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Biology > TOPIC 2 cells > Flashcards

TOPIC 2 cells Flashcards

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1
Q

Define the terms eukaryotic and prokaryotic cells

A

eukaryotic: DNA is contained in a nucleus, contains membrane bound specialised organelles

prokaryotic: DNA is ‘free’ in cytoplasm
no organelles e.g bacteria and archaea

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2
Q

state the relationship between a system and specialised cells

A

specialised cells —> tissues that perform specific functions —> organs made of several tissue types —> organ systems

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3
Q

describe the function and structure of the cell surface membrane

A

‘fluid mosaic’ phospholipid bilayer with extrinsic and intrinsic proteins embedded

• isolates cytoplasm from extracellular environment

• selectively permeable to regulate transport of substances

• involved in cell recognition

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4
Q

explain the role of cholesterol, glycoproteins and glycolipids in the cell surface membrane

A

CHOLESTEROL: steroid molecule connects phospholipids and reduced fluidity

Glycoproteins: cell signalling, cell recognition (antigens) , and binding cells together

glycolipids: cell signalling and cell recognition

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5
Q

describe the structure of the nucleus

A

• contains DNA coiled around chromatin into chromosomes

• controls cellular processes:
gene expression determines specialisation and site of mRNA transcription, mitosis, semiconservative replication

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6
Q

describe the structure of a mitochondrion

A

• surrounded by double membrane folded inner membrane forms cristae: site of electron transport chain

• fluid matrix : contains mitochondrial DNA, respiratory enzymes, lipids, proteins

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7
Q

Describe the structure of a mitochondrion

A

• surrounded by double membrane folded inner membrane forms cristae: site of electron transport chain

• fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids, proteins

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8
Q

describe the structure of a chloroplast

A

• vesicular plastid with double membrane

• thylakoids: flattened discs stack to form grana: contains photosystems with chlorophyll

• intergranal lamellae: tubes attach thylakoids in adjacent grana

• stroma: fluid filled matrix

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9
Q

state the function of mitochondria and chloroplasts

A

mitochondria: site of aerobic respiration to produce ATP

chloroplast: site of photosynthesis to converts solar energy to chemical energy

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10
Q

describe the structure and function of the golgi apparatus

A

Planar stack of membrane-bound, flattened sacs cis face aligns with rER

molecules are processed in cisternae
vesicles bud off trans face via exocytosis:

• modifies and packages proteins for export
• synthesises glycoproteins

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11
Q

describe the structure and function of a lysosome

A
  • Sac surrounded by single membrane
  • embedded H+ pump maintains acidic conditions
  • contains digestive hydrolase enzymes
  • glycoprotein coat protects cell interior

• digests contents of phagosome
• exocytosis of digestive enzymes

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12
Q

describe the structure and function of a ribosome

A

Formed of protein and rRNA
free in cytoplasm or attached to ER

• site of protein synthesis via translation:
large subunit: joins amino acids
small subunit: contains mRNA binding site

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13
Q

describe the structure and function of endoplasmic reticulum (ER)

A

Cisternae : network of tubules and flattened sacs extends from cell membrane through cytoplasm and connects nuclear envelope

• rough ER : many ribosomes attached for protein synthesis and transport

• smooth ER : lipid synthesis

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14
Q

describe the structure of the cell wall

A

• bacteria:
made of the polysaccharide murein

• plants:
made of cellulose microfibrils
plasmodesmata allow molecules to pass between cells, middle lamella acts as a boundary between adjacent cell walls

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15
Q

describe the functions of the cell wall

A

• mechanical strength and support
• physical barrier against pathogens
• part of apoplast pathway to enable easy diffusion of water (plants)

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16
Q

describe the structure and function of the cell vacuole in plants

A

surrounded by a single membrane: tonoplast

contains cell sap: mineral ions, water, enzymes, soluble pigment

• controls turgor pressure
• absorbs and hydrolyses potentially harmful substances to detoxify cytoplasm

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17
Q

explain some common cell adaptations

A

• folded membrane or microvilli increase surface area for diffusion

• many mitochondria = large amounts of ATP for active transport

• walls one cell thick to reduce distance of diffusion pathway

18
Q

state the role of plasmids in prokaryotes

A

• small ring of DNA that carries non essential genes

• can be exchanged between bacterial cells via conjugation

19
Q

state the role of flagella in prokaryotes

A

rotating tail propels organism

20
Q

state the role of the capsule in prokaryotes

A

polysaccharide layer:

• prevents desiccation
• acts as a food reserve
• provides mechanical protection against phagocytosis and external chemicals
• sticks cells together

21
Q

compare eukaryotic and prokaryotic cells

A

both have:
• cell membrane
• cytoplasm
• ribosomes

22
Q

contrast eukaryotic and prokaryotic cells

A

• prokaryotic cells are small cells and always unicellular whereas eukaryotic are larger cells and often multicellular

• prokaryotics have no membrane bound organelles and no nucleus
eukaryotics always have organelles and a nucleus

• prokaryotic have circular DNA not associated with proteins
eukaryotic has linear chromosomes associated with histones

• plants cell wall = cellulose
fungi cell wall = chitin
bacteria cell wall = murein

23
Q

why are virus’s referred to as particles instead of cells

A

• acellular + non living:
no cytoplasm, cannot self reproduce, no metabolism

24
Q

describe the structure of a viral protein

A

• linear genetic material and viral enzyme (reverse transcriptase)
• surrounded by capsid
• no cytoplasm

25
Q

describe the structure of an enveloped virus

A

• simple virus surrounded by matrix protein
• matrix protein surrounded by envelope derived from cell membrane of host cell
• attachment proteins on surface

26
Q

state the role of the capsid on viral particles

A

• protect nuclei acid from degradation
by restriction endonuclease
• surface sites enable viral particle to bind to and enter host cells or inject their genetic material

27
Q

state the role of attachment proteins on viral particles

A

enable viral particles to bind to complementary sites on host cell

28
Q

how do optical microscopes work

A
  1. lenses focus rays of light and magnify view of a thin slice of specimen
  2. different structures absorb different amounts and wavelengths of light
  3. reflected light is transmitted to the observer via the objective lens and eyepiece
29
Q

how could a student prepare a temporary mount of tissue for an optical microscope

A
  1. obtain thin section of tissue
  2. place plant tissue in a drop of water
  3. stain tissue on a slide to make structures visible
  4. add coverslip using mounted needle at 45° to avoid trapping air bubbles
30
Q

what are the advantages of using an optical microscope

A

✅ colour image
✅ can show living structures
✅ affordable apparatus

31
Q

what are the disadvantages of using an optical microscope

A

❌2D image
❌lower resolution than an electron microscope

32
Q

how does a transmission electron microscope work

A
  1. pass a high energy beam of electrons through thin slice of specimen
  2. more dense structures appear darker since they absorb more electrons
  3. focus image onto fluorescent screen or photographic plate using magnetic lenses
33
Q

advantages of using transmission electron microscope

A

✅electrons have shorter wavelength than light= high resolution, so ultrastructure visible

✅high magnification

34
Q

limitations of transmission electron microscope

A

❌2D image
❌requires a vacuum = cannot show living structures
❌extensive preparation may introduce artefacts
❌no colour image

35
Q

how does a scanning electron microscope work

A
  1. focus a beam of electrons onto a specimen’s surface using electromagnetic lenses
  2. reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate
36
Q

what are the advantages AND limitations of using a scanning electron microscope

A

✅3D image
✅electrons have shorter wavelength than light so high resolution

❌requires a vacuum so cant show living structures
❌no colour image
❌only shows outer surface

37
Q

define magnification

A

factor by which the image is larger than the actual specimen

38
Q

define resolution

A

smallest separation distance at which 2 separate structures can be distinguished from one another

39
Q

what happens during cell fractionation and ultracentifugation

A
  1. mince and homogenise tissue to break open cells and release organelles
  2. filter homogenate to remove debris
  3. perform differential centrifugation
  4. spin homogenate in centrifuge
  5. the most dense organelles in the mixture form a pellet
  6. filter off the supernatant and spin again at a higher speed
40
Q

which is the most dense organelle

A

nucleus

41
Q

which is the least dense organelle

A

ribosomes

42
Q

why are fractionated cells kept in a cold, buffered, isotonic solution

A

cold: slow action of hydrolase enzymes

buffered: maintains a constant pH

isotonic: prevents osmotic lysis

Biology (6 decks)

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