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Biology AS > Cell Structure and Division > Flashcards

Cell Structure and Division Flashcards

1
Q

Features of a eukaryotic cell

A

distinct nucleus, membrane-bound organelles

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2
Q

Function of the nucleus

A

contains genetic information, controls the cell by producing mRNA and tRNA needed for protein synthesis

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3
Q

Structure of the nucleus

A

Nuclear envelope, nuclear pores, nucleoplasm, chromatin, nucleolus

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4
Q

Function of the mitochondria

A

the site of aerobic respiration, whcih in needed to produce ATP.

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5
Q

Structure of the mitochondria

A
  • Double membrane - controls passage of substances in and out of the organelle.
  • Inner membrane is folded to produce cristae which provide a large surface area for enzymes and proteins involved in respiration.
  • Matrix - makes up the rest of the mitochondrion. In it are proteins, lipids, ribosomes and DNA so mitochondria can control their own protein production. There are also enzymes.
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6
Q

Function of the chloroplasts

A

Site of photosynthesis, so plants can use energy from the sun to produce organic molecules and ATP.

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7
Q

Chloroplast structure

A

Chloroplast envelope - double plasma membrane
which selects what can enter and exit.

Grana - stacks of thylakoids. Have a large surface area for proteins involved in photosynthesis.

Thylakoids - disk shaped structures which cotain chlorophyll and are joined by intergranal lamellae.

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8
Q

Types of endoplasmic reticulum, how are they different?

A

Rough and smooth.

Rough has ribosomes on its external surface but smooth does not.

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9
Q

Structure and role of rough endoplasmic reticulum

A

network of membranes called cisternae, ribosomes on the outer surface.
The membrane is continuous with the outer nuclear membrane.
Function: folds and processes proteins that have been made at the ribosomes.

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10
Q

Structure and role of smooth endoplasmic reticulum

A

Similar to RER but with no ribosomes on the surface. Synthesises and processes lipids

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11
Q

Structure of the golgi apparatus

A

Similar structure to SER (a network of membranes) although more compact, also made up of cisternae and also vesicles.

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12
Q

Function of the golgi apparatus

A
  • Proteins and lipids from the ER are transported here in a strict order. The Golgi apparatus modifies proteins by adding non protein components, for example carbohydrates to form glycoproteins.
  • Substances are also labelled so they can be sorted and transported to the right place. The modified substances are transported in vesicles, formed when the ends of cisternae are pinched off.
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13
Q

Structure and function of lysosomes

A

Vesicles from the Golgi apparatus which contain enzymes. This is important as enzymes need to be isolated from the rest of the cell.

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14
Q

Function of ribosomes

A

the site of protein synthesis

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15
Q

Structure and types of ribosomes

A

80S - found in eukaryotic cells, larger.
70S - found in prokaryotic cells, mitochondria and chloroplasts.
Ribosomes are made up of a large and a small subunit which contain ribosomal RNA and protein.

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16
Q

What is the nuclear envelope and what does it do?

A

A double membrane surrounding the organelle. The outer membrane continues into the endoplasmic reticulum. This controls the entry and exit of substances into the nucleus.

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17
Q

What is chromatin?

A

linear DNA found in the nucleoplasm

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18
Q

where can ribosomes be found?

A

on the surface of rough endoplasmic reticulum and in the cytoplasm.

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19
Q

Uses of lysozymes

A

They are hydrolytic enzymes which are stored in lysosomes and may be released outside a cell to destroy material there, released into a vacuole or used to digest old organelles.

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20
Q

Plant cell wall structure

A

Made up of microfibrils formed of cellulose, the middle lamella marks the boundary between two cell walls and sticks neighboring cells together.

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21
Q

What is the cell wall formed of in:

  • plants
  • algae
  • fungi
A
  • cellulose
  • cellulose +/ glycoproteins
  • chitin, a polysaccharide. contains nitrogen and glycoproteins.
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22
Q

Function of the cell wall

A

allows cell to become turgid without bursting and strengthens whole plant.

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23
Q

Vacuole structure and function

A

A sac with a single membrane called the tonoplast, which contains fluid.
The vacuole contains solution of mineral salts, sugars, amino acids, wastes and pigments.
It helps make the cell turgid, and sugars and amino acids can act as a temporary food source.

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24
Q

Cell membrane structure and function - basic

A

A double membrane containing a phospholipid bilayer which controls the passage of substances in and out of the cell.
May also be called a plasma membrane.

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25
Q

Main differencs between eukaryotic and prokaryotic cell structure

A
  • prokaryotes are much smaller
  • no membrane-bound organelles
  • smaller ribosomes
  • no nucleus; instead they have a single circular DNA molecule that
    is free in the cytoplasm and is not associated with proteins
  • a cell wall that contains murein, a glycoprotein
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26
Q

What are viruses?

A

acellular, non-living particles

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27
Q

Structure of viruses

A

Much smaller than prokaryotic cells.
genetic material - DNA or RNA, contained in a protein coat called a capsid.
There are attachment proteins on the virus surface which allow it to attach to host cells.

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28
Q

Additional features of prokaryotic cell structure

A

May have:
• one or more plasmids
• a capsule surrounding the cell
• one or more flagella.

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29
Q

Magnification

A

how many times larger the image is than the object

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30
Q

Magnification =

units …

A

image height/ object height

units need to be the same on the top and the bottom.

31
Q

Converting between m and mm, um and nm

A 
m = 1
mm = 10^-3
um = 10^-6
nm = 10^-9
32
Q

Resolution

A

the minimum distance apart two objects must be for them to be seen separately through a microscope.

33
Q

What does the resolving power of a microscope depend on?

A

the form of radiation used - smaller wavelength means greater resolution.

34
Q

Purpose of cell fractionation

A

to obtain large numbers of isolated organelles so they can be studied

35
Q

Features of the cell fractionation solution

A

cold, buffered and isotonic

36
Q

why does the cell fractionation have to be cold?

A

to reduce enzyme activity that could break down organelles

37
Q

why does the cell fractionation have to be isotonic?

A

same water potential as the organelles, so organelles do not burst or shrink due to osmotic gain or loss of water.

38
Q

why does the cell fractionation have to be buffered?

A

*** so the pH doesn’t fluctuate, as this could change protein and organelle structure.

39
Q

Stages of cell fractionation

A

homogenisation

ultracentrifugation

40
Q

Homogenation in cell fractionation

A

Cells are broken up in a homogeniser (blender) so that organelles are released. The homogenate is filtered to remove whole cells and large debris.

41
Q

Ultracentrifugation in cell fractionation

A
  • the filtrate is centrifuged at a slow speed.
    -the densest organelles sediment out.
  • the supernatant is transferred to another tube and spun at a faster speed.
    With each speed increase, the next densest organelles sediment out. This process continues until the desired organelle is separated out.
42
Q

what do eukaryotic cells that retain the ability to divide show?

A

a cell cycle

43
Q

in what stage of the cell cycle does DNA replication occur?

A

interphase

44
Q

What happens in mitosis? (overview)

A

a eukaryotic cell
divides to produce two daughter cells, each with the identical
copies of DNA produced by the parent cell during DNA replication

45
Q

What are the 4 stages of mitosis?

A

prophase
metaphase
anaphase
telophase

46
Q

Describe the appearance and behaviour of chromosomes during mitosis and explain how this results in the production of two genetically identical cells.

A
  1. Prophase: Chromosomes shorten and thicken / supercoiling
  2. Chromosomes appear as two identical chromatids joined by centromere - as DNA has been replicated
  3. Metaphase: Chromosomes move to cell equator
  4. Chromosomes are attached to individual spindle fibres by their centromere;
  5. Spindle fibres contract, causing centromeres to divide
  6. Anaphase: sister chromatids move to opposite poles
  7. Each pole receives identical copies of each chromosomes;
  8. Nuclear envelope forms around each group of chromosomes at each pole; Each chromatid uncoils and unwinds;
47
Q

What is cytokinesis, and what does it result in?

A

division of the cytoplasm, results in the production of 2 new daughter cells with identical copies of DNA.

48
Q

What can uncontrolled cell division lead to?

A

the formation of tumours and cancers

49
Q

What do many cancer treatments aim to do?

A

control the rate of cell division

50
Q

Describe the process of binary fission in prokaryotic cells.

A

• replication of the circular DNA and of plasmids

• division of the cytoplasm to produce two daughter cells, each with
a single copy of the circular DNA and a variable number of copies
of plasmids.

51
Q

What is the process of prokaryotic cell division called?

A

binary fission

52
Q

Do viruses undergo cell division? Why/ why not?

A

Viruses do not undergo cell division as they are non-living.

53
Q

How do viruses replicate themselves?

A

Viruses inject their nucleic acid into a host cell, which then replicates the virus particles.

54
Q

How do optical microscopes work?

A

they focus light using lenses to form an image.

55
Q

Principles of transmission electron microscopes

A

Electrons are passed through a thin specimen. denser parts absorb more electrons, so appear darker. The image can be photographed to produce a photomicrograph.

56
Q

Advantages and disadvantages of TEM

A

+ Electrons have short wavelength so give high resolution;
Limitations:
- Cannot look at living material as must be in a vacuum;
- Specimen must be very thin;
- Artefacts present;
- Complex staining method to produce a black and white image
- Image only in 2D

57
Q

Principles of the scanning electron microscope

A

A beam of electrons is passed back and forth over a specimen and electrons are scattered on its surface.
The pattern of electron scattering gives the 3D shape of the specimen.
Vacuum is required, so large samples cannot be viewed.

58
Q

SEM vs TEM

A
  • SEM can be used on thick specimens

- TEM gives a greater resolution/ more detail.

59
Q

https://quizlet.com/210371832/aqa-a-level-biology-long-answer-qs-flash-cards/

A

for long answer questions

60
Q

Plant cell vs animal cell

A

Plant cells have all the features of animal cells, as well as a cellulose cell wall, a vaccuole and chloroplasts.

61
Q

2 types of eukaryotic cell division

A

mitosis, meiosis

62
Q

Levels of organisation of specialised cells

4

A

Specialised cells are organised into

tissues, tissues into organs and organs into systems

63
Q

Cells in complex multicellular organisms become specialised…

A

for specific functions, in a process called differentiation.

64
Q

functions of mitosis

A

growth, reproduction (asexual/ producing a new individual after fertilisation), repair of damaged tissues

65
Q

How do different types of specialised cells vary?

A

due to the addition of extra features which make the cell adapted to its function.

66
Q

Limitations of optical microscopes compared to electron microscopes. Why?

A

light microscopes have a lower maximum magnification and resolution, because light has a longer wavelength than electrons.

67
Q

What are the 3 stages of the cell cycle?

A

interphase, mitosis, cytokinesis.

68
Q

How can you calculate the mitotic index?

A

number of cells in mitosis/ total number of cells observed.

cells in mitosis have visible chromosomes.

69
Q

What are artefacts?

A

Things seen using a microscope that aren’t part of the specimen being looked at.
There was a considerable
period of time during which the scientific community distinguished
between artefacts and cell organelles. (??)

70
Q

How can the size of an object being viewed with an optical microscope be measured?

A

Line the eyepiece graticule scale up with the stage micrometer and work out the values of the divisions on the eyepiece graticule at the magnification.
Now are able to measure the size of cells.

71
Q

Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells. (5)

A

Any five from:
1. Cell homogenisation to break open cells;
2. Filter to remove large debris / whole cells;
3. Use isotonic solution to prevent damage to mitochondria / organelles;
4. Keep cold to prevent damage by enzymes / use buffer to
prevent protein / enzyme denaturation;
5. Centrifuge at lower speed to separate nuclei/
heavy organelles;
6. Re-spin supernatant at higher speed to
get mitochondria in pellet at bottom.

72
Q

Describe the principles and limitations of using a transmission electron microscope to investigate cell structure
(5)

A

Principles:

  1. Electrons pass through thin specimen;
  2. Denser parts absorb more electrons;
  3. So denser parts appear darker;
  4. Electrons have short wavelength so give high resolution;

Limitations:

  1. Cannot look at living material / Must be in a vacuum;
  2. Specimen must be (very) thin;
  3. Artefacts present;
  4. Complex staining method;
  5. Image not in 3D / only 2D images produced.

Ignore ref to colour

73
Q

Explain how the events during interphase and mitosis lead to the production of 2 genetically identical cells. (4)

A
  1. DNA replicated during interphase;
  2. Involving complementary base-pairing;
  3. two sister chromatids;
  4. Each chromatid moves opposite poles of cell.

Biology AS (10 decks)

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