Module 2.1 - Cell Structure

Question 1

Role of the nucleus

Answer 1

Stores organism’s genome
Controls the cell
Transmits genetic information
Provides instructions for protein synthesis

Question 2

Role of chloroplasts

Answer 2

Site of photosynthesis
First stage of photosynthesis, light energy is trapped by chlorophyll and used to make ATP (occurs in grana)
Second stage of photosynthesis, hydrogen reduced carbon dioxide using energy from ATP to make carbohydrates (occurs in the stroma)

Question 3

Main points about light microscopes

Answer 3

Magnification up to x1500
Resolution up to 200nm
Stain using methylene blue or acetic orcein for DNA
Glass lenses
Light as radiation source
Dead specimen prepared on slide

Question 4

Role of smooth endoplasmic reticulum

Answer 4

Contains enzymes that catalyse reactions involved with lipid metabolism (e.g. synthesis of cholesterol, lipids/phospholipids needed by the cell and steroid hormones)
Involved with absorption, synthesis and transport of lipids

Question 4

Role of ribosomes

Answer 4

Those bound to exterior of RER are manly for synthesising proteins that will be exported outside the cell
Those free in the cytoplasm are mainly the site of assembly of proteins that will be used inside the cell

Question 5

Main points about TEMs

Answer 5

Magnification up to x500,000
Resolution up to 0.1nm
Stain using heavy metal or metal salt
Electromagnetic lenses
Electrons as radiation source
Dead specimen prepared as thin and trained
2D image

Question 7

Role of lysosomes

Answer 7

Keep powerful hydrologic enzymes separate from rest of the cell
Many of them in phagocytes
Engulf old cell organelles and foreign matter, digest them and return these components to the cell for reuse

Question 7

Role of centrioles

Answer 7

Spindle forms from centrioles before a cell divides

Involved in formation of cilia and undulipodia

Question 8

Main points about vacuoles

Answer 8

Large and permanent part of plant cells only

Tonoplast membrane is filled with water and sugars to push against the cell wall to keep the cell turgid

Question 9

Role of the nuclear envelope

Answer 9

Separates contents o nucleus from rest of the cell
Outer and inner membranes fuse so some dissolved substances and ribosomes can pass through
Pores in membrane allow larger substances (e.g. mRNA) to leave the nucleus or enter the nucleus (e.g. steroid hormones)

Question 10

Role of nucleolus

Answer 10

Contains RNA

Is where ribosomes are made

Question 12

Define magnification

Answer 12

The degree to which the size of the image is the larger than the size of the object itself

Question 13

Main points about actin microfilaments

Answer 13

2 intertwined strands of actin
7nm diameter
Maintain cell shape
Cause muscle contractions
Involved in cell division (cytokinesis)
Cause a certain type of movement called pseudopodia seen by amoeba and some white blood cells

Question 13

Main points about plant cell walls

Answer 13

Made of cellulose (a carbohydrate polymer)
Forms grid of strands which makes the wall strong
Supports the cell because of pressure from liquid in the cell, keeping it rigid and helping to support the plant

Question 15

Define cytoskeleton

Answer 15

Network of protein fibres within a cell that gives structure and shape to the cell and also moves organelles around the cell

Question 16

Main points about microtubules

Answer 16

Main part of cytoskeleton
Hollow cylinders of tubulin (protein) about 25nm diameter
Maintain cell shape
Connect organelles to each other to keep them in place
May be used to move microbes through liquid or waft liquid past a cell

Question 17

Role of mitochondria

Answer 17

Site of ATP (energy currency) production during aerobic respiration

Question 18

Main points about flagella

Answer 18

Structurally the same in all types of cells
Sticks out of surface
Cylinder with 9 microtubules in a circle and 2 more microtubules in a central bundle
Move using energy from ATP

Question 19

Role of rough endoplasmic reticulum

Answer 19

Intracellular transport system - cisternae form channels for moving substances between areas of the cell
Provides large surface area for ribosomes

Question 20

Main points about intermediate filaments

Answer 20

Thick cables made of keratin
10nm diameter
Maintain cell shape
Anchor nucleus and organelles

Question 21

Main points about vesicles

Answer 21

Membrane bound sacs

Carry substances around

Question 22

Role of Golgi apparatus

Answer 22

Modify proteins (e.g. add sugar molecules to make glycoproteins; add lipid molecules to make lipoproteins; fold into their 3D shape)
Proteins are packaged into vesicles and then either stored in the cell or moved to the plasma membrane

Question 23

What are the three parts of the cytoskeleton?

Answer 23

Microtubules
Intermediate filaments
Actin microfilaments

Question 24

Define resolution

Answer 24

The degree to which it is possible to distinguish between two objects that are very close together

Question 25

Advantages of light microscopes

Answer 25

Relatively cheap
Easy to use
Portable
Can be used to study whole living specimens

Question 26

Disadvantages of light microscopes

Answer 26

Lower magnification than electron microscopes

Lower resolution than electron microscopes

Question 27

Main points about SEMs

Answer 27

Magnification up to x100,000
Resolution up to 10nm
Stain using metal or metal salt
Electromagnetic lenses
Electrons as radiation source
Dead specimen
3D image

Question 29

Explain microtubules motors

Answer 29

They are proteins found on microtubules
Use ATP to move organelles or cell contents along the fibres
This is how chromosomes are moved in mitosis as spindle fibres are microtubules made by centrioles
This is how vesicles move from the ER to Golgi apparatus

Question 30

Main points about cilia

Answer 30

Occur in large numbers on ciliates epithelial tissue
Less than 10 micrometers long
Beat to and fro to move substances across cell surfaces
Move mucus across airway linings
Move egg down oviducts
Rare in plants

Question 30

Main points about laser scanning microscopes

Answer 30

Also called confocal microscopes
Use laser light to scan an object point by point and assemble the pixel information on the computer screen
Images are high resolution with high contrast
Able to observe whole living specimens