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2.1.1 Cell Structure > Ultrastructure of Cells > Flashcards

Ultrastructure of Cells Flashcards

1
Q

What is the structure and function of the cilia?

A

Structure:
- Hair like extensions that protrudes some cells
- Cilia can be mobile or stationary, and each cilium (singular for cilia) contains two central microtubules surrounded by nine pairs of microtubules like a wheel (this is known as the 9 + 2) arrangement

Function:
- Stationary cilia are present on the surface of many cells and have an important function in sensory organs e.g. nose
- Mobile cilia beat in a rhythmic manner, creating a current, and cause fluids or objects adjacent to the cell to move

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2
Q

What is the function of the vacuole?

A

For storage:
- Contains waste (later removed by the leaf)
- Contains pigments: anthocyanins -> to attract pollinators for seed dispersal
- Contains cell sap -> fluid containing salts, amino acids and sugars

Maintains turgor pressure:
- water enters the vacuole (swells), so contents of the cell push against the cell wall (pressure) and maintain a frigid framework for the cell

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3
Q

What is the structure and function of the mesosome?

A

Structure:
- Infolding of the membrane that increase the surface area

Function:
- Supports respiration and secretion
- Helps in the synthesis of the cell membrane, replication of DNA and protein synthesis

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4
Q

What is the endosymbiotic theory? And draw it.

A

Answers on revision card

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5
Q

What is the meaning of ‘ultrastructure’?

A

The structure within cells that are only visible at a resolution higher than that of a standard light microscope i.e. using an electron microscope.

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6
Q

What is compartmentalisation?

A

The separation of different parts of the cell with different functions by using membranes.

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7
Q

What is the function of the nucleus?

A
  • Nuclear envelope protects and encloses DNA from cytoplasmic enzymes
  • Nucleolus produces rRNA and ribosomes
  • Pores allow for mRNA and ribosomes to travel out as well as allowing enzymes and signalling hormones to enter
  • site of replication and transcription

There are two types of chromatin:
- heterochromatin -> gene expression is switched off
- euchromatin -> gene expression is switched on

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8
Q

Draw and label a bacterial cell.

A

Answers on revision card

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9
Q

Draw and label the nucleus.

A

Answers on revision card

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10
Q

What is the structure of the nucleus?

A
  • Contains genetic information
  • Surrounded by a double membrane nuclear envelope which contains nuclear pores
  • Contains chromatin made from histone proteins and DNA -> chromatin condenses to form chromosomes during cell division
  • Contains one or more nucleolus
  • The outer membrane is continuous with the RER
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11
Q

Draw and label the mitochondria.

A

Answers on revision card

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12
Q

What is the structure of the mitochondria?

A
  • Double membrane organelle
  • Contains a small amount of mt(mitochondrial) DNA
  • Inner membrane is folded to form cristae
  • Has a fluid centre called the matrix where ribosomes are found
  • The membrane forming the cristae contain the enzymes used in aerobic respiration
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13
Q

What is the structure and function of the vesicle?

A

Structure:
- A small fluid-filled sac in the cytoplasm surrounded by a membrane

Function:
- Has transport and storage roles
- Transports substances in and out of the cell via the plasma membrane and between organelles

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14
Q

What is the structure and function of lysosomes?

A

Structure:
- A round organelle surrounded by a membrane, with no clear internal structure
- Specialised forms of vesicles that contain hydrolytic enzymes, called lysozyme

Function:
- Enzymes are responsible for breaking down waste materials in cells, old organelles, storage molecules, breaking down pathogens (ingested by phagocytic cells) and plays a role in programmed cell death, apoptosis

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15
Q

How do the lysosome break down old organelles/ pathogen?

A

(1) Lysosome containing hydrolytic enzymes (lysozyme) produced by the golgi apparatus

(2) Phagocytosis of material e.g. bacteria in phagocytic white blood cells

(3a) Fusion of the membrane of the phagocytic vacuole with the membrane of the lysosome

(3b) (or) fusion of organelle with lysosome

(4) exocystosis of the digested material into the exterior of the cell

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16
Q

What is the function of the cytoskeleton and what are the three main components?

A

Function:
- Mechanical strength, stability, support and helps maintain integrity
- For cell movement
- For movement of organelles within the cell
- Holds organelles in place

Parts of the cytoskeleton:
- Intermediate filament
- Microfilaments
- Microtubules

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17
Q

What is the microtubule?

A
  • Globular tubulin protein polymerase to form tubes that are used to form a scaffold-like structure that determines the shape of the cell
  • Act as tracks for movement of organelles around the cell
  • Spindle fibres (which have a role in the physical segregation of chromosomes in cell division) are composed of microtubules
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18
Q

What are the intermediate filaments

A
  • Give mechanical strength -> helps resist compression forces
  • Helps maintain their integrity
  • Support and stability for cell shape -> holding organelles in place e.g. anchoring nucleus
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19
Q

What is the structure and function of centrioles?

A

Structure:
- Found in animal cells (not in flowering plants or fungi)
- Hollow fibres formed of microtubules
- Two centrioles at right angles to each other from centrosomes, which assembles and organises spindle fibres during cell division

Function:
- Involved in the separation of chromosomes

20
Q

How do cilia bring about motion?

A

Pairs of parallel microtubules slide over eachother causing the cilia to move in a beating motion

21
Q

What is the structure of SER and RER?

A
  • A network of membrane enclosing flattened sacs and tubules called cisternae
  • These sheets of membranes originate from/are continuous with the nuclear envelope (outer membrane of nucleus)
  • The surface of RER is covered in ribosomes
  • The surface of SER isn’t covered in ribosomes
  • The interior of the cisternae is called the lumen
22
Q

What is the function of the RER?

A
  • Site of protein synthesis (at the ribosomes)
  • Processes and folds newly formed polypeptides made at the ribosomes
  • Packages product into transport vesicles
  • Site of glycoprotein/protein synthesis and is responsible for the transport of these proteins
23
Q

What is the function of the SER?

A

Involved in the synthesis, processing and storage of lipids, carbohydrates and steroids

24
Q

What is the structure of ribosomes?

A
  • Found freely in the cytoplasm or is attached to endoplasmic reticulum forming RER
  • Made up of protein and ribosomal RNA (rRNA)
  • They are not surrounded by a membrane
  • 80S (sedimentation coefficient) ribosomes (composed of 60S large subunit and 40S small subunit) are found in eukaryotic cells
  • 70S (sedimentation coefficient) ribosomes (composed of 50S large subunit and 30S small subunit) are found in prokaryotic cells
25
Q

What is the function of ribosomes?

A
  • Site of translation in protein synthesis
  • Site of protein synthesis
26
Q

What is the structure of the golgi apparatus? And draw/label a diagram.

A
  • Stacks of fluid-filled membrane bound sacs called cisternae
  • Vesicles are often seen at the edge of the sacs

Diagram on the revision card

27
Q

What is the function of the golgi apparatus?

A
  • Processes and modifies proteins (from RER) and lipids (from SER) before packaging them into Golgi vesicles OR in secretory vesicles if the proteins are destined to leave the cell, or lysosomes, which stay in the cell

Modifications of the proteins and lipids include:
- Adding carbohydrates to proteins and lipids to form glycoproteins and glycolipids
- Prosthetic groups of protein added e.g. haemoglobin

28
Q

How are extracellular proteins produced, transported and secreted?

A

(1) mRNA copy of the gene for protein is made in the nucleus

(2) mRNA leaves the nucleus pores

(3) mRNA attaches to ribosome on RER. Ribosome translates the code to assemble the protein inside lumen of RER

(4) protein molecules ‘pinched off’ in transport vesicles to the golgi apparatus (vesicles fuses with it), which processes and modifies the protein

(5) package protein molecules are ‘pinched off’ in secretory vesicles from the golgi apparatus and move towards the plasma membrane (some vesicles form lysosomes which contain enzymes to be used in the cell)

(6) secretory vesicle fuses with plasma membrane which opens to release proteins (exocytosis)

29
Q

What is the structure of the cell wall?

A
  • A rigid structure that surrounds plants, algae and fungi etc
  • Consists of polysaccharides cellulose in plants, peptidoglycan in prokaryotes and chitin in fungi which provides the structural support for these cells
  • There is a thin boundary layer between adjacent cells called the middle lamella

Cell walls can contain:
- Lignin in wood
- Cutin in waxy cuticle
- Suberin in roots

  • Arrangement of cellulose fibres in plants determines leaf shape
30
Q

What is the function of the cell wall?

A
  • Provides mechanical support and strength
  • Provides osmotic support because the high tensile strength stops it from bursting
  • Highly permeable allowing water to pass through easily
  • Protects cells from invading pathogens
31
Q

What is the structure of the vacuole?

A
  • Membrane lined sacs containing cell sap
  • Its membrane is called the tonoplast which is selectively permeable
  • In plant cells vacuole are large and permanent while in animal, cells they are samll and not permanent
32
Q

What is the structure of the plasma membrane?

A
  • Phospholipid bilayer with cholesterol and protein embedded in the surface
  • A boundary between a cell and its environment
  • Glycoproteins and glycolipids are also in the surface
  • It is selectively permeable
33
Q

What is the function of the plasma membrane?

A
  • The fluid mosaic model of the membrane refers to the fluidity of the membrane and the range of molecules in the membrane
  • The cholesterol is for supports/strength and reduces the fluidity
  • Proteins are for transport
  • The glycoproteins and glycolipids are for cell recognition and act as receptors
  • Regulates what enters/exits the cell
  • Site for chemical reactions
  • Site for cell signalling
34
Q

What is the plasmodesmata?

A

Small gaps in cell wall and middle lamella where the cytoplasm of adjacent cells meet

35
Q

What is the structure of the chloroplast? And draw a diagram.

A
  • Surrounded by a double membrane and contains an inner network of membranes called thylakoids which contain chlorophyll
  • Thylakoids are stacked in some parts of the chloroplast and are called grana (plural granum)
  • Grana are joined together by lamella(e) (thin flat pieces of thylakoid membranes)
  • Has a fluid center called stroma
  • Contains small circular DNA and ribosomes used to synthesize proteins required for chloroplast replication and photosynthesis

Diagram on the revision card

36
Q

What is the structure and function of the flagellum?

A

Structure:
- Made of longer microtubules than cilia
- Whip like extension that protudes from the cell
- The flagella of prokaryotes are thinner than those of eukaryotes and doesn’t have 9+2 arrangement

Function:
- Used primarily to enable cell motility and contracts to provide cell movement
- In some cells they are used as a sensory organelle detecting chemical changes in the cell’s environment

37
Q

What is the structure and function of microvilli?

A

Structure:
- Found in specialised animal cells
- They are cell membrane projects

Function:
- Used to increase the surface area of the cell surface membrane to increase the rate of exchange of substances

38
Q

What is the structure and function of the capsule?

A

Structure:
- A layer of slime outside the bacterial cell wall, composed of mainly polysaccharides or polypeptides

Function:
- Protects bacteria from being engulfed by eukaryotic cells such as immune cells in the immune system
- Helps in adherence to surfaces

39
Q

How does a flagellum produce motion? Draw a diagram.

A
  • The basal body attaches the filament comprimising the flagellum to the cell surface membrane of a bacterium
  • A molecular motor causes the hook to rotate giving the filament a whip-like movement whih propels the cell

Diagram on the revision card

40
Q

What is the structure and function of secretory vesicles?

A

Structure:
- Enclosed by an outer membrane known as the bilayer of lipids
- This bilayer consists of clusters of hydrophilic tails

Function:
- Moving molecules outside of the cell, through a process called exocytosis in response to extracellular signals
- The secreted product can either be a small molecule (such as histamine) or a protein (such as hormones or digestive enzymes)

41
Q

What is the structure and function of pili?

A

Structure:
- Short hair-like structures on the cell surface of prokaryotic cells

Function:
- Attaches the other bacterial cells
- They are involved in adherence to surfaces which facilitates infection

42
Q

What is the microfilament?

A
  • Contractile fibres formed from the protein actin
  • Responsible for cell movement and contraction during cytokinesis (where cytoplasm of a eukaryotic cell divides to form two daughter cells)
43
Q

What are the 3 stages of aerobic respiration?

A

1st stage: Glycolysis
- Occurs in the cytoplasm (outside the mitochondria)

2nd stage: Link reaction and krebs cycle
- Occurs in the matrix

3rd stage: Oxidative phosphorylation, electron transport chain and chemiosmosis
- Occurs in the mitochondrial matrix

44
Q

What is the function of the mitochondria?

A
  • Site of aerobic respiration and ATP production
  • Double membrane isolates reactions of the krebs cycle and electron transfer chain from the general cytoplasm
  • Inner membrane provides increased surface area for attachment of coenzymes and enzymes involved in the ETC
45
Q

What is the function of the chloroplast?

A
  • Internal membrane provides increased surface area for enzymes, proteins and pigment molecules necessary for photosynthesis
  • Site of photosynthesis

There are 2 stages of photosynthesis:
- 1st stage: light dependent reactions -> light energy is transferred to chemical energy (this occurs in the thylakoid membranes)

  • 2nd stage: light independent reactions -> CO2 is fixed into sugars (occurs in the stroma)
46
Q

What is the structure of sterols/cholesterol?

A

It is made up of a four carbon ring structure with a -OH (hydroxyl) group on the end

2.1.1 Cell Structure (2 decks)

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