CELS191 Module 1 Flashcards
to learn module 1
1µm
1/1000 mm
1mm
1000µm
1µm
1000nm
Eukaryote cells range
10-100 µm
Prokaryote cells range
less than 5 µm
mitochondria size
1-10 µm
chloroplasts size
2-5µm
Evolution
When you have organisms that vary, pass on their
characteristics and survive differentially
Natural selection
the reproductive success of the members of a population best adapted to the environment
Phylogenetic Trees
identifying shared characters makes family trees of organisms.
Origin of life, 3 domains
Bacteria, Eukarya, Archaea
Endosymbiosis theory
Mitochondria are derived from proteobacteria, and chloroplasts from cyanobacteria.
Prokaryotic VS Eukaryotic Cells
membrane-enclosed organelles are present in eukaryotes
Prokaryotic no nucleus
Amino acids, Nucleobases, Simple carbohydrates, Fatty acids
Building blocks
Macromolecules
Proteins ,DNA, RNA, Complex carbohydrates, Lipids
Super molecular assemblies
Membranes, Ribosomes, Chromatin
Organelles
Nucleus, Mitochondria, Golgi, ER
4 Levels of carbohydrates
- Monosaccharides (single unit)
- Disaccharides (two joined)
- Oligosaccharides (3-10 complex)
- Polysaccharides (more than 10)
Functions of Carbohydrates
Recognition, Energy, Structure
Nucleic acids
polymers of nucleotides
Proteins
polymers of amino acids
the 20 amino acids differ by their ‘R’ group
Lipids
Not polymers
Heterogeneous - fats and steroids
Hydrophobic
Functions of Lipids
Structural, Regulatory, Energy
What must a cell do?
Manufacture cellular materials
Obtain raw materials
Remove waste
Generate the required energy
Control all of the above
Plasma membrane
At the boundary of each cell, Provides special conditions within the cell and acts as a semi-permeable barrier
Plasma membrane is made of
double layer of phospholipids with various embedded
or attached proteins
Membrane Proteins are involved in
Signal Transduction, Cell Recognition, Intercellular Joining, Linking Cytoskeleton & Extracellular Matrix, Membrane Transport
Passive Transport (no energy)
Diffusion, They move down their
concentration gradient and thus do
not require energy
Facilitated diffusion
No energy is required but some channels open or close in
response to signals
Carriers undergo a shape change
to help guide the molecule
osmosis
The movement of water across a cell membrane requires channels called aquaporins. High-concentration to low concentration
Active Transport (needs energy)
Move specific substances against their concentration gradient Active transport allows a cell to have an internal concentration of a substance that is different from its surroundings
Co-transport
indirect active transport
one substance is pumped across the membrane and its concentration gradient is used to power the movement of a second substance against its concentration gradient
Organelles
Provide special conditions for
specific processes.
Keep incompatible processes
apart
Only animal cells have
Lysosomes
Only plant cells have
Chloroplasts & Central vacuole
The Endomembrane System
a membrane system interconnected by direct physical contact or transfer by vesicles
Smooth Endoplasmic Reticulum (sER)
Metabolism of carbohydrates
Lipid synthesis for membranes
The amount of sER can be increased or decreased
to meet demand
Rough Endoplasmic Reticulum (rER)
Rough appearance due to ribosomes
Involved in protein synthesis
Secreted and membrane-bound proteins enter the
lumen (interior) of the rER and are processed by the rER and the rest of the endomembrane system for release from the cell or retention on the cell membrane
Function of the Golgi complex
- Vesicles from endoplasmic reticulum arrives at the cis face and processed vesicles leave at the trans face
- Sorting proteins, Adds molecular markers to direct proteins to the correct vesicles before ”budding” from the trans face
- Directing vesicle trafficking, Adding molecular “tags” to
vesicles leaving the trans face to direct them to the
correct targets
Glycosylation
Addition (or modification) of
carbohydrates to proteins
Important for secreted or
cell surface proteins
Types of vesicles
Transport vesicles
Secretory vesicles
Vacuoles
Exocytosis
Transports material (glycoproteins) out of the
cell or delivers it to the cell surface
Endocytosis
the cell takes in molecules and
particulate matter at the
plasma membrane
Phagocytosis
uptake of “food” particles
pha = ATE
Pinocytosis
up-take of extracellular fluid
containing various solutes
such as protein and sugars
Pino = drink
Receptor-mediated endocytosis
allows the cell to take up bulk
quantities of specific substances
which may be present only
low concentrations in the
extracellular fluid
Lysosomes
membrane-bound organelles made by the
rER and Golgi body containing hydrolytic enzymes
Lysosomes digest and recycle unwanted cellular materials
Vacuoles
Large vesicles derived from the rER and Golgi
can perform lysosome-like functions
large central vacuole absorbs water allowing plant cells
to grow without a large increase in cytoplasm
Adenosine Triphosphate (ATP)
ATP is an energy carrier
The cell needs energy for
for mechanical work
to make new materials
for transport
to maintain order
The Site of Cellular Respiration
Mitochondria
The Mitochondrion: Structure
Has two membranes: inner & outer mitochondrial membranes
- Inner membrane highly folded (cristae) functionally important
- Intermembrane space functionally important
- Mitochondrial matrix inside the inner membrane
CR: Cellular Respiration: Stage 1 - Glycolysis
In the cytosol
Sugar – glucose is converted into two pyruvate molecules
Generates: 2ATP – energy carrier
AND
electrons are transferred to the high
energy electron carrier - NAD+ making NADH
CR: Stage 2 – Pyruvate Oxidation & Citric Acid Cycle
In the Mitochondrial Matrix:
pyruvate molecules are
converted to 2 Acetyl CoA
molecules.
2 Acetyl CoA molecules
enter the citric acid cycle.
Output is energy carrier
ATP and high energy
electron carriers NADH &
FADH2.
CR: Stage 3 – Oxidative Phosphorylation
Inner Membrane of the Mitochondrion
Part 1: The Electron Transport Chain
electrons move through protein complexes embedded in the inner membrane. As the electrons move, protons (H+) are pumped across the membrane
Part 1: A Proton Gradient is Generated
Protons (H+) accumulate in the intermembrane space
Part 2: Chemiosmosis
The proton gradient across the inner membrane powers ATP synthesis
Part 2: Chemiosmosis
ADP + Pi ATP
Cellular respiration
Glucose and oxygen are consumed
Carbon dioxide, water and ATP are produced
The Site of Photosynthesis
Chloroplasts
Chloroplasts: Structure
Three Membranes
Outer
Inner
Thylakoid
Three Compartments
Intermembrane space
Stroma
Thylakoid space
Chloroplasts: Function
Light reactions take place on the thylakoid membrane.
Carbon fixation occurs in the stroma
The Light Reactions
The thylakoid membrane contains chlorophyll
Chlorophyll absorbs light energy
The light energy absorbed by chlorophyll
results in the movement of high-energy electrons
The Photosynthetic Electron Transport Chain
High energy electrons produced from chlorophyll move through the Photosynthetic electron transport chain
Photosystem II Photosystem I
The Calvin Cycle
The output of the Calvin cycle is a 3 carbon sugar
that, when combined with another 3 carbon sugar, is
converted to glucose.
The ATP and NADPH produced in the light reactions
are only used in the Calvin Cycle
Energy Supply in Plants & Animals:
Glucose
Both plants and animals breakdown
glucose in cellular respiration to
generate ATP
Plants generate glucose during
photosynthesis and then break this down
during respiration
Energy Supply in Plants
& Animals: ATP
ATP is generated in both
respiration and photosynthesis
This requires a proton gradient
across a membrane in both the
chloroplast and mitochondrion
Plant Cell Components
Plasmodesmata
The Cell Wall + The Protoplast
Cell Wall Structure: Cellulose - A Major Component
Cellulose Forms Microfibrils
Two phases of cell wall structure
Phase 1: Microfibrils, Cellulose
Phase 2: Matrix
Pectin polysaccharides
Hemicellulose polysaccharides
Hemicellulose
a heterogeneous group of polysaccharides. Long chain of one type of sugar and short side chains form a rigid structure.
Pectin
branched, negatively charged polysaccharides. Bind
water and have gel-like properties
Extensin cross-linking of pectin and cellulose
dehydrates the cell wall, reduces extensibility and increases strength
Constitutive exocytosis
releases extracellular matrix proteins
Cytoskeleton
A network of microtubules, microfilaments (and
intermediate filaments) that extend throughout the cytoplasm.
It Helps maintain the cell shape and position of organelles
within cells.
the cytoskeleton rapidly disassembles and reassembles
Synthesis of the Primary Cell Wall
Cellulose-producing rosettes are protein complexes
(enzymes) that span the plasma membrane.
Cell Wall Functions in
Regulating Cell Shape
influences cell morphology
provides structural support
prevents excessive water uptake
Orientation of the cellulose microfibrils influences
cell morphology
a) Randomly oriented.
The cell will expand equally in all directions.
b) Right angles to the ultimate long axis of
the cell. The cell will expand longitudinally
along that axis.
How The Cell Wall: Provides Structural Support
The protoplast pushes against the cell wall. The cells become
rigid and this maintains the plant structure.
Water loss from cells reduces the protoplast volume and the
protoplast does not press on the cell wall
The Cell Wall: Prevents Excessive Water Uptake
As water enters the cell by osmosis, the protoplast expands and pushes against the cell wall.
Pressure from the cell wall limits the volume of water that can
be taken up.
Vacuoles are important in this process because they contain
water and make such a large portion of the protoplast.
Vacuoles: Structure
A vacuole is an organelle surrounded by a single
membrane. It is highly selective, controlling much of what enters and leaves the vacuole. Water moves in the vacuoles
by osmosis (passive transport)
Vacuoles: Function in Regulation of Cell Shape
The plant cell wall limits
water uptake and prevents
the cell bursting.
Plant cells build up a large internal pressure that contributes to plant structural support.
The Secondary Cell Wall
Not all plant cells have a secondary cell wall
Produced only after cell growth has stopped
Thicker and stronger than primary cell walls
Provides more structural support than the primary cell wall
Secondary Cell Wall: Structure
Made up of multiple layers. Microfibrils in each layer have different orientations. This strengthens the secondary wall
Lignin
The second most abundant organic macromolecule
Lignin is a complex polymer
Confers strength and rigidity to the secondary cell wall and acts to exclude water
Plasmodesmata: Cell Communication
Plasmodesmata are intercellular connections, that
enable cell-to-cell communication.
Microtubules
Microtubules are composed of tubulin subunits. They may radiate out from an organising centre (centrosome).
Microtubules resist compression,Thus help maintain cell shape
Microtubules can also provide cell motility
Flagella: “snake-like” motion
Cilia: “rowing-like” motion
If cells are fixed in place beating of cilia moves fluid past
them
Microtubules are also involved in organelle
motility within the cell
ATP-powered motor proteins can “walk” organelles along
microtubules. Allows vesicles, or other organelles, to be
transported to specific targets within the cell
Microfilaments
Microfilaments are a double
chain of actin subunits
Microfilaments resist tension
The cortical network under
the plasma membrane helps
make this region less fluid and
thus maintains cell shape
Intermediate Filaments
Are made of various proteins
including:
keratins in hair.
lamins in the nucleus.
neurofilaments in neurons.
Supercoiled into “cables”
Less dynamic than
microtubules or microfilaments
Intermediate Filaments form
relatively permanent cellular
structures
Three major types of Cell Junctions
Tight Junctions
Desmosomes
Gap Junctions
Tight Junctions
Hold neighbouring cells tightly
pressed together
May form a continuous seal
Prevents movement of fluid
across cell layers
Desmosomes
Anchoring junction
Provide attachments between
sheets of cells e.g. muscle
Act like rivets (a “torn muscle” is
a torn desmosome)
Connected into the cell by
intermediate filaments
Gap Junctions
A point of cytoplasmic
contact between two cells
Ions and small molecules can
pass from cell to cell
Allows rapid cell to cell
(intercellular) communication
How Are Cells Joined Together?
The Extracellular Matrix
Extracellular Matrix (ECM)
The ECM is composed of material secreted by cells
This secretion occurs by constitutive exocytosis
Most ECM proteins are glycoproteins
The most abundant ECM glycoprotein is collagen
proteoglycan complex matrix
Proteoglycans are proteins with extensive sugar additions. Proteoglycans trap water within the ECM. Water resists compression and thus helps retain tissue shape
Ribosomes: Structure
Complexes made of ribosomal RNAs & proteins
Found in two
locations: bound ribosomes attached to rough ER
free ribosomes in the cytoplasm
Ribosomes: Function
Carry out translation
The more protein synthesis
a cell needs to do, the
more ribosomes it has
The Nucleus
The most prominent organelle (5-10 µm diameter)
One nucleus per cell (in most cases)
Contains most of the cell’s genes
The Nucleus: Structure
Surrounded by the nuclear envelope
Has channels called nuclear pores
Contains tightly packaged DNA
Has a prominent area called the nucleolus
The Nucleus Envelope
Composed of two membranes
outer and inner membranes with perinuclear space in between
Each membrane is a
phospholipid bilayer
Outer membrane
continuous with ER
Nuclear Lamina
The inner surface of nuclear envelope is lined by the nuclear
lamina, Which is composed of intermediate filaments
Maintain the shape of the the nucleus
Helps organise the packing of the DNA within the nucleus
Nuclear Pores
Channels made of proteins
(nucleoporins) that form the
Nuclear Pore Complex
Spans nuclear envelope
1000 per cell
Controls the movement of molecules out of, or into, the
nucleus (nucleo-cytoplasmic exchange)
Nucleus to Cytoplasm
mRNA, tRNA and
ribosomal subunits move
from nucleus to cytoplasm
Cytoplasm to Nucleus
Control signals, building materials and energy
move from cytoplasm to nucleus
The Nucleolus
A prominent nuclear structure within non-dividing cells
Non-membrane bound specialised region within the
nucleus. Responsible for making ribosomal RNA & ribosomal
subunits
The DNA helix interacts with specific proteins called
histones
karyotype
Chromosomes can be
displayed as a karyotype
which can be used to screen
for chromosomal defects
Euchromatin
less dense, contains genes
being used by that cell
Allows access
Heterochromatin
more dense, contains genes not being used by
that cell
