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Bio Alevel > Cells > Flashcards

Cells Flashcards

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1
Q

Structure of nucleus

A
  • nuclear envelope
  • nuclear pores
  • nucleoplasm
  • chromosomes
  • nucleolus
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2
Q

What is the nucleolus

A

Site of rRNA production and makes ribosomes

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3
Q

Function of nucleus

A
  • site of DNA replication and transcription
  • contains the genetic code for each cell
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4
Q

Structure of eukaryotic cells

A
  • cell-surface membrane
  • nucleus
  • mitochondria
  • chloroplast
  • golgi apparatus + vesicles
  • lysosomes
  • ribosomes
  • RER + SER
  • cell wall
  • cell vacuole
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5
Q

RER + SER structure

A
  • both have folded membranes called cisternae
  • RER have ribosomes on the outer surface but SER don’t
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6
Q

RER + SER function

A

RER: provides large SA for protein synthesis + provides pathway for the transport of materials

SER: synthesise, store and transport carbohydrates and lipids

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7
Q

Golgi body functions

A
  • add carbs to proteins to form glycoproteins
  • produce secretory enzymes
  • transport, modify and store lipids
  • form lysosomes
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8
Q

Lysosomes structure

A
  • Contain digestive enzymes like proteases and lipases
  • they also contain lysozymes
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9
Q

What are lysozymes and what happened to them

A
  • enzymes that hydrolyse the cell walls of certain bacteria
  • lysosomes isolate these enzymes from the rest of the cell and then release them either to the outside or into a phagocytic vesicle within the cell
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10
Q

Functions of lysosomes

A
  • break down material ingested by phagocytosis
  • release enzymes outside the cell (exocytosis)
  • digest warn out organelles
  • completely break down cells after they’ve died (autolysis)
  • hydrolyse phagocytic cells
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11
Q

Mitochondria structure

A
  • double membrane -> outer one controls entry + exit of materials whilst inner is folded to form cristae
  • matrix
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12
Q

What do mitochondria cristae do

A

Provide a large SA for the attachment of enzymes + are involved in respiration

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13
Q

What does the mitochondria matrix do

A

Contains proteins, lipids and traces of DNA and also its own ribosomes -> so mitochondria can control the production of their own proteins

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14
Q

Mitochondria function

A
  • site of aerobic respiration
  • site of ATP
  • DNA to code for enzymes needed in respiration
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15
Q

Ribosomes structure

A

Made up of 2 sub-units containing protein and rRNA:
- 80S -> found in eukaryotic cells
- 70S -> found in prokaryotic cells, mitochondria and chloroplasts

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16
Q

Ribosomes function

A

The site of protein synthesis

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17
Q

Vacuole structure

A

Filled with fluid surrounded by a single membrane called tonoplast

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18
Q

Vacuole function

A
  • make cells turgid and so provide support
  • temporary store of amino acids and sugars
  • the pigments may colour petals to attract pollinators
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19
Q

Chloroplasts structure

A
  • double membrane
  • contain thylakoids -> folded membranes with pigment
  • fluid filled strings contains enzymes for photosynthesis
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20
Q

Chloroplasts function

A

Site of photosynthesis

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21
Q

Cell wall structure (plants and fungi)

A

Plants: made of micro fibrils of cellulose polymer

Fungi: made of chitin -> a nitrogen containing polysaccharide

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22
Q

Cell wall function

A

Provide structural strength to the cell

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23
Q

Cell membrane structure

A
  • phospholipid bilayer -> molecules embedded within and attached on the outside
    ( proteins, carbohydrates, cholesterol)
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24
Q

Cell membrane function

A

Controls entry and exit of molecules

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25
Q

What things do cell membranes contain

A
  • cholesterol
  • glycoproteins
  • glycolipids
  • proteins
  • phospholipids
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26
Q

Vacuole structure

A
  • fluid filled sac, bound by a single membrane called a tonoplast
  • a plant vacuole contains a solution of mineral salts, sugars, amino acids, wastes and pigments such as anthocyanins
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27
Q

Function of vacuole

A
  • sugars and amino acids act as temporary food stores
  • keeps the cells turgid
  • pigments may colour petals to attract pollinating insects
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28
Q

Object

A

Material under microscope

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29
Q

Image

A

Appearance of material under a microscope

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30
Q

Resolution

A

The minimum distance apart that 2 objects can be in order for them to appear as separate items

Greater resolution = greater clarity

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31
Q

Light microscope

A

Uses light rays that pass through a specimen and are focused by the objective lens and eyepiece lens to produce an image

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32
Q

Light microscope resolution

A

Have a poor resolution due to the long wavelength of light

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33
Q

Electron microscope

A

Uses a beam of electrons -> an electromagnet is used to focus the beam of electrons on the specimen

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34
Q

Electron microscope resolution

A

Better resolution due to a shorter wavelength

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35
Q

What are the 2 types of electron microscope

A

Transmission and scanning

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36
Q

TEM Limitations

A
  • whole system must be in a vacuum so living specimens can’t be observed
  • a complex staining process
  • image may contain artefacts
  • only black and white
  • specimen must be very thing, resulting in a flat 2D image
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37
Q

TEM Limitations

A
  • whole system must be in a vacuum so living specimens can’t be observed
  • a complex staining process
  • image may contain artefacts
  • only black and white
  • specimen must be very thing, resulting in a flat 2D image
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38
Q

Scanning electron microscope

A

Directs a beam of electrons onto the surface, rather than penetrate it -> has a lower resolving power than the TEM

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39
Q

SEM limitations

A
  • whole system must be in a vacuum so living specimens can be observed
  • complex staining process
  • image may contain artefacts
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40
Q

Why is cell fractionation possible

A

Due to the different densities or the organelles

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41
Q

What is cell fractionation

A

Process where cells are broken up and different organelles are separated out

42
Q

What must you do before cell fractionation

A

Put the tissue in cold, buffered and isotonic solution

43
Q

Why must the solution be cold, buffered and isotonic

A

Cold - to reduce enzyme activity that might break down the organelles

Buffered - to maintain constant pH as a change in pH could alter the structure of organelles or affect their functioning

Isotonic - to prevent any osmotic gain or loss of water so organelles don’t burst or shrink

44
Q

What are the steps of cell fractionation

A
  1. Place in cold, buffered and isotonic solution
  2. Homogenisation
  3. Ultracentrifugation
45
Q

What happens in homogenisation

A
  • cells are broken up by a homogeniser -> this releases organelles
  • the resultant fluid (homogenate) is filtered to remove any debris + complete cells
46
Q

What happens in ultracentrifugation

A
  • the fragments in the filtered homogenate are separated out in an ultracentrifuge
    -> this spins tubes of homogenate quick to create a centrifugal force
47
Q

What speed is the tube spin in ultracentrifugation

A
  • slow at first -> the heaviest organelle (nucleus) is forced to the bottom where it forms a thin sediment or pellet
  • the supernatant is removed and spun at a faster speed so the next heaviest organelle is forced to the bottom
48
Q

How does a cell become specialised

A

Every cell contains genes needed for it to develop into a different cell BUT only some of these genes are switched on (expressed) and the rest of switched off

49
Q

What is a tissue

A

A collection of similar cells that perform specific function

50
Q

Examples of tissues

A

Epithelial and xylem

51
Q

What is an organ

A

A combination of tissues coordinates to perform a variety of functions

52
Q

What tissues does the stomach have

A
  • muscle to churn and mix the contents
  • epithelium to protect the stomach wall and produce secretions
  • connective tissues to hold other tissues together
53
Q

What tissues do leaves have

A
  • palisade mesophyll made from palisade cells for photosynthesis
  • spongy mesophyll for gaseous diffusion
  • epidermis to protect the leaf and allow gaseous diffusion
54
Q

What are the organ systems in animals

A

Digestive, respiratory and circulatory

55
Q

Are eukaryotes or prokaryotes bigger

A

Eukaryotes are bigger

56
Q

Structure of a bacterial cell

A

Cell wall - physical barrier that excludes certain substances and protects against mechanical damage and osmotic lungs

Capsule - protects bacterium from other cells and helps groups of bacteria stick together

Cell-surface membrane - controls entry + exit of chemicals

Circular DNA - holds the genetic info for the replication of bacterial cells

Plasmid - holds the genes that may aid the survival of bacteria in adverse conditions

57
Q

Virus structure

A

(Acellular, nonliving)

  • contain nucleic acids (like DNA or RNA) as genetic material -> enclosed within a protein coat called a capsid
  • some viruses have a lipid envelope -> the lipid envelope (if present and capsid if not) have attachment proteins that allow a virus to identify and attach to a host cell
58
Q

Prokaryotic and eukaryotic properties

A

Prokaryotic
- no nucleus
- DNA is not associated with proteins
- some DNA may be in the form of plasmids
- no membrane-bounded organelles
- no chloroplasts
- ribosomes are smaller (70S)
- cell wall are made of murein (peptidoglycan)
- may have a mucilaginous layer called a capsule

Eukaryotic
- have a nucleus with a nuclear envelope
- DNA is associated with proteins called histones
- no plasmids
- membrane - bounded organelles like mitochondria are present
- chloroplasts present in plants and algae
- ribosomes are larger (80S)
- where present cell wall is made out of cellulose (chitin in fungi)
- no capsule

59
Q

What is the cell wall in fungi made out of

A

Chitin

60
Q

Functions of membranes within cells

A
  • control exit + entry of materials in organelles like mitochondria and cytoplasm
  • separate organelles from cytoplasm so specific reactions can take place within them
  • provide an internal transport system eg ER
  • isolate enzymes that might damage the cell eg lysosomes
  • provide surfaces on which reactions can occur eg protein synthesis on ribosomes on the ER
61
Q

Structure of cell surface membrane

A

Phospholipid bilayer

62
Q

What significant about phospholipids

A

They are polar as they have 2 ends that act differently

63
Q

Function of the phospholipid bilayer in the cell membrane

A
  • allow lipid soluble substances to enter and leave the cell
  • prevent water soluble substances from entering and leaving the cell
  • make the membrane flexible
64
Q

What 2 ways are proteins embedded in the cell surface membrane bilayer

A
  1. Some are in the surface or partly embedded -> give mechanical support or act as cell receptors
  2. Others completely span the bilayer - some are protein channels to transport water soluble molecules across the membrane + others are carrier proteins that change shape and carry molecules across the membrane
65
Q

Functions of proteins in the cell membrane

A
  • structural support
  • act as channels, transporting water soluble substances
  • allow active transport across the membrane
  • act as receptors
  • help cells adhere to each other
66
Q

How permeable is the cell surface membrane

A

Gene really most molecules don’t freely diffuse across it

67
Q

Why don’t molecules generally freely diffuse across the cell membrane

A
  • too large to pass through channels
  • not soluble in lipids
  • are the same charge as the charge on the protein channels > so are repelled
  • are polar > so can’t pass through the non-polar hydrophobic tails
68
Q

What does cholesterol do in the cell membrane

A
  • add strength to the membranes
  • very hydrophobic so help prevent loss of water and dissolved ion from the cell
  • they also pull the fatty acid tails of the phospholipid molecules -> limiting their movement without making it too rigid
69
Q

Function of cholesterol in the cell membrane

A
  • reduces lateral movement of other molecules including phospholipids
  • make the membrane less fluid at high temps
  • prevent leakage of water + dissolved ions from the cell
70
Q

What are glycolipids made from

A

A carbohydrate covalently bonded with a lipid

71
Q

What other components does the cell membrane have

A

Cholesterol
Glycolipids
Glycoproteins

72
Q

Function of glycolipids in the cell membrane

A
  • act as recognition sites
  • helps maintain the stability of the membranes
  • helps cells to attach to one another and so form tissues
73
Q

What are glycoproteins

A

Carbohydrate chains attached to extrinsic proteins on the outer surface

74
Q

Function of glycoproteins in the cell membrane

A
  • act as cell surface receptors
  • act as recognition sites
  • help cells to attach to one another and so form tissues
  • allows cells to recognise one another
75
Q

The fluid-mosaic model

A
  • fluid -> the phospholipid molecules can move relative to one another
  • mosaic -> proteins are embedded in the surface of the membrane like a mosaic
76
Q

Types of movement across the cell membrane

A
  • diffusion
  • facilitated diffusion
  • active transport
  • osmosis
77
Q

What is diffusion

A

Net movement of molecule or ions from an area of high concentration to an area of low concentration until evenly distributed

-> passive process (no energy needed)

78
Q

What affects rate of diffusion

A
  • conc gradient -> the greater the difference the faster
  • area over which it takes place
  • thickness of exchange material -> the thinner the faster
79
Q

What is facilitated diffusion

A

Exactly like diffusion but protein and/or carrier proteins are involved

80
Q

What proteins are involved in facilitated diffusion

A

Carrier proteins and protein channel

81
Q

Structure of Protein channels

A

Water filled hydrophilic channels across the membrane

82
Q

What do protein channels do

A
  • allow specific water soluble ions to pass through
  • the channels are selective -> only open in the presence of a specific ion which binds to them and causes them to change shape so it opens on 1 side and closes on the other
83
Q

How do carrier proteins work

A
  • when a specific molecule binds with the protein it causes it to change shape so that the molecule is released on the other side of the membrane
84
Q

What is active transport

A

The movement of molecules of ions or out a cell from an area of lower concentration to an area of higher concentration using ATP and carrier proteins

85
Q

How does active transport differ from passive forms of transport

A
  • metabolic energy in form of ATP is needed
  • substances are mixed against concentration gradient
  • carrier proteins are used
  • very selective process
86
Q

Why does a graph of facilitated diffusion level off

A

Protein channels are saturated

87
Q

What is osmosis

A

The movement of water from a region of high water potential to an area of lower water potential through a partially permeable membrane

88
Q

What is water potential

A

The pressure created by water potential

89
Q

What is the water potential of pure water

A

Under standard conditions of temp and pressure it is 0

90
Q

What does the addition of a solute to pure water cause

A

It will lower the water potential, so the water potential of a solution is always less than 0 (so a negative value)

91
Q

What is hypotonic

A

The solution has a higher water potential than the inside of the cell so water moves in by osmosis

92
Q

Hypotonic solution in animal cell

A

Animal cells swell up and will eventually burst as their cell membrane isn’t strong enough to withstand pressure (lysis)

93
Q

Hypotonic solution in a plant cell

A

They swell up but don’t burst because their cell wall protects them -> their vacuoles expand and they become turgid as the cell membrane pushes on the cell wall

94
Q

What is isotonic

A

No difference in water potential between the cell and surrounding solution so no net movement of water

95
Q

What is hypertonic

A

When the solution has lower water potential than the inside of the cell so water will move out of the cell by osmosis

96
Q

Hypertonic solution in animal cell

A

Animal cells will shrivel as they lose water from their cytoplasm

97
Q

Hypertonic solution in plant cells

A

Plant cells are protected from shrinking but their vacuoles shrink and eventually their cell membranes pull away from the cell walls -> this is plasmolysis

98
Q

Increasing the rate of movement across the ileum

A

The epithelial cells lining the ileum have microvilli which provide more SA for the insertion of carrier proteins

99
Q

Why must active transport happen as well as diffusion in absorption

A

Because diffusion only works until the concentrations are equal meaning not all glucose and amino acids are being transported so active transport is used

100
Q

What is the name for how amino acids and glucose are absorbed into the blood and why

A

Co-transport because the glucose or amino acids have been transported in along with sodium ions which have been actively transported out by the sodium-potassium pump

101
Q

Where and how does the co-transport of glucose happen

A

In one type of protein-carrier molecule

  1. Na+ are actively transported out of the epithelial cells into blood
  2. This now leads to a lower concentration of Na+ in the cell
  3. This causes Na+ to move into the epithelial cells from the ileum by facilitated diffusion -> this also brings in a glucose molecule (co-transport)
  4. Glucose now moves down the concentration gradient from the epithelial cell to the blood by facilitated diffusion
102
Q

What is it that powers the movement of glucose and amino acids into cells and why

A

Not ATP but the sodium ion concentration gradient as the glucose molecules are moving against the concentration gradient and the sodium ions are moving down it easily

Bio Alevel (5 decks)

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