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OCR A LEVEL BIOLOGY > M2, C2 Basic Components of Living Systems > Flashcards

M2, C2 Basic Components of Living Systems Flashcards

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1
Q

Name all the organelles in a cell

A 
Vesicles
Nucleolus
Nucleus
Golgi apparatus
Cell membrane
Cytoplasm
Ribosome
Centriole
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Cytoskeleton
Secretory vesicles
Mitochondria
Microtubule network
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2
Q

Define ultrastructure

A

Features which can be seen using an electron microscope

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3
Q

Define hydrolysis

A

Splitting up using water ( a chemical reaction)

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4
Q

Define compartmentalisation

A

Each organelle provides a compartment with the ideal conditions for a specific set of chemical reactions. Membranes are selectively permeable and control the movement of substances in/out of cells/organelles

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5
Q

What’s the function of a nucleus?

A

Contains coded genetic information in DNA. It directs synthesis of proteins. Also it controls the metabolism. (Overall it controls the cell)

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6
Q

What’s the structure of the nucleus?

A

Biggest organelle in the cell. DNA is contained within a double membrane called a nuclear envelope. This contains nuclear pores which allows molecules to move in and out of the nucleus. DNA associates with histones to make chromatin which condenses to make chromosomes.

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7
Q

What’s the function of the nucleolus

A

An area within the nucleus which produces ribosomes

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8
Q

What’s the structure of the nucleolus

A

Made of proteins and RNA which produces ribosomal RNA. This is then combined with proteins to form ribosomes for protein synthesis

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9
Q

What’s the function of mitochondria?

A

Where the final stages of cellular respiration happens. The energy stored in the bonds of complex, organic molecules is made available for the cell to use by the production of the molecule ATP. Very active cells have lots of mitochondria

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10
Q

What’s the structure of mitochondria?

A

They have a double membrane. The inner membrane is highly folded to form cristae and the matrix. The membrane forming the cristae contains the enzymes used in aerobic respiration. They contain a small amount of DNA and they produce their own enzymes and reproduce themselves.

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11
Q

What’s the function of lysosomes?

A

Specialised forms of vesicles that contain hydrolytic enzymes. They break down waste materials in cells. Very important in immune system cause they break down pathogens.

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12
Q

What’s the structure of lysosomes

A

Membrane sacs that have storage and transport roles. They consist of a single membrane with fluid inside. Contain hydrolytic enzymes

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13
Q

What’s the function of smooth endoplasmic reticulum?

A

Lipid and carbohydrate synthesis and storage

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14
Q

What’s the function of rough endoplasmic reticulum?

A

Has ribosomes bound to the surface and is responsible for the synthesis and transport of proteins.

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15
Q

What’s the structure of endoplasmic reticulum?

A

Network of membranes enclosing flattened sacs called cisternae. It’s connected to the outer membrane of the nucleus.

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16
Q

What’s the function of ribosomes?

A

Protein synthesis which then repairs damage or directs chemical reactions.

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17
Q

What’s the structure of ribosomes?

A

Free floating in the cytoplasm or attached to the endoplasmic reticulum forming rough ER. They are not surrounded by a membrane. Constructed of RNA molecules made in the nucleolus of the cell. Chloroplasts and mitochondria contain ribosomes.

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18
Q

What’s the function of the Golgi apparatus?

A

Modifies proteins and packages them into vesicles

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19
Q

What’s the structure of the Golgi apparatus?

A

Similar to the smooth ER - compact structure formed of cisternae and doesn’t contain ribosomes.

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20
Q

What are the 5 steps for protein synthesis in cells?

A

1) Protein are synthesised on the ribosomes on the rough ER.
2) They then are packaged into transport vesicles.
3) Vesicles containing the newly synthesised proteins move towards the Golgi apparatus via the cytoskeleton.
4) The vesicles fuse with the Golgi apparatus and the proteins enter. The proteins are structurally modified before leaving the Golgi apparatus in vesicles
5) Secretary vesicles carry proteins that are to be released from the cell. The vesicles move towards and fuse with the cell-surface membrane, releasing their contents by exocytosis. Some vesicles form lysosomes - these contain enzymes for use in the cell.

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21
Q

What are the functions of proteins and give examples

A 
enzymes - protease
transport - haemoglobin (in red blood cells)
movement - muscles (actin and myosin)
cell recognition - antigens
channels - membrane proteins
structure - collagen and keratin
hormones - insulin
protection - antibodies
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22
Q

What’s the function of the cell wall?

A

to give a plant cell shape and supports the plant as a whole. it also acts as a defence mechanism protecting the cell from pathogens

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23
Q

What’s the structure of the cell wall?

A

made of cellulose - a complex carbohydrate. they’re freely permeable so substances can pass in an out of the cell

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24
Q

What’s the function of a vacuole?

A

very important in the maintenance of turgor so that the contents of the cell push against the cell wall and maintain a rigid framework for the cell.

25
Q

what’s the structure of a vacuole?

A

membrane lined sacs in the cytoplasm containing cell sap. the membrane of a vacuole in a plant cell is called the tonoplast. it’s selectively permeable which means that some small molecules can pass through it but others can’t.

26
Q

whats the function of chloroplasts?

A

responsible for photosynthesis in the plant cell. they convert light energy into sugars that the cell uses

27
Q

whats the structure of chloroplasts?

A

found in cells of the green parts of the plant like the leaves and stem. they have a double membrane structure like mitochondria. the fluid enclosed in the chloroplast is called the stoma. they have an internal network of membranes which form flattened sacs called thylakoids. several of them are called a granum. the grana are joined by membranes called lamellae. grana contain chlorophyll pigments. chloroplasts also contain dna and ribosomes which means they can make their own proteins.
the internal membranes provide a large surface area needed for the enzymes, proteins and pigment molecules in photosynthesis.

28
Q

what’s the function of the cytoskeleton

A

shapes and strengthens the cell
keeps organelles in position
movement of the actual cell
movement of organelles within the cell

29
Q

what are the three features in the cytoskeleton

A

microfilaments
microtubules
intermediate fibres

30
Q

Do prokaryotic and eukaryotic cells have a nucleus?

A

prokaryotic: no
eukaryotic: yes

31
Q

Do prokaryotic and eukaryotic cells have DNA?

A

prokaryotic: yes - circular
eukaryotic: yes - linear

32
Q

How do prokaryotic and eukaryotic cells organise DNA ?

A

prokaryotic: proteins fold and condense DNA
eukaryotic: associated with proteins called histones

33
Q

Do prokaryotic and eukaryotic cells have extra chromosomal DNA?

A

prokaryotic: circular DNA called plasmids
eukaryotic: only present in certain organelles such as chloroplasts and mitochondria

34
Q

Are prokaryotic cells membrane bound?

Are eukaryotic cells membrane bound?

A

prokaryotic: non-membrane bound
eukaryotic: both membrane bound and non-membrane bound

35
Q

Do prokaryotic and eukaryotic cells have a cell wall?

A

prokaryotic: yes made of peptidoglycan
eukaryotic: yes - chitin in funghi, cellulose in plants but not present in animals

36
Q

Do prokaryotic and eukaryotic cells have ribosomes?

A

prokaryotic: yes smaller (70s)
eukaryotic: yes larger (80s)

37
Q

Do prokaryotic and eukaryotic cells have a cytoskeleton?

A

prokaryotic: yes
eukaryotic: yes, more complex

38
Q

What type of reproduction do prokaryotic and eukaryotic cells have?

A

prokaryotic: binary fission
eukaryotic: asexual or sexual

39
Q

What cell type are prokaryotic and eukaryotic cells?

A

prokaryotic: unicellular
eukaryotic: unicellular and multicellular

40
Q

Do prokaryotic and eukaryotic cells have a cell-surface membrane?

A

prokaryotic: yep
eukaryotic: yep

41
Q

What are centrioles?

A

component of the cytoskeleton
composed of microtubules
two associated centrioles form the centrosome
Separate chromosomes

42
Q

how do cilia move

A

contain two central microtubules surrounded by nine pairs of microtubules. this is known as 9+2 arrangement. pairs of parallel microtubules slide over each other causing the cilia to move in a beating motion

43
Q

what’s the equation for the actual size of the object in a microscope

A

size of image / magnification

44
Q

what two lenses does a light microscope have? what does each one do

A

objective lens - produces a magnified image which is placed near to the specimen
eyepiece lens - through which specimen is viewed and magnifies the image again

45
Q

how do you get from a centimetre to a nanometre

A

x10 x1000 x1000

X10^7

46
Q

how do you get from a nanometre to a millimetre

A

/ 1000 /1000

X10^-6

47
Q

if the image was 24 mm and the actual size was 120nm then what is the magnification

A

24 x 1000 x1000 = 24000000nm
mag = image / actual
24000000 / 120 = 200000
magnification = X 200000

48
Q

what magnification does an electron microscope produce and what mag does a light microscope produce

A

x 500000 - electron

x 2000 - light

49
Q

what are some details for electron microscopy

A

fires a beam of electrons with a wavelength of less than 1nm which illuminates the specimen
gives a more detailed version of the ultrastructure
very expensive
only used in controlled environments
two types of electron microscope: TEM and SEM

50
Q

what do TEM and SEM stand for and whats the difference between them

A

Transmission Electron Microscope - electrons transmitted THROUGH the specimen and produces an IMAGE. has the best resolution - 0.5 nm

Scanning Electron Microscope - electrons sent across the SURFACE of a specimen (reflected electrons collected). resolution not as good - 3-10nm but can produce 3D images

51
Q

why do samples need to be processed in a specific way in electron microscopy?

A

inside the microscope there is vacuum so electron beams travel in a straight line

52
Q

how are specimens prepared for electron microscopes

A

Fixation using chemicals or freezing
Staining with heavy metals and dehydration with solvents
TEM samples will then be set in resin and may be stained again
SEM samples may be fractured to expose the inside and then coated with heavy metals

53
Q

why do specimens need to be prepared the way they do

A

fixation - stabilises sample / prevents decomposition
dehydration - prevents vaporisation of water in vacuum
vaporisation would damge sample
embedding allows thin slices to be obtained
staining with heavy metals creates contrast in electron beams

54
Q

what are the 4 ways to prepare samples for light microscopy and give details for each one

A

dry mount - solid specimens viewed whole or cut in thin slices. cover piece placed over sample

wet mount - specimens suspended in solution. cover slip placed on from an angle

squash slides - wet mount first prepared. lens tissue is used to gently press down the cover slip. good technique for soft samples

smear slides - edge of slide is used to smear sample. cover slip placed over it

55
Q

why do people stain samples

A

to increase contrast between different components in the sample
to identify different cellular componenets

56
Q

what are the steps for staining

A
  1. sample placed on slide and allowed to air dry
  2. heat-fixed by passing through a flame
  3. sample stick to slide and will take up stains
57
Q

what’s an eyepiece graticule?

A

fitted on the eyepiece on a microscope. it’s a transparent ruler with numbers and no units

58
Q

how do you take readings off an eyepiece graticule

A

Look in revision guide page 19

59
Q

state the resolution and magnification of light microscopes, TEM and SEM

A

Light microscopes:
200nm and X1500

TEM:
0.2nm and X1,000,000

SEM:
2nm and X500,000

OCR A LEVEL BIOLOGY (23 decks)

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