Brainscape's Knowledge GenomeTM

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


See full index

A Level Biology > Topic 3 > Flashcards

Topic 3 Flashcards

1
Q

Name the difference between prokaryotic and eukaryotic cells

A

Eukaryotic contain a nucleus

Prokaryotes have cell walll

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

Name the things that can be found in a eukaryotic cell

A

Nucleus
Nucleolus
Smooth endoplasmic recticlum

Rough endoplasmic recticulum 
Ribosomes 
Cell surface membrane 
Golgi apparatus 
Centrioles 
Mitochondria 
Lyosome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the role of the nucleus and what two things does it contain

A

It controls cell activity it contains genes that control protein synthesis

Chromatin(made from DNA and proteins ) and nucleolus

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

What is the role of the nucleolus

A

It is within the nucleus and it’s where ribosomes are made

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

What is the role of rough endoplasmic rectilum

A

It folds and processes proteins that have been made at the ribosomes

It contains ribosomes also

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

What is the role of the smooth endoplasmic rectilium

A

They make steroids and lipids they don’t contain ribosomes

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

What is the role of the ribosomes

A

It’s the site of proteins synthesis in the cell

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

What is the cell surface membrane

A

It’s a partially permeable barrier that’s made up of phospholipid bilayer

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

What is the function of the Golgi apparatus

A

They modify proteins and package them in vesicles it also makes lipids and lysomes

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

What is the function of lysosome

A

They contain digestive enzymes that help in breaking down any unwanted structures

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

What is the function of centrioles

A

They are involved in the separation of chromosomes in mitosis

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

What is the function of mitochondria

A

They are the site of respiration in a cell

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

Describe the stages in proteins transport after translation

A

The protein made in the ribosomes enter the rough endoplasmic reticulum where it’s processed and folded to develop its 3D shape

They are transported in vesicles from the rough er to the Golgi apparatus

In the Golgi apparatus they are modified further ie more sugar chains are added

After they move into vesicles and fuse to the CSM to be released

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the two gamates

A

Sperm

Ovum

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

Give the characteristics of the ovum

A

It’s unable to move

It contains protein and lipid reserves for energy in its cytoplasm for the developing embryo

Zona pellucida which prevents any more sperm entering after fertilisation

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

How do the flagellum and mitochondria enable the sperm to move

A

The mitochondria releases energy that powers the flagellum to move

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

State the stages in fertilisation

A

Sperm enters the vagina and swims through to the uterus

The ovum releases chemicals that attract the sperm towards it

The acrosome swells and fuses with the sperm cell membrane and releases digestive enzymes,the acrosome reaction takes place in which digestive enzymes break down the zona pellucida and the haploid Nuclues of both gamates fuse meaning fertilisation has taken place

Cortical reaction takes place in which cortical granules are released which rethickens the zona pellucida preventing more sperm cells entering

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

What is a zygote

A

It’s produced when the nucleus of the sperm and egg fuse

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

What is meant by gamates being haploid

A

They only have 23 chromosomes

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

What are the two types of cell division

A

Meiosis and mitosis

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

What are cortical granules and what occurs in the cortical reaction

A

Cortical granules by exocytosis are released and they thicken the zona pellucida preventing any more sperm cells entering the egg

They are lysosomes so secetory vesicles

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

What is mitosis

A

The cell division of normal body cells in which the full diploid number is maintained

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

What is meiosis

A

The cell division of sex cells which produces haploid number of 23 chromosomes

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

Give two important reasons of meiosis

A

Creates genetic variation creates haploid number which are needed for diploid number

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

Give two ways in which meiosis provides us with genetic variation

A

Independent assortment

Crossing over

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

What is independent assortment

A

The separation of chromosomes and random placement of them in gamates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is crossing over

A

When chromosome pairs line up they cross over and exchange genetic material and so exchange pieces of chromosomes

Same genes but different combo of alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the region at which the chromosomes cross over called

A

The chiasmata

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the cell cycle and state it’s function

A

Series of events that occur in a cell that led to its division and duplication of its DNA to produce two daughter cells

It repairs,replaces dead and work out cells

The cells produced are genetically identical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Give the 3 stages of the cell cycle

A

Interphase
Mitosis
Cytoplasmic division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is a sex linked characteristic

A

When the locus of the allele that codes for it is on a sex chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

State two sex linked characteristics

A

Colour blindness

Haemophilia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Out of males and females who are most likely to develop sex linked characteristics and why

A

Males as they contain only one X chromosome so contain only one allele for sex linked gene,so they either express the characteristics or not even if it’s a recessive characteristic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What occurs in interphase

A

New cell components ie memebranes and organelle are synthesised also DNA replicates and its ready for dvision

DNA unravels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Give the 3 stages of interphase and what happens in each stages

A

G1-cells grows and proteins are made

S-this is where DNA synthesis occurs ready to divide

G2- organelles are still being made

Results in one cell with that contains twice the amount of organelles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What does nucleoi contain and what effect does it have on the nucleoi

A

It has ribosomes which make it dark

37
Q

Give the four stages of mitosis

A

Prophase
Metaphase
Anaphase
Telophase

38
Q

What happens in prophase

A

Chromosomes condense and become fatter and shorter and become visible as two strands called chromatids

Micro tubles form the spindle and centrioles position themselves at opposite sides of the cell for the two poles of spindles

Between the spindle poles spindle fibres form with the widest part called the equator

Prophase end is signified by the breakdown of the nuclear envelope

39
Q

What occurs in metaphase

A

This is when the centromeres of the chromosomes attach at the equator to spindle fibres

40
Q

What is the centromere

A

The region which two chromosomes join the middle

41
Q

What happens in anaphase

A

This is when spindle fibres shorten pulling centromere apart with the chromatids going in opposite directions

Once the chromstids reach the poles the spindle breaks down

42
Q

What happens in telophase

A

Chromatids unravel and become chromosomes and the nuclear envelope reforms around each group of chromosomes which gives two sets of genetic info(Nuclues)

43
Q

What happens in cytoplasmic division

A

The cell membrane constricts around the cell centre which causes it to split into two

Actin and myosin are said to be responsible for the contraction

44
Q

Why is mitosis important

A

As it creates genetic consistency which is important for growth and repair of cells

Enables old damaged cells to be replaced by new identical copies

All cells contain the same genetic information

45
Q

How do u work out mitotic index

A

Number of cells with visible chromosomes
/
Total cells observed

46
Q

How does asexual reproduction occur

A

By mitosis in which the offspring produced is genetically identical to the parent

47
Q

How do yeast cells reproduce and describe the process

A

By a sexual budding. In which a yeast bud will grow from a parent cell and DNA replication will follow

48
Q

What is meant by cells being totipotent

A

That they have the potential to become any type of cell ie human being

49
Q

What is a blastocyst

A

It’s a hollowball of cells

50
Q

In a blastocyst what does the outer and in layers go onto form

A

Outer layer forms placenta while the inner cell goes into to form the tissues in an embryo

51
Q

What is meant by pluripotent cell

A

Cells that have the potential to form most types of cells

52
Q

What is cell differentiation

A

When cells become specialised for particular purposes

53
Q

What to do plants cells have the ability to do

A

As they are totipotent they can reduffereniate to develop new plants

54
Q

Describe the stages in plant tissue culture

A

Explants are surface sterilised and are then placed in a solid agar medium with nutrients and growth regulators

The cells divide to form a callus which is a mass of undifferentiated cells

By altering the growth regulators in the medium the callous can be made differentiate to form a group of cells that are similar to plant embryos

The embryos can develop into complete plants that are genetically identical

55
Q

What is the epigenome and what is its role

A

It influences which genes are switched on or off and they are chemical markers on the surface of DNA and Histones

56
Q

What is DNA wrapped around

A

A Histone protein

57
Q

When is a gene switched off

A

When a methyl group ie attached to the DNA of a gene meaning RNA polyermise can’t bind to it and transcription and translation can’t take place

58
Q

When DNA replicates what is copied as well

A

The epigentic markers meaning that the next cell will have the same active genes

59
Q

What does the lac operon model show

A

The switching on of individual genes in an ecoli bacteria which is prokaryote

60
Q

When lactose isn’t present in the environment why won’t the gene for the Enzyme B galactosidase be produced

A

As a lactose repressor molecule will bind onto the DNA which prevents the B galactosidase gene being expressed so it won’t be transcribed as RNA polymerase can’t bind

61
Q

When lactose is present in the environment what happens in the lac operon model

A

Lactose will bind onto the lactose repressor molecule preventing it from binding onto the DNA at the promoter region

This means that RNA polymerase can bind to the DNA promoter region and the gene for B galactosidase can be transcribed and translated

62
Q

What is the B galactosidase used for

A

To break down lactose into glucose and galactose

63
Q

How are genes switched in eukaryotes

A

The enzyme RNA polymerase will bind onto the promoter region and transcription of the gene occurs

Regulator protein can help in this process

64
Q

In eukaryotes how is transcription of genes prevented

A

By a repressor molecular binding onto the DNA printer region or regulator protein

65
Q

How can cells recognise the same type of cells as themselfves and stick to each other

A

Cells have adhesion molecules on the cell surface which a specific recognition proteins which allows them to recognise one another as

66
Q

What are cells,tissues,organs,organ systems

A

Cells are specialised for a particular function

Tissue group of specialised cells working together to carry out a function

Organ- group of tissues working together to carry out a particular function

Organ system- group of organs working together to carry out a particular function

67
Q

During development how do epigentic changes cause specialisation of cells

A

Signals within and out of the cells cause changes to occur in the epigenome which results in genes being transcribed at specfic times and locations and in DNA replication the epigenome is copied and ensures the changes carry on to new cells

68
Q

What is meant by discontinuous variation

A

Characteristics that are only controlled by our genotype

69
Q

What is a continuous variation

A

When characteristics are affected by our genotype and the environment

Ie weight

70
Q

What is polygenic inheritance

A

When genes at different loci is responsible for a characteristic at

71
Q

What is meant by multifactoral

A

This is when several genetic factors and one or more environmental factors are involved

72
Q

What is melanin

A

A dark pigment found in both skin and hair

73
Q

Where is melanin made

A

In melanocytes found in roots

74
Q

How is the making of melanin activated

A

By melanin stimulating hormone which has receptors on the melanocytes

75
Q

Once the melanocytes make melanin what happens next

A

They place it in organelles called melanosomes which after they are then transferred to hair and skin cells where they collect around the nucleus and provide protection for the DNA

76
Q

What effect does uv light have on the amount of msh and msh receptors

A

It increases it

77
Q

Why won’t hair darken with an increase in uv light even tho it darkens skin

A

Physical changes and chemical changes occur in the melanin and other proteins in hair cells as a result of the uv light

78
Q

What environmental factors can impact our epigenome

A

Diet
Toxins
Drugs
Medicine

79
Q

What is cancer

A

When the rate of cell multiplication is more than cell death

80
Q

How can cancer occur

A

As a result of DNA mutations occur which occur when DNA is damaged by uv light

81
Q

What two genes are responsible for causing Cancer

A

Oncogenes

Tumour suppressor genes

82
Q

What is the role of oncogenes and how can they cause cancer

A

They stimulate transition into the next stage of the cell cycle

However less methylation/DNA mutations can mean their is no break in the cycle as the gene is still active which leads to excessive cell division resulting in a tumour developing

83
Q

What is the role of Tumor suppressor genes

A

They produce suppressor proteins that halt the cell cycle

More methylation,causes inactive genes means again their no brake in the cycle ie p53

84
Q

Give some causes of cancer

A

Uv light
Asbestos
Smoking
Virus infection

86
Q

How can tissue cultures be prevented from contamination

A

Surface sterilise agar plate

Sealing the container

87
Q

Exaplain why contamination of tissue culture have to be avoided

A

It can cause infection of plant tissue

Leads to poor growth

88
Q

State two similarities between nucleus of an egg cell and sperm

A

They are both produced by meiosis

They are both haploid

89
Q

Give 3 issues with stem cell used as treatment

A

Could cause cancer

Rejection

Use of immunosuppressant drugs increases chance of infection

90
Q

What does the attachment of acetyl groups enable

A

They allow for the gene to be active

As they make the chromatin to be less condense

A Level Biology (9 decks)

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