Chapter 3: The cells, tissues and organisation of the body Flashcards
Cells
Are the smallest functional unit of the body
Cells are grouped together to form
Tissues
Different tissues are grouped together to form
Organs
Organs are grouped together to form
Systems
Zygote
The human body develops from a single cell, which is the result of the fusion of the ovum and the spermatozoon
A cell consists of
Plasma membrane
Cytoplasm
Organelles - incl Nucleus
Types of organelles
Nucleus, mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes and cytoskeleton
Plasma membrane
Two layers of phospholipids with protein and sugar molecules embedded in them, plus lipid cholesterol is present.
Phospholipid
Hydrophillic, electrically charged head
Hydrophobic, no charge tail
Nucleus
Is the largest organelle and contained within the nuclear envelope with pores in order for substances to pass between it and the cytoplasm
Nucleus contains the genetic material
46 chromosomes - DNA
Chromatin
During cell division the chromosomes resemble a fine network of threads
A roughly spherical structure contained within the nucleus
Nucleolus
Mitochondria
Sausage shaped structure
Power house of the cell
Synthesis of ATP
Ribosomes
- Tiny granules composed of RNA and protein
- Synthesise proteins from amino acids
- Found on the outer surface of the nuclear envelop or on rough endoplasmic reticulum
Endoplasmic reticulum
- Extensive series of interconnecting membranous canals in the cytoplasm
- Smooth ER synthesises lipids and steroid hormones
Rough ER is studded with ribosomes and is used for protein synthesis
Golgi apparatus
- Consists of stacks of closely folded membranous sacs
* Proteins from Rough ER are packaged into secretory granules
Lysomes
- Break down fragments of organelles and large molecules inside the cell
- Or in white blood cells ingest foreign material
Cytoskeleton
- Consists of an extensive network of tiny protein fibres
- Microfilaments
- Microtubules
- Centrosome
- Cell Extensions
Microfilaments
The smallest fibres, provide structural support and maintain shape of the cell
Microtubules
Larger contractile protein fibres that move organelles in the cell, chromosomes during cell division and cell extensions
Centrosome
This directs organisation of microtubules within the cell. It consists of a pair of centrioles and plays an important part during cell division
Cell extensions
- Microvilli - tiny projections (greatly increase surface area)
- Cilia - hair like projections (beat in unison eg to move mucus upwards in the respiratory tract
- Flagella - single long whip projections
Most body cells have 46 chromosomes and divide by
Mitosis - two new genetically identical daughter cells
The formation of gametes, ova and spermatozoa
Meiosis
The period between two cell divisions is known as
The cell cycle
There are two phases of the cell cycle that can be seen on light microscopy
Mitosis (M phase)
Interphase
Interphase
Longer phase with three stages:
- First gap phase (G1) the cell grows in size and volume
- Synthesis of DNA (S phase) Chromosomes replicate forming two identical copies of DNA (96 chromosomes)
- Second gap phase (G2) further growth and preparation of cell division
Mitosis
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
Prophase
The replicated chromatin become tightly coiled and easier to see. The chromosomes pair with its copy and are joined to each other at the centomere. Mitotic apparatus consists of two centrioles seperated by the mitotic spindle. The centrioles migrate one to each end of the cell and the nuclear envelope disappears.
Metaphase
The chromatids align on the centre of the spindle attached by the chromosomes
Anaphase
Cetromeres seperate and one pair of the sister chromatids migrate to each end of the spindle as the microtubules form the mitotic spindle
Telophase
The mitotic spindle disappears, the chromosomes uncoil and the nuclear envelope reforms.
Cytokinesis
The cytoplasm, intracellular organelles and plasma membrane split forming two identical daughter cells