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Biology > Cell structure > Flashcards

Cell structure Flashcards

1
Q

eukaryotic cells

A

-larger than prokaryotic cells
-DNA contained in a nucleus
- most eukaryotic cells are part of complex multicellular organisms containing a range of specialised cells to perform a variety of functions
-specialized cells with similar structures and functions are organised into tissues
-animals, plants and fungi are all eukaryotic organisms.

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2
Q

organisms inside a eukaryotic cell

A

-cell surface membrane
-nucleus
-mitochondria
-chloroplasts
-golgi apparatus and golgi vesicles
-lysosomes
-ribosomes
-RER (rough endoplasmic reticulum)
-SER ( smooth endoplasmic reticulum)
-cell wall
-cell vacuole

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3
Q

cell surface membrane

A

-found in all cells
-phospholipid bilyaer- molecules embedded within and attached on the outside (proteins carbohydrates, cholesterol)

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4
Q

function - cell surface membrane

A

controls the entrance and exit of molecules

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5
Q

nucleus

A

-nuclear envelope- double membrane
-nuclear pores
-nucleoplasm- granular jelly-like material
-chromosomes- protein bound linear DNA
-nucleolus- smaller sphere in the nucleoplasm which is the site of rRNA production and ribosome synthesis

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6
Q

function of the nucleus

A

-site of DNA replication and transcription (making mRNA)
-contains the genetic code for each cell.

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7
Q

mitochondria

A

-double membrane
-an inner membrane called the cristae
-the fluid centre called the mitochondrial matrix
-contains 70s ribosomes and circular DNA

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8
Q

mitochondria function

A

site of aerobic respiration and ATP production

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9
Q

chloroplasts

A

-surrounded by a double membrane
-contains thylakoids (folded membranes embedded with pigment)
-the fluid filled stroma contains enzymes for photosynthesis
-found in plants
-contains 70s ribosomes
-contains 70s ribosomes and circular DNA

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10
Q

chloroplast function

A

site of photosynthesis

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11
Q

golgi apparatus and vesicles

A

folded membranes making cristernae
-secretory vesicles pinch off from the cisternae

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12
Q

function of golgi apparatus and vesicles

A

-add carbohydrates to proteins to form glycoproteins
-produce secretory enzymes
-secrete carbohydrates
Transport store and modify lipids from lysosomes
molecules are labelled to reach their destination
-finished products are transported to the cell surface in golgi vesicles where they fuse with the membrane and the contents are released via exocytosis.

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13
Q

lysosomes

A

Bags of digestive enzymes- can contain 50 different enzymes

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14
Q

function of lysosomes

A

-hydrolyse pathogens in phagocytosis
-completely break down dead cells (autolysis)
-exocytosis-release enzymes outside of the cell to destroy material
-digest worn-out organelles for reuse of materials

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15
Q

ribosome

A

-small granuels made up of two subunits of protein and rRNA
-80s large ribosomes found in eukaryotic cells
-70s smaller ribosomes found in prokaryotic cells

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16
Q

function of ribosome

A

the site of protein synthesis

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17
Q

RER - rough endoplasmic reticulum

A
  • have ribosomes on the cisternae
    -both rer and ser have folded membranes called cisternae
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18
Q

function of the RER

A

protein synthesis

19
Q

smooth endoplasmic reticulum

A

has ( along with RER ) has folded membranes called cristernae

20
Q

function of the SER

A

synthesises and stores lipids and carbohydrates

21
Q

cell wall

A

-in plants and fungal cells
-in plants - made of microfibrils of the cellulose polymer
-fungi- made of chitin, a nitrogen-containing polysaccharide

22
Q

function of the cell wall

A

provides structural strength to the cell

23
Q

cell vacuole

A

filled with fluid surrounded by a single membrane called tonoplast

24
Q

function of cell vacuole

A

-makes cell turgid and therefore provides support
-temporary store of sugars and amino acids
-the pigments are responsible for coloured petals which attract pollinators

25
Q

prokaryotic cells

A
  • smaller than eukaryotic cells
    -no membrane bound organelles
    -smaller ribosomes (70s)
    -no nucleus
    -a cell wall made of murein
26
Q

bacteria as a prokaryotic cell

A

-bacteria still contains DNA, but it is not stored in a nucleus ( free floating DNA) instead DNA is found as a single circular molecule in the cytoplasm and is not associated with the histone proteins
-prokaryotic cells do have cell walls, but they do not contain cellulose or chitin, instead they are made of a glycoprotein called murein

27
Q

three additional features of bacteria

A

-contain plasmids, which are rings of DNA containing genes linked to survival such as antibiotic resisitance
-some have a capsule surrounding their cell wall, which provides protection from other cells and helps bacteria aggluntinate (stick together)
-some have flagella which are used for locomotion (the movements of objects from one place to another)

28
Q

viruses

A

-non living and cellular
-even smaller than bacteria and only contain genetic material, a capsid and attachment proteins
e.g HIV is a virus

29
Q

methods of studying cells that allow us to know the internal structure of cells

A

-microscopes
-cell fractionation
-ultracentrifugation

30
Q

what are the three key types of microscopes

A

-optical microscopes
-transmission electron microscopes
-scanning electron microscopes

31
Q

what is magnification

A

how many times larger the image is compared to the object

32
Q

what is resolution

A

the minimum distance between two objects in which they can still be viewed as seperate

33
Q

how the resolution is determined
-optical microscope

A

the wavelength of light

34
Q

how the resolution is determined-
-electron microscope

A

wavelength of the beam of electrons

35
Q

optical (light) microscope

A
  • a beam of light is condensed to create the image
    -A glass lens is used to condense the beam of light
    -poorer resolution due to the light having a longer wavelength
    -lower magnification
    -coloured images
    -can view living samples

small organelles in a cell are not visible using an optical microscope, but living samples can be examined and a coloured image is obtained

36
Q

electron microscope ( scanning or transmission)

A
  • a beam of electrons is condensed to create an image
    -electromagnets are used to condense the beam
    -higher resolving power as electrons have a shorter wavelength
    -higher magnification
    -black and white images
    -the sample must be in a vacuum, and therefore non-living

electrons are absorbed by air, which is why samples must be in a vacuum. the image remains in black and white although the samples are stained

37
Q

Transmission electron microscopes

A

-extremely thin specimens are stained and placed in a vacuum
- an electron gun produces a beam of electrons that passes through the specimen
-some parts absorb the electrons and appear dark
-the image produced is 2D and shows detailed images of the internal structure of cells

38
Q

scanning electron microscopes

A

-specimens do not need to be thin, as the electrons are not transmitted through, instead the electrons are beamed onto the surface and the electrons are scattered in different ways depending on the contours
-this produces a 3D image

39
Q

how to calculate magnification

A

image size = actual size x magnification

I=AM

40
Q

eyepiece graticule

A

-the scale on the glass disc inside optical microscopes
-can be used to measure the size of objects you are viewing under the microscope
- however when you change the objective lens, and therefore the magnification, you have to calibrate the eyepiece to work out what the distance is between each division at that magnification

41
Q

what is used to calibrate the eyepiece lens

A

a stage micrometer
-this is a glass slide with a scale on it which you can place on the stage
-the scale on the stage micrometer is typically 2mm long and the sub-divisions are 10 um apart

42
Q

calibration steps

A
  1. line up the stage micrometer and the eye piece graticule whilst looking through the eyepiece

2.count how many divisions on the eyepiece graticule fit into one division on the micrometer scale
e.g in this example 20 divisions of the eyepiece graticule fit into 10 divisions of the micrometer, meaning two divisions fit into 1 division of the micrometer

  1. each division on the micrometer is 10 um, so this can be used to calculate what one division on the eyepiece graticule is at that current magnification

now that the graticule is calibrated you can measure the size of cells or organelles

43
Q

cell fractionation

A

cells are broken down so that the organelles are free to be seperated. this is done using a homogeniser (blender)

44
Q

conditions during homogenisation

A
  • kept in a cold solution- to reduce enzyme activity to prevent the breakdown of cell components

-solution must be isotonic to prevent any movements of water by osmosis which could result in organelles shrivelling or bursting

-solution must be buffered to resist pH changes. This is to prevent damage to organelles and enzymes. once the cell has been broken open the solution must be filtered to remove larger pieces of debris.

Biology (4 decks)

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