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Cell Structure Flashcards

eukaryotic, prokaryotic and microscopes

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1
Q

List the features of a plant cell

A

-Amyloplast containing starch
-Golgi apparatus
-Smooth endoplasmic reticulum
-Ribosomes
-Nucleolus
-Nuclear envelope
-rough endoplasmic reticulum
-cell wall
-plasma membrane
-vacuole
-mitochondrian
-organelles suspended in cytoplasm

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2
Q

List the features of an animal cell

A

-rough endoplasmic reticulum
-mitochondrian
-ribosome
-nuclear envelope
-lysosome
-Golgi apparatus
-plasma membrane
-smooth endoplasmic reticulum
-nucleolus
-nucleus

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3
Q

Compare animal and plant cells

A

-animal cells have centrosomes and lysosomes whereas plant cells do not
-plants have a cell wall, chloroplasts and large permanent vacuole whereas animal cells do not

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4
Q

Structure and function of nucleus

A

-surrounded by double membrane (nuclear envelope), has pores
-control the centre of cell, stores organisms genome, provides instructions for protein synthesis

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5
Q

Structure and function of nucleolus

A

-contains RNA
-makes ribosomes, location where chromosomes unwind

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6
Q

Structure and function of chromatin (genetic material)

A

-consists of DNA wrapped around histone proteins; when cell not dividing chromatin is spread however when it is, coils tightly

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7
Q

Structure and function of nuclear envelope

A

-double membrane
-separates contents of nucleus

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8
Q

Why does the nucleus contain pores

A

-enables larger substances such as messenger RNA (mRNA) to leave, some steroid hormones can enter from cytoplasm

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9
Q

Structure and function of rough endoplasmic reticulum

A

-system of membranes containing fluid-filled cavities (cisternae)
-coated with ribosomes
-lumen in the middle
-intracellular transport system, cisternae form channels for transporting substances
-provide large surface area for ribosomes which assemble amino acids to proteins - transported to Golgi apparatus for modification and packaging

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10
Q

Structure and function of smooth endoplasmic reticulum

A

-system of membranes containing cisternae
-no ribosomes on its surface
-contain enzymes that catalyse reactions involved with lipid metabolism; synthesis of cholesterol lipids/phospholipids needed by cell steroid hormones - testosterone etc
-involved absorption, synthesis and transport of lipids

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11
Q

Structure and function of Golgi apparatus

A

-consists of stack of membrane-bound flattened sacs
-secretory vesicles bring materials to and from Golgi apparatus for packaging and processing
-proteins are modified - for example by add sugar molecules to make glycoproteins, folded into their 3D shapes
-proteins are packaged into vesicles that are pinched off then stored in cell or moved into plasma membrane

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12
Q

Structure and function of mitochondria

A

-contain own DNA and are endosymbionts
-may be spherical, rod shaped, or branched, 2-5um long
-surrounded by 2 membranes with fluid-filled space between them, inner membrane folded into cristae
-inner part mitochondria is fluid filled matrix
-site of ATP production, aerobic conditions
-self-replication - make more if cell need it
-abundant in cells. much metabolic activity - e.g. liver cells, synapses

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13
Q

Structure and function of vacuole

A

-surrounded by a membrane called the tonoplast, contains fluid
-only plants cells have large permanent vacuole
-filled solutes, water and cell is turgid to sustain cell stability
-all plant cells turgid to help support plant, especially non woody

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14
Q

Structure of chloroplasts

A

-large organelles 4-10um long
-found only in plant cells and protoctista
-surrounded by double membrane or envelope
-inner membrane continuous with stacks of membrane stacks called thykaloids containing chlorophyll - each stack called granum
-fluid filled matrix called stoma
-chloroplasts contain loop of DNA and starch grains

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15
Q

Function of chloroplasts

A

-site of photosynthesis
-first stage - when light energy trapped by chlorophyll to make ATP, occurs in grana, water split to supply hydrogen ions
-second stage - hydrogen reduce CO2 using energy from ATP, making carbohydrates, occurs in stoma
-abundant in leaf cells, palisade and mesophyll layer

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16
Q

Structure and function of lysosomes

A

-smalls bags formed in Golgi apparatus, surrounded by single membrane
-contain powerful hydrolytic (digestive) enzymes
-abundant in phagocytic cells that can ingest and digest invading pathogens - eg bacteria
-keep powerful hydrolytic enzymes separate from rest of cell
-engulf old organelles and foreign matter, digest them and return to cell for reuse

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17
Q

Structure and function of cilia and undulipodia

A

-protusions from cells and surrounding cell surface membrane
-contains microtubules which follow 9+2 arrangement
-formed from centrioles
-epithelial cells lining your airways have hundred of cilia that move the mucus
-contains receptors and allows cells to detect immediate movement
-undulipodia enable sperm to move

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18
Q

Structure and function of ribosomes

A

-small spherical organelles, 20nm in diameter
-made ribosomal RNA
-made in nucleolus as 2 separate subunits, pass through nuclear envelope into cell cytoplasm then combine
-some remain free, some attach to endoplasmic reticulum
-bound to exterior RER, synthesising proteins
-ribosomes free are primarily the site of assembly proteins to be used inside the cell

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19
Q

Structure and function of centrioles

A

-consist of two bundles of microtubules, 90 degrees to each other
-made of tubulin protein subunits, arranged to form cylinder
-before cell divides, spindle threads of tubulin forms from centrioles
-chromosomes attach middle of spindle, motor proteins pill chromosomes opposite ends of cell
-before cilia form, centrioles multiply and line up beneath the cell surface membrane
-microtubules sprout from each centriole forming cilium or undulipodium
-centriole usually absent from cells of plants but present in some unicellular green algae e.g. chlamydomonas

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20
Q

Structure and function of cellulose cell wall

A

-of plants, cell wall on outside of plasma membrane
-made from bundles of cellulose fibres
-absent animal cells, strong and prevent plant cells from bursting when turgid
-provide strength and support
-maintain cells shape
-contribute to strength and support of whole plant
-permeable, allow solutions to pass (solvent and solutes)
-fungi have cell walls, containing chitin not cellulose

21
Q

Structure of cytoskeleton

A

-network of protein structures in cytoplasm
-rod like microfilaments made of subunits of protein actin; polymers of actin, each 7nm in diameter
-intermediate filaments, 10nm in diameter
-straight, cylindrical microtubules, tubulin 18-30nm diameter
-cytoskeletal motor proteins - myosins, kinesins, dyeins - molecular motors
-also enzymes, site that allows hydrolysis of ATP as energy source

22
Q

Function of cytoskeleton

A

-protein microfilaments - support and mechanical strength - cells shape stable and allow cell movement
-microtubules - shape, support, allow substances and organelles to move through cell cytoplasm
-form track along, which dyeins and kinesins walk along and drag organelles
-form spindle fibres before cell division which allow chromosomes to be moved
-MT also make cilia, undulipodia, centrioles
-intermediate filaments - anchor nucleus, extend between cells allowing cell-cell signalling, stabilising tissues

23
Q

Describe how a protein is made and secreted

A
  1. TRANSCRIPTION - gene that has coded instructions for protein, e.g. insulin, is transcribed into a length of messenger RNA (mRNA)
  2. many copies of mRNA are made, pass out of the pores in nuclear envelope to ribosomes
  3. TRANSLATION- at ribosomes, instructions are translated and insulin molecules are assembled
  4. insulin molecules pass into cisternae of RER along hollow sacs
  5. vesicles with insulin inside are pinched off from RER, pass via microtubules and motor proteins to Golgi apparatus
  6. these insulin molecules move towards plasma membranes
  7. EXOCYTOSIS - fusion of secretory vesicles with plasma membrane
  8. plasma membrane opens to release insulin molecules outside
24
Q

List similarities between eukaryotic and prokaryotic cells

A

-have a plasma membrane, cytoplasm, ribosomes for assembling amino acids into proteins, DNA and RNA

25
Q

List differences between eukaryotic and prokaryotic cells

A

-much smaller, 1-5um long
-less well developed cytoskeleton with no centrioles
-don’t have a nucleus
-don’t have membrane bound organelles - e.g. mitochondria, chloroplasts, Golgi apparatus
-have organelles not covered by membrane - e.g. ribosomes
-wall made of peptidoglycan not cellulose
-smaller ribosomes
-naked DNA, not wound around histone proteins but floats free in cytoplasm as loop, in comparison to linear chromosomes

26
Q

List other features of prokaryotic cells

A

-protective waxy capsule surrounding their cell wall
-small loops of DNA, plasmid, as well as large loops of DNA
-flagella - long whip like projections that enable them to move - structure of this differs from eukaryotic undulipodia
-pili - smaller hair like projections, enable the bacteria to adhere to host cells or to each other, allow passage of plasmid DNA from one cell to another

27
Q

Describe how prokaryotic cells divide

A

-prokaryotic cells divide by binary fission not mitosis as they don’t have linear chromosomes
-before division, their DNA is copied so each new cell receives large loop of DNA and any smaller plasmids

28
Q

What are bacteria

A

-bacteria are microorganisms because they are very small
-they are also prokaryotes because of their cell structure
-not all microorganisms however are prokaryotes
-yeast, a single celled fungus, and amoebae have eukaryotic cells
-viruses are microscopic but do not have cells

29
Q

Describe the endosymbiont theory

A

-evidence indicates that eukaryotic cells evolved from prokaryotes 1.5-2 billion years ago - some prokaryote cells with infolded membranes (for making ATP or containing chlorophyll) engulfed by some other prokaryotes but not digested
-invaded prokaryotes plasma membrane folded inwards around invading cell producing double membrane of what are not chloroplasts and mitochondria, therefore share characteristics with prokaryotic cells
-have small ribosomes, loops of DNA, contain RNA, can divide by binary fission

30
Q

What is mesomene in prokaryotes

A

-produces ATP, site of aerobic respiration

31
Q

Define magnification

A

the number of times larger an image appears, compared with the size of the object (actual size)

32
Q

Define resolution

A

clarity of an image, the higher the resolution, the clearer the image - can be measured in nm. The lower the number, the higher the resolution is

33
Q

How is total magnification calculated

A

magnifying power of the objective lens x magnification power of the eyepiece lens

34
Q

Define photomicrograph

A

photograph of the image seen using an optical microscope (light microscope)

35
Q

Describe the development of optical microscopes (light microscopes)

A

-development of optical microscopes played key role in understanding cell structure
-they are still used in schools, colleges etc as they are relatively cheap, easy to use, portable and able to be used in fields as well as laboratories, used to study whole living specimens
-look different to 17th century but both lenses rely on beam of light - use visible light, part of electromagnetic spectrum that has wavelength 400-700nm
-structures closer together than 0.2um will appear as one object due to low resolution
-ribosomes very small cannot be seen

36
Q

Describe laser scanning microscopes

A

-aka confocal microscopes
-use laser light to scan object, point by point and assemble by computer. the pixel information to one image
-images high resolution and show high contrast
-typically black and white images produced
-have depth selectivity, can focus on structures at different depths within the specimen - e.g. can be used to observe whole living specimens as well as living cells
-used in medical professions and biological research - e.g. observe fungal filaments within cornea to five swift diagnosis and treatment

37
Q

Describe electron microscope

A

-used to view dead specimens
-use beam of fast-travelling electrons with wavelength of 0.004nm - greater resolution than optical microscopes, gives clear and highly magnified images
-electrons fired from cathode, focused by magnets
-fast travelling electron have 125,000 times smaller wavelength than central past visible light spectrum- better resolution

38
Q

Describe transmission electron microscope

A

-specimen must be fixed chemically by dehydration and stain
-beam of electrons pass through specimen, strained with metal salts, focused on screen or photographic plate
-electrons form 2D grey scale image - called electron micrograph - can produce a magnification of 2x million

39
Q

Describe scanning electron microscopes

A

-developed 1960s
-cause secondary electrons to bounce off specimens surface
gives 3D image with magnification form 15x up to 200,000x
-image black and white but software can add false colour
-specimen needs to be put in vacuum and coated
-both EM are large and expensive and need a great deal of skill and training to use

40
Q

What are the resolutions and magnifications of the microscopes

A

RESOLUTION
LM- 0.2um
SEM- 3-10nm
TEM- 0.5nm
MAGNIFICATION
LM- 1500x (maximum) - cannot view small organelles
SEM- 200,000x
TEM- 2,000,000x

41
Q

What can you view using optical microscopes

A

-living organisms - e.g. Paramecium and amoeba
-smear preparations of human blood and cheek cells
-thin sections of animal, plant and fungal tissue - e.g. bone, muscle, leaf, root or fungal hyphae

42
Q

How are unstained specimens viewed

A

-many biological structures are colourless and transparent
-some microscopes use light interference rather than light absorption - produce clear image without staining
-some use dark background against illuminated specimens
-living specimens can be observed by light microscope by adjusting iris diaphragm to reduce illumination

43
Q

Describe the process of staining specimens

A

-stains are coloured chemicals that bind to molecules on specimens to increase the contrast so its easier to see - e.g. methylene blue is an all purpose stain
-differential staining - some stains bind to specific cell structure, staining each structure differently so structures can be easily identified within single preparation
-acetic orcein binds to DNA and stains chromosomes dark red
-eosin stains cytoplasm
-sudan red stains lipids
-iodine in potassium iodide solution stains cellulose in plant cell walls yellow, starch granules blue/black

44
Q

Why do we use stains

A

-to see the cells
-use different stains to distinguish different organelles
-to increase contrast

45
Q

What is the magnification equation

A

Magnification= Image/Actual

46
Q

How are specimens prepared

A
  1. Fixing - formaldehyde to preserve
  2. Dehydrating - ethanol
  3. Embedding - resin/ wax form hard block
  4. Sectioning - microtome to thin slice it
  5. Staining
  6. Mounting
47
Q

What is an eyepiece and stage graticule

A

EYEPIECE- measuring device, placed in eyepiece of microscope and acts as ruler when you view and object under microscope
STAGE- precise measuring ruler, 1mm long with small scale. Placed on microscope stage and used to calibrate value of eyepiece divisions at different magnifications

48
Q

List each eye piece unit for the different lenses

A

RED(x4) 1 epu= 23um
YELLOW (X10) 1 epu=10um
BLUE(x40) 1 epu=2.5um

49
Q

Describe how to use a stage graticules to calibrate the eyepiece graticule

A
  1. Insert eyepiece graticule into x10 eyepiece of microscope
  2. Place stage graticule on microscope stage and bring into focus using power (x4) objective - total magnification x40
  3. Align eyepiece graticule and stage graticule - check value of one eyepiece division at this magnification
  4. For example, stage graticule (1mm/1000um) corresponds to 40 eyepiece divisions therefore each eyepiece division is 1000/40um=25um
  5. Use x10 objective lens on your microscope (total magnification now x100) and focus on stage graticule
  6. Align them both
  7. In example, 100 eyepiece divisions corresponds to 1000um therefore one eyepiece division is 1000/100=10um

Biology (9 decks)

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