Snab Biology Topic 3 - The Voice Of The Genome

Front 1

What does a eukaryotic cell contain?

Back 1

Eukaryotic cells contain:
-A nucleus containing genetic material that is surrounded by a double membrane or envelope.
-Organelles (structures) in the cytoplasm, each surrounded by one of two membranes.

Front 2

What is ultrastructure?

Back 2

Ultrastructure is the name for the fine structure that is revealed when using a powerful microscope such as an electron microscope.

Front 3

What is the nucleus?

Back 3

-The nucleus contains all of the genetic material for the cell and controls the cell.
-It is surrounded by a double membrane/envelope.
-There are pores in the nuclear envelope for mRNA to leave the nucleus in protein synthesis.
-Dark staining area, called nucleolus, within the nuclear envelope can be seen on an electron micrograph.

Front 4

What is the rough endoplasmic reticulum?

Back 4

-A series of single, flattened sacs enclosed by a membrane.
-Ribosomes on the surface.
-Involved in the making and moving of proteins through the cell.

Front 5

What are centrioles?

Back 5

-Two hollow cylinders arranged at right angles to each other.
-Near the nucleus.
-Involved in the development of spindle fibres in cell division.

Front 6

What is the smooth endoplasmic reticulum?

Back 6

-A series of single, tubular, sacs made of membrane.

Front 7

What is the lysosome?

Back 7

-Enclosed by a single membrane.
-Containing digestive enzymes.

Front 8

What is a mitochondria?

Back 8

-Used for respiration.
-Surrounded by a double membrane (envelope).
-Inner membrane folded into finger-like projections called cristae (singular, crista).
-Central area contains a jelly called the matrix.
-Floating in the matrix are ribosomes and DNA (as a loop).

Front 9

What is the Golgi apparatus?

Back 9

-Involved in the making and moving of proteins through the cell.
-Enclosed by a single membrane.
-Containing digestive enzymes.

Front 10

What is a ribosome?

Back 10

-A minute particle consisting of RNA and associated proteins.
-Found in large numbers in the cytoplasm of living cells.
-They bind messenger RNA and transfer RNA to synthesize polypeptides and proteins.

Front 11

How are proteins transported within eukaryotic cells?

Back 11

1. Amino acids are made into proteins on the ribosomes.
2. Newly made protein stored in rough endoplasmic reticulum cavity.
3. Protein is packed at the end of the rER. Membrane closes forming a vesicle.
4. Vesicles pinched off the rER, transport protein towards the Golgi apparatus.
5. Protein being modified in Golgi apparatus.
-The proteins leave the cell by exocytosis, when the vesicles fuse with the cell surface membrane.

Front 12

What modified proteins are exported out of the cell?

Back 12

Extracellular enzymes e.g. amylase and protease.

Front 13

What is a eukaryotic cell?

Back 13

-Plant and animal cells are eukaryotic.
-DNA is found as separate strands and slime capsules are never present.
-Plant cells have a cell wall, Animal cells sometimes have complex flagella.
-Animal cells are medium and plant cells are large.

Front 14

What is a prokaryotic cells?

Back 14

-Bacteria cells.
-DNA is found as a loop and slime capsules are sometimes present.
-The flagella rotates for movement.
-The cell is relatively small.

Front 15

What does a prokaryotic cell contain?

Back 15

-Glycogen granules, lipid droplets.
- Cell surface membrane.
-Small ribosomes.
-Cell wall.
-Plasmids (not present in all bacteria).
-Loop of DNA.
-Photosynthetic membranes (not present in all bacteria).
-Flagellum.

Front 16

How many levels of organisation are there in eukaryotic cells?

Back 16

4

Front 17

What are the 4 levels of organisation in eukaryotic cells?

Back 17

Cells, Tissues, Organs, Systems

Front 18

Cells?

Back 18

- All cells of multicellular organisms are eukaryotic. Palisade cells and liver cells are examples.

Front 19

Tissues?

Back 19

- Consist of one or a few different types of cell that work together to perform a function. Epidermal tissue and muscle tissue are examples.

Front 20

Organs?

Back 20

- Are made up of various tissues grouped to work together and perform their function efficiently. Leaf and heart are examples.

Front 21

Systems?

Back 21

- Systems comprise various organs that work together to perform a large-scale function. Many people believe there are no systems in plants. The digestive system in humans is an example.

Front 22

How can a leaf be considered an organ?

Back 22

-An organ is made up of several tissues.
-Palisade tissue and epidermal tissue and spongy tissue--> Three visible tissue, hence is an organ.

Front 23

How do you calculate true size?

Back 23

true size= image size/magnification

-Make sure all dimension are in the same units before calculating.

Front 24

What is mitosis?

Back 24

- A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.

Front 25

What is the cell cycle?

Back 25

The cell cycle is the sequence of events from the formation of that cell until it divides to form daughter cells and includes three stages called interphase, mitosis, and cytokinesis.

Front 26

What does the cell cycle and mitosis allow?

Back 26

Asexual reproduction

Front 27

What happens during interphase?

Back 27

-Newly formed cell grows.
-Cell undertakes its normal function.
-Cell prepares for divide by: replicating its chromosomes, Chromosomes start to condense, some organelles increase in number.

Front 28

What happens during mitosis?

Back 28

Four phases are recognised, called:
-Prophase
-Metaphase
-Anaphase
-Telophase

Front 29

What happens during cytokinesis?

Back 29

-Organelles become equally arranged at opposite sides of cell.
-Cytoplasm divides.
-Cell divides to form two daughter cells.

Front 30

What happens in prophase?

Back 30

- Chromosomes continue to condense (and become visible).
-Nuclear envelope breaks down.
-Nucleolus disappears.
-Spindle forms.
-Centrioles move to opposite poles of the cell. (Only in animal cells).

Front 31

What happens in metaphase?

Back 31

- Chromosomes (as paired chromatids) line up at the cell equator (middle).
- Chromosomes attach to spindle fibres.
-Fibres attach at the centromere.

Front 32

What happens in anaphase?

Back 32

-Spindle fibres contract.
-Fibres pull chromatids apart with the centromere leading.

Front 33

What happens in telophase?

Back 33

- Chromosomes decondense (and become invisible).
- Nuclear envelope reforms.
- Nucleolus reappears.

Front 34

What is meiosis?

Back 34

Meiosis is a form of nuclear division whose functions are:
-Production of gametes; each gamete has half the number of chromosomes found on a body cell.
-Allows genetic variation to occur.

Front 35

How is genetic variation achieved?

Back 35

1. Crossing over.
2. Independent assortment.

Front 36

What is crossing over?

Back 36

-During meiosis, each homologous pair of chromosomes can line up as shown.
-All four components/chromatids are now different from each other as two have swapped some alleles/genetic information.

Front 37

What is independent assortment?

Back 37

-During the first division of meiosis, each homologous pair of chromosomes can line up as shown.
-Since each of the 23 pairs of homologous chromosomes in humans can line up either way round, it is highly likely that daughter cells will end up with different chromosome combinations when homologous chromosomes separate.

Front 38

How is the sperm specialised for its function?

Back 38

-Haploid nucleus- for full complement restored at fertilisation.
-Flagellum for movement- whips back and forth to move sperm along towards ovum.
-mid region with mitochondria- To provide useable energy to drive the flagellum.
-Acrosome- contains digestive enzymes to enable sperm to penetrate zona pellucida (jelly layer).

Front 39

How is the egg specialised for its function?

Back 39

-Haploid nucleus.
-Cytoplasm full of energy rich material.
-Follicle cells.
-Special vesicles (cortical granules)- these contain a substance that helps stop more than one sperm fertilising the egg.
-Zona pellucida (jelly layer)- to stop more than one sperm fertilising the egg.

Front 40

What is fertilisation?

Back 40

The fusion of gametes.

Front 41

What are mammalian gametes?

Back 41

Sperm and ovum.

Front 42

What are the gametes in flowering plants?

Back 42

Pollen and egg.

Front 43

Why is fertilisation important in sexual reproduction?

Back 43

-It restores the full complement (diploid number) of chromosomes, 46 in humans.
-It allows genetic variation.

Front 44

What is the sequence of events that take place for fertilisation in mammals?

Back 44

1. Acrosome reaction.
2. Membranes fuse.
3. Egg cell response (cortical reaction).
4. Meiosis restarted.
5. Fertilisation.

Front 45

What happens in the acrosome reaction?

Back 45

Acrosomes releases digestive enzymes when sperm head meets the zona pellucida of egg.
Enzymes digest a channel in zona pellucida for sperm to burrow through to the cell surface membrane of egg cell.

Front 46

What happens when the membranes fuse?

Back 46

Cell surface membrane of sperm and egg fuse enabling haploid nucleus from sperm to enter cytoplasm of egg cell.

Front 47

How does the egg cell respond?

Back 47

Special vesicles (cortical granules) move towards and fuse with the cell surface membrane. They release their contents (through exocytosis), which cause changes in surface layers of egg that stop other sperm from entering the egg cell.

Front 48

What happens when meiosis is restarted?

Back 48

The presence of the sperm nucleus in the cytoplasm of the egg cell causes the second division of meiosis to occur.

Front 49

What happens during fertilisation?

Back 49

The chromosomes from the haploid sperm nucleus and from the haploid egg nucleus combine to restore the full complement of chromosomes, the diploid number.

Front 50

How does fertilisation occur in flowering plants?

Back 50

1. Pollen lands on stigma (of carpel). Pollen tube begins to grow towards embryo sac.
2. Pollen tube grows down style. It secretes enzymes and digests style tissue and uses the products to continue tube growth. Two haploid nuclei are near the tube tip. One controls tube growth (pollen tube nucleus), the other is called the generative nucleus.
3.Pollen tube reaches embryo sac (inside ovule). Fuses and pollen tube nucleus breaks down. Generative nucleus divides to produce two male gametes.

Front 51

Where does double fertilisation occur in plants?

Back 51

-One male gamete fusing with an egg cell to form a diploid zygote.
-One male gamete fusing with two polar nuclei to form a triploid primary endosperm nucleus that develops into the seeds storage tissue, endosperm.

Front 52

What are stem cells?

Back 52

1. Undifferentiated (unspecialised) cells.
2. Which can keep dividing.
3. And that give rise to other cell types.

Front 53

What is a totipotent stem cell? (from early embryos)

Back 53

A totipotent stem cell can give rise to all cell types including embryonic cells.

Front 54

What is a pluripotent stem cell? (from older embryos)

Back 54

A pluripotent stem cell can give rise to most cell types but not embryonic cells.

Front 55

How can you demonstrate totipotency?

Back 55

-Take a few cells of one type, called explants.
-Place on agar which has certain growth regulators (growth hormones) added.
-Cells divide by mitosis to form a cluster of cells.
-Divide cluster and then place in containers with agar.
-Add different growth regulators to above to the agar which stimulate plant cells to differentiate into roots, stem and leaves, etc.

Front 56

How do undifferentiated cells become differentiated cells?

Back 56

When they develop a particular structure due to differential gene expression.

Front 57

How do cells become specialised?

Back 57

-Correct stimulus is given to the unspecialised cells, e.g a chemical stimulus.
-Some genes are switched on and become active; other genes are switched off.
-Messenger RNA (mRNA) is made from the active gene only.
-The mRNA moves to the ribosomes; the ribosomes read the mRNA and the appropriate protein is made.
-The protein can permanently alter the structure and function of the cells.

Front 58

What are two examples of differentiated blood cells derived from bone marrow stem cells?

Back 58

-Erythrocytes (red blood cells)
-Leucocytes (white blood cells)

Front 59

What are some sources of stem cells?

Back 59

-Early embryos.
-Older embryos.
-Differentiated cells.

Front 60

How can early embryos be used as stem cells?

Back 60

Cells show totipotency- can make any type of cell.

Front 61

How can older embryos be used as stem cells?

Back 61

Inner clusters of cells show pluripotency- can make most types of cell.

Front 62

How can differentiated cells be used as stem cells?

Back 62

Some are multipotent stem cells (e.g. in bone marrow, possibly all tissue) but most can only make cells of one or a few types.

Front 63

Embryonic stem cells advantages and disadvantages?

Back 63

Advantage:
-Easy to extract and grow.

Disadvantage:
-Ethical issues.
-Possible rejection by patients body.
-Risk of infection when cells received.
-Risk of stem cells becoming cancerous in body.