and features of the Rough ER?

Answer 18

• found in plant+animal cells
• covered in ribosomes
• formed from continuous folds of membrane continuous with the nuclear envelope
  -processes proteins made by the ribosomes

Question 19

What is the function and features of the Smooth ER?

Answer 19

• found in plant+animal cells
• does not have ribosomes on surface
• involved in the production, processing and storage of lipids, carbohydrates and steroids