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Biology Year 1 > Topic 3 > Flashcards

Topic 3 Flashcards

1
Q

what is a nucleus?

A

a large organelle surrounded by a NUCLEAR ENVELOPE (double membrane), which contains many PORES.
the nucleus contains CHROMATIN (made from DNA and proteins) and a NUCLEOLUS.

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2
Q

what is the function of a nucleus?

A

controls the cell’s activities by controlling the transcription of DNA. the pores allow substances such as RNA to move between the nucleus and the cytoplasm.
the nucleolus makes ribosomes.
the DNA in the chromosomes contain the genes that control the synthesis of proteins.

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3
Q

describe a lysosome.

A

a round organelle surrounded by a membrane with no clear internal structure.

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4
Q

what is the function of a lysosome?

A

contains DIGESTIVE ENZYMES.
these are kept separate from the cytoplasm by the surrounding membrane, and can be used to digest invading cells or to break down worn out components of the cell.
the acrosome is a specialised lysosome.

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5
Q

describe a ribosome.

A

a very small organelle that either FLOATS FREE in the cytoplasm or is attached to the ROUGH ENDOPLASMIC RETICULUM.
it is made up of proteins and RNA.
it is not surrounded by a membrane.

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6
Q

what is the function of a ribosome?

A

the site of protein synthesis

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7
Q

describe the rough endoplasmic reticulum (RER).

A

a system of membranes enclosing a fluid-filled space. the surface is covered with ribosomes.

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8
Q

what is the function of the rough endoplasmic reticulum (RER)?

A

folds and processes proteins that have been made at the ribosomes.
proteins made at these ribosomes are transported through the ER to other parts of the cell in vesicles.

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9
Q

describe the smooth endoplasmic reticulum (SER).

A

a system of membranes enclosing a fluid-filled space.
similar to the RER but with no ribosomes.

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10
Q

what is the function of the smooth endoplasmic reticulum (SER)?

A

synthesises and processes lipids.

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11
Q

describe the golgi apparatus.

A

a group of fluid-filled, membrane-bound, FLATTENED SACS.
vesicles are often seen at the edges of the sacs.

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12
Q

what is the function of the golgi apparatus?

A

processes and packages new lipids and proteins in vesicles.
also makes lysosomes.

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13
Q

describe a mitochondrion.

A

oval-shaped.
have a double membrane - the inner one is folded to form CRISTAE.
inside is the MATRIX, which contains enzymes involved in respiration.

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14
Q

what is the function of mitochondria?

A

the site of aerobic respiration where ATP is produced.
they are found in large numbers in cells that are very active and require a lot of energy.

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15
Q

describe a centriole.

A

small, hollow cylinders, made of MICROTUBULES (tiny protein cylinders).
found in animal cells but only some plant cells.

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16
Q

what is the function of a centriole?

A

involved with the separation of chromosomes during cell division.
involved in the formation of a spindle during nuclear division.

17
Q

what are the signs that a cell is metabolically active?

A

lots of mitochondria
extensive RER
many golgi apparatus

18
Q

what are the steps of protein trafficking (the production of proteins and their route through the cell) ?

A

1) transcription of DNA to mRNA.
2) mRNA leaves the nucleus through the nuclear envelope.
3) protein made on ribosomes enter rough ER.
4) protein moves through the rough ER assuming three-dimensional shape en route (tertiary protein structure).
5) vesicles pinched of the rough ER contain the protein.
6) vesicles from the ER fuse to form the flattened sacs of the golgi apparatus.
7) proteins are modified within the golgi apparatus.
8) vesicles pinched of the golgi apparatus contain the modified protein.
9) vesicle fuses with cell surface membrane releasing protein.

18
Q

describe the role of the RER and golgi apparatus in the formation of extracellular enzymes.

A

extracellular enzymes such as digestive enzymes move to the cell surface membrane and are secreted.

19
Q

describe the cell wall in a prokaryotic cell.

A

the cell wall supports the cell and prevents it from changing shape.
it is made of MUREIN (a glycoprotein).

20
Q

describe the capsule in a prokaryotic cell.

A

a mucilaginous layer of slime.
helps to protect bacteria from attack by cells of the immune system.

21
Q

describe the plasmid in a prokaryotic cell.

A

small loops of DNA that are not part of the main circular DNA molecule.
contain genes for things like antibiotic resistance and can be passed between prokaryotes.
plasmids are not always present.

22
Q

describe the flagellum in a prokaryotic cell.

A

a long hair-like structure that rotates to make the prokaryotic cell move.
not all prokaryotes have a flagellum and some have more than one.

23
Q

describe the pili in a prokaryotic cell.

A

short hair-like structures.
help prokaryotes stick to other cells and can be used in the transfer of genetic material between cells.

24
Q

describe ribosomes in a prokaryotic cell.

A

smaller than in eukaryotic cells.

25
Q

describe mesosomes in a prokaryotic cell.

A

inward folds in the plasma membrane.
still debate over what their function is.
some believe that they play a role in various cellular processes such as respiration but some think they are not natural and are just artefacts produced when the cells are being prepared for viewing with an electron microscope.

26
Q

describe the cytoplasm in a prokaryotic cell.

A

has no membrane-bound organelles unlike an eukaryotic cell.

27
Q

describe circular DNA in a prokaryotic cell.

A

prokaryotic cells do not have a nucleus.
the DNA floats free in the cytoplasm.
it is present as one long coiled-up strand.
it is not attached to any histone proteins.

28
Q

describe a light microscope.

A

use light to form an image.
have a maximum resolution of 0.2 micrometres (um) (therefore cannot use a light microscope to view organelles smaller than 0.2 um).
the maximum useful magnification of a light microscope is x1500.

29
Q

describe an electron microscope.

A

use electrons to form an image.
have a maximum resolution of 0.0002 micrometres (um).
the maximum useful magnification is x1500000

30
Q

how many micrometres (um) are in a millimetre (mm)?

A

1 um = 0.001 mm
to convert from um to mm, divide by 1000.

31
Q

describe transmission electron microscopes (TEMS).

A

uses electromagnets to focus a beam of electrons, which is then transmitted through the specimen.
denser parts of the specimen absorb more electrons, which make them look darker on the image.
have high resolution images so can see the internal structure of organelles.
can only be used on thin specimens.

32
Q

describe scanning electron microscopes (SEMs).

A

scan a beam of electrons across a specimen which knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image.
the images show the surface of the specimen and can be in 3D.
can be used on thick specimens.
giver lower resolution images than TEMs.

33
Q

how many eyepiece graticule divisions equals a stage micrometre division?

A

4.5 eyepiece divisions = 1 stage division
1 division of a stage micrometre = 0.1 mm
1 division on an eyepiece = 0.022 mm

34
Q

what is the definition of fertilisation?

A

when the nuclei of the male and female gametes fuse creating a diploid zygote.

35
Q

how are egg cells specialised for their function?

A

nucleus contains haploid set of chromosomes.
follicle cells secrete chemicals that activate release of enzymes from sperm.
the cytoplasm is very large so that egg can divide immediately.
lipid droplets are of energy for growth and division.
ZONA PELLUCIDA is a glycoprotein layer which hardens once the sperm nucleus has penetrated the ovum which stops entry of other sperms into the ovum, avoiding polyspermy.
lysosomes release chemicals that cause zona pellucida to harden.

36
Q

how are sperm cells specialised for their function?

A

nucleus contains haploid set of chromosomes.
neck contains lots of mitochondria which releases energy in the form of ATP to propel the sperm forwards.
flagellum made from proteins and microtubules which uses ATP to propel the sperm forwards.
ACROSOME contains digestive enzymes to hydrolyse the egg cell’s zona pellucida allowing the cell membranes of the sperm and ovum to fuse.

37
Q

how does fertilisation occur (including the acrosome reaction, the cortical reaction and the fusion of nuclei)?

A

Biology Year 1 (4 decks)

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