Unit 1: Chapter 1 + 2 Flashcards
Cells
Are the basic structural and functional units of life, all living organisms are built of one or more cells.
How big are cells?
Most cells are microscopic, only a few such as a human egg cell and amoeba can be seen with the naked eye.
Are viruses living or non-living?
Both, because of they;
don’t have a structure
cannot carry out metabolic activities
cannot self-replicate
Shape and functions
The size of the cells vary and therefore impacts on function
Motor neuron cells
Star-shaped
Have a long axon
Transmit nerve impulses from a person’s spinal cord to voluntary muscles
Smooth muscle cells
Contain proteins that crisscross the cell and when contracted they shorten
Found in the gut wall, walls of blood vessels and uterus
Can generate sustained involuntary contractions
Shapes of microbial cells
Rod-shaped
Corkscrew-shaped
Spherical
Are there fixed shapes for all cells?
No, some cells are able to move actively and therefore have a flexible plasma membrane
Cells capable of self-propelled movement
Cancer cells
White blood cells
Amoebas
Site of exchange
Plasma membrane - where materials are moved in and out of a cell to maintain essential functions
Rate of exchange
Must be quick enough that the materials are delivered fast enough but slow enough to avoid accumulation of waste materials
Surface area to volume ratio
Is the surface area of a plasma membrane available to supply material or remove wastes from the cytoplasm of a cell
Rules of SA: V ratio
As an object increases in size the SA: V ratio gets smaller
As an object decreases in size the SA: V ratio gets bigger
The higher the ratio the greater the efficiency of the exchange
Why are cells so small?
Beyond a given cell size, the 2-way exchange of materials across the plasma membrane cannot occur fast enough to sustain the volume of the cell contents
Prokaryote
Any cells or organisms without a membrane-bound nucleus (bacteria and archaea)
typically smaller (1-2 micrometres)
DNA is dispersed
Unicellular
Eukaryotes
Cell or organism with a membrane-bound nucleus (plants, animals, fungi)
typically larger (10-100 micrometres)
DNA stored as chromosomes in the nucleus
Unicellular/Multicellular
Similarities between eukaryotes and prokaryotes
Both have;
- ribosomes
- cell membrane
- cytosol
- vacuole
Cytoskeleton
3D networks of fine protein filaments and microtubules within the cell, to give it support and structure
- determines cell chape
- moves chromosomes during cell division
Organelles not enclosed in membranes
Ribosomes
Cilia and flagella
Centrioles
Animal cell organelles
Nucleus Mitochondria Nuclear envolope Nucleoulus Ribosome ER (smooth and rough) Lysosome Centriole Protein microtubule Golgi apparatus Vesicle Peroxisome Endosome Plasma membrane
Plant cell organelles
Nucleus Nucleolus Mitochondria Ribosomes Endoplasmic reticulum Plasma membrane Cell wall Microtubule Vacuole Chloroplast Peroxisome Vesicle Golgi apparatus Lysosome
Difference between animal and plant cell
Animals lack a cell wall, chloroplast and large central vacuole
Cell wall
Plant cell Outside cell membrane Fully permeable Provides strength and support to cells Prevents over expansion of cells from osmosis Made of cellulose
Cytosol
The fluid region in which the organelles exist
Which cells have secondary cell walls?
Woody plants and perennial grasses
Nucleus
Membrane bound organelle that controls the function of plant and animal cells
- has a double membrane (nuclear envelope)
- contains chromatin (DNA)
Nucleolus
Small part of the nucleus that makes ribosomes
Multinucleate
Many nucleus
Mitochondria
The site of cellular respiration
In animal and plant cells
Produces ATP for the cell to use as energy
Cellular respiration equation
O2 + C6H12O6 -> CO2 + H2O + ATP
Oxygen + Glucose -> Carbon dioxide + Water + Energy
Why would a cell need more mitochondria?
A cell that requires more energy ie; muscle cell
Ribosomes
Where amino acids are assembled to make proteins
In plant and animal cells
Attached to the Rough ER
Free floating
Rough endoplasmic reticulum
Organelle consisting of membrane-bound channels that transport substances within a cell with ribosomes attached to the outside
- transports proteins within the cell
- makes glycoproteins
- folding proteins
- assembling proteins (ribosomes)
- plants and animals
Smooth endoplasmic reticulum
Organelle consisting of membrane-bound channels that transport substances within a cell
- synthesises and transports lipids
- manufactures, detoxifies, stores and transports products
- plants and animals
Golgi complex
Organelle that packages material into vesicles for export from a cell
- transported from Rough ER in transition vesicles
- transported from Golgi body in secretory vesicles, merge with the plasma membrane and are excreted
- plants and animals
Lysosomes
A fluid-filled sac that contains digestive enzymes to break down excess macromolecules, old cell organelles and break down of substances
- animal and plant
Peroxisomes
The organelle containing enzymes that detoxify various toxic materials that enter the bloodstream
- oxidise fatty acids
- break down long chain fatty acids
- plants and animals
Chloroplasts
Organelle that converts light into energy for the cell to use
- contains chlorophyll (green colour)
- only in plant cells
Why is chloroplast only in some plant cells?
Because it converts energy from sunlight and therefore has to be exposed to light
Cilia
Cilia are short, hair like appendages extending from the surface of a living cell.
- short
- eukaryotic cells
Flagella
Flagella are long, threadlike appendages on the surface of a living cell.
- long
- Eukaryotic and prokaryotic cells
Difference between the plasma membrane and the cell membrane
Plasma membrane is the layer surrounding the organelles and the cell whereas the cell membrane is the layer surrounding the cell
Plasma membrane
AKA cell membrane
The partially permeable boundary of the cell separating it from its physical surroundings
Can exclude some substances from entering the cell while permitting entry of others
Structure of the plasma membrane
2 major components;
Phospholipids - bilayer
Proteins
Phospholipids
2 fatty acids joined to a phosphate group
Contains hydrophilic head (phosphate)
contains hydrophobic tail (fatty acid )
The hydrophilic and Hydrophobic arrangement
Hydrophilic heads are exposed to the external/internal
Hydrophobic tails face each other
Why is the plasma membrane flexible?
due to the fatty acids which are fluids and therefore flexible. this enables them to change shape
2 different types of proteins
Integral
Peripheral
Integral proteins
Are transmembrane (span the width of the membrane) have protein exposed on both sides
Glycoprotein
When carbohydrate groups are attached to the exposed part of the protein on the external side
Peripheral proteins
Anchored to the exterior of the membrane
Functions of the plasma membrane
Active and selective boundary
Denotes cell identity
Receives external signals
Transports materials
Factors that affect substances crossing the membrane
Size
Presence of charge (polar)
Solubility in lipids
Direction of concentration gradient
Molecular size
Some molecules are too big to fit across the membrane, the smaller ones can fit through the gaps ie; macromolecules
Presence of a charge (polar)
The bilayer is non-polar and therefore charged ions cannot cross the membrane
Solubility in lipids
Lipophilic molecules can cross easily but hydrophilic molecules cannot cross due to being repelled by water
Direction of concentration gradient
Movement against the concetration gradient requires energy and is much harder than with the concentration gradient
Ways of crossing the boundary
Simple diffusion
Facilitated diffusion
Active transport
Endocytosis/exocytosis
Simple diffusion
Net movement of substances across the membrane from a region of high concentration to low concentration until it reaches an equilibrium
- passive
- aims for equal concentration on both sides
- across a semi-permeable membrane
- for smaller, uncharged atoms
Osmosis
Movement of water across a semipermeable membrane
- From an area of higher water to an area of lower water
- From an area of low concentration to higher concentration
Hypotonic
having lower solute concentration than the cell contents
Isotonic
Having an equal solute concentration to that of the cells
Hypertonic
Having higher solute concentration than the cell contents
Water content in animal cells
Too much causes it to burst
Less causes it to shrink
Water content in plant
Too much causes membrane to swell and cell wall prevent breakage
Too little water causes the plasma membrane to break away from the cell wall
Facilitated diffusion
It is diffusion that is enabled by special protein transporters in the membrane, allows molecules that can not diffuse across the plasma membrane through channel proteins or carrier proteins
- passive
Channel proteins
They are transmembrane and have a pore that allows charged particles through
Carrier proteins
Is a specific size and shape to allow certain particles through, acting like a gate
Photosynthesis equation
6CO2 + 12H2O -> C6H12O6 + 6O2 + 6H2O
Rates of diffusion (simple)
The higher the concentration gradient the faster the substance will move by simple diffusion across a plasma membrane.
Rates of diffusion (facilitated)
The higher the concentration gradient the faster a substance will move across a membrane to a certain point when all the transporters are fully occupied.
Active transport
Moving dissolved substances from an area of low concentration to an area of high concentration
- active (requires energy)
Endocytosis
Is bulk transport of material into a cell
phagocytosis - solid
pinocytosis - fluid
Energy requiring process
Exocytosis
Bulk transport of material out of the cell
Energy required
Use of golgi body
Different microscopes
Light (optical) microscope
Electron (transmission) microscope
Differences between microscopes
Optical has lower levels of resolution and magnification
Optical is coloured, electron is b/w
Optical can be used for living cells
What organelles can not be seen with light microscope?
Ribosomes
Mitochondria
Peroxisomes
Living organisms can only exist where;
There is an energy source
Liquid water
Chemical building blocks (C,O,N,H)
Stable environmental conditions
Difference between prokaryotic and eukaryotic cells?
A prokaryotic cell is a very simple cell which contains no membrane-bound organelles and has a nucleoid which is circular DNA whereas a eukaryote is a very complex cell with many membrane-bound organelles
How does the cell maintain its essential functions
A constant exchange of material between the cell and its external environment
