1.2 Ultrastructure of Cells

Question 1

Features of Prokaryote cells

Answer 1

• simple, single-celled bacteria
• very small
• chromatin material or DNA is not held within a nuclear membrane
• DNA is not bound to proteins
• Chromosome is a simple SNA chain with ends joined to form a circle
• cells do not have membrane-bound organelles
• may be autotrophic, heterotrophic or chemotrophic

Question 2

Organelles in Prokaryote Cells

Answer 2

• Genetic material, strand
• Cytoplasm: internal fluid
• Plasmids: autonomous circular DNA molecules
• Ribosomes: responsible for polypeptide synthesis (70S)
• Cell membrane: semi-permeable, selective barrier
• Cell wall: rigid outer covering, maintains shape and prevents bursting
• Slime capsule: thick polysaccharide layer used for protection against desiccation and phagocytosis (drying out)
• Flagella: long projection that enables movement
• Pili: hair like extensions that enable adherence to surfaces

Question 3

Prokaryote reproduction

Answer 3

they reproduce asexually by binary fission

• the DNA is replicated semi conservatively
• the two DNA loops attach to the membrane
• the membrane elongates and pinches off (cytokinesis) forming two separate cells
• the two daughter cells are genetically identical

Question 4

Features of Eukaryote cells

Answer 4

• cells other than bacteria that have a ‘true nucleus’
• the chromosomes are enclosed within a nuclear membrane
• eukaryote chromosome is a folded length of DNA, wound around proteins called histones
• contain membrane bound organelles, form spindles during mitosis and meiosis (centrioles)
• ribosomes are 80S
  4 types: animal cells, plant cells, protoctists cells, fungal cells

Question 5

Organelles in Animal Cells

Answer 5

• Cell membrane: layer that transports materials in and out of the cell
• Cytoplasm: contains a soup of chemicals in which reactions occur, gives cell shape
• Nucleus: contains DNA and controls cell activity
• Mitochondria: site of cell respiration (converts food to energy)
• Ribosomes: site of protein synthesis
• Lysosome: manages cell waste with enzymes
• Smooth ER: transport system from nucleus (lipids)
• Rough ER: transport system from nucleus with ribosomes (protein)
• Golgi bodies: (apparatus and vesicles) packages protein for secretion into vesicles
• Centrioles: Makes spindle for cell division
• Small vacuoles: storage for food chemicals or water
• Nucleolus: works with nucleus to control cell activities
• Microvilli: some animal cells have these, to increase SA, (SA:V ratio)

Question 6

Organelles in Plant Cells

Answer 6

• Cell membrane: layer that transports materials in and out of the cell
• Cytoplasm: contains a soup of chemicals in which reactions occur, gives cell shape
• Nucleus: contains DNA and controls cell activity
• Chloroplasts: contains chlorophyll and is site of photosynthesis
• Cell wall: cellulose structure that maintains plant cell structure and shape
• Mitochondria: site of cell respiration (converts food to energy)
• Ribosomes: site of protein synthesis
• Smooth ER: transport system from nucleus (lipids)
• Rough ER: transport system from nucleus with ribosomes (protein)
• Golgi bodies: (apparatus and vesicles) packages protein for secretion into vesicles
• Large vacuole: storage (normally water)
• Nucleolus: works with nucleus to control cell activities

Question 7

Features of Fungal Cells

Answer 7

• can be unicellular or multicellular
• are eukaryotes with complex cell structure
• no chloroplasts or chlorophyll

Question 8

Organelles in Fungal Cells

Answer 8

• Nucleus
• Mitochondria
• Cell membrane
• Small vacuoles
• ER
• Golgi bodies
• Cell Wall: composed of chitin

Question 9

Cell Size order

Answer 9

Largest to Smallest:
Amoeba, Plant/Animal cells, Onion skin cell, Human skin cell, bacteria, cell organelles, viruses, plasma membrane, molecules

(remember nm are smaller than micrometres)

Question 10

Light Microscope

Answer 10

• magnify up to 1000x
• specimens must be thin
• resolution is 0.2 micrometres

Question 11

Electron Microscope

Answer 11

• have a much higher resolution than light microscopes (0.001 micrometres)
• use a beam of electrons to view the specimen
• magnification is 100 000x - 250 000x
• ultrastructure can be viewed under these microscopes

Question 12

What is resolution?

Answer 12

It is the shortest distance between two points that can be distinguished.

Question 13

Calculation for magnification

Answer 13

Magnification = scale bar measurement / scale bar label

make sure to make the same units - 1000 micrometres = 1 mm