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Biology Alevel > Cell Structure > Flashcards

Cell Structure Flashcards

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1
Q

Function of cell surface membrane?

A
  • Controls exchange of materials between internal cell environment and external environ
    -Partially permeable and formed from phospholipid
    bilayer
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2
Q

Function of cell wall?

A
  • in plant cells
  • offer support and structure by the polysaccharide cellulose in plants
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3
Q

Function of a nucleus?

A

Control cell activity
- Nucleus separated from cytoplasm by nuclear envelope - has pores
- pores important for allowing mRNA and ribosomes to travel out nucleus
- nucleus contains chromatin - material that makes up chromosomes

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4
Q

Function of mitochondria and structure?

A
  • Aerobic respiration in eukaryotes
  • surrounded by double membrane with inner membrane folded - cristae
  • matrix contains enzymes for respiration,to produce ATP
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5
Q

Chloroplasts function and structure?

A
  • Site of photosynthesis
  • Surrounded by double membrane
    Compartments called thylakoids stack to form grana -these are joined together by lamellae (thin thylakoid membranes )
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6
Q

Function of ribosomes?

A
  • Composed of 2 subunits and where proteins are produced
  • each ribosome consists of rRNA and proteins
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7
Q

Structure and function of endoplasmic reticulum?

A

RER - series of flattened sacs in a membrane with ribosomes on the surface
- formed from continuous folds of membrane continuous with the nuclear envelope
- folds and processes proteins made on ribosomes

SER- membrane bound sacs
- produces and processes lipids

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8
Q

Structure and function of Golgi apparatus?

A
  • Fluid filled flattened and curved sacs with vesicles on the edges
  • packages and modifies proteins and lipids
  • produces lysosomes
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9
Q

Function of large permanent vacuoles?

A

-a sac in plant cells surrounded by tonoplast

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10
Q

Function of vesicles?

A
  • In plant and animal cells
  • membrane bound sac for transport and storage
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11
Q

Function of lysosomes?

A
  • Specialist form of vesicles - contain hydrolytic enzymes
  • break down worn out organelles
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12
Q

Function of centrioles ?

A
  • Hollow fibres made of microtubules arranged at right angles to each other
  • involved is cell division
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13
Q

What is the cytoskeleton made up of?

A

2 types of protein fibres: microfilaments and microtubules
→ microfilaments - solid strands made from actin
- cause cell movement/ organelles

→ microtubules - tubular hollow strands made from tubulin
- organelles / other cell contents move along these fibres

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14
Q

Importance of cytoskeleton?

A

Strength and support - maintains shape of cell/ keeps organelles in place
Intracellular movement - form tracks along which organelles can move/ movement of chromosomes when they separate in cell division due to contraction of microtubules in spindle
Cellular movement - enables cell movement e.g movement of cilia and flagella a used by cytoskeletal protein filaments that run through them

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15
Q

How are prokaryotic cells different from eukaryote cells?

A

Prokaryotes have:
- cytoplasm that lacks membrane bound organelles
- smaller ribosomes (70S instead of 80S)
- no nucleus
- cell wall that contains MUREIN/peptidoglycan instead of cellulose and lignin
- SOMETIMES have PLASMIDS, CAPSULES and FLAGELLUM
- 0.5 - 5 um instead of 100um diameter
- cell division occurs by BINARY FISSION instead of mitosis and meiosis

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16
Q

Purpose of plasmids?

A

→ small loops of DNA
→ contain genes that can be passer between prokaryotes

17
Q

Purpose of capsules?

A

→ final outer layer
→ protects bacteria from drying out / attack from immune system cells

18
Q

Purpose of flagellum?

A

→ long hair like structure that rotates, enabling prokaryote to move

19
Q

Difference between magnification and resolution?

A

Magnification - how many times bigger image produced is than the real life object
Resolution - ability to distinguish between objects

20
Q

How are light microscopes useful?

A
  • max resolution of 200nm - used to observe eukaryotic cells/nuclei (maybe mitochondria and chloroplasts)
  • max magnification is 1500x
21
Q

Ad and dis of transmission electron microscopes?

A
  • beam of electrons are transmitted through the specimen - CAN SEE ULTRASTRUCTURE
    AD: high resolution images
  • Can see smaller structures

DIS: can only be used with very thin specimens
- can’t use live specimens
- lengthy preparation of specimens
- not colour image

22
Q

Ad and dis of scanning electron microscopes?

A
  • scan a beam of electrons across the specimen
  • beam bounces off surface of specimen/electrons are detected - forms image

AD: can be used on thick/3D specimens
- allow external 3D structure o be seen

DIS : lower resolution than TEMS
- cannot be used to see live specimens
- not a colour image

23
Q

Ad and dis of laser scanning confocal microscopes?

A

Type of light microscope:
Use laser beams to scan a specimen that is tagged with fluorescent dye - laser causes dye to give off light
Detectors connected to computer - generates IMAGE

AD: used on thick/3D specimens
- allows external 3D structure to be seen
- clear images - high resolution

DIS : - slow
- laser can cause photo damage to cells

24
Q

PAG 1 : microscopy

A
  1. Prepare slide :
    Using liquid specimen: ADD SPECIMEN TO SLIDE
    - cover liquid with coverslip/press to remove air bubbles
    - add stain on edge of coverslip dab with paper towel drawing it under coverslip
    Using solid specimen : cut small sample from tissue /peel away thin layer of cells from tissue sample
    - apply stain /apply coverslip
    - add drop of water to specimen can prevent dehydration of tissue
    - Calibrate Graticule
    - start with lower power objective lens
    - by using the scale on the graticule lens/ stage micrometer , can work out the size of 1 division on eyepiece graticule
    Take repeat measurement/calculate mean if taking measurements
25
Q

How is the structure of mitochondrial membranes related to function of mitochondria?

A
  • site of ATP synthesis
  • outer membrane is highly permeable to allow movement of molecules
26
Q

How to improve cell drawings?

A
  • label
  • add scale
  • add title
27
Q

Role of RER membrane?

A
  • Maintains different conditions between cytoplasm and RER (compartmentalisation)
  • separates proteins from cytoplasm
28
Q

How are organelles involved in protein synthesis?

A
  1. Nucleolus manufactures ribosomes for proteins synthesis in RER
    2) nucleus manufactures mRNA /attached to ribosome on RER
    3) proteins in RER are sent in VESICLES to Golgi body
    4) Golgi body processes proteins/sends them in vesicles to the PLASMA MEMBRANE
    5) vesicles fuse with plasma membrane to secrete finished protein product
29
Q

Types of dyes used in microscopy and what are they used for?

A

Acetic orcein —> bind to DNA/stain chromosomes dark red
Eosin- stains CYTOPLASM dark red/pink
Iodine - stain starch blue-black
Iodine in potassium iodide solution - stains CELLULOSE yellow
Haematoxylin - stains RNA/DNA purple/blue
Methylene blue - all purpose stain - blue

30
Q

Magnification formula?

A

Image size /actual size

31
Q

How is colorimeter calibrated? Why is it important to calibrate ?

A

Set to zero absorbance
- using distilled water

  • values all measured to same standard
32
Q

Micrometers to cm?

A

10,000 micrometer = 1 cm

33
Q

Compare magnification and resolution of Light microscope, TEM and SEM?

A

Microscope type LIGHT. TEM. SEM
Resolution 0.2 micrometers 0.0002 micrometers 0.002 micrometers
Magnification X1500. >X1,000,000. < 500,000

34
Q

Stains used for electron microscopes?

A

Heavy metal compounds - absorb electrons well
So no colour

Biology Alevel (26 decks)

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