Chapter 2: Basic Components of Living Systems

Question 1

State cell theory.

Answer 1

• All organisms are composed of one or more cells.
• All cells come from pre-existing cells.
• The cell is the basic unit of structure and organisation in organisms.

Question 2

Outline the features of light microscope.

Answer 2

• 200 micrometers resolution.
• x1000 magnification.
• Living/non-living sample.
• Easy and cheap to create samples.

Question 3

Outline the steps of using a light microscope.

Answer 3

1. Light passes through a mirror under a stage through a condenser lens and through the specimen.
2. Beam of light focused through objective lens and through eyepiece lens.
3. Light microscopes have several objective lenses that can be rotated.
4. Eyepiece lens magnifies image again.

Question 4

Describe the different methods of preparing a specimen sample.

Answer 4

• Wet mount slide = made from sample suspended in water or immersion oil.
• Dry mount slide = made from placing whole specimen or a section of the specimen between a slide and a coverslip.
• Smear slide = produced by smearing a sample across a slide to produce a thin, even film.
• Squash slide = made by preparing a wet mount slide first then using a soft cloth or an eraser to gently apply pressure to the coverslip to squash the sample.

Question 5

Define magnification.

Answer 5

• How much larger the image is than the actual size of the object being viewed.
• M = i/a

Question 6

Define resolution.

Answer 6

• The ability to distinguish between two different objects as two separate entities.

Question 7

Outline features of transmission electron microscope.

Answer 7

• Magnification = x500,000
• Resolution = 0.1nm
• Non-living sample as it will die anyways –> unethical.
• 2D image.
• Beam of electrons transmitted through specimen and focused to produce an image.
• Difficult + expensive to set up and create samples.

Question 8

Why do we label/stain components with a dye?

Answer 8

• To show visible structural details.
• To differentiate between different structural details present.
• To show contrast.

Question 9

Outline features of scanning electron microscope.

Answer 9

• Magnification = x100,000
• Resolution = 0.1nm.
• Non-living sample.
• 3D image.
• Beam of electrons transmitted across surface of specimen and reflected electrons collected.
• Difficult + expensive to set up and create samples.

Question 10

Define artefact.

Answer 10

• Visible structural detail caused by the processing of the specimen.
• Not a feature of the specimen.

Question 11

Outline the process of using laser scanning confocal microscopy (LSCM).

Answer 11

1. LSCM moves a single spot of focused light across the specimen (point illusion).
2. Causes fluorescence from the components labelled with a dye.
3. Emitted light from specimen filtered through a pinhole aperture.
4. Only light emitted from focal plane is detected –> light emitted from other parts of specimen would reduce resolution and cause blurring.
5. Thin section of specimen examined + light from elsewhere removed –> high resolution images obtained.
6. Spot illuminating specimen is moved across specimen and 2D image is produced –> 3D images produced by creating images at different focal planes.

Question 12

Describe structure of mitochondria.

Answer 12

Matrix:

• Contains enzymes for Krebs Cycle + link reaction.
• Contains mitochondrial DNA.

Intermembrane Space:

• Proteins pumped into here by ETC.
• Small space –> concentration builds up quickly.

Inner Mitochondrial Membrane:

• Contains ETC + ATP synthase.

Outer Mitochondrial Membrane:

• Separates contents of mitochondrion from rest of cell.
• Provides cellular compartments with ideal conditions for aerobic respiration.

Cristae:

• Projections of inner membrane.
• Increase s.a. for oxidative phosphorylation.

Question 13

Describe structure of chloroplasts.

Answer 13

• Chlorophyll pigment –> absorb light –> embedded within thylakoid membrane.
• Network of membranes –> large s.a. to vol for increased absorption of sunlight.
• Thylakoids –> flattened sacs –> stack together to form grana.
• Grana joined by lamellae.
• Stroma –> fluid within chloroplasts where most chemical reactions happen –> form complex organic molecules.

Question 14

Describe structure of neutrophils.

Answer 14

• Many lysosomes.
• Many ribosomes.
• Many mitochondria.
• Many microfilaments
• Many receptors binding sites on cell surface membrane.

Question 15

Describe protein production process.

Answer 15

1. Nucleus contains gene for protein.
2. Ribosomes/RER site of protein synthesis.
3. Golgi modifies + packages proteins into transport vesicles.
4. Secretory vesicles move towards + fuse with cell surface membrane releasing contents by exocytosis.
5. Lysosomes contain hydrolytic enzymes for use in cells.

Question 16

Describe the features of the cytoskeleton.

Answer 16

• Cytoskeleton = network of protein fibres found within cells that give structure + shape to cells, and also move organelles around inside cell.

Microtubules:

• Determine shape of cell.
• Act as tracks for movement of organelles including vesicles around cell.
• Spindle fibres –> composed of microtubules.
• Microfilaments = fibres formed from actin that are responsible for cell movement and cell contraction during cytokinesis –> process in which cytoplasm of a single eukaryotic cell is divided to form two daughter cells.
• Intermediate Fibres = give mechanical strength to cell + help maintain integrity.

Question 17

Describe function + structure of vacuole.

Answer 17

• Importance in maintenance of turgor so that contents of cell push against cell wall + maintain rigid framework for cell.

Question 18

State roles of cytoskeleton.

Answer 18

• Whole cell support.
• Movement of cilia.
• Changing shape of cells.
• Movement of chromosomes.
• Organelles, vesicles, moved/held in place.

Question 19

State role of cell membrane within cells

Answer 19

• Compartmentalisation.
• Isolation of contents of organelles.
• Binding site for enzymes + receptors.
• Provides selective permeability.
• Creation of concentration gradients.

Question 20

Outline features of eukaryotic cells.

Answer 20

• Has nucleus.
• Has membrane bound organelles.
• Larger 80s ribosomes.
• Linear DNA.
• DNA organisation –> associated with proteins called. histones.
• Extra chromosomal DNA only present in chloroplasts + mitochondria.
• Cell wall –> chitin in fungi, cellulose in plants, not present in animals.
• Cytoskeleton present –> more complex.
• Asexual + sexual reproduction.
• Unicellular or multicellular.
• Cell surface membrane present.

Question 21

Outline features of prokaryotic cells.

Answer 21

• No nucleus.
• No membrane-bound organelles.
• Smaller 70s ribosomes.
• Circular DNA known as plasmids.
• DNA organisation –> proteins fold + condense DNA.
• Peptidoglycan cell wall.
• Reproduction by binary fission.
• Unicellular
• Cytoskeleton present.
• Cell-surface membrane present.

Question 22

Outline role of Golgi Apparatus.

Answer 22

• Lipid synthesis.
• Receives proteins from RER.
• Modify + package proteins into vesicles.
• Make lysosomes.
• Replenish cell surface/plasma membrane.

Question 23

State the process by which root epidermal cells absorb minerals from the soil + describe how these cells are specialised to achieve absorption.

Answer 23

• Active transport.
• Root pressure.
• Cells have extensions/thin hairs.
• Large s.a. to vol ratio.
• More mitochondria.
• Many carrier proteins in cell surface membrane.