Exam #2 Flashcards
Cells as building blocks
basic building blocks of the body
each type of cell serves specific functions
characteristics of cells
all cells
1. DNA is used to direct the synthesis of proteins through transcriptions & translation
2. they are too small to be seen with the naked eye
3. a plasma membrane
microscopy
microscopes are essential tools for studying cells due to their small size
different types of microscopes provide different views and levels of detail
light microscopes
use visible light that passes through lenses
used to view living organisms, but staining may be needed to view cellular components
fluorescence microscopes
uses light of specific wavelengths (ie,colors) together with complicated specimen preparation to visualize sub-celluar structures
electron microscopes
uses beams of electrons for higher magnification and resolution than light microscopes
cannot view live cells (preparation kills cells)
prokaryotic cells
- bacteria and archaea
- simple structure - lack nucleus and membrane-bound organelles
- key features: plasma membrane, cytoplasm, DNA (in the nucleoid region) and ribosomes
- cell walls (made of peptidoglycan in bacteria), sometimes with capsules, and use flagella for movement
eukaryotic cells
- animals, plants, fungi and protists
- more complex with membrane-bound nucleus and organelles
- larger than prokaryotic cells (10-100um)
- adaptations such as specialized organelles
help manage the large size and complex functions of eukaryotic cells
compartmentalized
eukaryotic cell structure
- compartmentalized for order and efficiency
- complex intracellular skeletal system - cytoskeleton
- cells of multicellular organisms are surrounded by extracellular substance, they also form a variety of cell junctions
- “cell junctions” - refers to sites of contact between adjacent cells
plasma membrane
- phospholipid bilayer with embedded proteins
- regulates the passage of substances in and out of the cell
- contains cholesterol and carbohydrates, which provide structural support
cytoplasm
- cell’s internal fluid
- organelles suspended in an an aqueous solution within which organelles reside called cytosol
- contains water, ions, proteins, sugars, fatty acids
- many metabolic reactions (protein synthesis) take place here
endomembrane system
- nuclear envelope
- rough er
- golgi apparatus
- vesicles
- plasma membrane
these structures work together to produce, modify, package and transport proteins to the lysosomes and plasma membrane
nucleus
control center of the cell
- contains DNA as chromosomes
- DNA is wrapped around proteins and is condensed into chromatin
- DNA directs transcription and protein synthesis
- The nucleus has two phospholipid bilayers called the nuclear envelope
- Nuclear pores allow for large or polar molecules to enter and exit the nucleus (this is how mRNA leaves the nucleus to be translated).
-The outer membrane of the nucleus is covered in ribosomes. The perinuclear space of the nuclear
envelope is continuous with the lumen of the rough ER
endoplasmic reticulum
- an extensive network of membranes organized in folds & stacks called cisternae
- ER membrane organization creates a tubular intracellular compartment – the inside is called the ER lumen
Rough ER
- Studded with ribosomes, it synthesizes and modifies proteins.
- Proteins synthesized on ER-bound ribosomes are transported into the ER lumen as they are
produced - Site where proteins transported by the endomembrane system are produced
- Site of protein modification (by enzymes) with carbohydrates (resulting in “glycoproteins”)
- Initiates transport of proteins toward their final destination by vesicular transport
- Proteins exported from the ER in vesicles travel first to the Golgi apparatus
smooth ER
Lacks ribosomes and is involved in lipid synthesis and detoxification (NOT PART OF
ENDOMEMBRANE SYSTEM)
golgi apparatus
- Functions as the “shipping & receiving center” of the cell
- This organelle modifies, sorts, and packages proteins and lipids for distribution within the cell or secretion outside the cell.
- the Golgi apparatus consists of a stack of flattened membranous sacs called cisternae & associated vesicles
- Like the ER, Golgi membranes are organized forming intracellular compartments called the Golgi
lumen
Lysosomes
- Found in animal cells, lysosomes contain digestive enzymes that break down cellular waste, old organelles, and foreign invaders.
- lysosome function is dependent on the endomembrane system, which delivers hydrolytic enzymes to lysosomes that then breakdown/digest substances within the organelle
Phagocytosis
(1) The internalization of extracellular substances (e.g., food for the cell) in vesicles
(2) The fusion between the vesicles with a lysosome, whereupon the hydrolytic enzymes break down the
substance
autophagy
(1) The encapsulation of a dysfunctional organelle into an intracellular vesicle
(2) The fusion between the vesicle with a lysosome, where the hydrolytic enzymes break down the dysfunctional organelle
Transport vesicles
- transport proteins and other cargo through the cells
(1) Bud a vesicle from the membrane of one compartment
(2) Sort proteins into vesicle while it is budding
(3) The transport vesicle moves to another target compartment
(4) The transport vesicle then fuses with the compartment, in turn releasing the contents within it
mitochondria
- Known as the cell’s powerhouses, mitochondria generate ATP (energy) through cellular respiration using glucose.
(1) All eukaryotic organisms have multiple mitochondria per cell
(2) Mitochondria contain an abundance of proteins that synthesize ATP, most of which are associated with the inner membrane
(3) The cristae folds increase the amount of inner membrane, which in turn increases the
number of proteins & amount of ATP production
(4) They contain their own circular DNA that contains several genes that encode proteins
essential for ATP production
(5) Mitochondria also contain their own ribosomes to synthesize proteins
chloroplasts (plant cells)
Chloroplasts are responsible for photosynthesis, converting light energy into
chemical energy stored as glucose.
(1) They have their own DNA and ribosomes, similar to mitochondria.
(2) contain membranous system of flattened, interconnected sacs called thylakoids
(3) Thylakoids contain a molecule called chlorophyll, which along with the many proteins is responsible for producing glucose from solar E
endosymbiosis
Endosymbiotic Theory: This theory suggests that mitochondria and chloroplasts originated as separate prokaryotic organisms. Ancient host cells engulfed aerobic bacteria and cyanobacteria, which then developed symbiotic relationships. Over time, these bacteria became specialized as
mitochondria (aerobic bacteria) and chloroplasts (photosynthetic bacteria) within the host cells.
- explains why mitochondria and chloroplasts have their own DNA and ribosomes, which are
similar to those found in bacteria.
vacuoles (plant cells)
The central vacuole functions as a storage site for water & organic compounds—it
has a phospholipid bilayer membrane
cell cytoskeleton
A network of protein fibers within the cytoplasm, the cytoskeleton maintains cell shape, anchors organelles, and facilitates movement. Actin filaments, intermediate filaments, microtubules
actin filaments
The thinnest filaments involved in cell movement and division.
Functions: Cell structure, cell shape, and cell movement
intermediate filaments
Provide structural support and anchor organelles.
Functions: Cell structure (One structural role of note is forming the nuclear lamina)
microtubules
Thick, hollow tubes that move organelles and chromosomes during cell division
and makeup structures like cilia and flagella.
Functions: Cell structure, Cell motility through cilia & flagella, Intracellular trafficking of vesicles & organelles (MTs act as railroad tracks and motor proteins as trains to move vesicles)
plant cells
Have a rigid cell wall made of cellulose.
Contain chloroplasts, which perform photosynthesis.
Have a large central vacuole that helps maintain turgor pressure
animal cells
Contain centrioles and lysosomes, which are absent in plant cells.
Do not have cell walls or chloroplasts.
tight junctions
In animal cells, these create a watertight seal, preventing leakage of materials, like
those found in epithelial cells lining organs
desmosomes
These structures connect adjacent animal cells, giving tissues like skin and muscle their
strength
gap junctions
Gap junctions form pores that allow communication between animal cells by enabling the exchange of ions and small molecules
Plasmodesmata
Similar to gap junctions, these are channels that connect plant cells, allowing for the
transport of nutrients and communication
Phospholipid bilayer
Membranes are composed of phospholipids + proteins
Membrane proteins attach (or “bind”) the ECM & cytoskeleton
Membrane proteins are classified based on how they are physically associated with the membrane
o Integral proteins – integrated into the phospholipid bilayer
o Transmembrane proteinsProteins that cross the bilayer
o Peripheral proteins – associated by binding to integral proteins
membrane proteins
cell-cell recognition
intercellular joining
attachment to the cytoskeleton and ECM
transport
enzymatic activity
signal transduction
passive transport
movement of molecules across membranes driven by the laws of diffusion
diffusion
type of passive transport
the tendency of molecules to spread out evenly within an available space (gases & liquids) from high to low concentrations
osmosis
diffusion of water across a semi-permeable membrane
net movement of water is drive by the concentration solutes that cannot cross the membrane on either side
water moves from hypotonic to hypertonic to become isotonic again
isotonic
equal concentrations
hypertonic
more solutes, less water
hypotonic
more water, less solutes
facilitated diffusion
type of passive transport
Large polar molecules & ions transit membranes through transmembrane proteins
a. A channel protein: Provide an open channel/pore to facilitate the diffusion of molecules
b. A carrier protein: Undergo shape changes (aka, conformational changes) to facilitate the
diffusion of molecules
c. NOTE: In both cases, molecules move according to laws of diffusion
active transport
Movement of molecules across membranes AGAINST or UP their concentration gradient
2 KEY REQUIREMENTS:
1. Protein transporter pump
2. ATP
A good example is a sodium-potassium pump
Note that the pump has different conformations (shapes) in each position
Conformational changes alter the affinity of the pump for sodium and potassium
Conformational changes are driven by energy from ATP
bulk transport
large molecules across the plasma membrane by vesicular transport
exocytosis
type of bulk transport
out of cell
endocytosis
type of bulk transport
into the cell
Phagocytosis: Internalization of large structures/substances
Pinocytosis: Internalization of smaller substances/molecules
Receptor Mediator Endocytosis: Internalization of SPECIFIC small substances/molecules
ATP
Adenosine triphosphate (ATP) is the primary energy-supplying molecule in cells.
Structure: ATP contains three components:
Adenine (a nitrogenous base)
Ribose (a five-carbon sugar)
Three phosphate groups connected in a series, making ATP high energy
ATP Hydrolysis: Removal of a phosphate group from ATP releases energy, converting it to ADP
(adenosine diphosphate). This energy powers cellular processes
cell respiration (step 1)
- Glycolysis: The First Step in Glucose Breakdown
Location: Cytoplasm of prokaryotic and eukaryotic cells.
Overview: Glycolysis converts one molecule of glucose (6-carbon) into two molecules of pyruvate (3-
carbon).
Process:First Phase: Uses energy (ATP) to split glucose into two molecules of pyruvate.Second Phase:
Produces ATP and NADH.
Products: 2 Pyruvate molecules, 2 ATP, 2 NADH
Importance: Glycolysis occurs in the absence of oxygen and is the sole source of ATP for cells like
mature red blood cells.
cell respiration (step 2)
- Citric Acid Cycle (Krebs Cycle)
Location: Mitochondrial matrix in eukaryotic cells.
Process:
* The 2 Pyruvate from glycolysis are converted into acetyl CoA, which enters the cycle.
* Produces 1 CO₂, 1 ATP (or equivalent), 4 NADH, and 1 FADH₂ from each pyruvate
* Functions as a closed loop with the regeneration of starting compounds.
Significance: Extracts energy from acetyl CoA, releasing high-energy electrons.
From 2 pyruvate Generates: 2 ATP, 8 NADH, 2 FADH
NADH and FADH are coenzymes that can transfer elections important during oxidative phosphorylation
cell respiration (step 3)
- Oxidative Phosphorylation
Location: Inner mitochondrial membrane (eukaryotes)
Process:
* Electrons are transferred through the electron transport chain (ETC) complexes, losing energy.
* This energy is used to pump H⁺ ions, creating an electrochemical gradient.
* The proton gradient allows H⁺ ions to flow through ATP synthase, regenerating ATP from ADP.
Oxygen’s Role: Acts as the final electron acceptor, forming water with hydrogen ions to keep the gradient
moving
Importance: Responsible for 90% of ATP production during aerobic respiration
fermentation
Definition: A process where NADH donates electrons to an organic molecule, regenerating NAD⁺ for
glycolysis in the absence of oxygen.
Types:
1. Lactic Acid Fermentation: Converts pyruvate into lactic acid (e.g., in muscle cells during oxygen shortage).
2. Alcohol Fermentation: Converts pyruvate into ethanol and CO₂ (e.g., by yeast in brewing
anaerobic respiration
Uses an inorganic molecule (other than oxygen) as the final electron acceptor in the ETC.
Example: Sulfate-reducing bacteria use sulfate to regenerate NAD⁺ and produce hydrogen sulfide (H₂S).
photosynthesis
Definition: A process used by certain organisms (photoautotrophs) to convert solar energy into chemical
energy in the form of glucose (food).
Importance: Directly or indirectly provides energy for almost all living organisms on Earth and releases oxygen
into the atmosphere.
Relevance: Every food product humans consume can be traced back to photosynthesis.
overview of photosynthesis
Reactants: Sunlight, water (H₂O), and carbon dioxide (CO₂).
Products: Glucose (C₆H₁₂O₆) and oxygen (O₂).
Summary: Organisms like plants, algae, and some bacteria use photosynthesis to produce carbohydrates and
oxygen. Humans, as heterotrophs, rely on autotrophs for their energy needs
structures of photosynthesis
Chloroplasts: Organelles where photosynthesis occurs, containing chlorophyll and other pigments.
Key Structures:
Thylakoids: Membrane-bound compartments within chloroplasts that contain chlorophyll. Stacks of thylakoids
form a granum.
Stroma: The fluid surrounding the thylakoids where the Calvin cycle occurs.
Stomata: Small openings in the leaves that allow gas exchange (CO₂ and O₂
first step of photosynthesis
Light-Dependent Reactions:
Location: Thylakoid membrane.
Purpose: Convert solar energy into chemical energy in the form of ATP and NADPH.
Process:
Light hits chlorophyll, exciting an electron.
Water molecules are split, producing O₂ as a byproduct.
Electrons travel through the electron transport chain, creating an electrochemical gradient.
ATP and NADPH are produced.
Photosystems I and II: Complexes in the thylakoid membrane where light energy is absorbed and transferred
to electrons.
Photon Absorption: A photon excites an electron, causing it to be transferred to an electron acceptor. Water
splits to replace lost electrons, releasing O₂.
Electron Transport Chain: Transfers excited electrons, pumping H⁺ ions and creating an electrochemical
gradient
second step of photosynthesis
- Fixation Stage:
Enzyme: RuBisCO catalyzes a reaction between CO₂ and RuBP (ribulose bisphosphate).
Process: Combines CO₂ with RuBP to form a six-carbon compound, which immediately splits into two
three-carbon molecules (3-PGA).
Key Term: Carbon Fixation — CO₂ is converted from its inorganic form to an organic molecule. - Reduction Stage:
Energy Input: ATP and NADPH from the light-dependent reactions are used to convert 3-PGA into G3P
Key Reaction: Reduction involves gaining electrons (supplied by NADPH).
Output: One G3P molecule exits the cycle to form carbohydrates like glucose. - Regeneration Stage:
Regeneration: The remaining G3P molecules are used to regenerate RuBP with the help of ATP.
Cycle Continuation: The regenerated RuBP allows the Calvin Cycle to continue fixing CO
Key points of calvin cycle
It takes six turns of the Calvin Cycle to produce one glucose molecule, fixing six CO₂ molecules.
Process: ATP and NADPH provide energy to convert CO₂ into GP3 molecules, which are used to make glucose
after 6 turns of the Calvin Cycle
light energy and pigments
Chlorophyll a: The main pigment involved in photosynthesis, absorbs blue and red light, reflects green
