Biology > Cell Structure > Flashcards

Cell Structure Flashcards

(55 cards)

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1
Q

Nucleus

A

-Surrounded by a nuclear envelope.
-Pores that allow DNA to leave.
-Contains chromatin (genetic material) that is spread out when cell is not dividing.
-Stores genome, transmits genetic information and provides the instructions for protein synthesis.

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2
Q

Nucleolus

A

-Dark space in nucleus.
-Contains RNA.
-Where DNA is used to synthesise ribosomes.

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3
Q

Cytoplasm

A

-Where organelles float.
-Soluble part is known as the cytosol.
-Water with dissolved substances.

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4
Q

Endoplasmic reticulum.

A

-Folded, fluid filled internal membranes called cisternae.
-Contains RER, SER and golgi.

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5
Q

Rough ER

A

-Near nuclear envelope.
-Contains ribosomes for protein synthesis.
-High energy cells have more RER.
-Intracellular transport system for substances around the cell.

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6
Q

Smooth ER

A

-On outside of RER.
-No ribosomes.
-Makes phospholipids.
-Contains enzymes that detoxify harmful products of the metabolism such as cholesterol and steroid hormones.
-Involved in absorption, synthesis and transport of lipids.

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7
Q

Vesicles

A

-Sacs that transport proteins and lipids through the cytosol.
-Also take modified proteins and lipids to fuse with the cell membrane.

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8
Q

Ribosomes

A

-Made of ribosomal RNA in the nucleus.
-Made of two separate subunits.
-Close together over an mRNA strand.
-Where proteins are synthesised from amino acids (from mRNA sequence).

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9
Q

Mitochondria

A

-Made up of two membranes with a fluid filled space between.
-Site of aerobic respiration.
-Where ATP is produced via oxidative phosphorylation during aerobic respiration.
-Abundant in cells where much metabolic activity takes place.

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10
Q

Chloroplasts

A

-Found in plants, abundant in leaf cells.
-Contains chlorophyll for photosynthesis.
-Surrounded by an envelope.
-Contain thylakoids, lamellae and the stoma (fluid filled matrix).

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11
Q

Thylakoids

A

-Membranes containing chlorophyll
-In stacks called granum
-Connected by lamellae

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12
Q

Stoma

A

-Empty area inside chloroplast membrane

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13
Q

Lysosome

A

-Sac containing digestive (hydrolytic) enzymes.
-Destroy bacteria, damaged organelles or damaged cells.
-Enzymes only work inside lysosome so as not to damage cytoplasm.
-Abundant in phagocytic cells such as neutrophils and macrophages.

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14
Q

Cilia/Flagella

A

-Thin extensions for movement in some cells
-Made of microtubules in 9+2 (9 outside, 2 inside) arrangement.
-Slide against each other for movement.

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15
Q

Centrioles

A

-In animal cells.
-Consist of two bundles of microtubules at right angles
-Form spindle fibres from threads of tubulin.
-Arranged in a cylinder.

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16
Q

Cell walls

A

-In plant cells (and chitin in fungi).
-Made of cellulose, reinforced by lignin.
-Retain cell structure, prevents bursting during turgidity, and retains shape.

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17
Q

Plasmodesmata

A

Pores within cell walls.

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18
Q

Vacuole

A

-Bound by a membrane called a tonoplast.
-Contains cell sap.
-Aid in turgor and support.

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19
Q

Cytoskeleton (Structure)

A

-Network of protein structures.
-Actin microfilaments made of subunits of actin.
-Tubulin microtubules, straight and cylindrical.
-Intermediate filaments.
-Motor proteins (Myosins, kinesins and dyneins), also act as enzymes.

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20
Q

Cytoskeleton (Purpose)

A

-Aids in transport in and out.
-Retains cell structure, keeps support and mechanical strength.
-Motor proteins transport organelles.
-Forms spindle fibres in cell division.
-Movement of cell.
-Anchor nucleus within cytoplasm.

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21
Q

Prokaryotes

A

-Before nucleus.
-No nucleus, mitochondria (membrane bound organelles).
-Plasmids instead of chromosomes.
-Peptidoglycan cell wall.
-70s ribosomes.
-But share a plasma membrane, cytoplasm and DNA/RNA with linear chromosomes.
-Divide by binary fission, win which each new cells receives a large loop of DNA as well as smaller plasmids.

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22
Q

Functions of cell membrane

A

-Separating cell from environment.
-Regulates transport of substances in and out (partially permeable).
-Enzymes involved in metabolic pathways.
-Antigens to recognise as self.
-Chemical signals to other cells.
-Receives signals from other cells through receptors.
-Site of chemical reactions.

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23
Q

Davson-Danielli model

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A

-Proteins along the edge
-Bilayer in the middle
-Proved wrong due to proteins being hydrophobic

24
Q

Fluid mosaic model

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A

-1972.
-Proteins inside the bilayer.
-Singer and Nicolson.
-Called mosaic due to patterns of proteins inside it.

25
Examples of membranes
-Cristae in mitochondria. -Thylakoids in chloroplasts, house chlorophyll. -Membrane in lysosome. -Epithelial cells in the small intestine that catalyse stages in the breakdown of sugers. These have chloride ion channels that regulate the composition of mucus.
26
Phospholipids
-Polar, hydrophilic phosphate head -Two non-polar, hydrophobic fatty acid tails
27
Phospholipid bilayer
-When exposed to water -Two parallel rows of phospholipids, with heads facing out and tail facing in
28
Intrinsic proteins
-Span the whole length of the membrane.
29
Extrinsic proteins
-Outer surface of the membrane.
30
Channel proteins
-Intrinsic. -Provide a hydrophilic channel through the membrane. -Polar molecules move along a conc gradient. -Passive. -Lined with hydrophilic amino acids.
31
Carrier proteins
-Intrinsic. -Change shape to transport molecules. -Can be active or passive.
32
Glycoproteins
-Protein molecules attached to carbohydrate chains. -Involved in cell adhesion and signalling. -Binds with chemical signals. -Can also act as enzymes.
33
Glycolipids
-Lipids attached to carbohydrate chains. -Allow the immune system to recognise the cell as self. -Also known as antigens.
34
Cholesterol
-Also has a hydrophilic head and hydrophobic tail. -Positioned between phospholipids. -Adds stability. -Regulates membrane fluidity (more cholesterol means less permeable membranes).
35
Diffusion
-Passive process due to kinetic energy of molecules. -Between two areas. -During equilibrium movement is equal in both directions (no net diffusion). -Down concentration gradient.
36
Diffusion in membranes
-Small molecules (CO2, O2) can pass right through. -Larger fat soluble molecules (hormones) can diffuse as they dissolve in the bilayer. -Water molecules, while polar and lipid insoluble, are in such great numbers that simple diffusion does occur. In some cells channel proteins called aquaporins are used to allow for an easier transport.
37
Factors affecting diffusion
-Higher temperature gives particles more kinetic energy, increasing diffusion. -Steeper concentration gradient increases overall movement. -Greater diffusion distance leads to slower diffusion. -Smaller molecules diffuse more rapidly. -A large surface area leads to more diffusion. Cells specialised for diffusion have microvilli to increase surface area.
38
Facilitated diffusion
-Through channel or carrier proteins around 0.8nm in diameter. -Takes place with polar (lipid insoluble) molecules such as glucose and ions.
39
Osmosis
-The net movement of water molecules down a water potential gradient. -Through a partially permeable membrane. -Passive process. -Affected by amount of solute of molecules added to the water.
40
Movement of water through the bilayer
-Molecules are small enough to pass directly through. -Aquaporins (protein channels) allow them to pass through more rapidly.
41
Hypertonic solution
-Conc of solutes is greater outside than inside the cell. -Higher water potential in cell, water moves out. -Leads to cell crenation (cell shrivelling) in animals. -In plants to cell membrane pulls away from the cell wall, leading to the cells being plasmolysed. Plant tissue with plasmolysed cells is flaccid.
42
Hypotonic solution
-Conc of solutes greater inside the cell that outside. -Lower water potential inside cell, water moves in. -Leads to cytolysis (cells swelling and potentially bursting). -This is prevented in plants by the cell wall, causing turgidity.
43
Water potential (ᴪ)
-Tendency of water molecules to diffuse from one region to another. -Measured in kilopascals (kpa) -Pure water has a ᴪ of 0, the highest possible value. -Concentrated solutions have a lower ᴪ.
44
Active transport
-Movement of substances against the concentration gradient. -Active process, requires energy from hydrolysis of ATP. -Involves carrier proteins through the membrane. These have a region that binds to and allows the hydrolysis of a molecule of ATP to release energy that allows it to change its shape,
45
Sodium/Potassium pump
-Moves Na ions outside cell and K ions inside. Two K are moved for every three Na. -Uses carrier proteins with a complementary shape to the molecule. Ions bind to a specific site on the protein. -Allows hydrolysis of ATP to ADP and phosphate, releasing energy. -Binding of the phosphate molecule to the protein causes the carrier to change shape. -Therefore the molecule can pass through.
46
Exocytosis
-Movement of substances out of a cell. -Substances contained in a vesicle and carried towards the membrane. -Vesicle fuses with membrane and empties contents outside. -Eg in synapses where chemicals in vesicles fuse with plasma membranes into the synaptic cleft.
47
Endocytosis
-Movement of substances into a cell. -Cell membrane bulges inwards and forms a vesicle. -An example of this is phagocytosis. -If this occurs with liquids it is known as pinoendocytosis. -ATP is needed to form and move vesicles using motor proteins.
48
Golgi apparatus
-Cis end faces nucleus, trans end faces cell wall -Consists of a stack of membrane-bound flattened sacs. -Secretory vesicles bring materials to and form the Golgi apparatus. -Modifies proteins by adding sugar or lipid molecules, or folding them into their 3D shape.
49
Making a protein in cells
-mRNA copy of gene for a protein leaves the nucleus through a nuclear pore. -Attaches to the ribosome on RER. -Instructions are translated and protein molecules are assembled. They are transported into and through the cisternae of the RER. -Vesicles are pinched off and pass through microtubules and motor proteins to the cis face of the golgi apparatus. -Protein molecules may be modified. Vesicles pinched off again from the trans face and fuse with the plasma membrane, releasing the protein to the outside of the cell.
50
Glycocalyx
-Carbohydrate molecules on the outside of membranes. -Very hydrophilic. -Attract water with dissolved substances, helping the cell interact with its watery environment and obtain dissolved substances.
51
Membranes in neurones
-Protein channels and carriers (for sodium and potassium ions) in the plasma membrane covering the long axon allow entry and exit of ions to the axon to bring about the conduction of nerve impulses. -Have a myelin sheath formed by flattened cells wrapped around several times, giving layers of cell membrane. -This layer is about 20% protein and 76% lipid. -At synapses there are calcium ion channels and chloride ion channels.
52
Membranes in white blood cells
-Contain special protein receptors that enable them to recognise the antigens on foreign cells (pathogens or tissue/organ transplants).
53
Membranes in root hair cells
-In plants. -Many carrier proteins to actively transport nitrate ions from the soil into the cells.
54
Inner membranes in mitochondria
-76% protein and 24% lipid. -This is because it contains electron protein carriers and hydrogen ion carriers associated with ATP synthase enzymes.
55
Movement of glucose through the bilayer
-Glucose molecules are too large to diffuse through the water-filled protein channel in a membrane. -Instead bind to a transmembrane carrier protein, which then opens to allow the glucose to pass out on the other side of the membrane.
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