Cell Biology - 1.2 Ultrastructure of cells

Question 1

Prokaryotic cells

Answer 1

Bacteria and Archaea

• No nuclear membrane (ie a nucleoid) (no definite nucleus) - DNA is stored in the cytoplasm
• DNA is not bound to proteins
• Division by binary fission (ie asexual)
• all unicellular (single-celled)
• VERY SMALL

Pili – shown as single lines
Flagella – shown as thicker and significantly longer lines than the pili
Ribosomes – labelled as 70S
Cell wall – labelled as being composed of peptidoglycan; thicker than cell membrane
Shape – appropriate for bacteria chosen

Question 2

Organelles

Answer 2

Tiny structures within the cytoplasm that preform specific jobs eg. ribosomes

Question 3

Eukaryotic cells

Answer 3

All other life (BUT BACTERIA AND ARCHAEA) eg. animals/plant/Protoctista (protist)/Fungal cells

• has a nucleus.
• bigger than a prokaryote
• division by binary fission, mitosis or meiosis
• unicellular or multicellular
• contain membrane-bound organelles (and form spindles during mitosis and meiosis)
• have a compartmentalized cell structure
• eukaryote chromosome (enclosed within a nuclear membrane) is a folded length of SNA - wound around proteins called histones

Question 4

Cell membrane

Answer 4

Responsible for regulating what materials move into and out of the cell

Question 5

Nucleoid

Answer 5

DNA with ends that come together to form a circle (and its NOT wrapped around proteins)

Question 6

Cytoplasm

Answer 6

Gel-like fluid substance (mostly water with many dissolved molecules), site of metabolic reactions

Question 7

Ribosomes

Answer 7

complexes of RNA and protein that are responsible for polypeptide synthesis and build proteins during translation

Question 8

Plasmid (Structure found in SOME but not ALL prokaryotic cells)

Answer 8

Extra pieces of small circular DNA that can be shared between bacteria (by conjugation), often contain genes for antibiotic resistance

Question 9

Cell wall

Answer 9

provides shape and allows the cell to withstand turgor pressure with bursting

Question 10

Pili (Structure found in SOME but not ALL prokaryotic cells)

Answer 10

enable the cell to attach to surfaces, swap DNA with other cells and may be used to harpoon DNA in the environment

Question 11

(slime) Capsule (Structure found in SOME but not ALL prokaryotic cells)

Answer 11

A thick polysaccharide layer Helps the cell keep from dehydrating (desiccation), phagocytosis and adhere to surfaces

Question 12

Flagellum (Structure found in SOME but not ALL prokaryotic cells)

Answer 12

Long extensions containing a motor protein that enable movement - used in cell locomotion

Question 13

Cytoplasm

Answer 13

The internal fluid component of the cell

Question 14

Cytoplasm

Answer 14

The internal fluid component of the cell - gives the cell shape

Question 15

Compartmentalized

Answer 15

= a separate section of a structure (cell) in which certain items ( can be kept separate from others) - occurs in Eukaryotic cells BUT NOT prokaryotic cells

Advantage = an organelle can create a compartment with controlled conditions - tailored to the specific functions of the organelle (a microenvironment)
- they are super-efficient

Question 16

Process of binary fission

Answer 16

1. Prepare for division (must have enough energy and resources)
2. DNA is replicated semi conservatively (and depends on the complementary base pairing
3. the two DNA loops attach to the membrane + cell growth
   4/5. the membrane elongates and pinches off (cytokinesis) forming two separate cells
4. Two cells = The two daughter cells are genetically identically
   = In ideal conditions this can occur every 20 minutes

Question 17

Asexual reproduction

Answer 17

= offspring arise from a single parent cell or organism
= the offspring are genetically identical to the parent

(Binary fission and mitosis are mechanisms of asexual reproduction)

Question 18

eukaryote cells -> Animal cells eg. skin, muscle, nerve etc. cells

Answer 18

• Multicellular, specialized cells
• Possess nucleus and membrane-bound organelles
• lack cell walls
• heterotrophic

Question 19

eukaryote cells -> Plant cells eg. leaf, root, skin etc. cells

Answer 19

• Multicellular, specialized cells
• possess nucleus and membrane-bound organelles
• contain chloroplasts
• cell walls of cellulose
• Autotrophic

Question 20

eukaryote cells -> Protoctista (protist) cells eg. amoeba, paramecium, chlorella etc. cells

Answer 20

• mostly free-living single cells

- some autotrophic, some heterotrophic

Question 21

eukaryote cells -> Fungal cells eg. yeasts, mushrooms, mould etc. cells

Answer 21

• possess a nucleus and membrane-bound organelles

- cell walls of chitin

Question 22

what does membrane-bound organelles mean?

Answer 22

The small structure inside the cell membrane that carries out various important cellular functions - organelles are bound by a membrane that allows for things to move in and out of the cell

Question 23

Nucleus

Answer 23

the control centre containing all genetic information (DNA) for the cell which controls all cell activities - contains the nucleolus

Question 24

ROUGH endoplasmic reticulum

Answer 24

series on connected flattened membranous sacs that play a central role in the synthesis and transport of proteins

• has ribosomes
• closer to the nucleus

Question 25

SMOOTH endoplasmic reticulum

Answer 25

smooth ER lacks ribosomes and is not involved in protein synthesis MAIN FUNCTIONS = the synthesis of phospholipids and cholesterol and the syntheses and repair of membranes

Question 26

Golgi apparatus

Answer 26

Package and release proteins from the cell: - modifies, sorts, concentrates and packs proteins from the RER into sealed droplets called vesicles - dispatched into either the lysosomes (organelles in the cell), Plasma membrane of secretion to outside of the cell

Question 27

Lysosome

Answer 27

- Small spherical organelles enclosed by a single membrane - contain enzymes that work in o2 poor areas and lower pH - Enzymes digest large nutrient molecules and/or degrade and recycle the components of the cell's own organelles when they are old/damaged (or the cell is starving - lack of nutrients)

Question 28

Mitochondria

Answer 28

- Location of aerobic cellular respiration which is used to make ATP - ATP is then used to duel the exocrine gland cells protein synthesis, active transport and exocytosis (cells convert food to energy via respiration)

Question 29

Small vacuoles (vesicles) - can not be seen on lab microscope

Answer 29

store food and chemicals and floating in the cytoplasm (Animals cells = many small) (Plan cells = ONE large central vacuole)

Question 30

Centrioles

Answer 30

Makes spindle for cell division

Question 31

Animal cells (organelle list)

Answer 31

``` Cell membrane cytoplasm nucleus mitochondria ribosomes lysosome smooth ER rough ER Golgi bodies centrioles small vacuoles nucleolus ```

Question 32

Plant cells (organelle list)

Answer 32

``` Cell membrane cytoplasm nucleus chloroplasts cell wall large vacuole mitochondria smooth ER rough ER ribosomes lysosome golgi bodies nucleolus ```

Question 33

Fungal cells (organelle list) = can be unicellular or multicellular

Answer 33

- have complex cellular organisation --> DON'T HAVE chloroplasts or chlorophyll ``` Cell membrane cytoplasm nucleus mitochondria ribosomes small vacuoles cell wall golgi bodies ```

Question 34

Protist cells (organelle list)

Answer 34

``` Cell membrane cytoplasm nucleus mitochondria ribosomes small vacuoles chloroplasts eyespot cilia or flagella golgi bodies contractile vacuole ```

Question 35

Cell size

Answer 35

Cells are usually measured in micrometres (μm) (1000 μm = 1 mm) Very small structures (and/or virsus) are measured in nanometers (nm) (1,000,000nm = 1mm or 1000nm = 1μm) (Plant cells are normally larger than animals cells)

Question 36

Resolution (in terms of microscopes)

Answer 36

= is the smallest interval distinguishable by the microscope which then corresponds to the degree of detail visible in an image created by the instrument ie. magnification is = but the resolution is better with the electron microscope Resolution is the shortest distance between two points that can be distinguished

Question 37

Ultrastructure

Answer 37

fine structure, especially within a cell, that can be seen only with the high magnification obtainable with an electron microscope.

Question 38

Light microscopes

Answer 38

- combination of lenses to magnify objects up to 1000x (eg. 10x eyepiece and e 40x objective = 400x magnification) - Specimens viewed must be thin and mostly transparent as light is focused up through the specimen - live specimens (eg. bacteria) can be viewed - Resolution is the shortest distance between two points that can be distinguished (resolution is 0.2μm)

Question 39

Electron microscopes

Answer 39

- uses a beam of electrons (rather than light) to produce an image - magnification = 100,000-250,000 x - specimens must be sections/placed on a special disc in a vacuum (live specimens can NOT be viewed) - Resolution is 0.001μm Two types: 1) Transmission EM (which can view organelles and micro-structure of cells) 2) scanning EM (which can view the outside surface features of cells and tissues

Question 40

Calculation of Magnification:

Answer 40

To calculate the linear magnification of a drawing or image, the following equation should be used: Magnification = Image size (with ruler) ÷ Actual size (according to scale bar)

Question 41

Calculation of Actual Size:

Answer 41

To calculate the actual size of a magnified specimen, the equation is simply rearranged: Image size (with ruler)/measured length ÷ Magnification = Actual/total Size