UNIT 2 - CELL STRUCTURE AND FUNCTION Flashcards
what is a cell?
-the basic unit of life
how do new cells arise?
-from preexisting cells
what is common among all living organisms?
-organized
-acquire materials + energy
-homeostatic
-respond to stimuli
-reproduce and have potential for growth
-evolutionary history
why are cells small?
-to maintain a high SA-V ratio
-large amount of SA in comparison to volume
-critical to survival
why is it important for cells to have a larger surface area in comparison to their volume? are there limits to this?
-allows for more nutrients and wastes to be cycles in/out of the cell
-a cell can get too large and not be efficient/metabolically active
what are the two categories of cells?
-prokaryotes + eukaryotes
what are distinct features of prokaryotic cells?
-lack a nucleus
-have 2 groups of bacteria (archaebacteria and eubacteria)
what are distinct features of eukaryotic cells?
-have a nucleus
-includes animals, plants, fungi, and protists
what do both eukaryotes and prokaryotes have?
-plasma membrane
-cytoplasm
what is the plasma membrane made of? what is its purpose?
-phospholipid bilayer
-contains proteins attached + embedded
-to separate the cells internal and external environments
what is special about the phospholipid bilayer?
-selectively permeable (controls what comes in and out)
what is the cytoplasm?
-semifluid substance inside the cell
-includes organelles
what were the first cells on earth? what evolved from these cells? what was specific about the atmosphere at this time?
-prokaryotes (archaeans)
-eukaryotes evolved
-it contained no oxygen
do archaeans survive today?
-in very inhospitable conditions (acid, hot, salt aka thermal vents)
how do we predict organelles developed in the eukaryotic cells? what is this idea called?
-eukaryotes engulfing prokaryotic cells
-endosymbiosis
how did cells gain a nucleus?
-from invagination of the plasma membrane
-eventually surrounding dna with a double membrane
how did the endomembrane system come about?
-proliferation of membranes (rapid growth of new parts of the membrane)
how did the cell gain mitochondria and chloroplast organelles?
-engulfing aerobic and photosynthetic bacteria (prokaryotes)
how does the behaviour of phospholipids cause the plasma membrane to form?
-when placed in water, they will naturally form a spherical bilayer
-hydrophilic heads = towards cytoplasm + extracellular fluid
-hydrophobic tails inward
what is the model used to describe the plasma membrane? why is it described this way?
-fluid mosaic model
-elements such as proteins are able to move freely laterally in the membrane
what helps support the plasma membrane?
-cholesterol
what 2 molecules act as receptors to identify cells as foreign or self? what kind of function is this?
-glycoproteins
-glycolipids
-immune
what makes glycoproteins and glycolipids/
-attached carbohydrate chains
what substances/molecules are able to pass freely through the plasma membrane? what are some examples?
-small hydrophobic substances
-ex: gases (oxygen, carbon dioxide, estradiol)
what substances/molecules need help passing the plasma membrane? what are examples?
-ions and larger molecules
-ex: water, Na+, K+
what is the membrane channel protein that allows water to pass through?
-aquaporin
what is simple diffusion?
-the random movement of molecules from a high to low concentration
-passive movement (no energy)
when does simple diffusion occur until?
-until molecules are equally distributed
-equal #s of molecules moving in and out of the cell
what is to be said about the movement of molecules in simple diffusion?
-move in both directions
-net movement is from high to low concentration
what is osmosis?
-the diffusion of water molecules from high to low water concentration
-passive movement (no energy)
what does it mean for a solution to be isotonic? how do cells react when placed in an isotonic solution (body fluid)?
-same concentration of impermeable solutes in comparison to a body fluid or cell
-cells do not change size (no net movement)
what does it mean for a solution to be hypotonic? how do cells react when placed in a hypotonic solution?
-solution with fewer solutes
-cells will swell and burst (more water movement into the cell)what
what is a cell swelling + bursting also referred to as?
-lysis (membrane breaking down)
what does it mean for a solution to be hypertonic? how do cells react when placed in a hypertonic solution?
-solution with more solutes
-cells will shrink (water movement out of the cell)
what is a cell shrinking also referred to as?
-crenation
what drives osmosis?
-osmotic pressure
what is facilitated transport?
-transport of molecules from a high to low concentration via a protein carrier
-passive movement (no energy)
-protein transporters are specific and only move certain molecules
what are the 2 main transport proteins?
-channels ( gated or ungated)
-uniporter carriers (open one side, close, then open other side)
what is active transport?
-movement of molecules from low to high concentration
what is primary active transport?
-a pump using ATP as energy
-uniport (one molecule)
-cotransport (2 different molecules going different ways)
what is secondary active transport?
-energy is provided by one molecules gradient and another molecule is moved using that energy
-symport (2 molecules move in the same direction)
-antiport (2 molecules move in opposite directions)
what is bulk transport?
-movement of large molecules across the membrane using endocytosis or exocytosis methods
what is endocytosis? what are the 3 methods that are used?
-transports molecules or cells into the cell via invagination of the plasma membrane to form a vesicle
-phagocytosis
-pinocytosis
-receptor-mediated endocytosis
what is phagocytosis?
-endocytosis of pathogens (bacteria)
-done by white blood cells
what is pinocytosis?
-endocytosis of fluid with small particles (solutes)
-microvilli of small intestine
what is receptor-mediated endocytosis?
-particles must bind to receptors in the plasma membrane to initiate endocytosis
-receptors cluster to form coated pits
-brings in useful substances (typically)
what is exocytosis?
-transports molecules outside the cell via the fusion of a vesicle with the plasma membrane
-reverse endocytosis
what is the nucleus?
-contains genetic instruction for making proteins involved in cell function
-contains DNA in chromatin form typically
do all cells contain the same genes?
-YES
what is the nucleoplasm?
-fluid inside the nucleus
what is the nucleolus?
-dark region inside the nucleus
-produces ribosomal RNA (rRNA)
what is the nuclear envelope?
-a double membrane (phospholipid bilayer) around the nucleus
what are the nuclear pores?
-holes in the nuclear envelope
-allow substances to pass in + out
what is the endomembrane system?
-series of membranous organelles that function to process and transport materials for the cell
-also for compartmentalization
what are ribosomes?
-made of rRNA and protein
-sites of protein synthesis
-attached to the outer nuclear membrane and the rough endoplasmic reticulum or free floating the cytoplasm
what are groups of free floating ribosomes called?
-polyribosomes
what organelles make up the endomembrane system?
-nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, and vesicles
what is the rough endoplasmic reticulum?
-folded membrane studded with ribosomes
-proteins made here go to nearly all areas of the cell
where do the proteins made by the free floating ribosomes go?
-cytosol
-mitochondria
-nucleus
what is the smooth endoplasmic reticulum?
-folded membrane that lacks ribosomes
-synthesizes lipids
what is the golgi apparatus?
-flattened membrane sacs
-modify proteins and lipids
-help in processing, packaging, and secreting
what are vesicles?
-small membranous sacs (phospholipid bilayer) used for transport
-break off from ER or golgi apparatus
what are lyososomes?
-vesicles containing hydrolytic enzymes that break off from the golgi apparatus
-break down molecules into smaller parts
-common in white blood cells (engulf disease causing microbes)
what is the cytoskeleton?
-protein fibers that help maintain cell shape + anchor and/or move organelles in the cell
-3 fibers
what are the 3 fibers that make up the cytoskeleton?
-microtubules
-intermediate filaments
-actin filaments
what are the characteristics/functions of microtubules?
-maintain cell shape
-largest fiber of the cytoskeleton
-help organelles move (act as tracks)
-assembly controlled by the centrosome
-forms spindle apparatus during cell division to help move chromosomes
-dynamic structure (elongates + shortens)
what are the characteristics/functions of intermediate filaments?
-internal structure + cohesion (anchoring) of cells (strength)
-consist of keratin or vimentin proteins
what are the characteristics/functions of actin filaments?
-cell movement (flagella + muscle)
-smallest fiber of the cytoskeleton
-long and very thin
-made of actin protein
what is characteristic of flagella and cilia? where can we see each?
-both contain microtubules
-both are used in movement
-cilia : respiratory tract to move mucus
-flagella : sperm cells to propel to the egg
what is the extracellular matrix?
-protective mesh of proteins and polysaccharides
-surrounds the cell that produces it
what is contained within the extracellular matrix?
-collagen (resists stretching)
-elastin (resilience/elasticity)
-fibronectin (adhesive protein) binds to integrin (integral membrane protein) connected to the cytoskeleton (role in cell signalling)
what are the types of cell junctions?
-adhesion junctions
-tight junctions
-gap junctions
-desmosomes
-nanotubes
what are adhesion junctions?
-attach cytoskeletons of adjacent cells (velcro belt)
-attach actin filaments
what are tight junctions?
-waterproof barrier
what are gap junctions?
-fuse of 2 channels (create clusters of joined channels)
-allows for communication between cells
what are desmosomes?
-strong disk like junctions joining 2 cells cytoskeletons
-attach intermediate filaments
what are nanotubes?
-actin containing protrusions that connect cells
-can form tunnels to transfer signals and various things (proteins, soluble molecules, and organelles (mitochondria))
what is special about the mitochondrion membrane?
-has an inner and outer membrane surrounding the matrix (space between)
-inner membrane is folded into cristae which contain enzymes for cellular respiration
what is the main function of the mitochondrion?
-convert chemical energy from glucose into ATP
what does cellular respiration use up? what does it give off?
-uses up oxygen
-gives off carbon dioxide
do mitochondria have their own DNA?
-YES
-mitochondrial DNA (some for proteins, tRNA, and rRNA)
-meaning they can multiply
what is the basic idea of what cellular respiration does?
-breaks down glucose into carbon dioxide and water
what are the 4 main steps of cellular respiration?
-glycolysis
-intermediate reaction
-citric acid cycle (Krebs cycle)
-electron transport chain
why do we say that 30 ATP are made per glucose molecule when 32 are actually produced/
-2 ATP are used to bring 2 NADH from glycolysis into the mitochondria
is NAD+ the oxidized or reduced form?
-oxidized
-oxidation is loss of electrons
is NADH the oxidized or reduced form?
-reduced
-reduction is gain of electrons
does NADH OR NAD+ act as the electron transporter?
-NADH
what are the basics of glycolysis?
-breaks glucose into 2 pyruvates
-occurs in the cytoplasm
-anaerobic (does not need oxygen)
-produces 2 NADH and 2 ATP molecules
what happens in the first half of glycolysis?
-2 ATP molecules are needed to phosphorylate glucose
what happens in the second half of glycolysis?
-phosphorylation occurs without the need of ATP
-2 NADH, 4 ATP, and 2 pyruvates are formed
what is the intermediate reaction?
-occurs when oxygen is available
-occurs in the mitochondria
-produces 2 NADH and 2 CO2 per glucose (1/2 per pyruvate)
-prepares pyruvates for the Krebs cycle
-pyruvates become acetyl CoA
what is the citric acid cycle?
-series of enzymatic reactions
-occurs in the matrix of the mitochondria
-completes the breakdown of glucose (breaks carbon bonds)
-produces 6 NADH, 2 FADH2, and 2 ATP per glucose (1/2 per acetyl CoA)
-releases 4 CO2
what carries hydrogen and electrons away in the citric acid cycle? where are the electrons taken?
-NADH
-FADH2
-electron transport chain
what can be converted into compounds that can enter the citric acid cycle?
-fats
-proteins
what makes up the electron transport chain?
-carrier protein complexes embedded in the mitochondrion’s cristae
what occurs along the electron transport chain?
-each carrier accepts 2 electrons and passes them along
-H+ ions get transferred between the inner and outer mitochondria membrane (more from NADH, less from FADH2)
-oxygen is the final acceptor
is the electron chain anaerobic or aerobic?
-aerobic (needs oxygen)
what happens once the oxygen accepts the electron?
-combines with hydrogen atoms to become water
how does our breathing relate to cellular respiration?
-we breath in oxygen to be used as the electron acceptor
what are the total net products of cellular respiration?
-30 ATP
-10 NADH
-2 FADH
what is fermentation?
-occurs when oxygen is not available (anaerobic)
-glycolysis still occurs
-produces lactate (toxic) instead of acetyl CoA
-cori cycle gets rid of lactate
-2 ATP produced per glucose
