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Biology- Mrs Bell > Cell structure > Flashcards

Cell structure Flashcards

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1
Q

Features of the nucleus

A

Nuclear envelope- double membrane
Nuclear pores
Nucleoplasm- jelly- like material
Chromosomes- protein bound linear DNA
Nucleolus- smaller sphere inside which is site of rRNA production and makes ribsomes

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2
Q

Function of the nucleus

A
  • Site of DNA replication and transcription
  • Contains the genetic code for each cell
  • Controls the cells actions
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3
Q

Features of endoplasmic reticulum

A
  • Rough and smooth ER both have folded membrane called cisternae
  • Rough ER have ribosomes have ribosomes on the cisternae
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4
Q

Function of endoplasmic reticulum

A

RER- protein synthesis
SER- synthesis and store lipids and carbohydrates

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5
Q

Features of golgi apparatus and vesicles

A
  • Folded membranes making cisternae
  • Secretary vesicles pinch off from the cisternae
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6
Q

Function of the golgi apparatus and vesicles

A
  • Add carbohydrates to proteins to form glycoproteins
  • Produce secretary enzymes
  • Secrete carbohydrates
  • Transport, modify and store lipids
  • Form lysosomes
  • Molecules are “labelled” with their destination
  • Finished products are transported to the cells surface in golgi vesicles where they fuse with the membrane and the contents are released
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7
Q

Features of lysosomes

A

Bags of digestive enzymes- can contain 50 different enzymes

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8
Q

Function of lysosomes

A
  • Hydrolyse phagocytic cells
  • Completely break down dead cells
  • Exocytosis- release enzymes to outside of cell to destroy material
  • Digest worn out organelles for reuse of materials
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9
Q

Features of mitochondria

A
  • Double membrane
  • Inner membrane called cristae
  • Fluid centre called the mitochondrial matrix
  • Loop of mitochondria DNA
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10
Q

Function of mitochondria

A
  • Site of aerobic respiration
  • Site of ATP production
  • DNA to code for enzymes needed in respiration
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11
Q

Features of ribosomes

A
  • Small, made up of 2 sub- units of protein and rRNA
    80s- large ribosomes found in eukaryotic cells
    70s- smaller ribosome found in prokaryotic cells, mitochondria and chloroplasts
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12
Q

Function of ribosome

A

The site of protein synthesis

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13
Q

Features of vacuole

A

Filled with fluid surrounded by a single membrane called a tonoplast

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14
Q

Function of vacuole

A
  • Make cells turgid and therefore provide support
  • Temporary store of sugars and amino acids
  • The pigments may colour petals to attract pollinators
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15
Q

Features of chloroplast

A
  • Surrounded by a double membrane
  • Contains thylakoids
  • Fluid filled stroma contains enzymes for photosynthesis
  • Found in plants
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16
Q

Function of chloroplasts

A

Site of photosynthesis

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17
Q

Features of the cell wall

A

Plants- made of microfibrils of the cellulose polymer
Fungi- made of chitin, a nitrogen- containing polysaccharides

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18
Q

Function of the cell wall

A

Provides structural strength to the cell

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19
Q

Features of plasma membrane

A

Phospholipid bilayer- molecules embedded within and attached on the outside (proteins, cholesterol, carbohydrates)
Found in all cells

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20
Q

Function of plasma membrane

A

Controls the entrance and exit of molecules

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21
Q

Define magnification

A

The magnification of a microscope refers to how many times larger the image is compared to the object

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22
Q

Define resolution

A

The resolution of a microscope is the minimum distance between two objects in which they can still be viewed as separate

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23
Q

Features of a light microscope

A
  • A beam of light is condensed to create the image
  • Poorer resolution due to light having a longer wavelength
  • Lower magnification
  • Colour images
  • Can view living samples
24
Q

Features of an electron microscope

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 short wavelength
  • Higher magnification
  • Black and white images
  • Sample must be in a vacuum, and therefore non- living
25
Q

Negatives of using a light microscope

A

They have poor resolution due to the long wavelength of light. Small organelles in a cell cannot be visible

26
Q

Positives of using a light microscope

A

Living samples can be examined and coloured images can be obtained

27
Q

What is a transmission electron microscope (TEM)

A

Extremely thin specimens are stained and placed in a vacuum
An electron gun produces a beam of electrons that pass through the specimen
Some parts absorb the electrons and appear darker
The image produced is 2D and shows detailed images on the internal structure of cells

28
Q

What is a scanning electron microscope (SEM)

A

The specimen does not need to be thin
Electrons are beamed onto the surface and the electrons are scattered in different ways depending on the contours
This produces a 3D image

29
Q

How to calculate magnification

A

magnification= image size/ actual size

30
Q

What is cell fractionation?

A

This enables individual organelle structures and functions to be studied

31
Q

What are the 2 processes involved in cell fractionation

A
  1. Homogenisation
  2. Ultracentrifugation
32
Q

What happens during homogenisation?

A

The cell must be broken open using a blender. The cells are blended in a cold, isotonic and buffered solution. The solution is then filtered to remove any large cell debris.

33
Q

What must you do to cells before they undergo cell fractionation?

A

Cold- to reduce enzyme activity. When the cell breaks open and enzymes are released, it could damage the organelles
Isotonic- must be the same water potential to prevent osmosis as this could cause the organelles to shrivel or burst
Buffered- the solution has a pH buffer to prevent damage to organelles

34
Q

What happens during centrifugation?

A
  • The centrifuge spins and the centrifugal forces causes pellets of the most dense organelles to form at the bottom
  • The centrifuge is first spun at a low speed and the process is repeated at increasingly faster speeds
  • Each time the supernatant is removed, leaving behind a pellet of organelles
35
Q

Organelles heaviest to lightest

A
  • Nuclei
  • Chloroplast (if using plant tissues)
  • Mitochondria
  • Lysosomes
  • Endoplasmic reticulum
  • Ribosomes
36
Q

How do eukaryotic, prokaryotic and viruses replicate?

A

Eukaryotic- cells enter the cell cycle and divide by mitosis or meiosis
Prokaryotic- replicate by binary fission
Virus- replicate inside the host cell, they invade by injecting their nucleic acid in the cell to replicate the virus particles

37
Q

What are the 3 stages of the cell cycle

A

Interphase- G1, S, G2
Nuclear division- mitosis and meiosis
Cytokinesis

38
Q

What happens during interphase

A

It is the longest stage. Interphase is when the organelles double, the cell grows and then DNA replicates

39
Q

What happens during nuclear division?

A

Can either be mitosis (creating 2 identical diploid cells), or meiosis (creating 4 genetically different haploid cells). Mitosis creates cells with identical DNA for growth and repair, where as meiosis creates gametes

40
Q

What happens during cytokinesis?

A

It is the final stage. It is the division of the cytoplasm to create the new cells

41
Q

What happens in G1, S and G2?

A

G1- Growth
S- DNA synthesis
G2- Growth and preparation for mitosis

42
Q

What happens during prophase?

A

Chromatin condenses into chromosomes and becomes visible and the nucleolus disappears. The centrioles separate and move to opposite poles of the cell. The centrioles are responsible for creating spindle fibres which are released from both poles

43
Q

What happens during metaphase?

A

Chromosomes align along the equator of the cell. The spindle fibres released from the poles now attach to the centromere and chromatid

44
Q

What happens during anaphase?

A

The spindle fibres start to retract and pull the centromere and chromatids towards opposite poles. This causes the centromere to divide into 2 and the individual chromatids are pulled to opposite poles. This stage requires energy in the form of ATP which is provided by respiration in the mitochondria

45
Q

What happens during telophase?

A

The chromosomes are now at each pole of the cell and become longer and thinner again. The spindle fibres disintegrate, and the nucleus starts to reform. The final stage in the cell cycle is when the cytoplasm splits in 2 to create the 2 new genetically identical cells

46
Q

How to calculate the mitotic index

A

mitotic index= the number of cells in mitosis/ the total number of cells x 100

47
Q

Process of binary fission

A

Replication of the circular DNA and of plasmids. Division of the cytoplasm to produce 2 daughter cells, each with a single copy of the circular DNA and a variable number of plasmids

48
Q

What are membranes described as?

A

Fluid-mosaic model due to the mixture and movement of the phospholipids, proteins, glycoproteins and glycolipids it is made of

49
Q

What does cholesterol do in the membrane?

A

Cholesterol- restricts the lateral movement of other molecules in the membrane. This is useful as it makes the membrane less fluid at high temperatures and prevent water and dissolved ions leaking out of the cell

50
Q

Proteins in the membrane

A

Proteins are embedded across he cell surface membrane either peripheral (do not extend completely across the membrane) and integral (span across form side of the bilayer to the other)

51
Q

What do peripheral proteins do?

A

They provide mechanical support, or they are connected to proteins or lipids to make glycoproteins and glycolipids. The function of these is cell recognition, as receptors

52
Q

What do integral proteins do?

A

They are protein channels or channel proteins involved in the transport of molecules across the membrane

53
Q

What do protein channels do?

A

They form tubes that fill with water to enable water soluble ions to diffuse through

54
Q

What do carrier proteins do?

A

They will bind with large molecules, such as glucose and amino acids, and change shape to transport them to the other side of the membrane

55
Q

What molecules can pass through the membrane?

A

Lipid soluble substances (some hormones) and very small molecules (CO2, O, H2O)

56
Q

What molecules cannot pass through the membrane?

A

Water soluble (polar) substances ( sodium ions) and large molecules (glucose)

Biology- Mrs Bell (4 decks)

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