[3.2.1] Cell Structure

Question 1

Describe the features of an eukaryotic cell

Answer 1

• membrane-bound nucleus
• numerous membrane-bound organelles
• several rod-shaped chromosomes
• 10-100μm in size
• have 80s ribosomes

Question 2

Name the structures found in eukaryotic cells and define their roles

Answer 2

• The Nucleus → the “control centre” of the cell through the production of (m&t)RNA and protein synthesis, retain genetic material as DNA and chromosomes, manufacture ribosomal RNA and ribosomes.
• The Mitochondria → responsible for the production of ATP.
• The Chloroplast → carry out photosynthesis (plants only)
• The Endoplasmic Reticulum → to produce proteins for the rest of the cell to function. Can be split into the SER and RER
• The Golgi Apparatus: → adds carbohydrates to proteins to make glycoproteins
• The Lysosomes: → hydrolyse materials ingested by phagocytic cells
• Ribosomes: protein synthesis
• Cell Wall: provide structural strength in cell to prevent bursting under osmosis [found in plants]
• Vacuole: a fluid-filled sac bounded by single membrane

Question 3

Name the structures found in the nucleus

Answer 3

Nuclear Pores: allow large molecules out of the nucleus
Nucleoplasm: jellylike material that makes up the bulk of the nucleus
Chromosomes: consists of protein-bound, linear DNA
Nucleolus: manufactures ribosomal RNA and assembles ribosomes

Question 4

Name the structures found in the mitochondria

Answer 4

A Double Membrane: control the entry and exit of material
Cristae: extensions of the inner membrane → provides larger surface area for enzyme actions and other proteins for respiration
The Matrix: contains lipids, proteins, ribosomes and DNA to control the production of DNA

Question 5

What function do the SER and RER play in the cell

Answer 5

Smooth Endoplasmic Reticulum = [tubular appearance] to synthesise, store and transport both lipids and carbohydrates
Rough Endoplasmic Reticulum = [has ribosomes on membrane] provide a large surface area for protein synthesis and glycoproteins, provide a pathway for transport of proteins throughout the cell

Question 6

Function of the Golgi apparatus

Answer 6

→ adds carbohydrates to proteins to make glycoproteins
→ produce secretory enzymes
→ secrete carbohydrates
→ transport/ modify & store lipids
→ form lysosomes

Question 7

Function of lysosomes

Answer 7

hydrolyse materials ingested by phagocytic cells
→ release enzymes to the outside of the cell in order to destroy material around the cell
→ digest worn out organelles
→ break down dead cells

Question 8

Features of cell wall

Answer 8

Made from the polysaccharide cellulose
Have a thin layer called the middle lamellae → the cementing layer between the primary wall and the adjacent wall
Contribute to the movement of water through the plant

Question 9

Describe the features of a prokaryotic cell

Answer 9

• Unicellular & smaller than eukaryotic cells (0.1 - 0.5μm compared to 10 - 100μm)
• No membrane-bound organelles
• No nucleus, mitochondria, (rough & smooth) endoplasmic reticulum or golgi apparatus
• Have free-floating chromosomes instead of a nucleus
• Have plasmids
• Have a smaller ribosome (70s)
• Have cell membranes
• Have cell walls (made from murein instead of cellulose/chitin)
• (SOME) contain a cell capsule
• Have a flagella
• Plasmids - The plasmid DNA often carries genes essential for bacterial survival (eg: antibiotic resistant genes)
• Prokaryotic Capsule - Can protect bacteria from the immune system of organisms that they can invade.

Question 10

Describe the features of a virus

Answer 10

• They are not living cells and are acellular
• They are smaller than bacteria (ranging from 20 - 30nm)
• They contain nucleic acids such as DNA or RNA as genetic material but only multiply inside living host cells.
• Nucleic acid enclosed in a “capsid” (a protein coating)
• (SOME) are surrounded by a lipid envelope
• Have “attachment proteins” - allows virus to identify and attach to host cell