bio hl final short answer

What are phospholipids? What are their properties?

Cell membranes are primarily composed of phospholipids; they are Amphipathic; meaning they have both hydrophilic and hydrophobic; phospholipids are made from a polar head, which is hydrophilic; it contains phosphate and glycerol; also contains two non-polar fatty acid tails; which are hydrophobic;

What structures do phospholipids spontaneously form in water?

Phospholipids spontaneously arrange into a bilayer; Hydrophobic tail regions face inwards and are shielded from the surrounding polar water/fluid; the hydrophilic phosphate and glycerol in the head region attracts to the water outside and inside the cell; Phospholipids are held together in a bilayer by hydrophobic interactions (weak associations) of the fatty acid tails;

How do lipid bilayers serve as barriers around cells? What is the basis of this?

The lipid bilayers in cell membranes act as selective barriers; which are impermeable to and block the entry of large molecules, ions, and polar substances; due to the hydrophobic region in the middle made of fatty acid tails; This selective permeability is essential for maintaining the internal environment of the cell;

What molecules can use simple diffusion to cross membranes?

An example of simple diffusion is the exchange of oxygen and carbon dioxide across cell membranes; these molecules are small and non-polar and can cross the cell plasma membrane easily; without using energy; following their concentration gradients; This process is vital for cellular respiration, where oxygen is required for energy production, and carbon dioxide is a waste product to be expelled;

What are Integral and peripheral proteins in membranes?

Integral proteins are embedded in one or both of the lipid layers of a membrane; Peripheral proteins are attached to one or other surface of the bilayer. they have diverse structures, locations and functions; including transport channels and receptors;

What are some of the functions of proteins in the membrane?

Transport Proteins: Facilitate molecule movement in and out of cells, including channel and carrier proteins. Channel Proteins: Form pores for molecule passage. Carrier Proteins: Change shape to transfer molecules across the membrane. Recognition: Act as cellular 'name tags' for cell-cell recognition, crucial in immune system functioning. Receptors: Bind to chemical signals like hormones, triggering intracellular reactions. Enzymes: Catalyse reactions, e.g., glucose-6-phosphatase in the endoplasmic reticulum. Cell Adhesion & Motility: Aid in cell adherence and movement

How do water molecules move across membranes?

Water moves across membranes always via osmosis: This due the random movement of water molecules; water moves from areas of lower solute concentration to areas of higher solute concentration; solutes cannot pass the through the membrane easily as it is not very permeable to them; water can move through aquaporins; which are specialized channel proteins facilitating water movement;

What are channel proteins what process of membrane transport uses them? Give examples

Channel proteins are proteins which cross the plasma membrane; they allow specific ions to diffuse through when open; due to the amino acids which make up the inside of the channels, so they only attract certain ions/molecules; e.g. glucose; through the GLUT channels; contributing to selective permeability;

What are pump proteins? What process uses them? Give examples

Active transport is the passage of materials against a concentration gradient (from low to high); This process requires the use of protein pumps which use the energy from ATP to translocate the molecules against the concentration gradient; The hydrolysis of ATP causes a conformational change in the protein pump resulting in the forced movement of the substance; Protein pumps are specific for a given molecule, allowing for movement to be regulated (e.g. to maintain chemical or electrical gradients); e.g. Na+/K+ pump which is involved in the generation of nerve impulses; 3 sodium pumped out for every 2 potassium pumped in to the axon;

What is permeability? How are membranes selectively permeable?

Permeability is ability of a membrane to allow molecules to pass through; selective permeability is when a membrane does not allow the free movement of all molecules and is permeable only to certain molecules; due to specific channel proteins; pump proteins; which only allow specific molecules to pass, e.g. Calcium or sodium ions

What is the structure, function, and location of glycoproteins and glycolipids?

Glycoproteins are carbohydrate structures linked to proteins in membranes; glycolipids are carbohydrate structures linked to lipids in membranes; They are both exclusively on the extracellular side; they are used in crucial for cell adhesion; and cell recognition; e.g. as receptors;

What is the fluid mosaic model of membrane structure?

the Fluid mosaic model was proposed by Singer and Nicolson; it says that both integral and peripheral proteins are embedded in the fluid bilayer, forming a mosaic pattern; Lipids and proteins can move laterally within the membrane; meaning it is fluid; Fluidity depends on fatty acid types in phospholipids and the cholesterol content

What is the relationship between fatty acid composition of lipid bilayers and their fluidity?

The fatty acid composition of the membrane can affect its fluidity; if there are more unsaturated fatty acids; which contain double bonds, leading to lower melting points; this makes the lipid bilayer more fluid and flexible; if there are more saturated fatty acids which do not have double bonds; this results in higher melting points

What is cholesterol? What is the impact of cholesterol on membrane fluidity in animal cells?

Cholesterol is hydrophobic found embedded within the lipid bilayer; between hydrophobic fatty acid tails; as it has a hydrophilic region as well; making it amphipathic; Function: it acts as a fluidity regulator; cholesterol reduces fluidity; making membranes more stable at higher temperatures; it also prevents crystallization at lower temperatures;

What is membrane fluidity?

Fluidity is the ability of the membrane to move in a flexible way; It also describes the way that membranes can fuse; and the way membranes can form smaller regions of membrane without breaking

What is endocytosis? What is an example?

endocytosis is a process where large amounts of substances can enter the cell; during endocytosis the membrane can wrap around; and pinch off; forming a vesicle; due to fluidity of membrane; it can remain unbroken; e.g. phagocytosis of bacteria by phagocytes

What is exocytosis? What is an example?

exocytosis is a process where large amounts of proteins; synthesized by rough endoplasmic reticulum; are packaged into vesicles; which pinch-off or bud-off; from the rough endoplasmic reticulum; and are carried to the golgi apparatus; vesicles fuse with the flattened-sac membranes of the Golgi; modification and processing of proteins to put them in their final form takes place; vesicles bud-off again; travel to the plasma membrane; or other locations in cell; fuse with the membrane to secrete contents outside the cell;

How are gated ion channels used in neurons?

voltage-gated channels open and close in response to electrical charge; they are carrier proteins; if there is a change in voltage around the channel causes it to open; potassium channel open; when there are more positive charges inside the cell than outside; K+ can flow through; down the concentration gradient; aids in repolarization of axon as positive potassium flow down concentration gradient out of cell

What is the sodium-potassium pump? How is it an example of an exchange transporter?

Active transport of sodium and potassium uses energy from ATP to pump; the Sodium potassium pump transports 3 sodium ions OUT of cell for every 2 potassium ions IN; sodium ions bind to interior of pump on inside of axon; ATP hydrolysis allow phosphate to bind to pump; causes a conformational change (change in shape) of pump; releasing sodium outside the cell; 2 potassium bind to pump outside of the cell; causing the release of phosphate; causing a conformational change in the pump; releasing potassium inside the cell

What are sodium-dependent glucose co-transporters? How are they an an example of indirect active transport?

Sodium-dependent glucose co-transporters facilitate glucose transport into cells; alongside sodium ions; it is a form of indirect active transport; sodium ions are pumped out of cells; leading to a concentration gradient; as they flow back down their gradient the energy can be used to transport glucose into cells

How do cells adhere to form tissues? What are CAMs?

Cell-Adhesion Molecules (CAMs) are proteins that allow cells to adhere to each other, forming stable tissues; Different forms of CAMs are used in different types of cell-cell junctions

What are organelles? Which cell parts are considered organelles? Which are not?

Organelles as discrete (separate) subunits of cells that are adapted to perform specific functions; nuclei, vesicles, ribosomes and the plasma membrane are considered organelles; cell wall, cytoskeleton and cytoplasm are not considered organelles

Why are the nucleus and cytoplasm separated into different compartments? What is the advantage of this

Separation allows for distinct processes in different compartments of Eukaryotic cells; Gene Transcription: Occurs in the nucleus. Translation: Happens in the cytoplasm. Post-transcriptional modification of mRNA can occur before it reaches ribosomes in the cytoplasm; in contrast with prokaryotes there is No separation, leading to immediate interaction between mRNA and ribosomes.

What are the advantages of compartmentalization in the cytoplasm of cells? What structures are compartmentalized?

the advantage of compartmentalization is that the concentration of specific metabolites and enzymes in particular areas can be increased; biochemical processes can be separated where they would negatively affect each other; enhancing efficiency and safety. examples Lysosomes: Digestive enzymes are kept separate from other cell parts Phagocytic Vacuoles: Contain enzymes for engulfing and digesting foreign substances; which are kept separate;

What are the adaptations of the mitochondrion for the production of ATP by aerobic cell respiration?

Double Membrane: Allows optimum concentrations of enzymes used in respiration, eg. Krebs cycle Small Intermembrane Space: Allows buildup of high concentration of protons (H+) ions Cristae: Large surface area and increases space for electron transport and ATP synthesis; Matrix Compartmentalization: Houses enzymes and substrates for the Krebs cycle, optimizing conditions for ATP production;

What are the adaptations of the chloroplast for photosynthesis?

Thylakoid Membranes: Large surface area with embedded photosystems for light absorption. Thylakoid Fluid: Small volume allows for buildup of high concentration of protons (H+ ions) Stroma Compartmentalization: Contains enzymes and substrates for the Calvin cycle, facilitating glucose synthesis.

What are the functional benefits of the double membrane of the nucleus?

Nuclear Pores: Allow selective exchange of materials between nucleus and cytoplasm; allows mRNA to leave and for DNA to be protected within nucleus; Allows environment to be different than in the cytoplasm, with a different concentration of nucleotides; and for DNA to be protected; Vesicle Formation: Membrane breaks into vesicles during mitosis and meiosis for chromosome segregation.

What is the structure and function of free ribosomes?

Free ribosomes are made of a small and large subunit; they are protein and RNA; they synthesize proteins which are kept within the cell; not for export

What is the structure and function of the rough endoplasmic reticulum?

made of a series of flattened membranes; with ribosomes bound to it; Responsible for processing and secretion of proteins; Modifies proteins received from the rough endoplasmic reticulum and prepares them for export; creates vesicles containing proteins which bud off

What is the structure and function of the Golgi apparatus?

Made up of stacked, flat pouches; made of membrane; Modifies and sorts proteins and lipids; Packages materials for different cell parts or for release from the cell; through exocytosis

What is the structure and function of vesicles in cells? What is clathrin

Vesicles are small, single membrane-bound sacs within the cytoplasm; they transport materials within the cell and to the cell membrane; they are involved in processes like endocytosis and exocytosis; they help store and move nutrients, enzymes, and waste; Clathrin is a protein used in vesicle formation in cells. Clathrin aids in vesicle budding; it forms a Cage-like Structure around membrane areas destined to become vesicles; creating a Clathrin-Coated Pit; allowing the shaping and pinching off of the membrane to create a vesicle.; after, the clathrin coat disassembles through hydrolysis into individual molecules.

What cell is produced by fertilization? How does this cell turn into different cell types in the body?

a zygote is formed; it is an unspecialized cell, known as a stem cell; this cell divides and some cells undergo differentiation; where certain genes are expressed; in particular cell types; leading to different cell

What are the unique properties of stem cells?

Stem cells have the capacity to divide indefinitely; and can differentiate into various cell types, following different pathways

What is the location and function of stem cell niches in adult humans? 2 examples only

Bone marrow stem cells; Maintains and promotes the proliferation and differentiation of blood cells; Hair follicles; support the growth and regeneration of hair by maintaining and differentiating stem cells

What are the differences between totipotent, pluripotent and multipotent stem cells

Totipotent cells (early-stage embryos) can form any cell type, including extraembryonic tissues like the umbilical cord and placenta; Pluripotent cells can form almost any cell type but not extraembryonic tissues; Multipotent cells (like in bone marrow) can form a limited range of cells related to a specific tissue; e.g. only blood cells in the bone marrow

How is cell size an aspect of specialization?

The size of a cell is intricately linked to its function; For instance, small red blood cells are optimally sized for efficient oxygen transport; while large neurons can transmit signals over long distances; Similarly, striated muscle fibers are large to allow contraction over a long distance;

How does surface area-to-volume ratio limit cell size?

The surface area-to-volume ratio is crucial in determining a cell's efficiency in exchanging materials with its surroundings; A higher surface are to volume ratio, found in smaller cells, allows for faster nutrient uptake and waste removal relative to the cell's volume; This ratio limits cell size, as larger cells cannot exchange materials fast enough

What are the adaptations that increase surface area-to-volume ratios of cells?

Cells adapt to increase their surface area through structures like microvilli or flattening; For example, erythrocytes are flattened and biconcave to maximize surface area for gas exchange; while cells in the proximal convoluted tubule have microvilli for efficient reabsorption

What are the adaptations of type I and type II pneumocytes in alveoli?

Type I pneumocytes are extremely thin, maximizing their surface area for gas exchange; and reducing diffusion distance; increasing the rate of exchange; Type II pneumocytes are specialized for producing and secreting surfactant, which reduces surface tension in the lungs and prevents alveolar collapse.

What are the adaptations of cardiac muscle cells and striated muscle fibres?

synchronized contraction; with a Y shaped structure; Striated muscle fibers are long and multinucleated, allowing for powerful, coordinated contractions; Both contain densely packed myofibrils for efficient muscle contraction; striated muscle could be considered acellular, as it has multiple nuclei without a specific cell membrane separating it from other cells

What are the adaptations of sperm and egg cells?

Sperm Cells Long, streamlined, with a flagellum for mobility; have an acrosome which contains enzymes that help penetrate the egg. have mitochondria in the midpiece provide energy for movement Egg Cells Largest cell in the human body, providing ample nutrients for the embryo; Zona pellucida and corona radiata protect and regulate sperm entry; Cortical Granules prevent polyspermy by altering the zona pellucida after the first sperm enters

explain the need for gas exchange

Vital function, essential for life, all organisms need it Allows organisms to take in gasses for cellular processes like and remove waste products made during metabolic reactions

What process allows gas exchange to occur

gas exchange occurs via a process called diffusion The random net movement of particles from an area of high to low concentration. Leads to equilibrium - an equal distribution of particles.

What is the effect of size on the surface area-to-volume ratio

As size of organisms increase, SA to V ratio dec, distance between surface of organism and cells inside organism increases.

What is the effect of organism size on surface area to volume ratio

Small organisms (single celled bacteria and yeast) use simple diffusion for gas exchange because of high SA to V ratio Larger organisms have low SA to V ratio. Diffusion across body surface is inefficient They need special structures like highly folded or branched organs to increase SA for effective gas exchange.

What are necessary properties of gas exchange surfaces

large SA - more membrane surface available for gases to diffuse across permeability - the exchange surface must have pores or openings that allow gases to be exchanged across its surface composed of a thin tissue layer - so that there is a short distance across which gases need to move having a moist surface -this helps to dissolve gases before they diffuse across the exchange surface (for example, alveolar fluid in the alveoli) concentration gradient -for diffusion to occur there has to be a difference in concentration of the gas between two areas. (high to low)

What are the adaptations of capillaries for exchange of materials between blood and the internal or external environment

Adaptations should include a large surface area due to branching and narrow diameters, thin walls, and fenestrations in some capillaries where exchange needs to be particularly rapid.

state the function of a capillary

smallest blood vessel; brings nutrients and oxygen to the tissues and absorbs carbon dioxide and waste products. wall is only one layer thick

State the function an artery

A blood vessel that carries blood under high pressure away from the heart. Thick walls, narrow lumen

State the function of a vein

A vessel that returns blood under lower pressure to the heart. Thinner walls, larger lumen, has valves to prevent back flow of blood

Discuss how pocket valves, thin walls and skeletal muscles maintain the flow of blood through a vein.

Pocket valves prevent backflow; thin walls allow veins to be compressed by muscles; skeletal muscles squeeze veins to push blood toward the heart.

What is a lumen

space within a tubular part or organ, such as the space within a blood vessel

State the unit of measurement of a pulse

Beat of the heart as felt through the walls of the arteries. Pulse rate is measured in beats per minute (bpm). Methods to determine heart rate include palpation at pulse points (e.g., wrist, neck) and using electronic heart rate monitors.

What is coronary heart disease

the clogging of the vessels that nourish the heart muscle; the leading cause of death in many developed countries. Strong correlation with diet of saturated fats

What is atherosclerosis

condition in which fatty deposits called plaque build up on the inner walls of the arteries.

What are risk factors for atherosclerosis

age, genetic, gender, high blood pressure, obesity, physical inactivity, smoking, diet high in saturated fats

Capillaries have a small lumen diameter,