Chapter 6 Flashcards
WHAT IS THE CELL CYCLE?
It is when cell’s reproduce by duplicating their DNA and splitting into two daughter cells.
Describe the following stages of cell division:
- G1
- S
- G2
- M
- G1: Cell organelles divide, cell grows bigger. RNA is made.
- S: DNA replicates
- G2: cell grows even more as organelles further divide.
- M: Mitosis occurs. DNA splits and then the whole cell splits.
WHAT THREE THINGS IS MITOSIS REQUIRED FOR?
Asexual reproduction
Growth
Tissue repair
PROPHASE
Chromosomes replicate and coil and condense.
Nuclear envelope breaks down.
Centriole divides.
METAPHASE
Chromosomes line up on the metaphase plate at the equator.
ANAPHASE
Chromosomes are pulled apart by the spindle fibres to the poles of the cell by their centromeres.
TELOPHASE
Nuclear envelope reforms.
CYTOKINESIS
Cell splits into two, cell membrane pinches in the middle and splits into two identical daughter cells.
WHAT IS MEIOSIS USED FOR?
WHAT ARE HOMOLOGOUS CHROMOSOMES?
- Important for sexual reproduction to form gametes.
- Homologous chromosomes are when 23 come from the mother and 23 from the father. They pair up to form homologous chromosomes. Though they have the same genes they have different alleles causing genetic variation.
PROPHASE I
CORSSING OVER
Chromosomes coil and condense and become visible. Nuclear envelope breaks down. Genetic variation occurs by crossing over. This is when a pair of homologous chromosomes get tangled when pulling away from each other resulting in alleles being swapped over.
METAPHASE I:
homologous pairs of chromosomes line up at the equator. Genetic variation occurs here because when the homologous pairs line up they are random with either member facing any pole.
ANAPHASE I
homologous pairs are moved apart to the poles of the cell by spindle fibres contracting.
TELOPHASE I
two knew nuclear envelopes form. Cell divides may enter short interphase before repeating.
PROPHASE II
nuclear envelopes break down, chromosomes coil and condense to become visible.
METAPHASE II
chromosomes line up on the equator, but now are randomly arranged.
ANAPHASE II
chromosomes pulled apart by centromeres, by spindle fibres.
TELOPHASE II
nuclear envelopes reform.
WHAT THREE FACTORS CAUSE GENETIC VARIATION?
- Crossing over in prophase I
- Independent assortment of chromosomes in anaphase I
- Independent assortment of chromatids in anaphase II
/WHAT IS DIFFRENTIATION?
Differentiation is required for large multicellular organisms which have a smaller surface area to volume ratio. Special cells are required to carry out certain jobs, which are not possible to be done by diffusion or simple transport.
Differentiation occurs when certain genes are turned on and off. This makes the proportion of organelles within the cell to change, the shape changes and also the contents of the cell may change.
HOW ARE ERYTHROCYTES ADAPTED FOR THIER ROLE?
Carry oxygen from lungs to body cells.
• They have a large SA:V allowing oxygen to reach all the components inside the cells.
• Flexible so they can move through narrow capillaries.
• No nucleus, mitochondria or endoplasmic reticulum, increases SA:V
HOW ARE NEUTROPHILS ADAPTED FOR THIER ROLE?
Ingest invading pathogens.
• Twice the size of erythrocytes
• Ingest pathogens by phagocytosis
• Lobed nucleus so can be flexible and move through small gaps
WHY DO PLANTS REQUIRE A SPECILIASED TRANSPORT SYSTEM?
Plants are also have specialised cells because they have a large SA:V so need special cells to carry out certain functions.
DESCRIBE FOUR ADAPTATIONS OF PALISADE CELLS.
Are adapted for photosynthesis:
Long and cylindrical so pack close but with space for air to circulate.
Large vacuole pushes the chloroplasts closer to the periphery of the cell allowing a shorter diffusion distance.
Many chloroplasts increases photosynthesis rate. Chloroplasts can move closer to the edge of the cell.
HOW DO GAURD CELLS WORK?
Use light energy to produce ATP. ATP is used to pull in magnesium ions from surrounding cells. This lowers the water potential of the cell allowing water to move in by osmosis from neighbouring cells. This increases the turgidity of the cell allowing it to open, forming a stoma through which gas exchange can occur.
WHAT DO ROOT HAIR CELLS DO?
Are hair like projections which greatly increases the surface area to volume ratio.
They transport ions in by active transport and have special carrier proteins which do this. This intake decreases water potential within the cell allowing water to come in by osmosis.
DESCRIBE EPITHELIAL TISSUE.
Made of cells entirely. The cells form sheets which are connected together. They have no blood vessels and receive nutrients by tissue fluid. Some are smooth whilst others have cilia or microvilli. Short cell cycles and divide up to two or three times a day.
DESCRIBE CONNECTIVE TISSUE.
Non-living tissues containing a matrix of proteins and polysaccharides. Separates living tissues allowing them to withstand weight.
DESCRIBE CARTILAGE TISSUE.
When immature, cartilage contains chondroblasts which secretes extracellular matrix. After this secretion it matures forming less active chondrocyte. This maintains the matrix. There are three types: • HYALINE: forms the embryonic skeleton. Covers end of long bones, joins ribs to sternum, is in the voice box etc.
FIBROUS: in the discs between the vertebrae in the backbone and in the knee joint.
ELASTIC: makes up the outer ear and the flap that closes when you swallow.
DESCRIBE MUSCLE TISSUE.
Vascularised, has many blood vessels. Elongated. Has the myofilaments called actin and myosin which allows muscles to contract.
DESCRIBE SKELETAL MUSCLE
Joined to bones by tendons. Contractions make bones move. Has a lot of connective tissue.
DESCRIBE CARDIAC MUSCLE
Makes up the heart and allows it to contract.
DESCRIBE SMOOTH MUSCLE
Within intestines and blood vessels, moves substances along.
DESCRIBE EPIDERMAL TISSUE IN PLANTS
Flattened cells which form a protective layer around stems, roots and leaves. Some have a waxy layer called a waxy cuticle.
DESCRIBE VASCULAR TISSUE?
Forms the vascular bundle. Made of xylem and phloem. Xylem transports water and mineral ions. Phloem, transports assimilates such as sucrose and proteins.
DESCRIBE MERISTEMATIC TISSUE.
Stem cell tissue found in cambium. Can divide to form other cells.
How xylem and phloem are formed from meristematic tissue:
- Cambium cells can divide to form xylem cells. Lining is deposited inside which waterproofs and kills the cell. Ends break down so xylem forms long columns with a wide lumen which can carry water.
- Cambium can also differentiate into phloem cells. It forms sieve tubes elements which loses most of its organelles, sieve plates develop between them. Companion retain their organelles and produce ATP.
DESCRIBE THE ORGAN LEAF.
Photosynthesis
DESCRIBE ROOT
Anchorage, absorption of mineral ions and water. Storage.
DESCRIBE STEM
Support, holds up leaves so they are exposed to sunlight. Transportation of water and mineral ions. Storage.
DESCRIBE FLOWER
Sexual reproduction
DESCRIBE THE DIGESTIVE SYSTEM
Nutrition to provide ATP and materials for growth and repair
DESCRIBE THE CIRCULATORY SYSTEM
Transport to and from cells
DESCRIBE THE RESPIRATORY SYSTEM
Breathing and gaseous exchange excretion
DESCRIBE THE URINARY SYSTEM
Excretion and osmoregulation
DESCRIBE THE INTEGUMENTARY SYSTEM
Waterproofing, protection and temperature regulation.
DESCRIBE THE MUSCULO-SKELETAL SYSTEM
Support, protection and movement.
DESCRIBE THE IMMUNE SYSTEM
Protection against pathogens
DESCRIBE THE NERVOUS SYSTEM
Communication, control and coordination.
DESCRIBE THE ENDOCRINE SYSTEM
Communication, control and coordination.
DESCRIBE THE REPRODUCTIVE SYSTEM
Reproduction
DESCRIBE THE LYMPH SYSTEM
Transports fluids back to the circulatory system
WHAT ARE STEM CELLS?
These are cells that can divide to form potentially any cell. They are pluripotent and are capable of expressing any of their genes. They are useful in medical research.
WHERE ARE STEM CELLS FOUND
- Embryonic stem cells: present in early embryos when a zygote is formed.
- Umbilical cord
- Adult stem cells: found in bone marrow
- Induced pluripotent stem cells. Can be made in a lab.
EXPLAIN POTENTIAL USES OF STEM CELLS
- Bone marrow replacement. Can be used to treat diseases such as anaemia and leukaemia. It can also be used to replace blood in cancer patients after treatment.
* Drug research, new drugs can first be tested here
* It can be used to study developmental biology. Can see how cells develop.
* Repair of damaged or lost tissues:
DISCUSS ETHICAL ISSUES
discuss
