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AQA A Level Biology > 3.2.1 Cell structure > Flashcards

3.2.1 Cell structure Flashcards

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1
Q

Define Eukaryotic

A

DNA is contained in a nucleus and contains membrane bound specialised organelles

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2
Q

Where are Eukaryotic cells found?

A
  • Plants
  • Animal
  • Fungi
  • Protists
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3
Q

Details about the Cell surface membrane

A

‘Fluid mosaic’ phospholipid bilayer in which intrinsic and extrinsic proteins are embedded
- Involved in cell signalling and cell recognition
- Selectively permeable to regulate transport of substances

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4
Q

Details about the Endoplasmic reticulum

A

Flattened membrane bound sacs (cisternae) which are continuous with the outer nuclear membrane
- Rough has ribosomes
- Smooth no ribosomes
- Smooth ER synthesis , stores and transports lipids and carbs
- Rough ER transports proteins made on attached ribosomes

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5
Q

Details about the Cell wall (plants/algae/fungi)

A

Made of cellulose microfibrils , plasmodeta allows molecules to pass between cells , middle lamella acts as boundary between adjacent cell walls
- Mechanical strength and support
- Physical barrier against pathogens
- Part of the apoplast pathway for the easy diffusion of water

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6
Q

Details about the Cell vacoule (plants)

A

Surrounded by single membrane called the tonoplast which contains cell sap
- Controls turgor pressure
- Absorbs and hydrolyses potentially harmful substances to detoxify cytoplasm

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7
Q

Details about the Mitochondria

A

Surrounded by a double membrane serrated by a fluid filled space called the matrix which contains lipids , proteins , respiratory enzymes and mitochondrial DNA. Inner membrane is folded to form Cristae which gives a large surface area and is the site of electron transport chain
- Site of aerobic respiration to produce ATP

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8
Q

Details about the Golgi apparatus

A

Consists of a stack of membranes that make up flattened sacs with vesicles
- Forms lysosomes , synthesis glycoproteins and modifies and packages proteins for export

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9
Q

Details about Lysosome

A

Type of golgi vesicle that releases lysozymes and is a sac surrounded by a single membrane. The glycoprotein coat protects cell interior and embedded H+ pump maintains acidic conditions
- Exocytosis of digestive enzymes and digests contents of phagosome

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10
Q

Details about Ribosomes

A

Formed of protein and rRNA and free in cytoplasm or attached to endoplasmic reticulum
- In eukaryotic cells: 80s
- Site of protein synthesis via translation
- Large subunit joins amino acids
- Small subunit contains mRNA binding site

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11
Q

Details about Chloroplast (plants/algae)

A

Vesicular plastid with double membrane , thylakoids are flattened discs stacked to form the grand which contains photosystems with chlorophyll and fluid-filled matrix called the stroma
- Site of photosynthesis
- Converts solar energy to chemical energy

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12
Q

Details about the Nucleas

A

Contains chromosomes consisting of protien bound linear DNA and is a sac surround by a nuclear envelope (double membrane) , nuclear pores allow substances to enter and exit
- Manufactures ribosomal RNA and ribosomes
- Contains DNA coiled around chromatin into chromosomes
- Controls cellular processes

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13
Q

Define Prokaryotic

A

DNA is free in cytoplasm and no organelles e.g. Bactria/archaea

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14
Q

What are Plasmids?

A

Small rings of DNA that carry non essential genes

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15
Q

What is a Flagella?

A

Rotating tail which propels organism

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16
Q

What is a Capsule and what is its role?

A

Polysaccharide layer
- Prevents desiccation
- Acts as a food reserve
- Provides mechanical protection against phagocytosis and external chemicals
- Sticks cells together

17
Q

What do Eukaryotic and Prokaryotic cells have in common?

A
  • Cell membrane
  • Ribosomes
  • Cytoplasm
18
Q

Contrast Eukaryotic and Prokaryotic cells

A

Prokaryotic
- unicellular and small
- no membrane bound organelles and no nucleus
- circular DNA not associated with proteins
- small ribosomes = 70s
- murein cells walls
- contains capsule and sometimes plasmids
Eukaryotic
- often multicellular and large
- always have organelles and nucleus
- linear chromosomes associated with histone proteins
- larger ribosomes = 80s
- cellulose cell wall
- no capsule and no plasmids

19
Q

What are Viruses?

A
  • Acellular and non living
  • No cytoplasm
  • Can’t self reproduce
  • No metabolism
20
Q

Structure of a Viral particle

A
  • No cytoplasm
  • Surrounded by capsid which is a protein coat made of capsomeres
  • Linear genetic material and viral enzymes
21
Q

Structure of an Enveloped virus

A
  • Simple virus surround by matrix protein
  • Matrix protein surrounded by envelope
  • Attachment proteins on surface
22
Q

Role of the Capsid on viral particles

A
  • Protects nucleic acid from degradation
  • Surface sites enable viral particle to bind to and enter host cell or inject their genetic material
23
Q

Role of attachment proteins on viral particles

A

Enable viral particle to bind to complementary site on host cell

24
Q

Formula for Microscopy

A

I
A M actual size = image size/magnification

25
Q

State the order of sedimentation of organelles during differential centrifugation

A

Most dense to least dense
- nucleus
- mitochondria
- lysosomes
- rer
- plasma membrane
- ser
- ribosomes

26
Q

Define Magnification

A

Factor by which the image is larger than the actual specimen

27
Q

Define Resolution

A

Smallest seperation distance from which 2 separate structures can be distinguished from one another

28
Q

Outline what happens during cell fractionation and ultracentrifugation

A
  • Mince and homegneize tissue to break open cells and release organelles
  • Filter homogenate to remove debris
  • Perform differential centrifugation
  • Spin homogenate in centrifuge
  • The most dense organelles in the mixture form a pellet
  • Filter off the supertant and spin again at a higher speed
29
Q

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

A

Cold: slow action of hydrolyse enzymes
Buffered: maintains constant PH
Isotonic: Prevents shrinking of organelles

30
Q

Explain how the length of a cell could be estimated

A

Measure using a graticule and calibrate against a scale of known lengths

31
Q

Describe how a Scanning electron microscope (SEM) works

A
  • Focus a beam of electrons onto specimens surface using electromagnetic lenses
  • Reflected electrons hit a collective device and are amplified to produce an image on a photographic plate
32
Q

Advantages of using SEM

A
  • 3D image
  • Electrons have a shorter wavelength than light so a high resolution
33
Q

Disadvantages of using SEM

A
  • Only shows outer surface
  • No colour image
  • Requires a vacuum so can’t show living structures
34
Q

Describe how a Optical microscope works

A
  • Lenses focus rays of light and magnify the view of a thin slice of specimen
  • Different structures absorb different amounts and wavelengths of light
  • Reflected light is transmitted to the observer via the objective lens and eyepiece
35
Q

Advantages of using Optical

A
  • Colour image
  • Shows living structures
  • Affordable apparatus
36
Q

Disadvantages of using Optical

A
  • 2D image
  • Lower resolution than electron microscopes so can’t see ultrastructures
37
Q

Describe how a Transmission electron microscope (TEM) works

A
  • Pass a high energy beam of electrons through thin slice of specimen
  • More dense structures appear darker since they absorb more electrons
  • Focus image onto fluorescent screen or photographic plate using magnetic lenses
38
Q

Advantages of using TEM

A
  • High magnification as electrons have a shorter wavelength than light so a high resolution so ultrastructure is visible
39
Q

Disadvantages of using TEM

A
  • 2D image
  • No colour image
  • Requires a vacuum
  • Extensive preparation needed

AQA A Level Biology (23 decks)

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