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A Level Biology > Topic 3 > Flashcards

Topic 3 Flashcards

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1
Q

Name the difference between prokaryotic and eukaryotic cells

A

Eukaryotic contain a nucleus

Prokaryotes have cell walll

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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
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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

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4
Q

What is the role of the nucleolus

A

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

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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

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6
Q

What is the role of the smooth endoplasmic rectilium

A

They make steroids and lipids they don’t contain ribosomes

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7
Q

What is the role of the ribosomes

A

It’s the site of proteins synthesis in the cell

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8
Q

What is the cell surface membrane

A

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

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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

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10
Q

What is the function of lysosome

A

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

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11
Q

What is the function of centrioles

A

They are involved in the separation of chromosomes in mitosis

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12
Q

What is the function of mitochondria

A

They are the site of respiration in a cell

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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

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14
Q

What are the two gamates

A

Sperm

Ovum

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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

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16
Q

How do the flagellum and mitochondria enable the sperm to move

A

The mitochondria releases energy that powers the flagellum to move

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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

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18
Q

What is a zygote

A

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

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19
Q

What is meant by gamates being haploid

A

They only have 23 chromosomes

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20
Q

What are the two types of cell division

A

Meiosis and mitosis

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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

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22
Q

What is mitosis

A

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

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23
Q

What is meiosis

A

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

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24
Q

Give two important reasons of meiosis

A

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

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25
Give two ways in which meiosis provides us with genetic variation
Independent assortment Crossing over
26
What is independent assortment
The separation of chromosomes and random placement of them in gamates
27
What is crossing over
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
28
What is the region at which the chromosomes cross over called
The chiasmata
29
What is the cell cycle and state it's function
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
30
Give the 3 stages of the cell cycle
Interphase Mitosis Cytoplasmic division
31
What is a sex linked characteristic
When the locus of the allele that codes for it is on a sex chromosome
32
State two sex linked characteristics
Colour blindness | Haemophilia
33
Out of males and females who are most likely to develop sex linked characteristics and why
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
34
What occurs in interphase
New cell components ie memebranes and organelle are synthesised also DNA replicates and its ready for dvision DNA unravels
35
Give the 3 stages of interphase and what happens in each stages
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
36
What does nucleoi contain and what effect does it have on the nucleoi
It has ribosomes which make it dark
37
Give the four stages of mitosis
Prophase Metaphase Anaphase Telophase
38
What happens in prophase
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
What occurs in metaphase
This is when the centromeres of the chromosomes attach at the equator to spindle fibres
40
What is the centromere
The region which two chromosomes join the middle
41
What happens in anaphase
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
What happens in telophase
Chromatids unravel and become chromosomes and the nuclear envelope reforms around each group of chromosomes which gives two sets of genetic info(Nuclues)
43
What happens in cytoplasmic division
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
Why is mitosis important
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
How do u work out mitotic index
Number of cells with visible chromosomes / Total cells observed
46
How does asexual reproduction occur
By mitosis in which the offspring produced is genetically identical to the parent
47
How do yeast cells reproduce and describe the process
By a sexual budding. In which a yeast bud will grow from a parent cell and DNA replication will follow
48
What is meant by cells being totipotent
That they have the potential to become any type of cell ie human being
49
What is a blastocyst
It's a hollowball of cells
50
In a blastocyst what does the outer and in layers go onto form
Outer layer forms placenta while the inner cell goes into to form the tissues in an embryo
51
What is meant by pluripotent cell
Cells that have the potential to form most types of cells
52
What is cell differentiation
When cells become specialised for particular purposes
53
What to do plants cells have the ability to do
As they are totipotent they can reduffereniate to develop new plants
54
Describe the stages in plant tissue culture
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
What is the epigenome and what is its role
It influences which genes are switched on or off and they are chemical markers on the surface of DNA and Histones
56
What is DNA wrapped around
A Histone protein
57
When is a gene switched off
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
When DNA replicates what is copied as well
The epigentic markers meaning that the next cell will have the same active genes
59
What does the lac operon model show
The switching on of individual genes in an ecoli bacteria which is prokaryote
60
When lactose isn't present in the environment why won't the gene for the Enzyme B galactosidase be produced
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
When lactose is present in the environment what happens in the lac operon model
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
What is the B galactosidase used for
To break down lactose into glucose and galactose
63
How are genes switched in eukaryotes
The enzyme RNA polymerase will bind onto the promoter region and transcription of the gene occurs Regulator protein can help in this process
64
In eukaryotes how is transcription of genes prevented
By a repressor molecular binding onto the DNA printer region or regulator protein
65
How can cells recognise the same type of cells as themselfves and stick to each other
Cells have adhesion molecules on the cell surface which a specific recognition proteins which allows them to recognise one another as
66
What are cells,tissues,organs,organ systems
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
During development how do epigentic changes cause specialisation of cells
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
What is meant by discontinuous variation
Characteristics that are only controlled by our genotype
69
What is a continuous variation
When characteristics are affected by our genotype and the environment Ie weight
70
What is polygenic inheritance
When genes at different loci is responsible for a characteristic at
71
What is meant by multifactoral
This is when several genetic factors and one or more environmental factors are involved
72
What is melanin
A dark pigment found in both skin and hair
73
Where is melanin made
In melanocytes found in roots
74
How is the making of melanin activated
By melanin stimulating hormone which has receptors on the melanocytes
75
Once the melanocytes make melanin what happens next
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
What effect does uv light have on the amount of msh and msh receptors
It increases it
77
Why won't hair darken with an increase in uv light even tho it darkens skin
Physical changes and chemical changes occur in the melanin and other proteins in hair cells as a result of the uv light
78
What environmental factors can impact our epigenome
Diet Toxins Drugs Medicine
79
What is cancer
When the rate of cell multiplication is more than cell death
80
How can cancer occur
As a result of DNA mutations occur which occur when DNA is damaged by uv light
81
What two genes are responsible for causing Cancer
Oncogenes Tumour suppressor genes
82
What is the role of oncogenes and how can they cause cancer
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
What is the role of Tumor suppressor genes
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
Give some causes of cancer
Uv light Asbestos Smoking Virus infection
86
How can tissue cultures be prevented from contamination
Surface sterilise agar plate Sealing the container
87
Exaplain why contamination of tissue culture have to be avoided
It can cause infection of plant tissue Leads to poor growth
88
State two similarities between nucleus of an egg cell and sperm
They are both produced by meiosis They are both haploid
89
Give 3 issues with stem cell used as treatment
Could cause cancer Rejection Use of immunosuppressant drugs increases chance of infection
90
What does the attachment of acetyl groups enable
They allow for the gene to be active As they make the chromatin to be less condense

A Level Biology (9 decks)

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