B1 Flashcards
What are eukaryotic cells
Eukaryotic cells have a cell membrane,
cytoplasm and genetic material (DNA)
enclosed in a nucleus.
Animal and plant cells are eukaryotic cells
What are prokaryotic cells
These are smaller than eukaryotic cells. The genetic material is not enclosed in a nucleus. The DNA is a single loop and there may be one or more rings of DNA called plasmids.
Bacterial cells are prokaryotic cells
Nucleus
Contains genetic material, which controls the
activities of the cell
Animal and Plant
Cytoplasm
Most chemical processes take place here, controlled
by enzymes
Animal and Plant and Bacteria
Cell membrane
Controls the movement of substances into and out of
the cell
Animal and Plant and Bacteria
Mitochondria
Most energy is released by respiration here
Animal and Plant
Ribosomes
Protein synthesis happens here
Animal and Plant
Cell wall
Strengthens the cell – made of cellulose (not bacteria)
(algal cells also have a cell wall)
Plant and bacteria
Chloroplasts
Contain chlorophyll, absorbs light energy for
photosynthesis
Plant only
Permanent vacuole
Filled with cell sap to help keep the cell turgid
Plant only
Bacterial DNA
Loop of DNA NOT found in a nucleus
Bacteria only
Plasmid (DNA)
Small ring of DNA often used as a vector in genetic
modification
Bacteria only
Sperm Cells
Function : To fertilise an egg
Characteristics : Streamlined with a long tail to swim the egg
Large number of mitochondria in the middle section release energy for movement
Nerve Cells
Function : To carry electric signals
Characteristics : Long to carry signals long distances
Branched connections to send signals all over the body
Insulated sheath to enhance electric signals
Muscle Cells
Contain a large number of mitochondria to
release energy from respiration for movement.
Long so that there is enough space to contract
Root hair cells
Function : Absorb water and minerals from
the soil
Characteristics - Hair like projections to increase the surface area
Xylem
Function : To carry water and minerals in plants
Characteristics - Form hollow xylem tubes made of dead tissue
Long cells with walls toughened by lignin
Water and minerals flow from the roots towards the
leaves only in one direction in a process called
transpiration
Phloem
Function : Carry glucose around the plant
Characteristics - Form phloem tubes made of living tissue
Cells have end plates with holes in them
Glucose in solution moves from the leaves to growth and storage tissues in a process called translocation
Cell differentiation
Cell differentiation occurs as organisms develop, the cell changes and becomes specialised. As the cell differentiates, it forms different sub-cellular structures, e.g. the tail on a sperm cell or the hairs on a root hair cell.
Resolution
The shortest distance between two
objects that can be seen clearly
Stages of the cell cycle
Stage 1 – Growth: Before a cell can divide it needs to grow and increase the
number of sub-cellular structures such as ribosomes and mitochondria.
Stage 2 - DNA synthesis: The DNA replicates to form two copies of each chromosome.
Stage 3 – Mitosis: One set of chromosomes is pulled to each end of the cell and the
nucleus divides. Then the cytoplasm and cell membranes divide to form two cells
that are identical to the parent cell.
Stem Cells
Stem cells are undifferentiated cells within an organism. They can produce other stem cells that can then differentiate into many different types of cells
Diffusion
The spreading of particles from a high to a low concentration
Factors that affect diffusion
- The Concentration Gradient
- The Temperature
- The Surface Area of the Membrane
Active Transport
Active transport moves substances and particles against the concentration gradient from a lower to a higher concentration
Osmosis
Osmosis is the diffusion of water from a
dilute solution to a concentrated
solution through a partially permeable
membrane.
Adaptations of the Small Intestine
Internal surface is covered in millions of
folds called villi.
Villi increase the surface area.
Villi have a very good blood supply. This
maintains the concentration gradient.
Membranes of the villi are very thin to
allow for a short diffusion distance.
Adaptations of the lungs
Lungs contain millions of tiny air sacs
called alveoli.
Alveoli increase the surface area.
Alveoli have a very good blood supply.
This maintains the concentration
gradient.
Membranes of the alveoli are very thin
to allow for a short diffusion distance.
Adaptations of fish gills
Each gill is made of lots of thin plates called
gill filaments, water with low oxygen flows over
them (however, the oxygen in the blood surrounding
the gills is lower) .
Gill filaments increase the surface area.
Gill filaments are covered with lamella
that increase the surface area more.
Lamella have a very good blood supply. This maintains
the concentration gradient as water flows in the opposite direction.
Membranes of the lamellae are very thin to allow for a short diffusion distance.
Adaptation of roots
The root surface is covered in millions of
root hair cells.
Root hair cells increase the surface area.
Present on the mature parts of the roots.
Absorb water and minerals from the soil.
Adaptation of Leaves
Large surface area to absorb more light.
Thin so short distance for carbon dioxide
to diffuse into leaf cells.
Chlorophyll absorbs sunlight for
photosynthesis.
Xylem and phloem to support the leaf
and transport water and glucose.
Stomata on the lower side of the leaf to
allow gases to diffuse into and out of the
leaf.
