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A-Level Biology > 2.1.1 Cell structure > Flashcards

2.1.1 Cell structure Flashcards

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1
Q

resolution definition

A

ability to distinguish between two points on an image, smallest distance between 2 distinguishable points

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2
Q

magnification definition

A

size of an image compared to size of object

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3
Q

optical microscope pros

A

relatively cheap
easy to use
portable (use in field)
study whole living specimens

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4
Q

optical microscope magnification and resolution

A

x1500

200 nanometers

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5
Q

total magnification formula

A

total magnification = eyepiece lens magnifying power x objective lens magnifying power

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6
Q

photomicrograph definition

A

photograph of an image seen using an optical microscope

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7
Q

laser scanning microscopes

A

confocal microscopes
laser light scans object point by point and image produced by computer
depth selective
high resolution, high contrast
used in medical professions and biological research

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8
Q

how transmission electron microscope works

A 
chemically fixed (dehydrated and in vacuum) and stained (metal salts)
electrons pass through specimen and focused on screen / photographic plate
forms 2D black/white image
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9
Q

transmission electron micrograph magnification and resolution

A

x500,000

0.05 nanometers

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10
Q

scanning electron microscope magnification and resolution

A

x100,000

10 nanometers

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11
Q

how scanning electron microscope works

A

chemically fixed (dehydrated and in vacuum) and stained (metal salts)
electrons cause secondary electrons to bounce off specimen (focused on to screen)
produces 3D black/white image

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12
Q

electron microscope cons

A

large (not portable)
very expensive
need great deal of skill and training to use

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13
Q

how to observe unstained specimens

A

light interference
dark background behind illuminated specimen
adjusting iris diaphragm to control illumination of specimen
useful for observing living specimens

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14
Q

stain definition

A

coloured chemicals that bind to molecules / structures in / on specimen
makes specimen easier to see

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15
Q

methylene blue

A

all-purpose stain

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16
Q

differential staining definition

A

coloured chemicals binding to specific structures / molecules on specimen

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17
Q

acetic orcein

A

stains DNA and chromosomes dark red

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18
Q

eosin

A

cytoplasm

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19
Q

Sudan red

A

stains lipids

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20
Q

iodine in potassium iodide solution

A

cellulose in cell walls yellow

starch granules blue/black (purple under microscope)

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21
Q

how specimens prepared in laboratory

A

dehydrating specimen
embedding in wax (prevents distortion during slicing)
special instrument used to make thin cliches (sections)
sections stained and mounted in special chemical to preserve them

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22
Q

formula between image size, actual size and total magnification

A

image size = total magnification x actual size

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23
Q

longitudinal definition

A

lengthways

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24
Q

transverse definition

A

crossways

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25
Q

oblique definition

A

slanting

26
Q

eyepiece graticule definition

A

measuring device
placed in eyepiece
acts as ruler

27
Q

stage micrometer definition

A

precise measuring device
small scale placed on microscope stage
used to calibrate value of eyepiece units at different magnifications
1mm

28
Q

features of eukaryotic cells

A 
nucleus (surrounded by nuclear envelope, containing DNA organised and wound into linear chromosomes)
nucleolus within nucleus
cytoplasm
cytoskeleton 
plasma membrane
membrane-bound organelles 
smell vesicles 
ribosomes
29
Q

organelle definition

A

sub-cellular structure that performs one or more specific jobs

30
Q

membrane-bound meaning

A

covered by membrane that keeps organelle separate from rest of cell

31
Q

nucleus structure and function

A 
surrounded by nuclear envelope
chromatin around nucleolus
nucleolus at centre (no membrane)
control centre of cell
stores genome
transmits genetic information 
provides instruction for protein synthesis
32
Q

nuclear envelope structure and function

A

double membrane
separates contents of nuclear from rest of cell
pores allow dissolved substances (e.g. steroid hormones) ribosomes and mRNA through

33
Q

nucleolus function

A

where ribosomes made

contains RNA

34
Q

chromatin structure and function

A

consists of DNA wound around histone proteins
when not dividing, spread out or extended
when about to divide, chromatin condenses and coils into chromosomes
makes up nearly all organism’s genome

35
Q

rough endoplasmic reticulum structure

A

system of membranes, continuous with nuclear membrane
contains cisternae
covered with ribosomes
made up of phospholipid bilayer

36
Q

rough endoplasmic reticulum function

A

compartmentalisation (maintains specific conditions needed in RER)
separating proteins from cell cytoplasm
holds ribosomes in place
packaging proteins into transport vesicles

37
Q

smooth endoplasmic reticulum structure

A

system of membranes, continuous with nuclear membrane
contains fluid-filled cavities (cisternae)
no ribosomes on its surface

38
Q

smooth endoplasmic reticulum function

A

contains enzymes involved with lipid metabolism (synthesis of cholesterol, (phospho)lipids, steroid hormones)
involved with synthesis and transport of lipids

39
Q

Golgi apparatus structure

A

stack of membrane-bound flattened sacs

secretory vesicles bring materials to and from Golgi apparatus

40
Q

Golgi apparatus function

A 
modifies proteins (adds sugar/lipids to make glyco/lipoproteins, folds into 3D shape)
protein packaged into vesicles (pinched off then stored in cell or moved to be part of plasma membrane or exported outside of cell)
41
Q

mitochondria structure

A 
spherical, rod-shaped or branched
2-5 micrometers long
surrounded by two membranes (fluid-filled space in between)
inner membrane folded into cristae 
inner part = fluid-filled matrix
42
Q

mitochondria function

A

site of ATP production / aerobic respiration (doesn’t produce ATP!!)
self-replicating
abundant in cells with more metabolic activity

43
Q

chloroplast structure

A

4-10 micrometers long
only found in plant cells and some protoctists
surrounded by double membrane
inner membrane = continuous with stacks of flattened membrane sacs containing chlorophyll (thylakoids)
thylakoid stack = granum
fluid-filled matrix = stroma
contains loops of DNA and starch granes

44
Q

chloroplast function

A

site of photosynthesis
first stage = light energy trapped by chlorophyll to make ATP (in granum)
water split to supply hydrogen ions
second stage = hydrogen reduces carbon dioxide (energy from ATP) to form carbohydrates (in stroma)

45
Q

vacuole structure

A

surrounded by membrane (tonoplast)

contains fluid

46
Q

vacuole function

A

only plant cells have large permanent vacuole
filled with water and solutes
maintains cell stability (pushes against cell wall, makes cell turgid)
helps support plant if all cells turgid

47
Q

lysosome structure

A 
small bags
formed from Golgi apparatus 
surrounded by single membrane 
contains hydrolytic (digestive) enzymes
abundant in phagocytic cells (ingest and digest invading pathogens)
48
Q

lysosome function

A

separates hydrolyitc enzymes from rest of cell
can engulf and digest old cell organelles and foreign matter
returns digested components to cell for reuse

49
Q

cilia and undulipodia structure

A

protrusion from cell
surrounded by cell surface membrane
contain microtubules
formed from centrioles

50
Q

cilia and undulipodia function

A

movement of cell
movement of mucus
can contain receptors to detect signals from environment

51
Q

organelles without membranes

A

ribosomes
centrioles cytoskeleton
cell wall

52
Q

ribosome structure

A

small (20nm)
spherical
made of ribosomal RNA
made in nucleolus (2 separate sub units then reassemble in cytoplasm)
some free in cytoplasm, others attached to ribosome

53
Q

ribosome function

A

protein synthesis
free in cytoplasm = protein for inside cell
bound to RER = mainly for proteins exported out of cell

54
Q

centriole structure

A

two bundles of microtubules at right angle to each other
microtubules (tubulin protein subunits) form cylinder to create bundle
absent from cells of (higher) plants

55
Q

centriole function

A

spindle forms from centrioles before cell division
centrioles multiply and line up beneath cell surface membrane
microtubules sprout outwards from each centriole to form cilium or undulipodium

56
Q

cellulose cell wall structure

A

mesh of bundles of cellulose fibres

57
Q

cellulose cell wall function

A

provide strength and support (of cell and whole plant)
maintains shape of cell
permeable (allows solutions through)
prevents plant cells from bursting when turgid
fungal cell walls made of chitin

58
Q

cytoskeleton structure

A

network of protein structures in cytoplasm
consists of:
-rod-like microfilaments made up of subunits of actin. polymers of actin (7nm diameter)
-intermediate filaments made up of variety of proteins (10nm diameter)
-straight, cylindrical microtubules (18-30 nm diameter)
-cystoskeletal motor proteins (myosins, kinesins, dyneins) molecular motors. enzymes that can bind to and allow hydrolysis of ATP as energy source)

59
Q

cytoskeleton function

A

microfilaments give support and mechanical strength, keeps shape stable and allows cell movement
microtubules provide shape and support, helps substances and organelles to move in cell (forms spindle fibres and track where motor proteins walk on)
intermediate filaments anchor nucleus
also extend between cells in some tissue for cell-cell signalling and adhering to basement membrane (stabilising tissues)

60
Q

making and secreting protein method

A

gene (in chromatin) with instructions for protein is transcribed onto mRNA
mRNA copied and exits nucleus via pores to ribosomes on RER
instructions translated and protein assembled
protein molecules pass into and through cisternae and hollow sacs of RER
vesicles with protein within pinched off (by microtubules and motor proteins) and passed to Golgi apparatus
vesicles fuse with Golgi apparatus for protein modification / packaging
vesicles pinched off Golgi apparatus and go to plasma membrane
vesicles fuse to plasma membrane and protein released to outside of cell (exocytosis, requires energy)

61
Q

prokaryote structures

A 
plasma membrane
cytoplasm
smaller ribosomes
DNA and RNA (plasmid and nucleoid)
less developed cytoskeleton 
cell wall (peptidoglycan)
waxy capsule 
flagella 
pili

A-Level Biology (24 decks)

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