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OCR AS-level Biology > 2.1.6 cell division, cell diversity & cellular organisation > Flashcards

2.1.6 cell division, cell diversity & cellular organisation Flashcards

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1
Q

What are the differences between chromosomes and chromatids

A

chromosomes have no centromeres

Chromatids have a centromere and are identical sisters. they are like two chromosomes together

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2
Q

state what the cell cycle is an outline the names of its stages

A

The cell cycle is the regulated cycle of division with intermediate growth periods

Interface, mitosis/meiosis, cytokinesis

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3
Q

outline what happens during interphase

A

G1: Cell synthesises proteins + organelles for replication e.g.tubulin for spindle fibres and cell size doubles

S: DNA replicates = chromosomes consist of two sister chromatids joined at a centromere.

G2: organelles divide. This is where the cell grows, energy stores are increased, and duplication errors are looked for

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4
Q

What is the purpose of mitosis

A

produces to genetically identical daughter cells for growth, cell replacement/tissue repair and asexual reproduction

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5
Q

Name the stages of mitosis

A

Prophase
Metaphase
Anaphase
Telophase

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6
Q

Outline what happens during prophase

A

chromosomes condense and super coil (become visible)

The nucleolus disappears and the nuclear membrane breaks down so chromosomes are free in the cytoplasm

The centrioles migrate to the poles and spindle fibres form

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7
Q

Outline what happens during metaphase

A

centrioles release spindle fibres which attach to chromosomes

Chromosomes align along the equator

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8
Q

Outline what happens during anaphase

A

spindle fibres contract (centromeres divide)

this separates the sister chromatids of the chromosomes. and The chromosomes are then pulled to the poles of the cell

spindle fibres break down

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9
Q

Outline what happens during telophase

A

nuclear envelope reforms around chromosomes

chromosomes will decondense (becoming invisible again)

cytokinesis occurs

two genetically identical daughter cells have been performed

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10
Q

How is the cell cycle regulated

A

checkpoints regulated by cell signalling proteins ensure damaged cells do not progress to next stage of cycle

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11
Q

Describe what happens at each key checkpoint in the cell cycle

A

G1 checkpoint: checks to see if DNA is damaged

G2 checkpoint: checks to see if DNA is replicated properly

prophase checkpoint: Spindle assembly checkpoint, checks for alignment of chromosomes

apoptosis: programmed cell death, if any checks fail then it goes to G0

G0= cell leave cycle To differentiate. DNA damaged, cel arrest, old cells

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12
Q

What is meiosis

A

A form of cell division that produces for genetically different haploid cells (cells with half the number of chromosomes found in the parent cell) Known as gametes

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13
Q

describe what happens during prophase I

A

chromosomes condense and they form homologous pairs by synapsis forming a bivalent

crossing over occurs between nonsister chromatids

nuclear envelope and nucleolus disappear and break down

centrioles move to the poles of the cell

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14
Q

Describe what happens during meta phase 1

A

spindle fibres from centrioles , Attach to the chromosomes at the centromere

The homologous pairs lineup along the equator by independent assortment (chromosome arrangement along the equator is random)

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15
Q

Describe what happens during anaphase 1

A

Chromosomes are pulled to the poles by spindle fibres

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16
Q

Describe what happens during telophase I

A

Nuclear envelope reforms, cytokinesis occurs, two cells are formed

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17
Q

describe what happens during prophase II

A

nuclear envelope breaks down

nucleolus disappears

centrioles migrate to the polls at 90° to prophase I

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18
Q

Describe what happens during metaphase II

A

spindle fibres attach to chromosomes and align along equator

Independent assortment of chromatids occurs

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19
Q

Describe what happens during anaphase II

A

Spindle fibres pull chromatids to poles

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20
Q

Describe what happens during telophase II

A

nuclear envelope reforms
nucleolus reforms
chromosomes unravel

cytokinesis occurs
For genetically non-identical daughter cells are made

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21
Q

Define haploid

A

Single set of unpaired chromosomes, half the genetic information e.g. egg and sperm (gametes)

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22
Q

Define diploid

A

Containing two complete sets of chromosomes, one from each parent. full set of genetic information

normal body cells have the normal number of chromosomes = 46 (2n). We call these deployed, it means that each body cell contains two of each chromosome is one from mum and one from dad

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23
Q

Define homologous pairs

A

A homologous chromosome is a set of one maternal chromosome and one paternal chromosomes that pair up with each other inside a cell during meiosis

. A homologous pair is a pair of chromosomes which have the same genes but different alleles

Gammys have half the normal number of chromosomes = 23 (n)

There is only one copy of each chromosome and at fertilisation a haploid sperm or fuse with a haploid egg which makes a cell with a normal diploid number of chromosomes

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24
Q

Define bivalent

A

A pair of homologous chromosomes. During meiosis prophase I . When they stick together they cross over and share genetic information

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25
Q

Define crossing over

A

The exchange of genetic material between homologous chromosomes

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26
Q

Define independent assortment

A

formation of random combinations of chromosomes along the equator in meiosis = variation

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27
Q

Define alleles

A

Different form of the same gene

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28
Q

define synapsis

A

The side-by-side pairing of homologous maternal and paternal chromosomes at the start of meiosis ie. how they stick together

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29
Q

How does meiosis produces genetic variation

A

crossing over during meiosis I

Independent assortment of analogous chromosomes and sister chromatids results in new combinations of alleles

30
Q

Which part of meiosis is what causes diploid cells to become haploid cells (2n to become n)

A

meiosis II

31
Q

How do cells become specialised

A

Some genes are expressed while others are silenced due to cell differentiation mediated by transcription factors. Cells produce proteins that determine their structure and function

32
Q

What is a stem cell

A

on differentiated cells that can divide indefinitely and turn into other specific cell types

33
Q

Name the two broad categories of stem cells

A

embryonic stem cells: the stem cells divide and differentiate into specialised embryonic tissues

adult stem cells: the stem cells are involved in repair and replacement of specialised cells eg blood, skin

34
Q

What must all stem cells be able to do

A

divide repeatedly

Differentiate into specialised cell types i.e. potency

35
Q

Name and to find the four types of stem cells

A

totipotent: can develop into any cell type including the placenta and embryo
pluripotent: can develop into any cell type excluding the placenta and embryo. They are capable of producing all cells drive from a particular German later e.g. ectodermal, endoderm

Multipotent: can only develop into a few different types of cells

Unipotent: can only develop into one cell type e.g. muscles stem cells

36
Q

Suggest some uses of stem cells

A

repair of damaged tissues

drug testing on artificially brown tissues

treating neurological diseases e.g. Alzheimer’s

Researching developmental biology e.g. formation of organs

37
Q

Describe embryonic stem cells

A

as the name implies they are taken from the embryo. In very early stages they are totipotent and from the in a mass of a blastocyst they are pluripotent. Developments suggest that these could be used for treatment of a variety of conditions e.g. Parkinson’s and growing new tissues. Their use is controversial and research tightly regulated

38
Q

Describe Adult stem cells

A

these have the ability to divide And differentiate. Generally they are multipotent and are usually referred to by where they are found. They have been successfully used to treat leukaemia

39
Q

once differentiated what do cells lose

A

their ability to divide and totipotency eg they lose the ability to do everything

40
Q

What are cells that can differentiate called in animals

A

animals: stem cells
plants: Meristematic cells

41
Q

describe the structure of erythrocytes (red blood cells) and how this relates to their function

A

Very small, so have a large surface area to volume ratio. This means oxygen can diffuse across the membranes and easily reach all regions inside the cell

biconcave shape: increases surface area to volume ratio

flexible: well developed cytoskeleton enables them to change shape so they can twist and turn to travel through narrow arteries

No nucleus: more space for haemoglobin

42
Q

What is the general function and location of red blood cells

A

They carry oxygen from the lungs to respiring cells and located in the bloodstream

43
Q

what is the structure of white blood cells and how does this relate to their function (neutrophils)

A

twice the size of RBC

Each white blood cell contains a multilobed nucleus: which provides flexibility to engulf pathogens

lots of mitochondria: to carry out aerobic respiration to produce ATP which provides a lot of energy to carry out phagocytosis

lots of lysosomes: provides lots of digestive enzymes to breakdown the engulfed particles

44
Q

What is the general function and location of white blood cells

A

They are located in the bloodstream after being produced in the bone marrow. They ingest bacteria and some fungi via phagocytosis and engulf pathogens.

45
Q

Describe the structure of sperm cells and how this relates to their function

A

they have lots of mitochondria: to carry out aerobic respiration to produce ATP

they are very small, long and thin: facilitates for easy movement

Acrosome: releases enzymes when sperm cell reaches the ovum. enzyme dissolves out of protective covering of the ovum allowing sperm head to enter

Head: contains haploid mail gamete nucleus and Acrosome

Tail: the energy provided by the mitochondria provides energy for the tail to move to propel the tail towards the ovum

Nucleus: haploid mail gamete nucleus containing DNA of cell

Receptors: has special receptors which enable cell to bind with an egg

46
Q

What is the general function of a sperm cell and where is it located

A

Located in the testicles of a male. It’s general function is to reach the ovum to penetrate and fertilise the female egg to produce new offspring

47
Q

Describe the structure of epithelial cells and relate this to the function

A

Squamous epithelium cells: smooth, flat, very thin, fit closely together - to produce smooth, low friction surface where fluids can move easily

Ciliated epithelial cells have cilia-move in synchronised wave to move particles away

48
Q

What is the general function and location of epithelial cells

A

located lining e.g. organs, blood vessels and make up tissues Which cover surfaces

49
Q

what is the structure of a Palisade cell and relate it to its function

A

Long and cylindrical: pack closely together with a bit of space between them for air to circulate, carbon dioxide diffuses into the cell and these air spaces

Large vacuole: chloroplast other for pointed nearer to the so, reducing diffusion distance for carbon dioxide

lots of chloroplasts: which carry out photosynthesis

Cytoskeleton threads: move the chloroplasts nearer to the upper surface of the leaf when sun light intensity is low, but further down when it’s high

50
Q

What is the general function and location of palisade cells

A

Located within leaves, enable photosynthesis to be carried out efficiently

51
Q

Describe the structure of guard cells and how this relates to the function

A

contain chloroplasts: site of photosynthesis

Surround is stomata: open and close tomato to allow for gassiest exchange required for photosynthesis

cell can become turgid: when turgid, outer walls stretch causing guard cell to bulge and form a pore (stomata) between them allowing gaseous exchange

52
Q

What is the general function and location of the guard cells

A

Located in Leaf epidermis, control the opening and closing of the stomata

53
Q

What is the structure of a root hair cell and How does this relate to its function

A

they have hair like projections: which greatly increases surface area for absorption of water and mineral ions eg nitrates from soil

Mitochondria: produce ATP to actively transport mineral ions into root hair cell

Large vacuole: maintain shape

54
Q

What is the general function and location of root hair cells

A

Located in epidermal cells of the outer layer of young plant roots. They absorb water and mineral ions from the soil

55
Q

What is the structure of epithelial tissue and related to its function

A

No blood vessels: sells receive nutrients by diffusion from tissue fluid in underlying connective tissue

squamous epithelial tissue : Single layer of fat cells: line the surface e.g. alveoli in the lungs providing a short diffusion pathway

ciliated Epithelial tissue: layer of column shaped cells: covered in Celia, work to move mucus which has small particles and micro organisms trapped

56
Q

What is the general function of epithelial tissue and where is it located

A

Located widespread throughout the body and forms a covering of a body services and other major tissue in glands

57
Q

Describe the structure of cartilage and how it relates to its function

A

Cartilage is a type of Smoove, elastic tissue that provides structural support to the body. It provides a framework, helps provide flexibility

58
Q

What is the general function of cartilage and where is it located

A

Located at various points within the body at joints between bones and is connective tissue

59
Q

ppq: Name the type of nuclear division that occurs in plant growth

A

Mitosis

60
Q

ppq: Name a location where growth occurs in a plant

A

Meristem

61
Q

ppq: the stages of meiosis in which the following events occur

independent assortment
formation of the spindle apparatus
separation of sister chromatids
formation of nuclear membranes
Chromosomes pulled to opposite poles
A

independent assortment = metaphase I and metaphase II

formation of the spindle apparatus= prophase I

separation of sister chromatids= Anaphase II
formation of nuclear membranes = telophase II
Chromosomes pulled to opposite poles= anaphase I

62
Q

ppq: Explain why meiosis needs to have twice as many stages as mitosis

A

To half the chromosome number e.g. reduce from 2N to N

also to separate On monikers pairs of chromosomes because DNA has been previously replicated and chromosomes are two chromatids at the start

63
Q

ppq: Before the division of the nucleus of a cell the genetic material must replicate explain why this is essential

A

cells are genetically identical so both daughter cells receive a full copy

Daughter cells have all the identical genetic material

64
Q

ppq: Explain what is meant by a homologous pairs of chromosomes

A

One maternal and one paternal, Carrie same jeans and are genetically identical

They have a central man in the same position and are of the same shape and size

65
Q

ppq: State what is meant by the term tissue

A

A group of cells specialised to perform A specific function

66
Q

ppq: Describe the function of squamous and ciliated tissue and a specific location in the human body

A

squamous: acts as a surface and is found in the alveoli

Ciliated: moves mucus and is found in the trachea

67
Q

ppq: complete the following paragraph

cells that are not specialised but still have the ability to divide are called ___ cells.
such cells can be found in the ____ of the long bones of mammals. The cells can ____ into other types of cell, such as red blood cells that carry oxygen in the blood. In plants ____ Tissue also contain cells that are not specialised

A

cells that are not specialised but still have the ability to divide are called STEM cells.

such cells can be found in the BONE MARROW of the long bones of mammals.

The cells can DIFFERENTIATE into other types of cell, such as red blood cells that carry oxygen in the blood.

In plants MERISTEM Tissue also contain cells that are not specialised

68
Q

ppq: In more advanced organisms, cells are organised into tissues consisting of one or more types of specialised cells. Describe how cells are organised into tissues, using xylem and phloem as examples

A

xylem: consists of vessels and one example of its specialisation is that its walls are lignified, has no end walls and is waterproof. and it moves water
phloem: has sieve tube elements and companion cells and one example of cell specialisation is that it has no nucleus and many plasmodesmata. it is where translocation occurs

69
Q

ppq: Name two parts of a plant where meristematic tissue can be found

A

Root and shoot

70
Q

ppq: State one way in which the product of meiosis are different from the products of nuclear division in meristematic tissue

A

In meiosis cells produced are not genetically identical

71
Q

ppq: During interphase the genetic material is copied, state to other processes that occur during interphase

A

Protein synthesis occurs, cell growth and ATP production

OCR AS-level Biology (12 decks)

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