Module 2.1.6 - cell division

Question 1

What is cell division needed for?

Answer 1

Growth and repair

Question 2

What are the 2 periods of a cell?

Answer 2

Cell growth and DNA replication (interphase)

Question 3

What is M phase?

Answer 3

• period of cell division
• involves mitosis and cytokinesis

Question 4

What separate growth stages is interphase divided into?

Answer 4

G1, S and G2

Question 5

What are the stages of interphase?

Answer 5

• cell prepares to divide
• cell’s DNA is unraveled and replicated (to double its genetic info)
• organelles are replicated so has spare ones and its ATP content in increased

Question 5

What is the cell cycle regulated by?

Answer 5

Checkpoints and occurring key points to make sure process is ok to continue

Question 6

What is mitosis?

Answer 6

• continuous process but is described as a series of stage: prophase, metaphase, anaphase and telophase
• needed for growth and repair, some animals, plants and fungi use it to reproduce asexually

Question 7

What is the structure of chromosomes in mitosis?

Answer 7

• chromosomes are made up of 2 strands joined by a centromere
• separate strands are called chromatids
• 2 strands on same chromosome are called sister chromatids
• 2 strands because each chromosome has already made an identical copy of itself during interphase
• when mitosis is over, chromatids end up as 1 strand chromosomes in new daughter cells

Question 8

What are the stages of prophase?

Answer 8

• chromosomes condense (get shorter and fatter)
• centrioles (tiny bundles of protein) move to the opposite ends of cell, forming protein fibers across it called the spindle
• nuclear envelope (membrane around the nucleus) breaks down and chromosomes lie free in cytoplasm

Question 9

What are the stages of metaphase?

Answer 9

• chromosomes line up along the middle of the cell (spindle equator) and become attached to spindle by their centromere
• at metaphase checkpoint, the cell checks all the chromosomes are attached to the spindle before mitosis can continue

Question 10

What are the stages of anaphase?

Answer 10

• centromeres divide/move apart, separating each pair of sister chromatids
• spindles contract, pulling chromatids to opposite ends of the cell, centromere first

Question 11

What are chromosomes made up of?

Answer 11

2 strands joined by a centromere

Question 12

What are 2 separate strands of a chromosome called?

Answer 12

Chromatids

Question 13

What are sister chromatids?

Answer 13

2 strands on same chromosome

Question 14

What are the stages of mitosis?

Answer 14

Interphase - before mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis - after mitosis

Question 15

What are the stages of telophase?

Answer 15

• chromatids reach opposite poles on the spindle
• uncoil and become long and thin again
• now called chromosomes again (not chromatids)
• nuclear envelope form around each group of chromosomes

Question 16

What are the stages of cytokinesis?

Answer 16

• cytoplasm divides
• a cleavage furrow forms to divide the cells
• 2 genetically identical daughter cells are formed

Question 17

Where does cytokinesis start and end?

Answer 17

Begins in anaphase and ends in telophase

Question 18

Where does cytokinesis occur in animal cells?

Answer 18

By the furrowing of the cytoplasm

Question 19

Where does cytokinesis occur in plant cells?

Answer 19

Is initiated with the formation of a cell plate in the middle of the cell

Question 20

How do you investigate mitosis?

Answer 20

• treat the tips of growing roots in HCL and break them open carefully and spread a few on a microscope
• add a few drops of stain
• squash under a coverslip
• view under a microscope

Question 21

What are egg and sperm cells called?

Answer 21

Gametes

Question 22

What is a zygote?

Answer 22

2 gametes joined together at fertiliasation

Question 23

What type of chromosomes do normal body cells have?

Answer 23

Diploid (contain 2 of each chromosome)

Question 24

What are homologous chromosomes?

Answer 24

Pair of matching chromosomes that make up each pair, are same size and have same genes, although could have different versions of those genes

Question 25

What type of chromosomes do gametes have?

Answer 25

Haploid (one copy of each chromosome)

Question 26

What is meiosis?

Answer 26

• cell division that produces gametes
• cells formed are genetically different because each cells end up with a combination of chromosomes

Question 26

What stage does meiosis begin with?

Answer 26

Interphase

Question 27

What happens during interphase in meiosis?

Answer 27

The cells DNA unravels and replicates to produce double-armed chromosomes (sister chromatids)

Question 28

What does meiosis involve?

Answer 28

2 divisions - M1 and M2

Question 29

What is meiosis 1?

Answer 29

• after interphase the cell enters m1
• m1 is the reduction division (it halves the chromosome number)

Question 30

What is differentiation?

Answer 30

Stem cells divide to become new cells, which then become specialised

Question 30

What is meiosis 2?

Answer 30

• the daughter cells produced undergo prophase 2, metaphase 2, anaphase 2, telophase 2 and cytokinesis
• these are the same stages in meiosis 1, except with half the number of chromosomes

Question 31

What is genetic variation?

Answer 31

• the difference that exists between individuals genetic material
• meiosis is important as it creates genetic variation
• during fertilisation, any egg can fuse with any sperm which also creates variation
• this means new individuals have a new mixture of alleles, making them genetically unique

Question 32

What are stem cells?

Answer 32

Unspecialised cells that can develop into different types of cell
- all multicellular organisms have some form of stem cells

Question 33

Where are stem cells found?

Answer 33

In bone marrow in human cells and in early embryos

Question 34

What is differentiation in animals?

Answer 34

Adult stem cells are used to replace damaged cells

Question 35

What are erythrocytes?

Answer 35

Red blood cells

Question 36

What are neutrophils?

Answer 36

White blood cells

Question 37

What is differentiation in plants?

Answer 37

• stem cells are used to make new roots and shoots
• can differentiate into various plant tissues
• stem cells are found in meristem

Question 38

How are stem cells used for heart disease?

Answer 38

Make replacement heart cells to repair damages heart tissue as body can’t replace them

Question 39

How are stem cells used for Alzheimer’s?

Answer 39

Nerve cells in brain die resulting in memory loss, sue stem cells to regrow healthy nerve cells in people with Alzheimer’s

Question 40

How are stem cells used for Parkinson’s?

Answer 40

Causes loss of nerve cells in brain, these release chemical called dopamine which controls movement. transplanted stem cells may help regenerate dopamine-producing cells

Question 41

What are specialised cells? (SC)

Answer 41

When cells differentiate they have a specific function, their structure is adapted to perform that function

Question 42

What are red blood cells? (SC)

Answer 42

• carry oxygen in blood
• biconcave disc shape, provides large SA for gas exchange
• no nucleus, more room for haemoglobin

Question 43

What are white blood cells? (SC)

Answer 43

• defend body against disease
• flexible shape, allows to engulf foreign pathogens
• many lysosomes in cytoplasm, contain digestive enzymes to break down engulfed particles

Question 44

What are epithelial cells? (SC)

Answer 44

• cover surface of organs
• cells are joined by interlinking membranes
• in airways to waft particles away
• small intestine have microvilli, folds in cell membrane that increase SA
• squamous epithelia in lungs are very thin to allow efficient diffusion of gases

Question 45

What are sperm cells? (SC)

Answer 45

• flagellum/tail, helps swim to egg cell
• many mitochondria, provide energy to swim
• acrosome, contains digestive enzymes to enable sperm to penetrate surface of egg

Question 46

What are palisade mesophyll cells? (SC)

Answer 46

• where photosynthesis occurs
• contain many chloroplasts to absorb sunlight
• thin walls so CO2 can diffuse easily into cell

Question 47

What are root hair cells? (SC)

Answer 47

• absorb water and mineral ions from soil
• large SA for absorption
• thin permeable cell wall, allows entry of water ions
• cytoplasm contains extra mitochondria, provide energy for active transport

Question 48

What are guard cells? (SC)

Answer 48

• found in pairs with gap between for stoma (tiny pore for gas exchange)
• in light, guard cells take up water and become turgid
• thin outer walls and thick inner walls force them to bend outwards, opening stomata, allowing gas exchange for photosynthesis

Question 49

What are tissues?

Answer 49

A group of cells that are specialised to work together o carry out a particular function
- can contain more than 1 cell type

Question 50

What is squamous epithelium tissue?

Answer 50

• Single layer of flat cells lining a surface
• found in alveoli of lungs and provides thin exchange surface for substances to a diffuse across quickly

Question 51

What is ciliated epithelium tissue?

Answer 51

• layer of cells covered in cilia
• found on surfaces where things need to be moved
  e.g. in trachea where cilia waft mucus along

Question 51

What is muscle tissue?

Answer 51

• made up of 2 bundles of elongate cells called muscle fibres
• 3 different types of muscle fibres : smooth, cardiac and skeletal

Question 52

What are the 3 types of muscle tissue?

Answer 52

Smooth - found lining inside of stomach
Cardiac - found in heart
Skeletal - use to move

Question 53

What is cartilage tissue?

Answer 53

• type of connective tissue found in joints
• shape and supports the ear, nose and windpipe
• formed when cells cells called chondroblasts secrete an extracellular matrix (jelly-like substance containing protein fibres) which they become trapped inside

Question 54

What is xylem tissue?

Answer 54

• plant tissue which transports water around the plant and supports the plant
• hollow xylem vessels which are dead and living parenchyma cells

Question 55

What is phloem tissue?

Answer 55

• transports sugar/sucrose around the plant
• arranged in tubes and is made up of sieve cells, companion cells and some ordinary plant cells
• each sieve cell has end walls with holes in them, so sap/sucrose can move easily through them, these end walls are called sieve plates

Question 56

What are organs?

Answer 56

• group of different tissues that work together to perform a particular function
• have elastic connective tissue and vascular tissue (in blood cells)
  e.g. lungs carry out gas exchange, contain squamous epithelium tissue in alveoli and ciliated epithelium in bronchi

Question 57

What are organs in plants?

Answer 57

leaf - carry out gas exchange and photosynthesis, contains palisade tissue as well as epidermal tissue (to prevent water loss from leaf) and xylem and phloem tissues in the veins

Question 58

What are organ systems?

Answer 58

Organs that work together to form organ systems, each has a particular function

Question 59

What are 2 types of organ systems and what do they do?

Answer 59

Respiratory system - made up of all organs, tissues and cells involved in gas exchange
Circulatory system- made up of organs involved in blood supply, heart, veins, arteries and capillaries