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biology a level OCR > cell structure > Flashcards

cell structure Flashcards

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1
Q

what is magnification

A

the number of times larger an image appears, compared with the size of the object being viewed

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2
Q

what is resolution

A

how clearly we can determine two points, the higher the resolution the greater the detail

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3
Q

what is wet mounting

A

specimens are suspended in a liquid such as water or immersion oil

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4
Q

what is dry mounting

A

solid specimens are viewed whole or cut into very thin slices

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5
Q

why must we place a cover slip on at an angle (when placing it onto a wet mount)

A

this is to prevent air bubbles forming under the cover slip

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6
Q

what is the maximum magnification and resolution of a scanning electron microscope (SEM)

A
  • 15 to 200,000 times (magnification range)
  • 3-10 Nm (resolution range
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7
Q

what is the maximum magnification and resolution of a transition electron microscope (TEM)

A
  • x 2 million (magnification range)
  • 0.5nm (resolution range)
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8
Q

what are the disadvantages of electron microscopes

A
  • the specimen has to be chemically fixed, by being dehydrated and stained
  • vacuum required
  • large and needs to be installed
  • expensive to buy/operate
  • specimens must be dead
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9
Q

what is the function of the mitochondrion
mean length = 0.5 to 1 um

A
  • to produce energy in respiration
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10
Q

what is the function of chloroplasts
mean length = 3-10 um

A

uses light energy in photosynthesis
- convert light energy in to stable chemical energy

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11
Q

what is the function of the Golgi apparatus
mean length = 0.5 to 2.0 um

A

to function as a factory in which proteins are processed and transported to the plasma membrane etc.

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12
Q

what is the function of the smooth ER
mean length =30nm to 50nm

A

it synthesis and stores lipids including cholesterol and phospholipids to produce new cellular membranes

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13
Q

what is the function of the rough ER
mean length = 20nm to 30nm

A

to produce proteins that will become part of the Endomembrane system, the plasma or will be secreted
(the endomembrane systems is all of the membranes within the cell)

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14
Q

what are centrioles

A
  • centrioles, move to the poles (opposite ends of the cell) of the cell
  • froms spindle fibres, which often attach to chromosomes
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15
Q

what are flagella

A
  • flagella are prokaryotes/ bacteria
  • ## whip like movement
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16
Q

what are cilia

A
  • same structure as the flagella, but shorter
  • beating movement
  • arranged in clusters
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17
Q

what are microfilaments

A
  • filaments found in the cytoplasm
  • help the cell move
  • change shape (endocytosis and exocytosis)
18
Q

what are microtubles

A
  • little tubes (microscopic)
  • form the spindle
  • make up cilia and undulipodia, so help, with the movement of substances
  • motor proteins, allow them to move via ATP
19
Q

what are intermediate fibres

A
  • extended between cells and help to stabilise the tissue
20
Q

what are lysosomes

A
  • Specialist forms of vesicles which contain hydrolytic enzymes (enzymes that break biological molecules down)
  • Break down waste materials such as worn-out organelles, used extensively by cells of the immune system and in apoptosis (programmed cell death)
21
Q

State some advantages and disadvantages of light microscopes

A

easy to use, portable, can be used to observe living specimens (tissues) DISADS: Limited magnification and resolution so fine detail cannot be observed

22
Q

State the maximum magnification and resolution for a light microscope

A

M = 1500 - 2000 times; R = 200nm (0.2µm)

23
Q

Describe reasons why we use staining in microscopy

A

Coloured chemicals that bind to molecules on the specimen, increasing contrast and making the specimen easier to see; some stains bind to specific cell structures in differential staining, e.g. acetic orcein binds to DNA and stains chromosomes dark red

24
Q

Describe differences in how the image is formed between TEMs, SEMs and LSCMs

A
  • TEM: electrons pass straight through specimen (2D black and white image);
  • SEM: electrons bounce off specimen surface and focused (3D black and white image);
  • LSCM: laser scans specimen point by point and stacks layers of the image at different depths (3D image)
25
Q

Describe 4 disadvantages of electron microscopy

A
  • Specimen has to be dead (as observed in a vacuum)
  • requires specialist training to use; heavy metallic salt stains hazardous to human health;
  • complex preparation process means artefacts may be produced (distorts image);
  • high energy electron beam can damage the specimen (distorts image)
26
Q

State 5 success criteria that must be considered when making a biological drawing of a specimen

A

Use a sharp pencil, ensure drawing has a title and a scale bar, make appropriate annotations detailing structure and function, use a ruler to draw label lines which do not overlap (with no arrowheads), ensure all lines in image are clear and continuous (unbroken), NO shading

27
Q

State the formula for calculating magnification

A

magnification = image size/actual size

28
Q

Describe the structures and functions of the various components of the nucleus

A
  • Nuclear envelope: separates contents of the nucleus from the rest of the cell, contains nuclear pores which allow movement of messenger RNA (mRNA) OUT of the nucleus
  • nucleolus: contains ribosomal RNA to synthesise ribosomes; nucleoplasm: contains chromatin which is where DNA is stored
29
Q

Describe the structure and function of the rough endoplasmic reticulum (rER)

A

A system of membranes containing fluid filled cisternae, continuous with nuclear membrane and covered in ribosomes. It acts as both an intracellular transport system and a site of protein synthesis (translation on ribosomes)

30
Q

Describe the structure and function of the smooth endoplasmic reticulum (sER)

A

Similar to rER but more tubular structure with NO ribosomes. Site of cholesterol, steroid hormone, lipid synthesis

31
Q

Describe the structure and function of the Golgi apparatus

A

A stack of membrane-flattened sacs; secretory vesicles bring materials to and from the Golgi. It is the site of protein modification (e.g. adding sugar groups to make glycoproteins), protein folding (e.g. into an enzyme/hormone). Modified proteins can then either be stored in the cell or exported via exocytosis at the plasma membrane

32
Q

Describe the structure and function of a mitochondrion

A

Double membrane with inner membrane folded into cristae (provides a large surface area for electron carrier proteins in aerobic respiration and significant ATP production); contains a fluid filled matrix containing enzymes (for respiration) and mitochondrial DNA (for self-replication and protein synthesis)

33
Q

Describe the structure and function of chloroplasts

A

Double membrane, inner membrane continuous with stacks of flattened membrane sacs called thylakoids (stacks of thylakoids are called grana) which contain chlorophyll; fluid-filled stroma (contains enzymes for photosynthesis); contains loops of DNA (for protein synthesis) and starch grains (carbohydrate storage)

34
Q

Describe the structure and function of the components of the vacuole

A

Contains cell sap (water and solutes which maintain cell stability by exerting pressure on the cell wall…turgid); surrounded by a tonoplast (vacuolar membrane)

35
Q

Describe the structure and function of lysosomes

A

Single-membrane bound vesicles containing hydrolytic enzymes; lysosomes are abundant in phagocytes (neutrophils and macrophages). Lysosomes can engulf dead/damaged organelles and foreign matter and recycle the digested components

36
Q

Describe the structure and function of centrioles

A

“9 + 3” arrangement of microtubules (made of tubulin); pairs of centrioles are arranged at right angles to each other. Responsible for spindle fibre formation during cell division

37
Q

Describe the structures and function of cilia and flagella

A

“9 + 2” arrangement of microtubules; cilia can be stationary (sensory role) or mobile (beat rhythmically to move mucus from airways); flagella used for cell motility

38
Q

Outline briefly the structures and functions of three components of the cytoskeleton

A

Microfilaments (composed of actin protein fibres; responsible for cell movement and contraction during cytokinesis); microtubules (composed of globular tubulin proteins; scaffold shale of cell and important in organelle movement working with motor proteins dynein and kinesin); intermediate fibres (many proteins; mechanical strength, anchor nucleus in cytoplasm)

39
Q

Describe how a protein is synthesised and modified before leaving the cell

A

Synthesised on ribosome (on rER or free floating), travel through rER in cisternae and pinched off into a vesicle; vesicle moves via microtubules towards Golgi; vesicle fuses with face of Golgi and is modified; modified protein leaves Golgi in vesicle and travels to plasma membrane; vesicle fuses with plasma membrane and exits the cell via exocytosis

40
Q

Describe the main differences between eukaryotes and prokaryotes

A

Prokaryotes are much smaller, they have no membrane-bound organelles, less well-developed cytoskeleton and no centrioles; cell wall made of murein (not chitin or cellulose); free-floating loop of DNA (and plasmids)

41
Q

Describe the similarities between chloroplasts/mitochondria and prokaryotes

A
  • Contain 70s ribosomes
  • Contain loops of DNA
  • contain RNA
  • divide by binary fission

biology a level OCR (32 decks)

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