PCAT Biology Flashcards
Metabolism can be divided into Two reactions. They are?
- Catabolic
2. Anabolic
What are catabolic reactions?
They BREAK DOWN large chemicals and RELEASE energy
What are Anabolic reactions?
They BUILD UP large chemicals and REQUIRE energy
What is Homeostasis?
The body’s metabolism functions to maintain its internal environment in a changing external environment.
What do Enzymes Do?
- They affect the reaction rate by decreasing the activation energy.
- They can speed up or slow down chemical reactions
What are Conjugated Proteins?
They are complex proteins consisting of amino acids COMBINED WITH OTHER SUBSTANCES. ( the other substances are known as prosthetic groups and they can be covalently bonded or positioned by other forces to the protein. )
What effects enzyme action and the reaction rate?
pH
Temperature
Concentration of enzyme and substrate
Lock and Key Theory
Spatial structure of an enzyme’s active site is exactly complementary to the spatial structure of its substrate. (triangle block fits into triangle space)
Induced fit Theory
When the appropriate substrate comes in contact with the active site, the conformation of the active site changes to fit the substrate
True or False: Most enzyme reactions are reversible
True
Maximal activity of many human enzymes occur at what pH?
7.2
What is pepsin and what pH does it operate in?
Enzyme found in stomach and works best in highly acidic conditions (pH = 2)
Where do pancreatic enzymes Operate and what pH do they work best in?
They operate mainly on the small intestine with an optimal pH of 8.5
Competitive Inhibition
If a similar molecule is present in a concentration comparable to the concentration of the substrate, it will COMPETE WITH THE SUBSTRATE for binding sites on the enzyme and INTERFERE with enzyme activity.
Solution to competitive inhibition?
Raise the concentration of the substrate
Noncompetitive Inhibition
a substance that forms strong covalent bonds with an enzyme and consequently may not be displaced by the addition of excess substrate. therefore, IT IS IRREVERSIBLE.
Allosteric inhibition
- Form of Noncompetitive inhibition
2. A non competitive inhibitor that inhibits at a site other than the active site ( rear end)
What does hydrolysis do?
- form of enzyme activity
2. digest large molecules into smaller components
What does Lactase do?
- form of enzyme activity
2. Hydrolyzes lactose to glucose and galactose
What does Protease do?
- form of enzyme activity
2. Degrade proteins to amino acids
What does Lipases do?
- Form of enzyme activity
2. breaks down lipids –> Fatty acids + Glycerol
What are synthesis reactions catalyzed by?
Which direction do they go in?
What are they important for?
- catalayzed by same enzymes as hydrolysis rxns except in reverse direction.
- required for growth, repair, regulation, protection, and production of food reserves such as glycogen and fat by the cell.
What are Cofactors?
How can they be obtained?
- Metal Cations ( Zn2+ or Fe2+) or small organic coenzymes that bind that enzyme by strong covalent bonds. (prosthetic groups)
- Cant be synthesized by body and obtained from diet.
What are prokaryotes?
“before nucleus” cells that lack nucleus(bacteria)
What are Eukaryotes?
Cells that have nucleus (us)
What is a Cell Membrane/plasma membrane?
- Regulates passage of materials into and out of the cell.
2. Consists of Phospholipid Bilayer with proteins embedded throughout.
Which parts are Hydrophobic and hydrophilic on the phospholipid bilayer?
The Head ( Hydrophilic) - phosphorous The Tail ( Hydrophobic) - C's and H's
Can Large charged ions and charged molecules cross the cell membrane ?
They can, only with the assistance of CARRIER proteins
What does the nucleus do?
What does it contain?
- Controls activities of the cell, including cell division
2. it contains DNA which is complexed with histones.
What are Histones?
- Proteins that are closely associated with DNA molecules,
- Responsible for forming chromosomes.
- Responsible for structure of chromatin and regulation of gene expression.
Whats special about the nucleolus?
Its a dense structure IN THE NUCLEUS where RIBOSOMAL RNA (rRNA) SYNTHESIS OCCURS
Whats special about ribosomes?
Two locations of ribosomes?
- they are synthesized by nucleolus
- site of protein production
Free ribosomes found in cytoplasm
Bound ribosomes line the outer membrane of Endoplasmic Reticulum (ER)
Purpose of endoplasmic reticulum (ER) ?
two types?
involved in TRANSPORT of materials throughout the cell
(materials that are going to be secreted by the cell)
Rough ER: has ribosomes attached to them
Smooth ER: has no ribosomes attached
Rough ER vs Smooth ER
Rough ER: where molecules and proteins are made
Smooth ER: Metabolizes certain compounds and synthesis of lipids and steroids. also secretes proteins into cytoplasmic vesicles that are transported to the golgi apparatus
what does Golgi Apparatus do?
- package and processes proteins, lipids etc. that are synthesized by the cell.
- Modifies and sorts them and repackages them into vesicles
Why is the mitochondria important?
- they are sites of aerobic respiration within the cell
2. provides energy for cell
What does the cytoplasm consist of?
what is it responsible for?
- consists of all of the contents outside of the nucleus and enclosed within the cell membrane of a cell.
- Fluid that fills up the cell
- Most of cells metabolic activity occurs here.
- helps to move materials around the cell and also dissolves cellular waste.
Cyclosis
It is the streaming movement within the cell that helps transports molecules within the cytoplasm
what is Exocytosis?
- the vacuole membrane fuses with the cell membrane
- the contents of the cell vacuole are then released outside the cell surface
- DUMPING STUFF OUT OF CELL
what are Vacuoles/Vesicles?
What do they do?
Membrane-bound sacs involved in transport and STORAGE of materials that are ingested, secreted, processed , or digested by the cell
- Storage bubbles found in cells
- store nutrients that cells need to survive
- store waste products to protect cell from contamination
What are centrioles?
what are they made up of?
- they are involved in spindle organization during cell division.
- composed of microtubules
- direct the separation of chromosomes during cell division
True or False: plant cells contain centrioles
False, only animal cells
what do Lysosomes contain?
what do they do?
Importance of lysosomal membrane?
- contains hydrolytic enzymes involved in digestion within the cell.
- Breaks down material ingested by the cell. 3. The products of the lysosomal digestion are released into the cytoplasm where they can be used by the cell.
- hydrolytic enzymes would digest cellular components without the lysosomal membrane (killing the cell)
What is autolysis?
- An injured or dying cell commits suicide by rupturing the lysosome membrane and releasing its hydrolytic enzymes.
- the DESTRUCTION of cells or tissues by their OWN ENZYMES
What is the significance of cytoskeleton?
- it supports the cell
- Maintains cell shape
- Functions as cell motility
What is the cytoskeleton composed of?
- Microtubules
- Microfilaments
- Intermediate filaments
What do microtubules do?
what are they composed of?
- Provide framework for organelle movement within the cell
2. composed of tubulin
What are cilia and flagella?
microtubules that extend from the surface of certain cells and are involved in cell motility and cytoplasmic movement
Difference between cilia and flagella?
Cilia mostly found in eukaryotic cells
Flagella found in both prokaryotic and eukaryotic cells. Flagella are the tails on sperm
What are microfilaments composed of?
What do microfilaments do?
- Solid rods of ACTIN
- important in cell movement and support
- Move materials ACROSS the cell membrane.
What is Simple Diffusion?
- Passive process that requires no external source of energy.
- Movement of dissolved particles from a region of higher conc –> region of lower conc
What is Osmosis?
- simple diffusion of water from a region of lower solute conc –> higher solute conc.
What is HYPERtonic?
When cytoplasm has [Solute] < [Solute] outside it
water will FLOW OUT OF the cell
Plasmolysis
Water will flow out of the cell causing it to shrivel because the concentration of solute in the cell’s cytoplasm is lower than the outside environment
What is HYPOtonic?
if the outside of the cell has [solute] < [solute] inside the cytoplasm, water will FLOW INTO the cell
What is passive transport?
- Movement of dissolved particles DOWN their concentration gradient VIA SPECIAL CHANNELS OR CARRIER PROTEINS in the cell membrane.
- does NOT require energy.
What is Active Transport?
- Movement of dissolved particles AGAINST their concentration gradient WITH THE HELP OF TRANSPORT PROTEINS.
- REQUIRES energy.
Importance of carrier molecules in active transport and the different types?
The carrier molecules aid in the regulation of the cell’s internal content of ions and large molecules
- Energy Independent Carriers
- Symporters
- Antiporters
- Pumps
What are Energy Independent Carriers?
- Carrier molecule
2. Facilitates the movement of compounds along the concentration gradient
What are symporters?
- Carrier Molecule
2. Move two or more ions or molecules
What are Antiporters?
- Carrier Molecule
2. EXCHANGE one more more ions ( or molecules ) for another ion or molecule
What are Pumps in active transport?
- Carrier molecule
- Energy-dependent carriers (REQUIRES ATP)
- ex sodium potassium pump
What is Endocytosis?
- Process which a cell membrane turns itself inside out to form a cavity . this forms a vesicle that contains extracellular medium.
- taking stuff INTO the cell (ingestion)
What is Pinocytosis?
Cell ingests fluids or small particles from the small vesicles from the cell membrane
2. taking in fluids or small stuff into cell via endocytosis
What is Phagocytosis?
engulfing of large particles (ex bacteria)
2. taking in big stuff into the cell via endocytosis
What is Circulation in cell terms?
The transportation of material within cells and throughout the body of a multi-cellular organism
Different types of intracellular circulation?
- Brownian movement
- Cyclosis or streaming
- Endoplasmic reticulum
What is brownian movement?
Kinetic Energy Spreads small suspended particles throughout the cytoplasm of the cell
What is cyclosis or streaming?
Circular motion of cytoplasm around the cell transports molecule
Different types of EXTRAcellular circulation?
- Diffusion
2. Circulatory system
What is Diffusion?
transport of food and oxygen from the environment to the cells based on the direct or close contact the cell has with its environment
What is circulatory system in means of circulation?
- Includes vessels to transport fluid and pumps to drive circulation
- for animals whose cells are too far to have direct contact with its external environment
Organelles Involved in ingestion for eukaryote cells?
Cell membrane and Vesicles via endocytosis
Organelles involved in Digestion for eukaryote cells?
Lysosomes, Vesicles, and Mitochondria.
Organelles involved in transport of protein for eukaryote cells?
ER and microtubules( in neurons)
Prokaryotes Vs. Eukaryotes in the organization of genetic material
Prokaryotes - genetic material Composed of single circular molecule of DNA localized in nucleoid
Eukaryotes - Highly coiled linear strands of DNA organized into chromosomes within a nucleus
Prokaryotes Vs. Eukaryotes in site cellular respiration
Prokaryotes - Cellular respiration occurs directly at cell membrane
Eukaryotes - cellular respiration occurs across the mitochondrial membrane within the mitochondria
Prokaryotes Vs. Eukaryotes in the presence of membrane bound organelles
Prokaryote - does not contain membrane-bound organelles
Eukaryotes - contains multiple. ex: nucleus, Lysosome, mitochondria, ER
Prokaryotes Vs eukaryotes similarity
They both have DNA and Ribosomes
What is Cell Division?
- Process by which a cell doubles its organelles and cytoplasm, replicates its DNA, and then divides into 2.
Cell division for unicellular organisms?
It just means reproduction
Cell division for multicellular organisms?
Its a method of growth, development, and replacement of worn-out cells
What two courses can cell division follow?
- Mitosis or
2. Meiosis
What is Mitosis?
Division and Distribution of the cell’s DNA to its two daughter cells such that each recieves a complete copy of the original genome.
What is karyokinesis?
Nuclear division that follows after cell division
What does a cell undergo before mitosis?
Interphase.
What is interphase?
How long does a cell stay in interphase?
- a process where the cell undergoes a period of growth and replication of genetic material
- a cell spends at least 90% of its life in interphase
- it is the growth period
What are the results of interphase?
each chromosome is replicated so that during division, a complete copy of the genome can be distributed to both daughter cells.
what is a Centromere?
the central region site where the two identical sister chromatids are held together
What is chromatin?
Uncoiled DNA during interphase
What are the four parts of interphase?
- G1
- S
- G2
- M
What happens in G1
- G1 INITIATES interphase.
- its the active growth phase
- Cell increases in size and synthesizes proteins
What happens in S
DNA is duplicated in preparation for cell division
What happens in G2
Cell prepares to divide.
It grows and synthesizes protein and cytoplasm for physical volume
What happens in M
- Cell division Occurs (mitosis)
2. Results in two identical daughter cells
What happens in Prophase?
- Chromosomes condense
- Centriole pairs separate and move towards opposite poles of the cell
- Nuclear membrane dissolves
What happens during metaphase?
- Centriole pairs now at opposite poles of cell
- Fibers of the spindle apparatus attach to each chromatid
- Chromosomes aligned aligned at the center of the cell Forming the metaphase plate
What happens during anaphase?
Centromere split so that each chromatid has its own distinct centromere.
- sister chromatids separate
- sister chromatids are pulled towards the opposite poles of the cell by shortening of the spindle fibers
What happens during telophase?
- Spindle apparatus disappears.
- Nuclear membrane forms around each set of newly formed chromosomes.
- Each nucleus contains same number of chromosomes (diploid number = 2N ) as the parent nucleus.
What happens during Cytokinesis?
Cytoplasm Divides into two daughter cells, each with a complete nucleus and its own set of organelles.
What is Meiosis?
- Process by which sex cells are produced.
- Similar to mitosis where cell duplicates its chromosomes before undergoing the process
- PRODUCES 4 HAPLOID (1N) Cells - Halving # of Chromosomes
What are Gametes?
- The haploid cells formed by meiosis
2. Specialized sex cells produced by each parent
What are Homologous Chromosomes?
Chromosomes that code for the same traits.
What is Synapsis in Meiosis?
When two homologous chromosomes come together and intertwine
Whats interesting about Prophase I in meiosis?
Chromatids of homologous chromosomes (one from each parent) break at corresponding points and exchange equivalent pieces of DNA. They cross over.
What is result of Recombination?
- Recombination among chromosomes results in increased genetic diversity within a species.
- Sister Chromatids are no longer identical after recombination occurs
Difference In Anaphase I of meiosis Vs anaphase of Mitosis
- Anaphase I of meiosis involves the HOMOLOGOUS pairs separating and pulled to opposite poles of the cell ( known as disjunction )
- For Mitosis in anaphase, the CHROMATIDS of the chromosomes get separated, NOT the entire chromosome.
Sexual Reproduction requires?
- Production of functional sex cells or gametes
- Union of Gametes ( Fertilization or Conjugation) to form a ZYGOTE
- Development of zygote in another adult
Why are Gonads Important?
Gametes are produced in these specialized organs.
What are male gonads and what do they do?
- Male Gonads = Testes
2. Produce sperm in seminiferous tubules
What are Female Gonads and what do they do?
- Female Gonads = Ovaries
2. They produce Oocytes ( eggs )
What are Hermaphrodites and examples?
- species that have both female and male gonads.
2. Hydras and Earthworms.
What is Spermatogensis?
- Production of Sperm in seminiferous tubules
2. Spermatogonia (diploid cells) undergo meiosis to produce FOUR haploid sperm.
Anatomy Of Sperm?
- Head - Consists of nucleus, which contains parental genome.
- Tail (flagellum) - Propels sperm
- Neck and Body - is the mitochondria that provides energy for movement.
What is Oogenesis?
- production of female gametes that occurs in ovaries
