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Biology > Cells > Flashcards

Cells Flashcards

1
Q

Describe the process of cell fractionation to separate organelles of a cell

A
  1. Tissue homogenization to break open cells and release organelles
  2. Filter homogenate to remove debris or whole cells
  3. Use isotonic solution which has same water potential organelles to prevent them from bursting to shrinking from osmosis
  4. Keep cold to slow down enzyme activity
  5. Centrifuge at low speed to separate heavy organelles, eg nuclei
  6. Re-spin supernatant at progressively higher speeds / for mention which pellet contains desired organelles
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2
Q

Describe how TEM works

A
  • beams of electrons penetrate specimen and focused using electromagnets
  • denser parts absorb more elections
  • so they appear darker in the electron micrograph
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3
Q

Role of Golgi Apparatus

A
  • involved in secretion
  • modifies polypeptide to form protein
  • adds lipid/ carbohydrate groups
  • packages into Golgi vesicle
  • transports to cell surface
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4
Q

Role of Mitochondria

A
  • Aerobic respiration
  • RELEASES energy
    (produces=no mark)
  • Produces ATP
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5
Q

Organelles in Eukaryotic cells only

A
  • Nucleus
  • Mitochondria
  • Endoplasmic Reticulum
  • Lysosome
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6
Q

Test for starch

A
  • add iodine

- turns blue-black from orange

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7
Q

Mitochondria

A
  • sites of aerobic respiration
  • produce ATP or release energy
    no mark for PRODUCE energy
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8
Q

Cell fractionation - why is solution cold

A
  • slow down enzyme activity

- to prevent DIGESTION (not damage) of organelles

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9
Q

Cell fractionation - why is solution isotonic

A
  • same water potential as organelles

- to prevent lysis (bursting) from osmosis

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10
Q

Magnification

A

How many times larger the object appears compared to its actual size

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11
Q

Resolution

A

The minimum distance apart two objects can be for them to appear as two distinct objects

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12
Q

Cell fractionation - buffered

A
  • pH does not change
  • structure of organelles is not altered
  • enzyme function is unaffected
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13
Q

Differences between eukaryotic and prokaryotic cells

A
  • no nucleus vs membrane bound nucleus
  • no membrane bound organelles vs several, eg mitochondria and ER
  • DNA not associated with proteins vs histones
  • 70s vs 80s ribosomes
  • capsule vs none
  • cell made from murein vs cellulose (if present)
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14
Q

Nucleolus function

A
  • synthesises ribosomal RNA

- manufactures ribosomes

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15
Q

Nucleus function

A
  • contains all genetic material
  • manufactures rRNA and ribosomes in nucleolus
  • controls DNA replication during cell division
  • controls gene expression > site of transcription
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16
Q

Cristae

A
  • inner membrane of mitochondrion

- provides a large surface area for attachment of enzymes for respiration

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17
Q

Adaptations of chloroplast

A
  • granal membrane has large surface area for attachment of chlorophyll and enzymes
  • stroma fluid posses all enzymes to synthesis sugars
  • chloroplasts contain DNA and ribosomes to quickly manufacture proteins for photosynthesis
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18
Q

Difference between RER and SER

A
  • RER has ribosomes but SER does not
  • RER synthesises proteins
  • SER store proteins and synthesises lipids and steroid hormones
  • RER is attached to nuclear envelope but SER is not
19
Q

Lysosome function

A
  • hydrolyse material ingested by phagocytes
  • digest worn out organelles
  • autolysis (break down dead cells) and exocytosis (destroy material around cell)
20
Q

Centrioles

A

Hollow, cylindrical tubes used in the production of spindle fibers

21
Q

Vacuole function

A
  • makes cell turgid
  • mineral salts and sugars are food store
  • pigments attract pollinating insects
22
Q

Capsule function

A
  • mucilaginous layer of slime
  • protects from other cells
  • or helps groups stick together for further protection
23
Q

Plasmid function

A
  • small circular pieces of DNA
  • replicate independently of nucleoid
  • possess genes to aid survival (e.g. antibiotic resistance)
  • transferred between bacteria
24
Q

Describe how bacteria divide

A
  • binary fission
  • circular DNA replicates and copies attach to cell membrane on opposite poles of cell
  • plasmids replicate
  • cell membrane forms in between and cytoplasm divides forming two daughter cells
  • each with a single copy of circular DNA
25
Q

Virus - accellular

A
  • no cell-surface membrane
  • very few organelles
  • lack ability to reproduce alone
26
Q

Virus - non living

A
  • cannot reproduce alone

- no metabolism

27
Q

Describe viral replication

A
  • viruses attach to host cell + inject viral genetic material
  • viral genome replicated (host cell DNA broken down)
  • transcription and translation of viral genome using components of host cell to assemble more viruses
  • cell lysis to release viruses
28
Q

Artefacts

A

Features not part of the specimens that results form the preparation process, eg scratches, bubbles

29
Q

Calibrating graticule

A

Align with microscope slide called stage micrometer

30
Q

Mitosis

A

Cell division to make two GENETICALLY identical daughter cells

31
Q

Explain all stages of interphase

A

G1 - cell grows and continues with normal cell function
S - DNA replication (form identical sister chromatids)
G2 - cell grows and replicates organelles

32
Q

Centromere

A

Part of chromosomes where sister chromatids are held together

33
Q

Mitosis Process

A 
Interphase - DNA replication creates identical sister chromatids
Prophase 
-chromosomes coil and because fatter/shorter (visible)
- spindle fibers form
- nuclear envelope breaks down
Metaphase
- spindle fibers attach to centromere 
- chromosomes line up in middle 
Anaphase 
- centromere divides
- spindle fibers contract + pull identical sister chromatids to opposite poles
Telophase 
- two sets of chromosomes on opposite poles
- new nuclear envelope
- chromosome becomes long/thin
Cytokinesis 
- cytoplasm divides
34
Q

Evaluate asexual reproduction

A
  • fewer stages so faster
  • produces clones
  • entire population susceptible to disease
35
Q

Evaluate sexual reproduction

A
  • creates genetic variation which aids survival of species
  • natural selection removes disadvantageous alleles
  • requires two parents
  • requires time and energy
  • not all favourable genes passed to offspring
36
Q

Compare TEM/SEM and OM

A
  • OM uses light and TEM uses electron beam
  • TEM has no colour but OM shows specimen in colour
  • TEM / SEM has higher resolution and magnification than OM
  • TEM allows internal structures of organelles to be observed compared to OM
  • OM allows for living specimen where TEM/SEM is dead only (require vacuum in tube)
  • TEM requires thinner specimens compared to OM
  • OM is simple specimen preparation where TEM/SEM is complex (requiring specialist equipment / training)
  • OM has fewer artefacts where TEM/ SEM has many due to preparation process
  • TEM is higher resolution / magnification than SEM
  • SEM produces 3D images
  • SEM allows surface of specimen to be viewed
37
Q

Difference between DNA found in prokaryotic compared to eukaryotic cells

A
  • not associated with histones / no chromosomes
  • non linear
  • no introns
38
Q

Suggest how to distinguish between smooth endoplasmic reticulum and Golgi body diagrammatically

A
  • smooth endoplasmic reticulum surround nucleus and extends from rough endoplasmic reticulum
  • Golgi body is found in the cytoplasm
39
Q

Describe how a polypeptide exits the cell as a functional protein

A
  • polypeptide synthesised by ribosomes on RER
  • travels in vesicle of RER to Golgi body
  • modified at Golgi body to form protein
  • carried by Golgi vesicle to cell surface for secretion
40
Q

Compare structure of chloroplast and mitochondria

A

similarities

  • double membrane
  • large surface area
  • contain DNA and RNA
  • contain similar coenzymes
  • contain membranes embedded with electron transport proteins and enzymes

differences

  • C contains photosynthetic pigments but M does not
  • C has smooth inner and outer membrane but M has highly folded inner membrane
  • C has membrane bound thylakoids (grana) but M folded into cristae
41
Q

Describe how lysosomes are formed

A

Golgi vesicle containing lysozymes (enzymes) fuses with endosomes (vesicles containing material taken up by cell)

42
Q

Retrovirus

A
  • RNA genetic material / contain reverse transcriptase

- replicate in host cells by reverse transcription

43
Q

Cell fractionation - buffered

A

enzymes/proteins do not DENATURE

Biology (14 decks)

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