Module2 & 3 Flashcards
(183 cards)
1
Q
prokaryotic cells
A
-No membrane-bound organelles.
-DNA is circular and floats freely in the cytoplasm (nucleoid).
-Has plasmids, ribosomes (70S), cell wall (peptidoglycan), cell membrane, and sometimes flagella.
1
Q
eukaryotic ce;;
A
-Have membrane-bound organelles (nucleus, mitochondria, etc.).
-DNA is linear and enclosed within a nucleus.
2
Q
size of eukaryotic cell
A
-Larger in size (10–100 µm).
3
Q
size of prokaryotic cell
A
Smaller in size (0.1–5 µm).
4
Q
what is the nucleus (eukaryotic)
A
-Contains DNA in the form of chromatin.
-Controls cell activities (via transcription).
-Surrounded by a nuclear envelope (double membrane) with nuclear pores.
5
Q
what is mitochondria (eukaryotic)
A
-Site of aerobic respiration (ATP production).
-Has a double membrane; the inner membrane is folded into cristae and surrounds the matrix.
-Contains its own DNA and ribosomes.
6
Q
what is ribosome (eukaryotic)
A
-site of protein synthesis.
-80S ribosomes in eukaryotes; made of rRNA and proteins.
-Found free-floating in cytoplasm or attached to rough endoplasmic reticulum (RER).
7
Q
what is rough endoplasmic reticulum (eukaryotic)
A
-Covered with ribosomes.
-Synthesizes and transports proteins to the Golgi apparatus.
8
Q
what is a smooth endoplasmic reticulum (eukaryotic()
A
-No ribosomes.
-storage and production of carbohydrates
-still transports protein .
9
Q
what is Golgi Apparatus (eukaryotic )
A
-Modifies, sorts, and packages proteins and lipids into vesicles.
-Produces lysosomes.
10
Q
what is Lysosomes (eukaryotic)
A
-Contains digestive enzymes (hydrolytic enzyme) to break down waste material and worn-out organelles.
-Involved in apoptosis (programmed cell death).
11
Q
what is Plasma Membrane? (eukaryotic)
A
-Phospholipid bilayer with embedded proteins.
-Controls the movement of substances in and out of the cell (selectively permeable).
12
Q
what is chloroplast (plants)
A
-Site of photosynthesis.
-Contains the pigment chlorophyll.
-Has double membrane, with internal structures called thylakoids stacked into grana surrounded by stroma.
13
Q
what is Cell Wall (plants)
A
-Made of cellulose.
-Provides structural support and protection.
14
Q
what is Vacuole (plants)
A
-Large, central structure in plant cells filled with cell sap (water, ions, sugars).
-Maintains turgor pressure for structural support.
15
Q
what is Plasmodesmata (plants)
A
Channels between adjacent plant cells allowing transport and communication.
16
Q
what is Cytoskeleton
A
-Network of protein fibers (e.g., microtubules, microfilaments, and intermediate filaments).
-Provides cell structure, shape, and facilitates intracellular transport and cell movement.
17
Q
light microscope
A
Max resolution ~0.2µm; limited detail.
18
Q
electron microscope
A
Higher resolution (~0.1nm); shows fine details of organelles.
19
Q
Transmission Electron Microscope (TEM):
A
Shows internal structures.
20
Q
Scanning Electron Microscope (SEM):
A
Shows 3D external surfaces.
21
Q
what is Centrioles:
A
small hollow cylinders made of microtubules
22
Q
What are microtubules
A
-tiny, tube-like structures can change their length
-help keep the cell’s shape and allow things to move around.
-help cells divide.
-component of cytoskeleton
23
Q
What is chromatin?
A
inside the nucleus
- made of DNA and proteins
–holds all the genetic information (DNA)
-chromatin condenses and forms chromosomes.
24
What is a Confocal Microscope?
-A type of light microscope that uses laser beams to scan a specimen.
-Produces high-resolution, 3D images of cells and tissues.
=Only collects light from a focused point, which gives sharp images.
25
How it Works:
1)A laser beam is directed at the specimen.
2)The beam passes through a pinhole to focus only on one part of the sample.
3)Light from out-of-focus parts is blocked, so the image is clearer.
4)The microscope builds a 3D image by scanning the specimen in layers.
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adv of confocal microscope
-3D imaging: Allows a detailed view of cell structure.
-Can view living cells in real time.
-Better image clarity compared to traditional light microscopes.
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disadvantage of confocal microscope
-Expensive and complex to use.
-Slower compared to some other microscopes because it scans in layers.
-Cannot be used for very thick samples.
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features of a confocal microscope
-Laser light for precise imaging.
-Produces high-resolution, detailed images.
-Can view live cells and structures like the cytoskeleton.
-Shows depth and layers of the sample (optical sectioning).
29
function of carbohydrates
-Energy storage (e.g., starch in plants, glycogen in animals).
-Structural support (e.g., cellulose in plant cell walls).
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bonds of carbohydrates
Glycosidic bonds formed by condensation reactions.
-C, H and O
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Monosaccharide
-Single sugar units, basic building blocks of carbohydrates.
Examples:
Glucose: Main energy source in cells.
Fructose: Found in fruit.
Galactose: Found in milk.
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features of monosaccharides
Soluble in water, sweet-tasting, used in respiration.
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types of disaccharides
Sucrose = Glucose + Fructose (table sugar).
Lactose = Glucose + Galactose (milk sugar).
Maltose = Glucose + Glucose (malt sugar).
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disaccharide
Formed when two monosaccharides join by a glycosidic bond through a condensation reaction (water is removed).
-Broken down into monosaccharides by hydrolysis (adding water).
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polysaccharides
-complex carbohydrates)
-Long chains of monosaccharides linked by glycosidic bonds.
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types of polysaccharides
-Starch: Energy storage in plants, made of amylose and amylopectin.
-Glycogen: Energy storage in animals (similar to starch but more branched).
-Cellulose: Structural component in plant cell walls, gives strength.
37
starch details (polysaccharides)
-Made of two components:
Amylose: Unbranched chain of alpha-glucose, forms a helix making it compacts so good for storage 1-4 glycosidic bond
Amylopectin: Branched chain of alpha-glucose, allows for quick energy release cuz side branches allows enzymes that break down molecules to get the glycosidic bonds easily. 1-4 &1-6 glycosidic bond
-Insoluble, so it doesn’t affect water potential, making it ideal for storage.
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glucose
-C₆H₁₂O₆, main energy source for respiration.
Exists as two isomers: Alpha-glucose & Beta-glucose
-Alpha-glucose forms starch and glycogen.
-Beta-glucose forms cellulose.
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glycogen detail (polysaccharides)
-Similar to amylopectin but more highly branched.
-Found in liver and muscle cells.
-Provides a rapid source of energy when broken down into glucose.
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cellose details (polysaccharides )
-Made of beta-glucose.
-Forms long, straight chains that run parallel and are linked by hydrogen bonds, creating strong fibers (microfibrils) for structural support in plant cell walls.
- main component of cell wall as strong cuz of hydrogen bond=support
-high tensile strength allows it to be stretched with breaking=withstand turgor pressure
40
what are lipids
-Organic molecules made mostly of carbon (C), hydrogen (H), and oxygen (O).
-Insoluble in water (hydrophobic).
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function of lipids
1)Energy storage
2)membrane structure
3)thermal insulation to reduce heat loss
4)waterproofing (on plant leaves)
5)electrical insulation
6)protection vital organs
7)buoyancy for aquatic animals
42
what is Triglycerides (fats and oils)-lipids
-Made of 1 glycerol molecule and 3 fatty acids.
-Formed by a condensation reaction between glycerol and fatty acids, creating ester bonds (removal of water). ESTERFICATON
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function of Triglycerides
-Energy storage: Triglycerides store more energy than carbohydrates, BECAUSE TAIL CONTAINS LOTS OF FATTY ACIDS WITH CHEMICAL ENERGY WHICH CAN be broken down.
-Insulation: Fat helps to keep organisms warm (e.g., blubber in animals).
-Protection: Fat around organs acts as a cushion.
-Insoluable: doesn't cause water to enter so bundle together as insoluble droplets.
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what is Phospholipids (membrane lipids)
-Made of 1 glycerol, 2 fatty acids, and 1 phosphate group.
-Hydrophilic head (phosphate group) and hydrophobic tails (fatty acids).
-Key component of cell membranes (phospholipid bilayer), allowing cells to have a barrier.
45
what is cholesterol (a steroid)-lipids
Small molecule found in cell membranes.
Provides stability to cell membranes by reducing fluidity.
Also used to make steroid hormones (e.g., estrogen, testosterone)
46
saturated fatty acids:
No double bonds between carbon atoms; solid at room temperature (e.g., butter).
47
Unsaturated fatty acids:
Have one or more double bonds, causing "kinks" in the chain; liquid at room temperature (e.g., oils).
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Bonds in Lipids?
-Ester bonds: Formed in triglycerides between glycerol and fatty acids during condensation reactions.
-Broken down by hydrolysis, adding water to break the ester bond.
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Testing for Lipids?
Emulsion Test:
Add ethanol to the sample and shake, then add water.
A positive result will form a milky white emulsion, indicating the presence of lipids.
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test for non-reducing sugars (like sucrose):
-Hydrolysis:
1)Mix the sample with dilute hydrochloric acid (HCl) in a test tube.
2)Heat it in a water bath for 5 minutes to break it down into reducing sugars.
-Neutralization:
3)Add sodium bicarbonate (baking soda) to neutralize the acid.
4)Make sure the solution is neutral (you can use pH paper).
-Benedict's Test:
5)Add Benedict's reagent to the neutralized solution.
6)Heat it in a water bath for 2-5 minutes.
-Results
Positive Result: A brick-red color change means non-reducing sugars are present.
Negative Result: No color change means there are no non-reducing sugars.
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results of r non-reducing sugars (like sucrose):
Positive Result: A brick-red color change means non-reducing sugars are present.
Negative Result: No color change means there are no non-reducing sugars.
52
testing for Carbohydrates
Benedict’s Test (for reducing ):
Add Benedict’s solution and heat. Positive test turns from blue to brick-red.
-Iodine Test (for starch):
Add iodine. Positive test turns from yellow-brown to blue-black.
53
biuret test for proteins?
1)Sample Preparation:
-Take a small amount of the sample (liquid or dissolved solid) and place it in a clean test tube.
-Add Biuret reagent (a blue solution containing copper(II) sulfate) to the sample.
-Gently mix the solution.
-Let it sit for a few minutes and then observe the color.
-Positive Result:
A violet/purple color indicates the presence of proteins.
-Negative Result:
If the solution remains blue, it means there are no proteins present.
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resultd of biuret test for proteins
Positive Result:
A violet/purple color indicates the presence of proteins.
-Negative Result:
If the solution remains blue, it means there are no proteins present.
55
why is there a colour change for biuret test
-The Biuret reagent reacts with the peptide bonds in proteins.
-The copper(II) ions in the reagent form a complex with the peptide bonds, resulting in the color change.
56
What is Benedict reagent
Copper (II) sulfate
57
Structure of Water
-formula: H₂O covalently bonded
-Polar molecule; Oxygen is more electronegative than hydrogen, creating a delta negative charge on oxygen and delta positive charges on hydrogen.
-Hydrogen bonds;Weak bonds between the hydrogen atom of one water molecule and the oxygen atom of another water molecule.
58
Important Properties of Water
-Cohesion and Surface Tension
-Adhesion
-High Specific Heat Capacity:
-High Latent Heat of Vaporization
-Solvent Properties
-Density and Ice
59
explain further universal solvent
Water is a universal solvent; it dissolves polar substances easily.
This makes it essential for transporting nutrients, gases, and waste in organisms (e.g., in blood or sap).
60
explain further High Latent Heat of Vaporization?
A lot of energy is needed to convert water from liquid to gas.
This property is important for cooling mechanisms like sweating in humans and transpiration in plants.
61
Explain further High Specific Heat Capacity:
Water requires a lot of energy to change temperature (due to hydrogen bonds).
This helps maintain stable temperatures in organisms and environments (important for homeostasis).
62
explain further adhesion
Water can stick to other substances, aiding processes like capillary action (important in plants for water transport).
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what is a Plasma Membrane
The plasma membrane is primarily made of a phospholipid bilayer.
Phospholipids have a hydrophilic (water-attracting) phosphate "head" and two hydrophobic (water-repelling) fatty acid "tails."
In water, phospholipids arrange themselves into a bilayer, with hydrophobic tails facing inward and hydrophilic heads facing outward.
63
Explain further Cohesion and Surface Tension?
Water molecules are cohesive (stick together) due to hydrogen bonding.
This creates surface tension, allowing organisms like insects (e.g., pond skaters) to walk on water.
64
Explain plasma membrane Fluid Mosaic Model
this model describes the plasma membrane as a dynamic structure with proteins moving within or on the fluid lipid bilayer. It’s "fluid" because of the phospholipid movement, and "mosaic" due to the scattered proteins embedded in it
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the proteins involved in plasma membrane
-Intrinsic (integral) proteins span the entire bilayer and are involved in transport, acting as channels or carriers.
-Extrinsic (peripheral) proteins are only on one side of the membrane, often involved in cell signaling or maintaining the structure of the membrane.
66
what is intrinsic (integral) protein
they are stuck within the membrane and often go all the way through it. These proteins help with moving things in and out of the cell, like a door or tunnel, allowing certain substances to pass through the cell membrane.
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porperty of plasma membrane
The plasma membrane is selectively permeable, meaning it allows some substances to pass through while blocking others. This helps maintain the internal environment of the cell.
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how does cholesterol involve in plasma membrane
Cholesterol is embedded within the bilayer and helps maintain membrane fluidity and stability, especially in varying temperatures.
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what is Cell Communication in plasma membrane
The plasma membrane contains receptors that bind to specific molecules (like hormones or neurotransmitters), allowing cells to respond to signals from their environment.
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Endocytosis:
The process of taking in materials by engulfing them with the plasma membrane.
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Exocytosis:
The process of releasing substances from the cell by fusing vesicles with the membrane.
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what are proteins
large, complex molecules
made up of amino acids
amino acid ->polypeptide->proteins
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amino acids
20 different types of amino acids.
R group – varies between different amino acids and determines their properties.
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Peptide Bond Formation:
Condensation reaction: A bond forms between the amino group of one amino acid and the carboxyl group of another, releasing water.
This creates a peptide bond, linking amino acids together to form a polypeptide (chain of amino acids).
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Protein Structure:
Protein Structure:
Primary structure: The sequence of amino acids in a polypeptide chain.
Secondary structure: Folding of the polypeptide into shapes like:
Alpha helix (coiled).
Beta pleated sheet (folded like a zigzag).
Tertiary structure: Further folding into a complex 3D shape due to interactions between R groups (e.g., hydrogen bonds, ionic bonds, disulfide bridges).
Quaternary structure: When multiple polypeptide chains join together (e.g., hemoglobin).
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what is function of nuclear pores
allow substances to move between the nucleus and cytoplasm
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What is vesicles ?
Small fluid filled sac in the cytoplasm surrounded by a membrane
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function of vesicle
Transports substances in and out of cell (via plasma membrane)
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function of centirole
invalid in separation of chromosomes during cell division
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cytoskeletons 4 function
1)microtubules and microfilaments supports cell organelle;keepin them in position
2)strengthen cell and maintain shape
3)movement of materials
4)protein of cytoskeleton causes cells to move
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what is hydrogen bonding?
when the delta negative oxygen attract delta positive hydrogen of other water molecules
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what is tRNA
Transfer RNA, brings amino acids to ribosome
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What is cholorestrol
Lipid (steroid)
Structure: Four carbon-based rings (steroid structure) with a hydrocarbon tail and a hydroxyl group (-OH).
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why is water less dense when solid
water molecules held further apart in that liquid because each water molecules form 4 hydrogen bonds to other water molecules creating a lattice shape making ice less dense so floats
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prepare wet mount
-Use a pipette to place a drop of the sample in the center of the slide.
-If the sample is dry or needs dilution, add a drop of distilled water next to the sample.
-Hold the coverslip at a 45-degree angle to the slide.
-Gently lower the coverslip onto the drop. This prevents air bubbles from forming.
-Use a microscope to observe the specimen.
***********
Avoid touching the underside of the coverslip to keep it clean.
Use a clean slide and coverslip for each new sample
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prepare dry mount
-Use tweezers to place the sample in the center of the slide.
-Carefully place the coverslip over the sample.
-Lower it straight down to avoid trapping air bubbles.
-Use a microscope to look at the specimen.
*Make sure the sample is thin enough to see through
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function of cholesterol
-fit in phosolipid molecules in membrane because of small size and flattened shape
-bind to hydrophobic tail of phospholipid, more pack together so reduces cell fluidity,increasing stability
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what is secondary structure held by
hydrogen bonds
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what is primary structure held by
peptide bonds
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what is tertiary structure held by
-ionic bonds
-disulfide bonds ( forms between two sulfur atoms, usually in the amino acids cysteine)
-hydrophobic and hydrophilic interactions (Hydrophobic: Avoids water, clumps together (like oil).
Hydrophilic: Loves water, dissolves in it (like sugar).)
-4hydrogen bonds
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structure of globular proteins
Globular proteins are round and compact.
Folding: They are folded in a way that makes them soluble in water.
Core and Surface: They have a hydrophobic (water-repelling) inside and a hydrophilic (water-attracting) outside.
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Explain tertiary structure of globular proteins
highly folded, complex tertiary structure, which makes them soluble in water.
-Hydrophobic interactions: Non-polar side chains are buried inside the protein, away from water.
-Hydrophilic interactions: Polar side chains are on the outside, interacting with water, making the protein soluble.
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explain the secondary structure of globular proteins
alpha-helices and beta-pleated sheets, which help in stabilizing their folded shape.
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Functions of Globular Proteins
Enzymes: Speed up chemical reactions (e.g., amylase helps digest starch).
Transport: Carry molecules in the body (e.g., hemoglobin carries oxygen).
Regulation: Act as hormones, like insulin, to control body functions.
Defense: Make up antibodies to fight infections.
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what are Conjugated Proteins
These are globular proteins with a non-protein part called a prosthetic group attached.
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what are Glycoproteins
These have carbohydrate groups attached and are involved in cell-cell recognition and signaling.
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what are Lipoproteins
Proteins with lipid groups attached, involved in transporting lipids in the blood.
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Hemoglobin?
-a conjugated protein.
It is composed of four polypeptide chains, each with a heme group that contains an iron ion. This prosthetic group allows haemoglobin to bind and transport oxygen efficiently.
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properties of Fibrous Proteins
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Semi conservative replication
1) **DNA helicase** breaks hydrogen bonds between complementary base pairs between the two strands within a double helix cause dna to unwind
2) Each of the separated parental DNA strand acts as **template strand**. Free floating **DNA nucleotides**within the nucleus are attracted to their **complementary base pairs**on the template strand of the parental dna
3)The **adjacent nucleotides ** are joined together, to form the phosphodiester bond, by a **condensation reaction **. **DNA polymerase** catalyses the joining together of **adjacent nucleotides** .
4) The two sets of daughter DNA contains **one strand of the parental** DNA and **one newly synthesised strand**
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Transcription
1) the dna helix unwinds to expose the bases to act as a template. By helical we which breaks hydrogen bonds between bases
2) only one chain of DNA acts as template, other is coding strand)
3) free mRNA nucleotides in the nucleus align opposite exposed complementary DNA bases.
4) RNA polymerase bonds together the RNA nucleotides to create a new RNA polymer chain. One entire gene is copied.
RNA polymerase moves along the template strand in the 3' to 5' direction
5)once copied, the mRNA is modified and leaves nucleus through nucleus envelope pores
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Translation
1) once modified mRNA leaves nucleus,it’s attached to a ribosome on the cytoplasm.
2) ribosome attached to a star codon.
3) the tRNA molecule with complementary anticodon to the start codon aligns opposite the mRNA, held in place by the ribosome.
4) the ribosome will move along the mRNA molecule to enable other complementary tRNA to attach to the next codon on the mRNA.
5) the 2 amino acid that have been delivered by the tRNA molecules are joined by a peptide bond. This is catalysed by and enzyme and requires atp.
6) continues until reaches stop codon.
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Structure of ATP
Adenine: Nitrogenous base
Ribose: 5-carbon sugar
3 Phosphate groups: Linked by high-energy bonds
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Role of ATP
Energy currency of the cell: Immediate energy source for biological processes.
ATP is small and water-soluble, allowing easy transport within cells.
Releases energy by breaking the high-energy phosphate bond.
101
How many bonds does adenine and thymine form
2 hydrogen bond
102
How many bond does cysteine and guanine form
3 hydrogen bonds
110
Vacuole?
Membrane lines sacs
Important in maintained of turgir
Membrane ie vacoulce = tonoplast, selectively permeable
111
Protein production
1)the nucleolus manufactures ribosomes for protein synthesis in the RER.
2)The nucleus manufactures mRNA, which is needed by ribosomes to make proteins. mRNA leaves through nuclear pore.
3)the ribosomes in the RER makes proteins
4)the RER processes the proteins which are then swnt in vesicles to the Golgi apparatus
5)The Golgi apparatus further process and modifies the proteins and sends them in to the plasma membrane
6) the vesicles fuses with the plasma membrane to secure the finished protein product (excocytosis)
112
Structure of collagen
-3 polypeptide chain help by hydrogen bond forms triple helix
-in primary structure every 1/3 amino acid is glycine
- convalent bonds cross links between r groups , hold the molecule together forming fibrils
113
Define degenerate (genetic code)
degenerate: multiple codons can code for the same amino acids
Limits effect of mutations
114
Point of gene/genetic code/triplet code
ensures the cell reads the DNA correctly and can produce the correct protein molecules that it requires to function properly.
115
What are the four types of stem cells based on potency?
1. Totipotent: Can differentiate into any cell type, including extraembryonic tissues (placenta).
2. Pluripotent: Can differentiate into any body cell but not extraembryonic tissues.
3. Multipotent: Can differentiate into a limited range of cell types (e.g., hematopoietic stem cells → blood cells).
4. Unipotent: Can only differentiate into one specific cell type.
116
Where can stem cells be obtained from?
1. Embryonic stem cells – from early embryos (totipotent/pluripotent).
2. Adult stem cells – found in bone marrow, skin, etc. (multipotent).
3. Induced pluripotent stem cells (iPSCs) – reprogrammed adult cells.
4. Umbilical cord stem cells – multipotent, used in medical treatments.
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What are some medical applications of stem cells?
• Regenerative medicine: Repairing damaged tissues (e.g., spinal cord injury).
• Blood disorders: Treating leukemia with bone marrow transplants.
• Diabetes: Creating insulin-producing beta cells.
• Drug testing: Testing new drugs on lab-grown tissues
118
What are the ethical concerns of using embryonic stem cells?
• Destruction of embryos – potential for human life.
• Consent issues – embryos cannot give consent.
• Alternative sources available (e.g., adult/iPSCs).
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Where are stem cells found in plants, and what is their function?
• Meristematic tissue (meristems) in root tips and shoot tips.
• Allow continuous growth and differentiation into xylem, phloem, etc.
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121
How are erythrocytes and neutrophils produced from a common stem cell?
• Both originate from hematopoietic stem cells (HSCs) in bone marrow.
• Erythropoiesis → HSCs differentiate into erythrocytes (red blood cells) under the influence of erythropoietin:
• Lose nucleus for more hemoglobin.
• Gain a biconcave shape for gas exchange.
• Flexible membrane for capillary passage.
• Granulopoiesis → HSCs differentiate into neutrophils (a type of white blood cell):
• Retain a multi-lobed nucleus to move through tissues.
• Develop granules containing enzymes for phagocytosis.
122
How are xylem vessels and phloem sieve tubes derived from a common stem cell?
• Both develop from meristematic stem cells in the vascular cambium.
• Xylem differentiation:
• Cells lose cytoplasm and organelles.
• Walls become lignified for structural support.
• End walls break down → continuous hollow tube for water transport.
• Phloem differentiation:
• Cells partially lose organelles but retain some cytoplasm.
• Develop sieve plates for sugar transport.
• Companion cells remain active to provide ATP for transport.
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How are erythrocytes (red blood cells) specialized for oxygen transport?
• Biconcave shape: Increases surface area for gas exchange.
• No nucleus: Maximizes space for hemoglobin.
• Flexible membrane: Allows passage through narrow capillaries.
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How are neutrophils specialized to fight infections?
• Multi-lobed nucleus: Facilitates movement through tissues.
• Granules in cytoplasm: Contain enzymes for digesting pathogens.
• Flexible shape: Allows engulfing of microorganisms.
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How are squamous epithelial cells specialized for diffusion?
• Thin, flat cells: Provide a short diffusion pathway.
• Smooth surface: Reduces friction in areas like blood vessels.
- permeable: allowing easy diffusion of gases
forms the structure of the alveolar wall and so is very thin and permeable for the easy diffusion of gases
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How are ciliated epithelial cells specialized for moving substances?
• Cilia on surface: Beat rhythmically to move mucus or eggs.
• Goblet cells nearby: Secrete mucus to trap particles.
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How are sperm cells specialized for fertilization?
• Flagellum: Enables motility to reach the egg.
• Mitochondria-rich: Provide energy for movement.
• Acrosome: Contains enzymes to penetrate the egg.
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How are palisade cells specialized for photosynthesis?
• Numerous chloroplasts: Maximize light absorption.
• Elongated shape: cells are Packs tightly to capture more light.
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How are root hair cells specialized for water and nutrient uptake?
• Long extensions (root hairs): Increase surface area.
• Thin cell wall: Facilitates easy water absorption.
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How are guard cells specialized to regulate gas exchange?
Inner cell walls are thicker, the outer cell walls are thinner. The difference in the thickness of the cell walls allows the cell to bend when turgid
The cytoplasm has a high density of chloroplasts and mitochondria. Scientists think that these organelles may play a role in the opening of the stomata
131
How are cells organized into tissues, organs, and organ systems?
• Cells: Basic functional units (e.g., muscle cells).
• Tissues: Groups of similar cells performing a common function (e.g., muscle tissue).
• Organs: Structures made of different tissues working together (e.g., heart).
• Organ Systems: Groups of organs performing related functions (e.g., circulatory system).
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What is the structure and function of squamous epithelium?
• Structure: Single layer of flat cells.
• Function: Provides a thin surface for diffusion (e.g., alveoli in lungs).
133
What is the structure and function of ciliated epithelium?
• Structure: Layer of cells with cilia on their surface.
• Function: Moves mucus and trapped particles (e.g., in the trachea).
134
What is the structure and function of cartilage?
• Structure: Flexible tissue
• Function: Provides support and flexibility (e.g., ear, joints).
-rings along the trachea, called Tracheal rings
These rings help to support the trachea and ensure it stays open while allowing it to move and flex while we breathe
135
What is the structure and function of muscle tissue?
• Structure: Bundles of elongated cells (muscle fibers).
• Function: Contracts to produce movement.
136
What is the structure and function of xylem tissue?
Structure: Hollow, lignified vessels.
• Function: Transports water & minerals, structural support and food storage
137
What are the key features of efficient exchange surfaces?
• Large surface area: Increases the area available for diffusion.
• Thin barrier: Reduces the diffusion distance.
• Steep concentration gradient: Maintained by good blood supply or ventilation to ensure rapid diffusion
138
Why is the surface area to volume ratio important in exchange surfaces?
• A larger surface area to volume ratio facilitates efficient exchange of substances.
• Small organisms have a high surface area to volume ratio, allowing simple diffusion to meet metabolic needs.
• Larger organisms have a lower ratio, necessitating specialized exchange surfaces.
139
How do single-celled organisms exchange gases?
• They rely on diffusion across their cell membrane due to a high surface area to volume ratio.
• The short diffusion distance allows efficient exchange of gases.
140
How do insects facilitate gas exchange?
• Through a tracheal system consisting of tracheae, tracheoles, and spiracles.
• Oxygen diffuses directly into tissues; carbon dioxide diffuses out.
• Spiracles can open and close to minimize water loss.
141
How do fish gills adapt for efficient gas exchange?
• Gills consist of filaments and lamellae, increasing surface area.
• A counter-current flow mechanism maintains a concentration gradient.
• Thin epithelial cells reduce diffusion distance.
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How are human lungs adapted for gas exchange?
• Alveoli provide a large surface area.
• Alveolar walls are one cell thick, minimizing diffusion distance.
• Rich capillary network maintains a concentration gradient.
143
How do plants facilitate gas exchange?
• Leaves have stomata controlled by guard cells to regulate gas exchange.
• Spongy mesophyll provides a large surface area and air spaces for diffusion.
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What are the structural components of the trachea, and what are their functions?
• Cartilage: C-shaped rings of hyaline cartilage maintain the trachea’s open structure, preventing collapse during inhalation and exhalation.
• Ciliated Epithelium: Lines the inner surface; cilia move mucus and trapped particles upward toward the pharynx for expulsion.
• Goblet Cells: Interspersed within the epithelium; secrete mucus to trap dust, pathogens, and other particles.
• Smooth Muscle: Connects the ends of the cartilage rings posteriorly; allows for slight adjustments in diameter during breathing.
• Elastic Fibers: Provide flexibility and recoil, aiding in the trachea’s ability to return to its original shape after stretching.
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How are the bronchi structured to perform their function?
similar structure to the trachea but they have thinner walls and a smaller diameter
cartilage in the bronchi does not form a c-shape, but can form full rings, and can also form irregular blocks
• Cartilage: Present as irregular plates; keeps the bronchi open and maintains airway patency.
• Ciliated Epithelium: Continues from the trachea; cilia move mucus and debris toward the throat.
• Goblet Cells: Present within the epithelium; produce mucus to trap inhaled particles.
• Smooth Muscle: Encircles the bronchi; regulates airway diameter by contracting or relaxing.
• Elastic Fibers: Provide elasticity, allowing bronchi to expand and recoil during breathing.
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What distinguishes bronchioles in their structure and function?
Bronchioles are narrow self-supporting tubes with thin walls
• Cartilage: Absent; bronchioles rely on surrounding lung tissue to remain open.
• Ciliated Epithelium: Present in larger bronchioles; cilia help clear mucus and debris.
• Goblet Cells: Sparse or absent; mucus production decreases to prevent airway obstruction.
• Smooth Muscle: Prominent; controls airflow resistance and distribution by adjusting the lumen diameter.
• Elastic Fibers: Abundant; facilitate recoil and maintain airway patency during respiration.
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What are the key structural features of alveoli that facilitate gas exchange?
• Cartilage: Absent; thin walls are necessary for efficient gas exchange.
• Ciliated Epithelium: Absent; not needed as alveoli are the sites of gas exchange, not air conduction.
• Goblet Cells: Absent; mucus would impede gas exchange.
• Smooth Muscle: Minimal or absent; alveoli are primarily passive structures for gas exchange.
• Elastic Fibers: Abundant; allow alveoli to stretch during inhalation and recoil during exhalation, aiding in efficient ventilation.
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What occurs during inhalation in mammals?
• Diaphragm Contraction: The diaphragm, a dome-shaped muscle, contracts and flattens, increasing the vertical dimension of the thoracic cavity.
• Intercostal Muscle Contraction: External intercostal muscles contract, elevating the rib cage and expanding the thoracic cavity’s lateral and anteroposterior dimensions.
• Thoracic Volume Increase: The combined muscle contractions enlarge the thoracic cavity, reducing intrathoracic pressure.
• Air Inflow: The pressure drop allows air to flow into the lungs, filling the alveoli where gas exchange occurs.
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What happens during exhalation in mammals?
• Muscle Relaxation: The diaphragm and external intercostal muscles relax, causing the diaphragm to rise and the rib cage to descend.
• Thoracic Volume Decrease: The thoracic cavity’s volume decreases, increasing intrathoracic pressure.
• Air Outflow: The pressure increase forces air out of the lungs.
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How does forced exhalation differ from passive exhalation?
• Active Process: Involves contraction of internal intercostal and abdominal muscles.
• Enhanced Pressure: These contractions further decrease thoracic volume, increasing pressure to expel air rapidly.
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When are accessory muscles utilized in breathing?
• During Labored Breathing: Accessory muscles in the neck and upper chest assist in elevating the rib cage to increase thoracic volume.
• Enhanced Ventilation: These muscles are engaged during intense physical activity or respiratory distress to facilitate increased air intake.
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How is ventilation regulated in mammals?
• Respiratory Centers: Located in the medulla oblongata and pons, these centers regulate the rhythm and depth of breathing.
• Chemoreceptors: Peripheral chemoreceptors in the carotid and aortic bodies detect changes in blood oxygen and carbon dioxide levels, adjusting ventilation accordingly.
• Central Chemoreceptors: Located near the medulla, they respond to pH changes in cerebrospinal fluid, influencing respiratory rate to maintain homeostasis.
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How does Enzymes speed up chemical reactions?
Enzymes speed up chemical reactions because they reduce the stability of bonds in the reactants
The destabilisation of bonds in the substrate makes it more reactive
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Example of intracellular and extracellular enzyme
intracellular= catalyse
extracellular= Amylase
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How does temp affect membrane permeability and structure
High temp, lipids more fluids,reduce the effectiveness of cell membrane as barrier to polar molecules (reversible)
At extreme high temp, many protein denature, disrupts membrane structure, not effective barrier (irreversible)
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What is bulk transport a form of?
Active transport as require energy
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Function of palisade cell
carry out photosynthesis to produce glucose and oxygen
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Phloem cell
Made of living cells, which are supported by companion cells
Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes that allow sugars and amino acids to flow easily through (by translocation)
Cells also have very few subcellular structures to aid the flow of materials
Function: transport of dissolved sugars
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Muscle cell adaptation an function
Function: contraction for movement
-All muscle cells have layers of protein filaments , these layers can slide over each other causing muscle contraction
-a high density of mitochondria to provide sufficient energy (via respiration) for muscle contraction
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Smooth muscle (gas exchange)
found throughout the walls of the bronchi and bronchioles
helps to regulate the flow of air into the lungs by dilating when more air is needed and constricting when less air is needed
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Elastic fibre (gas exchange)
present in all lung tissues
enable the lung to stretch and recoil
ability to recoil is what makes expiration a passive process
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Capillaries (gas exchange)
surrounded by an extensive network of capillaries
Carbon dioxide diffuses out of the capillaries and into the alveoli to be exhaled, while oxygen diffuses the other way from alveoli and into the capillaries to be carried around the body
diameter of around 3-4µm
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Structure of arterioles
have a lower proportion of elastic fibres and a large number of muscle cells
The presence of muscle cells allows them to contract and close their lumen to stop and regulate blood flow
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Structure of vein
-tunica media is much thinner in veins
There is no need for a thick muscular layer as veins don't have to withstand high pressure
- lumen of the vein is much large:
helps to ensure that blood returns to the heart at an adequate speed
A large lumen reduces friction between the blood and the endothelial layer of the vein
The rate of blood flow is slower in veins but a larger lumen means the volume of blood delivered per unit of time is equal
-contain valves
prevent the backflow of blood
-pulse is absent in veins
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Structure of venules
Venules connect the capillaries to the veins
few or no elastic fibres and a large lumen
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Structure and function of capillarie
very small diameter (lumen: forces the blood to travel slowly which provides more opportunity for diffusion to occur
large number of capillaries branch between cells: Substances can diffuse between the blood and cells quickly as there is a short diffusion distance
wall made from a single layer of endothelial cells: one cell thick , reduces the diffusion distance . cells of the wall have gaps called pores which allow blood plasma to leak out and form tissue fluid
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formation of tissue fluid?
As blood passes through capillaries some plasma leaks out through gaps in the walls of the capillary to surround the cells of the body
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The volume of liquid that leaves the plasma to form tissue fluid depends on what two opposing forces
Hydrostatic pressure & Oncotic pressure
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Hydrostatic pressure? Tissue fluid
This is the pressure exerted by a fluid.
The hydrostatic pressure in this example is the blood pressure, generated by the contraction of the heart muscle
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Oncotic pressure? Tissue fouid
This is the osmotic pressure exerted by plasma proteins within a blood vessel
Plasma proteins lower the water potential within the blood vessel, causing water to move into the blood vessel by osmosis
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At the arterial end? Tissue fluid formation
When blood is at the arterial end of a capillary the hydrostatic pressure is great enough to force fluid out of the capillary
Proteins remain in the blood as they are too large to pass through the pores in the capillary wall
The increased protein content creates a** water potential gradient (osmotic pressure)** between the capillary and the tissue fluid
At the arterial end **the hydrostatic pressure is greater than the osmotic pressure** so the net movement of water is out of the capillaries into the tissue fluid
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At the venous end? Tissue formation
At the venous end of the capillary the hydrostatic pressure within the capillary is reduced due to increased distance from the heart and the slowing of blood flow as it passes through the capillaries
The water potential gradient between the capillary and the tissue fluid remains the same as at the arterial end
At the venous end** the osmotic pressure is greater than the hydrostatic pressure **and **water begins to flow back into the capillary from the tissue fluid**
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Formation of lymph
1) Larger molecules that are not able to pass through the capillary wall enter the lymphatic system as lymph
2) The liquid moves along the larger vessels of this system by compression caused by body movement. Any backflow is prevented by valves
3) The lymph eventually reenters the bloodstream through veins located close to the heart
4) Any plasma proteins that have escaped from the blood are returned to the blood via the lymph capillaries
5) After digestion lipids are transported from the intestines to the bloodstream by the lymph system
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Valves in the heart:
Open when the pressure of blood behind them is greater than the pressure in front of them
Close when the pressure of blood in front of them is greater than the pressure behind them
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Where xylem & phloem found
Vascular bundle
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advantage of transpiration
cooling the plant via evaporative cooling
uptake of mineral ions
The turgor pressure of the cells provides support to leaves
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Symplast pathway?
Water travels via cell cytoplasm and vacuoles
water moves into root hair cells from the soil by osmosis, increasing the water potential of the root hair cell
water moves down its water potential gradient into neighbouring root cells, increasing their water potential
water continues to move across the root from high to low water potential
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Movement of water in leaves
WATER VAPOUR DIFFUSES FROM AIR SPACES THROUGH A STOMA BY A PROCESS CALLED TRANSPIRATION,
LOWERING THE WATER POTENTIAL
WATER EVAPORATES FROM A MESOPHYLL CELL WALL INTO
THE AIR SPACES, CREATING A TRANSPIRATION PULL
WATER MOVES THROUGH THE MESOPHYLL CELL WALL (APOPLASTIC
PATHWAY OR OUT OF THE MESOPHYLL CYTOPLASM INTO THE CELL
WALL (SYMPLASTIC PATHWAY)
WATER LEAVES A XYLEM VESSEL THROUGH A NON-LIGNIFIED AREA (e.g. PIT). IT MAY TRAVEL BY A SYMPLASTIC PATHWAY OR BY AN
APOPLASTIC PATHWAY
WATER MOVES UP THE XYLEM VESSELS (TRANSPIRATION STREAM)
TO
