Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-level Biology > Chapter 3 > Flashcards

Chapter 3 Flashcards

1
Q

Function of nucleus

A

Site of DNA replication and transcription (making mRNA)

Contains genetic code for each cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Structure of nucleus

A

Nuclear Envelope- double membrane

Nuclear Pores

Nucleoplasm - granular, jelly-like material

Chromosomes -protein-bound, linear
DNA

Nucleolus - smaller sphere inside which is the site of RNA production and makes ribosomes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Function of endoplasmic reticulum

A

RER - Protein Synthesis

SER - Synthesis and store lipids and carbohydrates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Structure of endoplasmic reticulum

A

Rough and smooth ER have folded membranes called cisternae

Rough have ribosomes on cisternae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Function of Golgi apparatus and vesicles

A

Add carbohydrates to proteins to form glycoproteins

• Produce secretory enzymes

Secrete carbohydrates

Transport, modify and store lipids

• Form lysosomes

Molecules are ‘labelled’ with their destination

Finished products are transported to cell surface in Golgi vesicles where they fuse with the membrane and the contents in released.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Structure of Golgi apparatus and vesicles

A

Folded membranes making cisternae

Secretary vesicles pinch off from the cisternae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Function of lysosomes

A

Hydrolyse phagocytic cells

• Completely break down dead cells (autolysis)

• Exocytosis - release enzymes to outside of cell to destroy material

• Digest worn out organelles for reuse of materials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Structure of lysosomes

A

Bags of digestive enzymes - can contain 50 different enzymes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Structure of mitochondria

A

Double membrane

Inner membrane called the cristae

Fluid centre called the mitochondrial matrix

Loop of mitochondria DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Function of mitochondria

A

• Site of aerobic respiration

Site of ATP production

• DNA to code for enzymes needed in respiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Structure of ribosomes

A

Small, made up of two sub-units of protein and rRNA

80s- large ribosome found it eukaryotic cells (25nm)

70S - smaller ribosome found in prokaryotic cells, mitochondria and chloroplasts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Function of ribosomes

A

Site of protein synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Structure of vacuole

A

Filled with fluid surrounded by a single membrane called a tonoplast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Function of chloroplasts

A

Site of photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Structure of chloroplasts

A

Surrounded by a double membrane

Contains thylakoids (folded membranes embedded with pigment)

Fluid filled stroma contains enzymes for photosynthesis

Found in plants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Function of cell wall

A

Provide structural strength to cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Structure of cell wall

A

In plant and fungi cells

Plants- made of microfibrils of the cellulose polymer.

Fungi - made of chitin, a nitrogen-containing polysaccharide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Function of plasma membrane

A

Controls entrance and exit of molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Structure of plasma membrane

A

Found in all cells

Phospholipid bilayer - molecules embed within and attached on the outside (proteins, carbohydrates, cholesterol)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Calc mitotic index

A

Count how many cells are visible in filed of view and number of cells visible that are in stage of mitosis

Mitotic index = (number of cells in mitosis / total number of cells) x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the 4 stages of mitosis

A

Prophase

Metaphase

Anaphase

Telophase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Info about mitosis

A

1 round of division

Genetically identical cells are made

Diploid cells are made

Growth and repair

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What happens in prophase

A

Chromosomes condense + become visible

Centrioles separate + move to opp ends of poles of cell

Nucleolus disappears

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What happens in anaphase

A

Spindle fibres start to retract + pull centromere and chromatids they’re bound to towards opp poles

Centromere divide in 2

Individual chromatids are pulled to each opp pole (chromatids now referred to as chromosomes)

Requires energy in form of atp - provided by respiration in mitochondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What happens in metaphase

A

Chromosomes align along equator

Spindle fibres released from poles now attach to centromere and chromatid

27
Q

What happens in telophase

A

Chromosomes at each pole become longer + thinner again

Spindle fibres disintegrate, nucleus starts to reform

Nuclear membrane reforms

Nucleoli reappear

Cytoplasm splits in 2 to create 2 new genetically identical cells

28
Q

What are the 3 stages of cell cycle

A

Interphase (G1, S, G2)

Nucelar division (mitosis + meiosis)

Cytokinesis

29
Q

What is interphase

A

Longest stage in cell cycle

When organelles double, cell grows and DNA replicates

30
Q

How do prokaryotic cells replicate

A

Binary fission and viruses don’t undergo cell division as they’re non-living

Viruses replicate inside of host cells they invade by injecting their nuclei acid into cell to replicate virus particles.

31
Q

What are 3 types of microscopes

A

Optical (light) microscopes

Transmission electron microscopes

Scanning electron microscopes

32
Q

Define magnification

A

how many times larger the image is compared to the object.

33
Q

Define resolution

A

the minimum distant between two objects in which they can still be viewed as separate.

34
Q

Optical (light) microscope

A

Light Beam condensed to create image

Poor resolution - light have longer wavelength

Low magnification

Coloured images

Can view living samples

35
Q

Electron microscope (scanning or transmission)

A

Electron beam condensed to create image
Electromagnets used to condense beam

High resolution - electrons have short wavelength

High magnification

Black and white images

Sample must be in vacuum + non-living

36
Q

Are small organelles visible in light microscope

A

No because of poor resolution of microscope - long wavelength of light

37
Q

Why must Samples be in vacuum in Electron microscope

A

As Electrons are absorbed by air

38
Q

Why must Samples be stained in Electron microscope

A

The image is in black and white

39
Q

How is an image produced in TEM

A

Extremely thin specimen stained and place in vacuum

Electron gun produces electron beam that passes through specimen

Some parts absorb electrons and appear dark

Image produced is 2d - shows detailed images on internal structure of cells

40
Q

How is an image produced in SEM

A

The specimens do not need to be thin, as the electrons are not transmitting through.

Instead, electrons beamed onto surface and electrons are scattered in diff ways depending on contours.

This produces a 3D image.

41
Q

Magnification equation

A

Magnification = image size / actual size

42
Q

Converting units

A

M - mm - micrometre - nm

——> x1000
<—— divide by 1000

43
Q

What is cell fractionation used for

A

To isolate diff organelles so they can be studied

This enable individual organelle structures and functions to be studied

44
Q

What happens in cell fractionation 1st

A

Cells are broken open to release contents and organelles are then separated

45
Q

Why must cells be prepared in cold, isotonic, and buffered solution

A

Cold:
To reduce enzyme activity. When cell is broken open enzymes are released which could damage organelles

Isotonic:
organelles must be same water potential as solution to prevent osmosis, as this could cause organelles to shrivel / burst.

Buffered:
solution has pH buffer to prevent damage to organelles

46
Q

What are the 2 main steps in cell fractionation

A

Step 1 = homogenisation

Step 2 = ultracentrifugation

47
Q

What happens in step 1 of cell fractionation

A

cells must be broken open (homogenised) and this is done using blender.

cells are blended in cold, isotonic and buffered solution.

48
Q

What happens in step 2 of cell fractionation

A

filtered solution is spun at high speed in centrifuge.
This separates organelles according to their density.

49
Q

The order of organelle fractionation

A

1st : (slowest speed 1st)

Nuclei

Chloroplasts

Mitochondria

Lysosomes

Endoplasmic reticulum

Ribosomes

Last:(fastest speed)

50
Q

How does the centrifuge separate the pellets

A

centrifuge spins at high speeds and centrifugal forces causes pellets of most dense organelle to form at bottom of tube.

process repeated at increasingly faster speeds, removing supernatant each time (liquid) leaving behind pellet ( isolated organelle).

supernatant is then spun again in centrifuge and process is repeated.

51
Q

Suggest and explain the function of enzyme ATP hydrolase in absorbing amino acids.

A

1.Hydrolysing ATP into ADP + Pi releases energy

  1. This energy actively transports sodium ions out of the epithelial cells into the blood
  2. This creates a sodium ion concentration gradient from the ileum into the epithelial cells
  3. Sodium ions are cotransported into the epithelial cells with amino acids
52
Q

(Mitosis practical) explain why the student used the 1st 5mm from onion root tip

A

This is where mitosis occurs

53
Q

(Mitosis practical) explain why the student pressed down on the cover slip firmly

A

To create a single layer of cells so that light can pass through the specimen

54
Q

(Mitosis practical) explain why the student added acid to the root

A

To break down links between cells/cell walls

55
Q

Describe how HIV replicates inside of helper T cells.

A
  1. RNA is converted into DNA using the enzyme reverse transcriptase
  2. The DNA is inserted into the DNA of the helper T cell
  3. The DNA is transcribed into mRNA
  4. This HIV mRNA is then translated into HIV proteins to make a new viral particles
56
Q

Function of the flagella in prokaryotic cell

A

Flagella rotates to enable bacteria to move

57
Q

What is the capsule made of and its function

A

A slimy layer made of protein

This prevents the bacteria from desiccating (drying out) and protects the bacteria against the host’s immune system.

58
Q

What are plasmids

A

small loops of DNA which only carry a few genes.

59
Q

What is the cell wall like in prokaryotic cell

A

Contains murein (a glycoprotein)

60
Q

What is the cell wall like in eukaryotic cell

A

In plant and fungi cells

Plants- made of microfibrils of the cellulose polymer.

Fungi - made of chitin, a nitrogen-containing polysaccharide

61
Q

Structure of nucleus in prokaryotic cell

A

No nucleus - Instead of a nucleus there is a single circular DNA molecule free in the cytoplasm which is not protein bound.

62
Q

What don’t prokaryotic cells contain

A

Membrane bound organelles
E.g. mitochondria, chloroplasts, endoplasmic reticulum, Golgi, nucleus

63
Q

What are the Key differences between prokaryotic cells and eukaryotic cells and what might prokaryotic cells also contain

A

The cells are much smaller.

No membrane bound-organelles

Smaller ribosomes

No nucleus

A cell wall made of murein

They may also contain:
Plasmids
A capsule around the cell
Flagella

A-level Biology (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions