Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Level Biology OCR > 2.1 > Flashcards

2.1 Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Define Magnification

A

How much bigger an image appears compared with the original object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define resolution

A

The ability to distinguish between two objects clearly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What do laser scanning microscopes do?

A
  • they use laser light to scan an object point by point and assemble the pixel image and display it on screen
  • the images are high resolution and show high contrast
  • have depth selectivity and can focus on structures at different depths with a specimen - therefore they can be used to clearly observe the whole living specimen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

TEM

A
  • specimen has to be chemically fixed by being dehydrated and stained
  • the beam of electrons passes through the speciemen
  • the electrons form a 2D black and white image - this is called an electron micrograph
  • has to be placed inside a vacuum
  • needs to be coated with a fine film of metal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

SEM

A
  • electrons cause secondary electrons to bounce off of the specimen’s surface and can be focussed on a screen
  • gives a 3D image
  • black and white
  • has to be placed in a vacuum
  • has to be coated with a fine film of metal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Both types of microscope:

A
  • are large and expensive
  • need a great deal of skill to use
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does staining a cell enable components to become visible

A

Stain = contrast
Images seen in higher detail
Distinguish/see whatever you are looking for

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why are the optical microscope’s resolution limited?

A

they use visible light to produce images, therefore the microscope can’t produce an image that is smaller than the wavelength of visible light (400-700nm)

Therefore objects smaller than 200nm will appear as one object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Steps for using a light microscope:

A
  1. The specimen on a slide is placed on the stage and clipped into place
  2. Use the lowest power objective lens
  3. Adjust the coarse focus knob while looking into the eyepiece until the image is clear and in focus
  4. Adjust the iris diaphragm for optimum light
  5. Now use the 10x objective lens, then use the fine focus knob to focus the image
  6. Repeat step 5 using the x40 objective lens
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a photomicrograph?

A

A photograph of the image seen using an optical microscope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why is the resolution of an electron microscope much greater than optical microscope?

A

They use a beam of fast travelling electrons with a wavelength of about 0.004nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How do electron microscopes work?

A

The electrons are fired from a cathode and focused by magnets (rather than glass lenses) on a screen or photographic plate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Both types of electron microscope are:

A
  • large and expensive
  • need a lot of skill to use
  • specimen ave to be dead
  • have to be viewed in a vacuum
  • metallic salt stains used may be hazardous to the user
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is an organelle?

A

Membrane bound compartment within the cell each providing distinct environments and therefore conditions for different cell reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why are most organelles in eukaryotes membrane bound?

A

This keeps the organelle separate from the rest of the cell, so that it is a discrete compartment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Rough endoplasmic reticulum (RER) structure

A
  • System of membranes, containing fluid filled cavities and are continuous with the nuclear membrane
  • coated with ribosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does iodine stain?

A

Stains cellulose in plant walls yellow
Chlorophyll - orange to blue black

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does methylene blue stain?

A

All purpose stain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does eosin stain/

A

Cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What does acetic orcein in do?

A

Binds to DNA and stains chromosomes dark red

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does Sudan red stain

A

Lipids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How to prepare specimen:

A
  • dehydrate
  • embedding them in a wax to prevent distortion during slicing
  • using a special instrument to make very thin slices called sections - these are stained and mounted in a special chemical to preserve them
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Function of the Rough endoplasmic reticulum

A
  • intracellular transport system, cisternae form channels for transporting substances from one area of a cell to another
  • provides a large surface area for ribosomes which assemble amino acids into proteins.
  • proteins pass through the membrane into the cisternae and are transported to the Golgi apparatus for modification and packaging
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Smooth endoplasmic reticulum (SER) structure

A
  • system of membranes containing fluid filled cavities (cisternae) that are continuous with the nuclear membrane
  • no ribosomes on its surface
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are cisternae?

A

Fluid filled cavities

26
Q

Function of the Smooth endoplasmic reticulum

A

Contains enzymes that catalyse reactions involved with lipid metabolism, such as:
- synthesis of cholesterol
- synthesis of lipids/phospholipids needed by the cell
- synthesis of steroid hormones

It is involved with absorption, synthesis and transport of lipids

27
Q

What is a vesicle?

A

A small fluid filled sac in the cytoplasm surrounded by a membrane, transports substances in and out of the cell, via the cell surface membrane and between organelles

28
Q

Golgi apparatus structure

A

Consists of a stack of membrane bound flatten sacs
Secretory vesicles bring materials to and from the Golgi apparatus

29
Q

Function of the Golgi apparatus

A

Proteins are modified for example by:
- adding sugar molecules to make glycoproteins
- adding lipid molecules to make lipoproteins
- being folded into their 3D shape

The proteins are packaged into vesicles that are pinched off and then:
- stored in the cell or
- moved to the plasma membrane, either to be incorporated into the plasma membrane or exported outside the cell

30
Q

Mitochondria structure

A
  • spherical, rod shaped or branched (2-5 um long)
  • surrounded by two membranes with a fluid filled space between them. The inner membrane is highly folded - cristae
  • the inner part o the mitochondrion is a fluid filled matrix
31
Q

Function of the mitochondria

A
  • the site of ATP production during aerobic respiration
  • self replicating, so more can be made if the cell’s energy needs increase
  • are abundant in cells where much metabolic activity takes place eg in liver cells and synapses
32
Q

Chloroplasts structure

A

Large organelles, 4-10um long
Surrounded by a double membrane or envelope. The inner membrane is continuous with stacks of flattened membrane sacs called thylakoids which contain chlorophyll. Each stack or pile of thylakoids is called a granum. The fluid filled matrix is called the stroma
Chloroplasts contain loops of DNA and starch grains

33
Q

Function of the chloroplasts

A
  • the site of photosynthesise
  • the first stage of photosynthesis (where light energy is trapped by chlorophyll and used to make ATP) occurs in the grana. Water is also split by H+ ions
  • the second stage (where hydrogen reduced carbon dioxide using energy from ATP to make carbohydrates) occurs in the stoma
    Chloroplasts are abundant in leaf cells, particularly in the palisade mesothelioma layer
34
Q

Vacuole structure

A

The vacuole is surrounded by a membrane called the tonoplast and contains fluid

35
Q

Vacuole function

A
  • Only plant cells have a large permanent vacuole
  • it is filled with water and solutes and maintains cell stability because when full it pushes against the cell wall, making the cell turgid
  • if call the plant cells are turgid then this helps to support the plant, especially in non woody plants
36
Q

Lysosomes structure

A

Small bags formed from the Golgi apparatus. Each is surrounded by a single membrane
- they contain powerful hydrolytic (digestive) enzymes
- they are abundant in phagocytise cells such as neutrophils and macrophages (types of white blood cell)that can ingest and digest invading pathogens such as bacteria

37
Q

Function of lysosomes

A
  • keep the powerful hydrolytic enzymes separate from the rest of the cell
  • lysosomes can engulf old cell organelles and foreign matter, digest them and return the digested components to the cell for reuse
38
Q

Cilia and undulipodia structure

A
  • stick out from the cell and are surrounded by the cell surface membrane
  • each contain microtubules
  • formed from centrioles
39
Q

Function of cilia and undulipodia

A
  • the epithelial cells lining your airways each have many hundreds of cilia that beat and move the band of mucus
  • nearly all cell types in the body have one cilium that acts as an antenna. It contains receptors and allows the cell to detect signals about its immediate environment
40
Q

Which organelles don’t have membranes:

A

Ribosomes
Centrioles
Cytoskeleton
Cell Wall

41
Q

Ribosomes structure

A
  • small spherical organelles about 20nm in diameter
  • made of ribosomal RNA
  • made in the nucleolus as 2 separate subunits which pass through the nuclear envelope into the cell cytoplasm and then combine
  • some remain free in the cytoplasm and some attach to the endoplasmic reticulum
42
Q

Ribosomes function

A
  • Ribosomes bound to the exterior or RER are mainly for synthesising proteins that will be exported outside the cell
  • ribosomes that are free in the cytoplasm, either singly or in clusters, are primarily the site of assembly of proteins that will be used in the cell
43
Q

Centrioles structure

A

The centrioles consist of two bundles of microtubules at right angles to each other. The microtubules are made of Tubulidentata protein subunits and are arranged to form a cylinder

9x3 arrangement

44
Q

Centrioles function

A
  • before a cell divides, the spindle, made of threads of tubular forms from the centrioles
  • chromosomes attach to the middle part of the spindle and other proteins walk along the Tubulidentata threads, pulling the chromosomes to opposite ends of the cell

Centrioles are nvolved in the formation of cilia and undulipodia
- before the cilia form, the centrioles multiply and line up beneath the cell surface membrane
- microtubules then sprout outwards from each centriole, forming a cilium or undulopodium

45
Q

What happens in the nucleolus

A

Ribosomes are made

46
Q

What is the significance of chromosomes?

A

They contain the organism’s genes

47
Q

Function of the nuclear envelope

A

Double membrane

Separates the contents of the nucleus from the rest of the cell

48
Q

What do the pores in the nuclear envelope do?

A

They enable larger substances (eg mRNA) to leave the nucleus
Also allow substances to enter the nucleus eg from the cytoplasm

49
Q

What is chromatin?

A

Genetic material consisting of DNA wound around histone proteins

50
Q

Cell wall function

A
  • contributes to the strength and support of the plant
  • maintains cell shape
  • permeable and allows solutions to pass through
51
Q

.

A

.

52
Q

On a photomicrograh, why may 1 section be split up?

A

With electron microscopes sections must be cut out

53
Q

9 steps for making and secreting a protein

A
  1. mRNA copy of the gene (instructions) for protein is made in the nucleus
  2. mRNA leaves the nucleus through pores
  3. mRNA attaches to a ribosome which is attached to the RER. Ribosome reads the instructions to assemble the protein
  4. Protein molecules are ‘pinched off’ in vesicles and travel to Golgi
  5. Vesicle fuses with Golgi
  6. Golgi processes and packages protein molecules for release
  7. Packaged insulin molecules are ‘pinched’ off in vesicles from Golgi and move towards plasma membrane
  8. Vesicles fuse with plasma membrane
  9. Plasma membrane opens to release protein molecules outside
54
Q

How are prokaryotic cells similar to eukaryotic cells?

A

They both have:

  • a plasma membrane
  • a cytoplasm
  • ribosomes
  • DNA and RNA
55
Q

How are prokaryotic cells different from eukaryotic cells?

A
  • smaller
  • much less well developed cytoskeleton with no centrioles
  • don’t have a nucleus
  • no membrane bound organelles eg RER
  • cell wall made of peptidoglycan NOT cellulose
  • smaller ribosomes
  • DNA in cytoplasm not nucleus
56
Q

Some prokaryotes also have:

A

Protective waxy capsule surrounding their cell walk
Plasmids
Flagella
Pili

57
Q

Plasmids detailed

A

Small loops of DNA containing extra genes

58
Q

What are flagella

A

Long whip like projections that rotate enabling them to move in liquids

59
Q

Function of the nucleus

A

Control centre of the cell
Stores the organism’s genome
Transmits genetic information
Provides the instructions for protein synthesis

60
Q

Cytoskeleton function

A

Provides strength and support to the cell
Holds organelles in place
Forms the track along which motor proteins transport organelles from one end of the cell to the other
Form the spindle for the movement of chromosomes

61
Q

Organelles found in animal cells but not in plant cells

A

Centrosomes
Lysosomes

A Level Biology OCR (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions