biology 2ABC 3A Flashcards
3A - m, what are all living things made up of?
cell’s
3A- what is the surface area determined by?
plasma membrane
3A- function of plasma membrane
3A- controls the transport of substances in and out of the cell.
(All cells have a plasma membrane. It is the thin boundary of the cell made up of lipids that
separates the intracellular and extracellular environments. It is selectively permeable,
which means that only particular molecules can enter and exit the cell. Thanks to the
plasma membrane, cells can have a specialised internal environment.)
3A- difference between intracellular and extracellular?
intracellular inside a cell
extracellular outside a cell
3A- what is a selective permeability?
a property
of cell membranes that ensures
only specific substances pass
across them. Also known as
semipermeable
3A- what is the structure of the plasma membrane
a phospholipid bilayer embedded with proteins, carbohydrates,
and cholesterol. Each molecule fulfils a specific function in the membrane.
3A- what are phospholipids?
main components of the plasma membrane are phospholipids.
They are arranged in a film called a phospholipid bilayer that consists of two layers
of phospholipids. Phospholipids have a phosphate head and two fatty acid tails.
The phosphate head and fatty acid tails are chemically very different from each other.
3A- structure of phospholipids?
The phosphate head is:
* made of a glycerol and phosphate group
* negatively charged, making it hydrophilic (‘water-loving’) and polar.
The two fatty acid tails are:
* made of long chains of carbon and hydrogen
* uncharged, hydrophobic (‘water-fearing’), and nonpolar.
3A- difference between polar/hydrophilic and non-polar/hydrophobic
hydrophilic having a tendency
to be attracted to and dissolve
in water/polar describes a molecule with
both a positive end and negative
end. These tend to be hydrophilic
hydrophobic having a tendency
to repel and be insoluble in water/ nonpolar describes a molecule
without a clearly positive or
negative end. These tend to
be hydrophobic
3A- what is a amphiathic molecule
Because phospholipids have both hydrophilic and hydrophobic parts, they are
amphipathic molecules. This amphipathic nature makes the plasma membrane stable:
the fatty acid tails are repelled from water whilst the phosphate heads are attracted to
water, so a stable bilayer naturally forms. This is shown in Figure 3 as phospholipids create
a bilayer around water, a polar substance. This is due to the nature of hydrophilic and
hydrophobic interactions. Phospholipids create a monolayer around oil, however, since oil
is a nonpolar substance
3A- what is embedded in the phospholipid bilayer?
Proteins, carbohydrates, and cholesterol
3A- what are the diffrent types of protein?
Integral protein – proteins that
are a permanent part of the
membrane
Transmembrane protein – integral
proteins that span the entire bilayer
Peripheral protein – are
temporarily attached to the
plasma membrane
3A- function of protein in the phospholipid bilayer?
Transport – channels or pumps that control
what enters and exits the cell, making the
plasma membrane selectively permeable
Catalysis – speeding up chemical reactions with
the help of a protein group
called enzymes
Communication – receive signals or recognise
cells and molecules. Often attached to the
cytoskeleton to transmit signals into the cell
Adhesion – stick to other cells,
3A- structure of carbohydrate in phospholipid bilayer?
Usually in chains that extend
outside the cell, rooted in the
membrane to lipids (glycolipids)
or proteins (glycoproteins)
3A- function of carbohydrate in phospholipid bilayer?
Aid with cell-cell communication, signalling,
recognition of self or non-self (foreign)
molecules, and adhesion
3A- structure of cholesterol in phospholipid bilayer?
a steroid-alcohol
that regulates fluidity in
plasma membranes
3A- function of cholesterol a steroid-alcohol
that regulates fluidity in
plasma membranes
Regulates the fluidity of the membrane.
At higher temperatures, the cholesterol
keeps phospholipids bound together. At lower
temperatures, cholesterol disrupts the fatty acid
tails, stopping phospholipids from becoming a
solid boundary
3A- what does the fluid mosaic model explain?
1) molecules that make up the membrane are not
held static in one place and 2) many different types of molecules are embedded in the
plasma membrane.
(Our current understanding of the structure of the plasma membrane is described by the
‘fluid mosaic model’. The plasma membrane is fluid because phospholipids continually
move laterally (side to side) in the membrane. Occasionally, phospholipids may ‘flip-flop’
between the two layers of the plasma membrane.
The ‘mosaic’ component of the model comes from the proteins and carbohydrates
embedded in the membrane (Figure 6). These molecules can also move fluidly around
the bilayer, like ice floating in a glass of water. Like looking at mosaic art that is made up
of many different tiles, scientists imagine that they would see a variety of molecules of
different shapes and sizes when they look down at a plasma membrane)
2A- characteristics of living things
Movement
Respiration
Sensitivity
Growth
Reproduction
Equilibrium
Excretion
Nutrition
2A - explain the cell theory
1 all living things are made up of cells
2 cells are the smallest and most basic units of life
3 all cells come from pre-existing cells.
2A- what are the 6 kingdoms?
Animalia, Archaea, Bacteria, Fungi, Plantae, and Protista.
2A- what are similarities between eukaryotes and prokaryotes?
both prokaryotes and eukaryotes contain a plasma membrane, cytosol,
ribosomes, and DNA.
2A- What is the key structural difference between eukaryotic and prokaryotic cells in terms of DNA organization and cellular components?
Eukaryotic cells contain many membrane-bound organelles,
multiple linear chromosomes of DNA packed in a nucleus,. Prokaryotic cells lack a nucleus, have a single loop of circular DNA, and may
contain some smaller circular units of DNA called plasmids.
2A- diffrence between eukaryotes and prokaryotes?
Paragraph 1:
Eukaryotic cells are characterized by their complex structure, including the presence of membrane-bound organelles such as the nucleus, where their DNA is organized into multiple linear chromosomes. These cells can be unicellular or multicellular, and their larger size, typically ranging from 10–100 µm, reflects their advanced functionality. Eukaryotic cells also reproduce through mitosis and meiosis, processes that ensure accurate division and distribution of genetic material.
Paragraph 2:
Prokaryotic cells, in contrast, are simpler in structure and lack membrane-bound organelles. Their genetic material is found as a single circular chromosome, often accompanied by smaller circular DNA units called plasmids. Prokaryotes are exclusively unicellular and significantly smaller in size, ranging from 0.1–5 µm. They replicate using binary fission, a straightforward process that allows for rapid reproduction. This simplicity makes prokaryotes highly efficient and adaptable to diverse environments.
