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biology aqa a-level > Cells > Flashcards

Cells Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What organelles does an animal cell have?

A

cell surface membrane (plasma membrane), cytoplasm,nucleus,nucleolus, nuclear envelope,ribosome,rough & endoplasmic reticulum,golgi apparatus and vesicles, mitochondrion, lysosomes.

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2
Q

What organelles does a plant cell have?

A

cell surface membrane (plasma membrane), cytoplasm,nucleus,nucleolus, nuclear envelope,ribosome,rough & endoplasmic reticulum,golgi apparatus and vesicles, mitochondrion, cellulose cell wall, chloroplast and vacuole, plasmodesmata.

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3
Q

What organelles does an algal cell have?

A

cell surface membrane (plasma membrane), cytoplasm,nucleus,nucleolus, nuclear envelope,ribosome,rough & endoplasmic reticulum,golgi apparatus and vesicles, mitochondrion, cellulose cell wall, chloroplast and vacuole. The chloroplast in an algal cell can be different size and shape to those in a plant cell, some may even have just one big chloroplast.

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4
Q

What organelles does a fungal cell have?

A

cell surface membrane (plasma membrane), cytoplasm,nucleus,nucleolus, nuclear envelope,ribosome,rough & endoplasmic reticulum,golgi apparatus and vesicles, mitochondrion, chitin cell wall, NO CHLOROPLAST does not photosythesise!!

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5
Q

Nucleus

A

Large organelle, surrounded by nuclear envelope. Controls the activity of the cell and contains chromosomes (which consist of protein bound linear DNA) . Contains 1 or more nucleolus.

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6
Q

Mitochondrion

A

Usually oval shaped, have a double membrane of which the inner folds to form cristae, inside is the matrix which contains enzymes for respiration. Is the site of aerobic respiration which produces ATP, a common energy source in cells. Found in large number in cells that require a lot of energy/ are very active.

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7
Q

Chloroplast

A

Small and flattened organelles, found in plant and algal cells. Have a double membrane as well as membrane inside call thylakoid membranes which stack up to form grana which are linked by lamellae. Where photosythesis takes place.

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8
Q

Golgi apparatus

A

Fluid filled membrane bound flattened sacs, Golgi vesicles often found at edges of the sacs. Processes and packages new lipids and proteins and also makes lysosomes.

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9
Q

Golgi vesicle

A

Small fluid filled sacs in the cytoplasm surrounded by the membrane produced by Golgi apparatus. Stores lipid and proteins and transports them out the cell.

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10
Q

Lysosome

A

small surrounded by membrane, with no clear internal structure. Contains hydrolytic enzymes, separated from the cytoplasm by the membrane. This means they can ingest invading cell/chemicals and break down worn out cell components.

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11
Q

Ribosomes

A

very small, free in cytoplasm or attached to Rough Endoplasmic Reticulum (RER). Made up of proteins and RNA. Site of protein synthesis.

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12
Q

Rough Endoplasmic reticulum

A

system of membranes enclosing fluid-filled space. Surface covered in ribosomes. Folds and processes Proteins that have been made in the ribosomes.

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13
Q

Smooth Endoplasmic reticulum

A

Similar to rough endoplasmic reticulum (system of membranes enclosing fluid filled space), but no ribosomes on the surface. Synthesises and processes lipids.

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14
Q

cell wall

A

Rigid, surrounds cell in plants, algae and fungi. Made of cellulose in algae and Plants but of chitin in fungi. Supports cells and prevents them from changing shape.

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15
Q

cell vacuole

A

membrane bound organelle in cytoplasm, contains sell sap (weak solution of sugar and salts). The membrane of the vacuole is called the tonoplast. Maintains pressure within the cell and stops plant from wilting. Involved in the isolation of unwanted chemicals in the cell.

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16
Q

In complex multicellular organisms, eukaryotic cells become specialised for specific______________.

A

In complex multicellular organisms, eukaryotic cells become specialised for specific FUNCTIONS.

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17
Q

Specialised cells are organised into ________, __________ into ________ and ________ into _________ systems.

A

specialised cells are organised into TISSUES, TISSUES into ORGANS and ORGANS into ORGAN systems.

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18
Q

How do prokaryotic cells differ from eukaryotic?

A

They are smaller, don’t have membrane bound organelles in the cytoplasm,no nucleus instead a single circular DNA loop that is free in the cytoplasm not associated with any proteins (histones), a cell wall containing murein (glycoprotein),smaller ribosomes 70s instead of 80s,no chloroplasts, some have one or more plasmids, a capsule and one or more flagella.

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19
Q

function of a capsule in a bacteria cell

A

protect bacterium from other cells helps group bacteria together to stick together for further protection.

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20
Q

functions of plasmids in bacterial cells

A

can be exchanged between bacteria, processes genes that aid survival of bacteria in adverse conditions e.g produce enzymes that produce antibiotics.

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21
Q

Viruses are _______ and non-living particles.

A

Viruses are ACELLULAR and non-living.

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22
Q

Viruses are _______ than bacteria.
And have no cytoplasm, ribosomes or surface ________.

A

viruses are smaller than bacteria (20-300nm).And have no cytoplasm, ribosomes or surface membrane .

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23
Q

Viruses can only _______ in living host cells.

A

viruses can only multiply in living host cells.

24
Q

Describe the structure of a virus

A

Unlike prokaryotic cells viruses don’t have a surface membrane,cytoplasm or ribosomes. They have a nucliec acid core (gentic material) which can be RNA or DNA, which is surrounded by a protein coat called a capsid. Some cell have and outer layer called an ‘envelope’ made from the membrane-phosolipids from the cell they were made in. On the surface there are attachment proteins which allow them to identify and attach to host cells.

25
Q

viral replication

A

1) viruses use their attachment proteins to attach to host cells receptor proteins.
2) viruses genetic material is released into the host cell.
3)genetic material and proteins are replicated by host cells ‘machinery’.
4)viral components assemble.
5) replicated viruses are released from host cells

Different viruses enter and leave host cells in different ways and are replicated by host cells in different ways e.g HIV releases capsid and genetic material into host cell.

26
Q

Formula for magnification

A

magnification = image size/actual size

27
Q

magnification

A

ratio of image to actual size; apparent enlargement of an object

28
Q

resolution

A

how well a microscope can distinguish between two points that are close together.

29
Q

Optical mircroscope

A

.uses a beam of light to radiate specimen
.glass lenses to magnify object
.max magnification x1500
.max resolution 2um
.so can’t see lysosomse or ribosomes or ER.
.may be able to see mitochondria but no detail
.can see nucleus
.can look at dead or living organisms
.specimens can be stained o show different features
.specimens have to be finely cut so light can pass through.

30
Q

what are microscope artefacts?

A

Artefacts are visible details that aren’t part of the specimen being observed, and are seen due to the microscope e.g dust, air bubbles, fingerprints.
common in electron micrographs because specimens need a lot of preparation before viewing.

31
Q

Transmission electron microscope (TEMs)

A

-use electromagnets to focus beam of electrons through specimen
-denser parts of specimen absorb more electrons so appear darker in the image.
-Have high resolution, can see the internal structure of organelles e.g chloroplast
-can’t look at living organisms as specimens have to be out in a vacuum.
-can only be used on thin specimens

32
Q

Scanning electron microscope

A

-scan a beam of electrons across a specimen, knocks of electrons from specimen which then gather in the cathode ray tube to form an image.
-image you end up with show surface of specimen, end up with 3D image.
-good because can be used on thick specimens
-cant be used on living organisms
-has a lower resolution than scanning electron microscope

33
Q

compare the magnification and resolution of electron and optical microscopes

A

optical max magnification approx. x1500
electron max magnification approx 1,500,000
optical max resolution approx. 0.2um
electron max resolution approx. 0.0002um

34
Q

Students should be able to appreciate that there was a considerable period of time during which the scientific community distinguished between artefacts and cell organelles. How did they do this?

A

They could only distinguish between artefacts and organelles by repeatedly preparing slides in different ways. if an object could be seen in one preparation but not another it was more likely to be an artefact.

35
Q

what processes are used to separate cell components?

A

cell fractionation and ultracentrifugation

36
Q

what 3 steps are involved in cell fractionation?

A

1.homogenisation
2.filtration
3.ultracentrifugation

37
Q

describe what is involved in homogenisation?

A

Breaks up the cells.
can be done by vibrating cells or grinding them up in a blender.
Breaks up the plasma membrane and releases organelles into solution.

38
Q

In what conditions must the homogenised solution be kept and why?

A

Ice cold- to reduce activity of enzymes that break down organelles.
should be isotonic- the concentration of chemicals in the solution should be the same as the concentration of the cells being broken down to prevent damage to cells through osmosis.
Buffer solution should be added to maintain the pH- to prevent proteins denaturing.

39
Q

describe what is involved in the step of filtration during cell fractionation

A

Homogenised solution is passed through a gauze to separate any large debris or tissue debris from the organelles.Organelles are much smaller than debris so can pass through the gauze.

39
Q

what is involved in cell ultracentrifugation?

A

-separating organelles from filtered solution
-cell fragments put into a tube which is put into a centrifuge and span at a low speed. the heaviest organelles i.e nuclei flung to the bottom forming a thick sediment called the pellet.
-the rest of the organelles remain suspended in the fluid above the sediment called the supernatant.
-supernatant is drained off and put into a different tube and spun at a higher speed, again the heaviest organelles are flung to the bottom
-the process is repeated higher and higher speeds until all organelles are separated out .

40
Q

what does a centrifuge do?

A

separates by spinning

41
Q

why would you use cell fractionation?

A

if you wanted to look at a specific cell organelle under an electron microscope, you would separate it from the rest of the cell first.

42
Q

In what order are cell organelles separated in ultracentrifugation

A

nuclei, chloroplast (in plants etc),mitochondria,lysosomes, endoplasmic reticulum, ribosomes
separated in order of mass heaviest to lightest.

43
Q

Within multicellular organisms, not all cells retain the ability to _________.

A

Within multicellular organisms, not all cells retain the ability to divide.

44
Q

What are the stages of the cell cycle?

A

Interphase-G1, S and G2
mitosis-prophase,metaphase,anaphase and telophase

45
Q

what is cytokinesis?

A

division of the cytoplasm

46
Q

what is interphase?

A

period of cell growth and DNA replication

47
Q

what happens in each stage of interphase?

A

G1-cell carries out normal metabolic functions but also prepares for DNA replication
S- synthesis phase, when DNA replication occurs
G2-Organelles replicate, ATP content increases

48
Q

what are the stages of mitosis?

A

prophase, metaphase anaphase,telophase

49
Q

what happens in prophase?

A

-Chromatids become visible
-centrioles move to opposite poles and spindle fibres form
-nuclear envelope disintegrates
-nucleolus disappears

50
Q

what happens in metaphase?

A

chromatids line up along the equator and spindle fibres attach to their centromere

51
Q

what happens in anaphase?

A

-centromere divides separating sister chromatids.
-spindles contract pulling chromatids to opposite poles centromere first.
-makes chromatids appear v shaped

52
Q

what happens in telophase?

A

-division of the cytoplasm (cytokinesis)
-chromosomes reach opposite poles and become indistinct.
-nucleolus reforms
- nuclear envelope reforms forming 2 nuclei
-spindle fibres disintergrate
-there are now 2 genetically identical daughter cells.

53
Q

As mitosis begins chromosomes are made up of two strands joined in the middle by a ___________.

A

As mitosis begins chromosomes are made up of two strands joined in the middle by a centromere.

54
Q

why are there two sister chromatids at the start of mitosis?

A

An identical copy of the chromosome is made during interphase.

55
Q

what is a chromatid?

A

one of the strands that makes up the chromosome during mitosis.

56
Q

Why are spindle fibres necessary?

A

to equally divide the sister chromotids.

biology aqa a-level (5 decks)

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