BIOLOGY FA2 > Cells > Flashcards

Cells Flashcards

eukaryotic cells, prokaryotic cells, microscopes and magnification, mitosis and cell membranes (78 cards)

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1
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A
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2
Q

Define a eukaryotic cell

A

Eukaryotic cells contain membrane bound organelles and a true nucleus

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3
Q

Define a prokaryotic cell

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Prokaryotic cells lack a nucleus and membrane bound organelles and have circular DNA

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4
Q

State key differences of DNA between eukaryotes and prokaryotes

A

Eukaryotes have linear DNA associated with histones prokaryotes have circular DNA often with plasmids

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5
Q

List unique prokaryotic features

A

Plasmids 70S ribosomes peptidoglycan cell wall and sometimes capsule and flagella

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6
Q

Describe eukaryotic cell ultrastructure

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Cell membrane cytoplasm nucleus mitochondria endoplasmic reticulum Golgi apparatus lysosomes and in plants chloroplasts vacuole and cell wall

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7
Q

Describe prokaryotic cell ultrastructure

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Cell membrane cytoplasm circular DNA plasmids 70S ribosomes and peptidoglycan cell wall

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8
Q

Function of the nucleus

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Contains genetic material and controls cell activity via gene expression

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9
Q

Function of mitochondria

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Site of aerobic respiration producing ATP

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10
Q

Function of ribosomes

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Site of protein synthesis

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11
Q

Function of rough endoplasmic reticulum

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Synthesises and transports proteins

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12
Q

Function of smooth endoplasmic reticulum

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Synthesises lipids and detoxifies substances

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13
Q

Function of Golgi apparatus

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Modifies sorts packages and transports proteins and lipids in vesicles

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14
Q

Function of lysosomes

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Contain hydrolytic enzymes to digest cellular waste and pathogens

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15
Q

Function of chloroplasts

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Site of photosynthesis containing chlorophyll and thylakoid membranes

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16
Q

Function of vacuole

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Maintains turgor stores substances and contributes to cell volume in plant cells

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17
Q

Function of plant cell wall

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Provides structural support and prevents excessive water uptake

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18
Q

Define magnification

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Magnification equals image size divided by actual size

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19
Q

Convert micrometres to millimetres

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Divide micrometres by one thousand to get millimetres

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20
Q

Convert nanometres to micrometres

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Divide nanometres by one thousand to get micrometres

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21
Q

Explain why staining is used

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Staining increases contrast so structures are more easily seen under a microscope

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22
Q

Define resolution

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Minimum distance at which two points can be seen as separate entities

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23
Q

State light microscope limitations

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Lower resolution due to wavelength of light and limited maximum useful magnification

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24
Q

State advantage of electron microscopes

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Higher resolution and greater magnification due to shorter electron wavelength

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25
Describe transmission electron microscope
TEM produces high resolution two dimensional images of internal ultrastructure from thin sections
26
Describe scanning electron microscope
SEM produces three dimensional images showing surface topography
27
Explain why TEM specimens must be thin
Thin sections allow electrons to pass through enabling internal structure imaging
28
Calibrate an eyepiece graticule
Use a stage micrometer to determine actual length per graticule division then convert graticule units to actual size
29
Explain magnification triangle use
Image size divided by actual size equals magnification
30
Define the cell surface membrane
Phospholipid bilayer with embedded proteins controlling movement of substances and cell recognition
31
Describe the fluid mosaic model
Phospholipids form a bilayer with proteins and other molecules moving within the layer creating a mosaic
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Role of cholesterol in membranes
Cholesterol stabilises membrane structure and modulates fluidity especially at different temperatures
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Role of glycoproteins in membranes
Glycoproteins function in cell recognition and as receptors for signals
34
Define diffusion
Net movement of particles from a region of higher concentration to a region of lower concentration down a gradient
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Define facilitated diffusion
Passive movement of specific molecules via channel or carrier proteins without energy input
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Define osmosis
Net movement of water from region of higher water potential to region of lower water potential across a partially permeable membrane
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Define active transport
Energy dependent movement of molecules against their concentration gradient using carrier proteins and ATP
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List factors affecting diffusion rate
Concentration gradient surface area temperature and diffusion distance
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Explain effect of temperature on membrane permeability
Higher temperature increases phospholipid movement and can denature membrane proteins increasing permeability
40
Explain effect of solvents on membrane permeability
Organic solvents disrupt lipid bilayer increasing membrane permeability often irreversibly
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Describe sodium potassium pump mechanism
Carrier protein uses ATP to export three sodium ions and import two potassium ions maintaining electrochemical gradients
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Define co transport
Transport where movement of one substance down its gradient drives movement of another substance against its gradient via a cotransporter
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Explain sodium glucose co transport
Sodium moving down its gradient into cell via cotransporter carries glucose into cell against its gradient
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Define endocytosis
Uptake of materials by invagination of the membrane forming vesicles
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Define exocytosis
Release of materials by fusion of vesicles with the cell membrane
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Explain surface area to volume ratio importance
Cells with higher surface area to volume ratio exchange materials more efficiently by diffusion
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Define mitosis
Mitosis is the division of the nucleus producing two genetically identical daughter nuclei
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What happens in prophase
Chromatin condenses into visible chromosomes spindle microtubules form and nuclear envelope disintegrates
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What happens in metaphase
Chromosomes align at the cell equator and spindle fibres attach to centromeres
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What happens in anaphase
Sister chromatids separate and are pulled to opposite poles by spindle fibres
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What happens in telophase
Chromatids arrive at poles nuclear envelopes reform and chromosomes decondense
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Define cytokinesis
Division of the cytoplasm producing two separate daughter cells
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State the order of the cell cycle
G1 S G2 mitosis cytokinesis
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Describe G1 phase
Cell growth synthesis of proteins and organelles and preparation for DNA replication
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Describe S phase
DNA replication producing sister chromatids attached at centromeres
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Describe G2 phase
Further cell growth and preparation for mitosis checking for DNA replication errors
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Describe the G1 checkpoint
Checks for cell size nutrient availability and DNA damage before entry to S phase
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Describe the G2 checkpoint
Checks for DNA replication completeness and cell readiness for mitosis
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Describe the metaphase checkpoint
Ensures chromosomes are correctly attached to spindle before anaphase proceeds
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Define mitotic index
Proportion of cells in a sample that are undergoing mitosis
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Calculate mitotic index
Number of cells in mitosis divided by total number of cells observed
62
Define cancer
Disease of uncontrolled cell division often caused by mutations in genes regulating the cell cycle
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Explain proto oncogene mutation effect
Gain of function mutation results in increased signalling for cell division
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Explain tumour suppressor gene mutation effect
Loss of function mutation removes inhibitory controls on cell division
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Explain role of apoptosis in preventing cancer
Programmed cell death removes damaged or abnormal cells preventing their proliferation
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Define binary fission
Prokaryotic process where circular DNA replicates and cell divides producing two daughter cells
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Contrast binary fission and mitosis
Binary fission is simpler with no nucleus and no spindle structures while mitosis uses spindle and occurs in eukaryotic cells
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Describe bacterial growth requirements
Bacteria require suitable nutrients appropriate temperature moisture and pH to grow
69
State RP2 aim for membrane practical
Investigate effect of temperature or organic solvents on membrane permeability using beetroot pigment leakage
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List RP2 control variables
Keep disc size incubation time solvent or solution volume and sample handling constant for fair test
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Explain expected RP2 trend with temperature
Higher temperatures disrupt membranes releasing more pigment due to increased lipid movement and protein denaturation
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Explain plasmid function in prokaryotes
Small circular DNA molecules that replicate independently and can carry advantageous genes such as antibiotic resistance
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Describe peptidoglycan cell wall structure
Polymeric network of polysaccharide chains cross linked by peptides providing rigidity in prokaryotes
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Explain marker enzyme use in cell fractionation
Use enzyme specific to an organelle to identify which fraction contains that organelle
75
Outline cell fractionation steps
Homogenise tissue filter to remove debris then centrifuge at increasing speeds to pellet organelles by size and density
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Define ultracentrifugation
High speed centrifugation used to separate cellular components by density and size
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Give typical organelle pelleting order
Large nuclei then mitochondria lysosomes and then ribosomes in subsequent centrifugation steps
78
State limitation of electron microscopy
Specimens must be dead and fixed and imaging is done in a vacuum so living processes cannot be observed
BIOLOGY FA2
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