12 Biology > A-level : Cell Structure > Flashcards

A-level : Cell Structure Flashcards

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1
Q

What organelles do bacteria and plant cells have in common?

A

Cytoplasm, cell wall, cell membrane and ribosomes

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2
Q

What does membrane bound mean?

A

A component that is surrounded by one or more lipid-bilayer membrane that creates a distinct separate component within the cell

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3
Q

What’s the pilli and where do find it?

A

It’s a fluffy outer layer on SOME prokaryotic cells.
It’s used for the exchange of plasmids and to be able to stick to the host cells

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4
Q

What’s the slime capsule and where do u find it

A

On the outer layer of SOME prokaryotic cells
It makes it harder to detect by the immune system and stops desiccation (drying out)

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5
Q

How is DNA stored in prokaryotic cells?

A

In a free floating ‘naked’ circular loop of DNA
Also can be found in plasmids in SOME cells

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6
Q

What’s the cell wall of prokaryotic cells made of

A

Murein

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7
Q

What’s the flagellum

A

Allows for prokaryotic cells to swim (not on all)

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8
Q

What size are the ribosome in prokaryotic cells?

A

70s - very small, smaller than eukaryotics 80s

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9
Q

What’s the cell walls of eukaryotic cells made of

A

Plants - cellulose

Fungi - chitin

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10
Q

What size are ribosome in eukaryotic cells?

A

80s

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11
Q

What’s the structure and function of the nucleus?

A

STRUCTURE: Surrounded by a double membrane called the nuclear envelope. The nuclear envelope has pores. The nucleolus does not have a membrane around it, it contains RNA. Also contains chromatin

FUNCTION: Is the control center of the cell, stores the organisms genomes, transmits genetic information and provides the instructions for protein synthesis.

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12
Q

What’s the double membrane surrounding a nucleus called?

A

The nuclear envelope, this contains pores.

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13
Q

What’s chromatin?
How does it change between when the cell is not dividing and when it is?

A

The genetic material consisting of DNA wound around histone proteins.
When the cell is not dividing, chromatin spreads out/extends. Whereas when the cell is about to divide, chromatin condenses and coils tightly into chromosomes.
These make us nearly all the organisms genome.

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14
Q

What’s the nucleolus?

A

Where ribosomes are made

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15
Q

At some point why does the inner and outer layer of the nucleus envelope fuse?

A

In some points of the nuclear envelope the inner and outer membrane fuse that allows dissolved substances and ribosomes to pass through. The pores also allow larger substances such as mRNA to leave the nucleus, also some other substances such as steroid hormones.

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16
Q

What’s the function and structure of a cell membrane?

A

STRUCTURE: Is a flexible barrier made of a phospholipid bilayer with embedded proteins and other molecules.

FUNCTION: Regulates the in/out movement of molecules through the cell membrane. Also aids with cell signaling and communication

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17
Q

What’s the function of the phospholipid bilayer in cell membranes?

A

Each phospholipid molecule has a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail. The hydrophobic tails face inwards, away from the aqueous environment, forming a barrier to water-soluble substance.

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18
Q

What’s the function of embedded proteins in cell membranes?

A

Channel and Carrier Proteins: facilitate the transport of specific molecules across the membrane.
Receptor proteins: bind to signaling molecules like hormones, triggering cellular responses.

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19
Q

What’s the function and structure of a cell wall?

A

STRUCTURE: On the outer layer of the plasma membrane. Made of cellulose in plant cells whereas in fungal cells its made of chitin. It is permeable so that stuff can pass though. In a cellulose wall it’s made of bundles of cellulose fibers.

FUNCTION: Holds the shape of the cell, contains mechanical protection to the cell and prevents bursting if an abundance of water enters the cell

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20
Q

What’s the function and structure of ribosomes?

A

STRUCTURE: Small spherical organelles, about 20nm in diameter. Made of ribosomal RNA. Produced in the nucleolus, as two separate subunits which pass through the nuclear envelope and into the cell cytoplasm in which they combine. Some remain free in the cytoplasm whereas some attach to the endoplasmic reticulum. (RER)

FUNCTION: Bind to the exterior of the RER, mainly for synthesizing proteins that will be exported outside the cell. Free enzymes in the cytoplasm (sometimes in bundles) are primary the site of assembly of proteins that will be used inside the cell.

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21
Q

What’s the function and structure of the rough endoplasmic reticulum?

A

STRUCTURE: A system of membranes, containing fluid filled cavities (cisternae) that are continuous with the nuclear membrane.
Coated in ribosomes

FUNCTION: Is the intracellular transport system: the cisternae form channels for transporting substances from one area of the cell to the other. Also provides a large surface area for ribosomes which assemble amino acids into proteins. These proteins then actively pass through the membrane of the cisternae and are transported to the Golgi apparatus for modification and packaging.

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22
Q

What’s the function and structure of the smooth endoplasmic reticulum?

A

STRUCTURE: A system of membranes, containing fluid filled cavities (cisternae) that are continuous with the nuclear membrane. NO ribosomes on the surface. Contains enzymes

FUNCTION: These enzymes catalyze reactions involved in lipid metabolism such as:
-synthesis of cholesterol
-synthesis of lipids/phospholipids needed by the cell
-synthesis of steroid hormones
It is also involved with absorption, synthesis and transport of lipids (from the gut)

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23
Q

What’s the structure and function of the golgi apparatus?

A

STRUCTURE: Consists of a stack of membrane-bound flattened sacs. Secretory vesicles bring material to and from the golgi apparatus.

FUNCTION: Where proteins are modified for example by: adding sugar molecules to make glycoproteins, adding lipid molecules to make lipoproteins, being folded into their 3d shape.
They are then packaged into vesicles that are pinched off and then stored in the cell or moved to the plasma membrane which are either incorporated into the plasma membrane or exported outside the cell

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24
Q

What’s the function and structure of the cytoplasm?

A

STRUCTURE: A jelly like substance that fills cells, has substances within it.

FUNCTION: The site of many chemical reactions and contains many substances (such as ribosomes)

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25
What’s the function and structure of mitochondria?
STRUCTURE: Spherical and rod-shaped, they are surrounded by a double membrane. Filled with fluid filled cavities that are highly folded and are considered a “matrix” FUNCTION: The site of ATP (energy currency) production during aerobic respiration. They are self replicating, so more can be made if the cells energy needs increase. Has an abundance of cells where metabolic activity takes place, for example in liver cells and at synapses between neurones where neurotransmitter is synthesized and released.
26
What does intra mean
Within
27
What does inter mean
Between
28
Whats cisternae?
Flattened folds of membrane
29
What's the structure and function of chloroplasts?
STRUCTURE: Larger organelles 4-10 micrometers long, found in plant cells and in some protoctists. Surrounded by a double membrane. The inner membrane is continuous of stacks of flattened membrane sacs called thylakoids, which contains chlorophyll. Each stack or pile or thylakoids is called a granum. The fluid filled matrix is called the stroma. Also contains loops of DNA and starch grains FUNCTION: The site of photosynthesis. The first stage of photosynthesis when light energy is trapped by chlorophyll and used to make ATP, occurs in the grana. Water is also split to supply hydrogen ions. The second stage, when hydrogen reduces carbon dioxide, using energy from ATP, to make carbohydrates, occurs in the stroma. Chloroplasts are abundant in leaf cells, particularly the palisade mesophyll layer.
30
What's the structure and function of vacuole?
STRUCTURE: Surrounded by a membrane called the tonoplast, and contains fluid FUNCTION: Only plant cells have a large permanent vacuole, filled with water and solutes to maintain cell stability, because when full it pushes against the cell wall making it turgid. When all of the plants cells are turgid then it helps to hold the overall plants shape, especially in non-woody plants.
31
What's the structure and function of lysosomes?
STRUCTURE: These are small bags, formed from the Golgi apparatus. Each is surrounded by a single membrane. Contain powerful hydrolytic enzymes. Abundant in phagocytic cells such as neutrophils and macrophages that can ingest and digest invading pathogens such as bacteria. FUNCTION: Lysosomes keep the powerful hydrolytic enzymes separate from the rest of the cells. Can engulf old organelles and foreign matter, digest them and return the digested components to the cell for reuse.
32
What's the structure and function of centrioles?
STRUCTURE: Consists of 2 bundles of microtubules at right angles to each other. The microtubules are made of tubulin protein subunits, and are arranged to form a cylinder. FUNCTION: Before a cell divides, the spindle, made of threads of tubulin, forms from centrioles. Chromosomes attach to the middle part of the spindle and motor proteins walk along the tubulin threads, pulling the chromosomes to opposite ends of the cell. Centrioles are involved in the formation of cilia and undulipodia. Centrioles are usually absent from higher cells of plants but may be present in some unicellular green algae.
33
What's the structure and function of cilia and undulipodia?
STRUCTURE: Protrusion from the cell and are surrounded by the cell surface membrane. Each contains microtubules. They are formed from centrioles FUNCTION: The epithelial cells lining your airways each have many hundreds of cilia that beat and move the band of mucus. Nearly all cell types in the body have one cilium that acts as an antenna. it contains receptors and allows the cell to detect signals about its immediate environment. The only type of human cell to have an undulipodium (a longer cilia) is a spermatozoon. The undulipodium enables the spermatozoon to move.
34
What's the structure and function of the cytoskeleton?
STRUCTURE: A network of protein structures within the the cytoplasm consisting of: rod-like microfilaments (made of actin) and microtubules (made of tubulin) The cytoskeletal motor proteins, myosins, kinesins and dyneins, are molecular motors. They are also enzymes and have a site that binds to and allows hydrolysis of ATP as their energy source FUNCTION: The protein microfilaments within the cytoplasm stabilize and hold mechanical strength of the cells shape and allows cell movement. Microtubules also provide shape and support to cells, and help substances and organelles move through the cytoplasm within a cell.
35
Whats ATP?
(adenosine triphosphate) is the primary energy-carrying molecule used by cells to power biological processes
36
How do microtubules in the cytoskeleton help to move substances and organelles through the cell?
They form the track along which motor proteins (dynein and kinesin) walk and drag organelles to from one part of the cell to the other. They form the spindle before a cell divides, these spindle threads enable chromosomes to be moved within the cell. Microtubules also make up cilia, undulipodia and centriholes.
37
What are intermediate filaments?
They're made of a variety of proteins. They: - Anchor the nucleus within the cytoplasm -Extend between cells in some tissues, between special junctions, enabling cell-cell signaling and allowing cells to adhere to a basement membrane, therefore stabilizing tissues
38
What's hydrolysis?
Hydrolysis is a chemical reaction where a water molecule is added to break a covalent bond, breaking down larger molecules (polymers) into smaller units (monomers)
39
How are centrioles involved in the formation of cilia and undulipodia?
Before the cilia form, the centriole multiply and line up beneath the cell surface membrane Microtubules then sprout outwards from each centriole, forming cilium or undulipodium
40
Whats the 2 main components of the cytoskeleton
Microfilaments and Microtubules
41
Whats the roles of the cyctoskeleton
Provides mechanical strength Holds organelles in place Role in cell division - form spindle fibres Maintains cell stability
42
Where is mRNA made?
In the nucleus, goes out through the pores. It must be produced as the nucleus is too big to exit the nucleus
43
How do proteins move around the cell?
Through motor proteins carrying them in veiscles along the cytoskeleton
44
Explain step by step protein synthesis
-The nucleolus synthesisers ribosomes for protein synthesis in the RER - mRNA is manufactured as a copy of the protein gene instruction. mRNA exits the nuclear envelope through pores. -mRNA attaches to the ribosome on the RER and produces protein -These proteins are "pinched off" into vesicles to travel toward the golgi apparatus - They enter through the golgis cis face where proteins processed and packaged, ready for release. - Theyre once again "pinched off" and taken out the trans face, theyre then carried alone the cytoskeleton by motor proteins. The vesicles then fuses with the plasma membrane which opens and releases protein molecules. (Exocytosis)
45
Whats a SEM?
Scanning Electron Microscope - a technique that uses a focused beam of electrons to scan a sample's surface, producing high-resolution images that are 3D and black and white.
46
Whats a TEM?
Transmission Electron Microscope - A type of microsopoe that passes a beam of electrons through a sample to produce a 2D black and white image of the inside of a cell. Only shows one cross section. It has the highest possible magnification and resolution.
47
Whats the name for using multiple stains to distinguish different parts of a specimen?
Differential staining
48
What angle and why should you place a cover slip?
45 degrees - to reduce the chances of air bubbles
49
Why use a stain?
To enhance contrast so its easier to distinguish between tissues,organelles etc
50
What can you change when looking at a microscope and what cant you? (m+r)
You can change magnification - cahnging the objective lenses and adjusting focusing knobs You cant change the resolution, you can only buy a higher resolution microscope
51
What are biological membranes composed of?
A bilayer of phospholipids with embeded cholesterol and free to move proteins (channels,antigens,carriers,enzymse and receptors). There are also glycoproteins and glycolipids on the surface. Together known as glycocalyx.
52
What do the head and tails look like in a biological membrane
The tails face inward as theyre hydrophobic and can therefore not access water.
53
What are phospholipids composed of?
Glycerol, 2 fatty acids and a phosphate group
54
How many molecules thick are the phospholipids?
2
55
Whats the cell walls of plants, fungi and bacteria made of?
Plants - Cellulose Fungi - Chitin Bacteria - Peptidoglycan
56
What's the function of biological membranes?
- They serve as a barrier between the inside and outside of the membrane - Organelle membranes seperate cell components to the cyctoplasm. - Holds enzymes and other ocmponents in place of some metabolic pathways - A site of chemical reactions -Controls what substances go in and out the cell as it has a partially permeable membrane - Has receptor signals to detect cells
57
Who proposed the fluid mosaic model?
Singer and Nicholson
58
What’s the structure and role of cholesterol in biological membranes?
STRUCTURE:Between the phospholipids, can span across the entire membrane or just a small part. FUNCTION: Regulates membrane fluidity. When cold the cholesterol between the heads keeps the phospholipids at a distance so they don’t freeze. When hot the cholesterol between the tails holds the bilayer together and therefore stabilises it. They also increase impermeability of the membrane and therefore stabilising and strengthening the cell
59
What’s the structure and function of proteins in biological membrane?
STRUCTURE: There’s a variety of protein structures. When attached to the outside they’re known as extrusive or peripheral. When across the entire membrane they’re known as transmembrane or transport proteins. When inside they’re known as intrusive or integral proteins. 2 transport proteins next to eachother are known as a channel protein. FUNCTION: Allows things to pass through their channels. Allow substances to attach at their binding sites.
60
What’s the structure and function of the glycocalyx?
STRUCTURE: They’re external components containing carbohydrate chains. Certain substances allow them to bind to the cells surface. The glycoproteins are proteins and carbohydrate chains whereas the glycolipids are lipids and carbohydrate chains. FUNCTION: They’re receptors of three main types: 1. Signalling of hormones and neurotransmitters. 2. Endocytosis 3. Cell adhesion and stabilisation. And cell markers/ antigens for cell recognition
61
What’s the function and structure of phospholipids?
STRUCTURE: Head is a phosphate group, non-polar and hydrophilic. The tail is a fatty acid which is polar and hydrophobic. Together they make a bilayer in biological membranes with the tails facing inwards. FUNCTION: Barrier between the inside and outside. It also stops water-soluble substances from passing through such as sugar and proteins
62
Why does membrane permeability increase as temperature increases?
Proteins (as the hydrogen + ionic bonds are broken) cytoskeleton and enzymes will begin to denature and therefore increase the permeability of the membrane. Furthermore there will be more kinetic energy and therefore more membrane fluidity, leaving areas where there may be pigment leakage. Cholesterol can again stabilise the membrane and reduces this increase. Infolding,cell signalling, enzymic reactions an also be affected by changes in fluidity.
63
Is saturated a double or single bond?
Single
64
What happens to membrane structure when temperature is decreased?
The saturated fatty acids become fluid and permeable. If however there are more unsaturated fatty acids in a membrane then they counteract this because as they become compressed the cholesterol in their tails push adjacent phospholipids away. Therefore this helps to maintain the fluidity as cholesterols presence stops the phospholipids from packing too closely together
65
How do solvents affect membranes
A solvent will dissolve lipids, therefore increasing the membranes permeability.
66
What 3 ways can things move across a cells membrane?
Diffusion (passive) Facilitated diffusion (passive) Active transport (requires active transport)
67
What’s diffusion
The movement of particles from a high to low concentration across a partially permeable membrane. It does not require ATP
68
Factors effecting the rate of diffusion
Temperature Surface area: Volume ratio Concentration gradient Diffusional Distance Size of diffusing particle (smaller=lighter=quicker)
69
When will diffusion “stop”
When there is no net diffusion - There’s no overall direction which all the particles are moving in. The particles will move around back and forth potentially but not in one direction.
70
What does simple diffusion move across? And why
Lipid soluble molecules Eg: steroid hormones Small molecules eg: CO2 BECAUSE they’re lipid soluble so can dissolve in the bilayer and diffuse across it. They’re small and can fit between the gaps in the phospholipid molecules
71
What does facilitated diffusion (carrier/channel) move across? And why
Channel proteins: Hydrophilic channels for ions and water Carrier proteins: Large glucose molecules - because the carrier proteins will move and change shapes to facilitate the shape and size of the molecule. Therefore the glucose moves through carrier proteins as they’re large and carrier proteins are the only ones who will facilitate it. Attach to transmembrane carrier proteins which will bind to one on one side and then bind on the other.
72
Whats the symbol and units of water potential?
A trident and its units are kilopascals (kPa)
73
What’s the water potential of pure water?
0
74
If you increase the concentration of salt in a glass of pure water, what happens to the water potential?
The water potential will decrease as the amount of solute dissolved increases. The water molecules no longer become free to move, as they become associated with the solute particles in solution.
75
Whats osmosis
The movement of free water molecules across a partially permeable membrane, from a region of high water potential to a region of lower water potential, until the water potentials on both sides of the membrane are equal.
76
What’s turgidity?
When a plant cell has a high internal water potential, therefore leading it to appear “full” Although it does not burst as its cell wall holds its structure.
77
Whats plasmolysis?
When a plant cell has an extremely low internal water potential leading the cell membrane to pull away from the cell wall as water leaves.
78
Whats haemolysis?
When an animal cell has a very high water potential internally, leading it to burst open.
79
Whats crenation?
When an animal cell has a low water potential internally leading it to shrink and appear wrinkled.
80
Whats exocytosis ?
How large molecules are exported out of cells by a vesicle containing them moves towards and then fuses to the plasma membrane. This requires ATP to move the vesicle and fuse to the membrane.
81
How much ATP is used when a motor protein moves along the cytoskeleton whilst dragging its cargo?
Every step the motor protein takes a molecule of ATP is hydrolysed.
82
Whats hypotonic,isotonic and hypertonic?
Hypotonic - Causes lysis - Higher water potential outside the cell Isotonic - Dynamic equilibrium Hypertonic - Causes crenation - Lower water potential outside the cell
83
Whats water potential
The tendency of free water molecules to diffuse from one region to another. Given with the trident symbol and the unit KPa
84
Whats active transport?
Active transport is the movement of molecules/ions into or out of a cell from a region of lower concentration to a region of high concentration using ATP and carrier proteins.
85
Whats endocytosis
Things entering a cell
86
Whats exotycosis
Things exiting a cell
87
Whats phagocytosis
Engulfing of something
88
Whats pinocytosis
The engulfing of liquid/drinking. For example a cell engulfing extra-cellular fluid
89
Does endo and exo cytosis require energy
Yes it does as theres energy required to form and move vesicles.
90
Explain active transport
1. Molecule binds to a carrier protein, on one side of the membrane 2. ATP is hydrolysed to produce ADP and P. 3. The phosphate binds to the carrier protein on the other side of the membrane causing the carrier protein to change shape. 4. The molecule travels through the newly opened channel 5. The ADP and P then recombine to ATP 6. The carrier protein returns to its original shape
91
Describe the pathway that a protein takes after translation
Transport vesicles move it along the RER Modification takes place at the golgi apparatus Theyre packaged into secretory vesicles and moved along the cytoskeleton by motor proteins. Vesicle fuses to the cell membrane surface and is secreted through exocytosis
12 Biology
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