exam revision bio semester 2 Flashcards
homeostasis
homeostasis the maintenance
of a relatively stable internal
environment in the body
despite changes in the external
environment
organism
a living thing made up
of one or more cells
what is 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.
prokaryotes
a group of
single-celled organisms with no
nucleus and a circular loop of
DNA. Bacteria and archaea are
both prokaryotic
eukaryotes
a group of
single-celled organisms with no
nucleus and a circular loop of
DNA. Bacteria and archaea are
both prokaryotic
do eukaryotes have membrane bound organelles
yes
do prokaryotes have membrane bound organelles
no
what is the DNA organisation of eukaryotes
More than one linear strand of
DNA packaged in a chromosome
in a nucleus
what is the DNA organisation of a prokaryotic cell
one circular chromosome and additional plasmids
what are eukaryotic organisms nature
can be unicellular or multicellular
what are prokaryotic organisms nature
unicellular
what is the size of(roughly) of a eukaryotic cell
larger
what is the size of(roughly) of a prokaryotic cell
smaller
what is the method of cell replication for eukaryotic cells
Mitosis and meiosis
what is the method of cell replication for prokaryotic cells
binary fission
mitosis
mitosis the cell division phase
which involves the complete
separation of sister chromatids
and nuclei
somatic cell
somatic cell any cell that is not a
reproductive cell (such as sperm
and egg cells). Somatic cells are
diploid (2n), meaning they contain
two sets of chromosomes – one
inherited from each parent
difference between prokaryotic cells and eukaryotic cells
Prokaryotes are cells that lack a nucleus and membrane-bound organelles. They are smaller and simpler and include bacteria and archaea. Eukaryotic cells are cells that do have a nucleus and membrane-bound organelles, which help to organize and compartmentalize functions in the cell.
what is the function of the nucleus
The nucleus is surrounded by a double membrane. Its role is to protect
and confine the genetic information (DNA) of the cell. Inside the
nucleus is a smaller structure known as the nucleolus which is the site of
ribosome production.
what is the function of ribosomes
Ribosomes are tiny structures made of ribosomal RNA (rRNA) and
proteins that fold into a large and small subunit. Cells have many
ribosomes, which either float freely in the cytoplasm or are attached
to the rough endoplasmic reticulum. Ribosomes assemble the building
blocks to make proteins
what is the function of the rough endoplasmic reticulum
A membranous chain of connected and flattened sacs which are
coated with ribosomes. This allows the rough endoplasmic reticulum
to synthesise and modify proteins. The rough endoplasmic reticulum
typically surrounds, or is close to, the nucleus
what is the function of the smooth endoplasmic reticulum
A membranous chain of connected and flattened sacs which are
not coated with ribosomes. The smooth endoplasmic reticulum is
responsible for the production of lipids in a cell.
what is the function of the Golgi apparatus
Stacked flattened sacs that are the sites of protein sorting, packaging, and
modification for use in the cell or export. Protein-filled vesicles often fuse
with or bud off from the Golgi apparatus. Also known as the Golgi body.
what is the function of lysosomes
A membrane-bound vesicle that contains digestive enzymes. It is
responsible for breaking down cell waste and toxins, acting like a
garbage disposal
what is the function of the mitochondria
An organelle with a highly folded inner membrane surrounded by a
second outer membrane. Mitochondria are the site of aerobic cellular
respiration, a chemical reaction that produces the ATP required to power
cellular processes. They also contain their own DNA and ribosomes.
what is the function of chloroplast
A double membrane-bound organelle that contains flattened, fluid-filled
sacs that are the site of photosynthesis. Chloroplasts also contain their
own DNA and ribosomes.
what is the function of a vacuole
A membrane-bound sac that is used for water and solute storage.
Vacuoles can also play a role in maintaining plant cell structure.
what is the function of the plasma membrane
The plasma membrane is a selectively permeable barrier between
the intracellular and the extracellular environment. It is made of a
phospholipid bilayer which is studded with many molecules.
what is the function of a cell wall
A sturdy border outside the plasma membrane that provides strength
and structure to plant, bacterial, and fungal cells. (not in animals)
what is the function of a vesicle
A small, membrane-bound sac that transports substances into or out of a
cell, or stores substances within a cel
what is the function of a cytoskeleton
A large network of protein filaments that start at the nucleus and reach
out to the plasma membrane. The cytoskeleton is critical for maintaining
shape and transporting vesicles around the cell. In the given fluorescence
microscopy photo, the purple represents the cytoskeleton
organelles which are not membrane-bound
ribsomes
cell wall
cytoskeleton
two key difference between animal and plant organelles
Unlike plants, most animals have evolved structures like skeletons
that provide structural support for the organism. Plants rely on their
strong cell walls to perform the same function. these cell walls made of cellulose is present in plant cells but not
animal cells.
Chloroplasts are found in plants as they are the site of photosynthesis, which is how plants source glucose for energy. Animals source their food through other methods. Chloroplasts are present in plant cells but not animal cells.
what organelles do plants have that animals do not
-chloroplast
-cell wall
what is a gene
gene a section of DNA that
carries the code to make a protein
what is a genome
genome the complete set of
DNA contained within an
organism’s chromosomes
what are alleles
alleles, which are different forms of the same gene but with small differences in
their base sequence.
what is the distinction between genes, genome and alleles
Genes are DNA segments that code for traits, while alleles are different versions of a gene. The genome is the complete set of genetic material in an organism, including all genes and alleles.
the nature of a pair of homologous chromosomes carrying the same loci
A pair of homologous chromosomes consists of two chromosomes, one inherited from each parent, that carry the same gene loci (specific positions of genes). While the genes at these loci are the same, the alleles (versions of the gene) may differ between the chromosomes. Homologous chromosomes are similar in size, shape, and genetic content but may carry different variants of genes (alleles).
explain autosomal chromosomes
Autosomes are the non-sex chromosomes, present in pairs in both males and females, and carry most of an organism’s genetic information. In humans, there are 22 pairs of autosomes.
explain sex chromosomes
Sex chromosomes determine an individual’s biological sex and are different in males and females. In humans, females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The sex chromosomes carry genes that influence sexual development and reproduction
difference between sex chromosomes and autosomal chromosomes
Autosomes are non-sex chromosomes that carry most of an organism’s genetic information and are the same in both sexes, while sex chromosomes determine biological sex and differ between males (XY) and females (XX).
how many chromosomes are present in humans
Human somatic cells mostly contain
46 chromosomes and therefore have a diploid number of 2n = 46.
explain chromosome size of humans compared to others
chromosome size can also vary greatly; for instance, human chromosomes are much larger in size compared to those of some other species like bacteria, which have a single, much smaller circular chromosome.
define karyotypes
a visual representation
of an individual’s entire genome
organised into homologous pairs
what is the purpose of a karyotype
When reading
karyotypes, scientists will check that the correct number of chromosomes are present and
that the size and length of each chromosome are correct. This information is used to check for possible genetic abnormalities. Can also be used to determine the species of the organism
What is meiosis?
Meiosis is the process of cell division that reduces a diploid cell (2 sets of chromosomes) to haploid gametes (1 set of chromosomes). It produces four genetically unique haploid cells (sperm or eggs).
How does meiosis affect chromosome number?
Meiosis reduces the chromosome number from diploid (two sets of chromosomes) to haploid (one set of chromosomes), ensuring that offspring have the correct chromosome number after fertilization.
What is crossing over, and why is it important?
Crossing over is the exchange of genetic material between homologous chromosomes during prophase I of meiosis. It creates new combinations of alleles, contributing to genetic diversity.