Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Level Biology > 2.1 Cell Structure > Flashcards

2.1 Cell Structure Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Define the terms eukaryotic and prokaryotic cell

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 archea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

State the relationship between a system and specialised cells

A

Specialised cells —> tissues that perform specific function —> organs made of several tissue types —> organ systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the structure and function 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 signalling/cell recognition
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain the role of cholesterol, glycoproteins and glycolipds in the cell surface membrane

A

Cholesterol: steroid molecule connects phospholipids and reduces fluidity

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

Glycolipds: cell signalling and cell recognition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe the structure of the nucleus

A

Surrounded by nuclear envelope, a semi-permeable double membrane

Nuclear pores allow substances to enter/exit

Dense nucleolus made of RNA and proteins assembles ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the function of the nucleus

A

Contains DNA coiled around chromatin into chromosomes

Controls cellular processes: gene expression determines specialisation and site of mRNA transcription, mitosis,semi conservative replication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe the structure of a chloroplast

A

Vesicular plastid with double membrane

Thylakoids: flattened discs stack to form grana; contain photosystems with chlorophyll

Intergranal lamellae: tubes attached to thylakoids in adjacent grana

Stroma: fluid-filled matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

State the function of mitochondria and chloroplasts

A

Mitochondria: site of aerobic respiration to produce ATP

Chloroplasts: site of photosynthesis to convert solar energy to chemical energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the structure and function of a lysosome

A

sac surrounded by single membrane

Contains a embedded H+ pump which maintains acidic conditions and digestive hydrolase enzymes.
glycoproteins coat protects cell interior:

Digests contents of phagosome
Exocytosis of digestive enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the structure and function of a ribosome

A

Made up of protein and rRNA
Can be found free in cytoplasm or attached to ER

Site of protein synthesis via translation
Large subunit: joins amino acids
Small subunit: contains mRNA binding site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe the structure and function of the endoplasmic reticulum (ER)

A

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

Rough ER: many ribosome attached for protein synthesis and transport

Smooth ER: lipid synthesis’s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the structure of the cell wall in plants and bacteria

A

Bacteria: made of polysaccharide murein

Plants: made of cellulose microfibrils
Plasmodesmata allow molecules to pass between cells, middle lamellla acts as boundary between adjacent cell walls

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

State the function of the cell wall

A

Mechanical strength and support
Physical barrier against pathogens
Part of apoplast pathway (plants) to enable easy diffusion of water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the structure and function of the cell vacuole in plants

A

Surrounded by single membrane: tonoplast contains cell sap: mineral ions, water, enzymes, soluble pigments

Controls turgor pressure
Absorbs and hydrolyses potentially harmful substances to detoxify the cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Explain some common cell adaptations

A

Folded membrane or microvilli increase surface area e.g. 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 (usually unicellular) organism

20
Q

State the role of the capsule in prokaryotes

A

A capsule is a polysaccharide layer that

Prevents desiccation
Acts as 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
Ribosome

22
Q

Contrast eukaryotic and prokaryotic cells

A

Eukaryotic

  • larger cells and often multicellular
  • always have organelles and nucleus
  • Linear chromosomes associated with histones

Prokaryotic

  • small cells and always unicellular
  • no membrane-bound organelles and no nucleus
  • circular DNA not associated with proteins
23
Q

Why are viruses referred to as ‘particles’ instead of cells

A

Acellular and non living: no cytoplasm, cannot self-reproduce, no metabolism

24
Q

Describe the structure of a viral particle

A

Linear genetic material(DNA OR RNA) and viral enzymes e.g. reverse transcriptase
Surrounded by capsid (protein coat made of capsomeres)
No cytoplasm

25
Q

Describe the structure of an enveloped virus

A

Simple virus surrounded by matrix protein.

Matrix protein surrounded by envelop derived from cell membrane of host cell

Attachment proteins on surface

26
Q

State the role of the capsid on viral particles

A

Protect nucleic acid from degradation by restriction endonucleases

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 particle to bind to complementary sites on his cell : entry via endosymbiosis

28
Q

Describe how optical microscopes work

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

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

A
  1. Obtain thin section of tissue e.g. using ultratome or by maceration
  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 degree to avoid trapping air bubbles
30
Q

Suggest the advantages and limitations of using an optical microscope

A 
\+ colour image 
\+ can show living structures 
\+ affordable apparatus
-2D image
-lower resolution than electron microscopes = cannot see ultra structure
31
Q

Describe how a transmission electron microscope (TEM) works

A

Passes 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

32
Q

Suggest the advantages and limitations of using a TEM

A

+ electrons have shorter wave length than light = high resolution so ultrastructure visible
+high magnification (X5000000)
-2D image
-requires a vacuum = cannot show living structures
-extensive preparation may introduce artefacts
No colour image

33
Q

Describe how a scanning electron microscope (SEM) works

A
  1. Focus a beam of electrons onto a specimens surface using electromagnetic lenses
  2. reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate
34
Q

Suggest the advantages and limitations of using an SEM

A

+3D image
+electrons have shorter wavelength than light = high resolution
-requires a vacuum = cannot show living structures
-no colour image
-only shows outer surface

35
Q

Define magnification and resolution

A

Magnification: factor by which the image is larger than the actual specimen

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

36
Q

Explain how to use an eyepiece graticule and stage micrometer to measure the size of a structure

A
  1. Place micrometer on stage to calibrate eyepiece graticule
  2. Line up scales on graticule and micrometer. Count how many graticule divisions are in 100 micro meters on the micrometer
  3. length of 1 eyepiece division = 100 micrometer / number of Divisions
  4. use calibrated values to calculate actual length of structures
37
Q

State an equation to calculate the actual size of a structure from microscopy

A

Image size = actual size X magnification

38
Q

Outline what happens during cell fractionation and ultracentrifugation

A
  1. Mince and homogenize tissue to break open cells and release organelles
  2. Filter homogenate to remove debris
    3.perform differential centrifugation
    A)spin homogenate
    B)the most dense organelles in the mixture form a pellet
    C)filter off the supernatent and spin again at a higher speed
39
Q

State the order of sedimentation of organelles during differential centrifugation

A

Most dense —> least dense

Nucleus—>mitochondria —>lysosome —>RER —>plasma membrane —>SER —>ribosomes

40
Q

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

A

Cold: slow action of hydrolase enzymes

Buffered: maintain constant pH

Isotonic: prevent osmotic lysis/shrinking of organelles

A Level Biology (33 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions