Biology Cells chapter 1 Flashcards
Characteristics of cells
- Basic building blocks of life
- They have all characteristics of life, needs food, water and air to survive
- Will eventually die, will grow, able to reproduce and respond to changes
- Many chemical reactions occur in the cell
Light micrograph
Magnifies 1000x on a cellular level
Electron micrograph
magnifies more than 200 000x able to see things on a molecular level
What does a cell consist of?
Protoplasm- which is everything in the cell membrane, including cell membrane, excluding cell wall. Made of cell surface membrane, cytoplasm and nucleus
Description of cell surface membrane
- Serves as a boundary (without it, everything in the cell would leak out and the cell would die)
- It is partially permeable
- Controls the substances entering or leaving the cell
Description of cytoplasm
- Most cell activities occur there
- It contains specialised structures called organelles like nucleus, vacuole
Description of nucleus and what it is made up of
-Contains genetic material
- controls all activities within the cell
- May contain one or more nucleoli and chromatin, which is a condensed form of DNA(genetic material)
Nucleoplasm- A small round denser protoplasm of the nucleus (all the fluid inside the nucleus)
Nuclear envelope- surrounds the nucleoplasm
Nucleolus- a protein that helps to replicate DNA
Description of Chromatin
- Compacted form of DNA
- It is a network of threadlike structures that controls cell activities e.g. cell division
- It’s made up of deoxyribonucleic acid (DNA) which carries hereditary information
- Chromatin threads condense into chromosomes when the cell is dividing
Cell wall
- Found in plant cells but absent in animals cells
- made of cellulose
- It protects the cell from injuries and gives the cell its shape
- It is fully permeable
How to do a longitudinal cut
Longitudinal section- cutting along the long axis of the cell
How to do a transverse cut
Transverse section- Cutting at right angles to the longitudinal plane
How to examine the cell clearly
By staining the cell with either iodine or methylene blue, as cells are usually transparent and colourless
What are the two types of endoplasmic reticulum(ER)?
Rough endoplasmic reticulum (RER)
Smooth endoplasmic reticulum (SER)
Rough endoplasmic reticulum description
- Appears rough because ribosomes are attached to its surface
- The ribosomes are required to make proteins
- The RER transports proteins to the Golgi apparatus for secretion out of the cell
- Ribosome can be found freely in the cytoplasm, they synthesise proteins which are used within the cell
Smooth endoplasmic reticulum description
- SER is more tubular and does not have ribosomes
- It synthesis’s substances such as fats and steroids (sex hormones)
- It is involved in detoxification
Organs rich in SER are the testes and the ovaries as sex hormones are steroids that are synthesised
Golgi apparatus description
- consists of flattened spaces surrounded by membranes
- It modifies substances made by the endoplasmic reticulum
- The Golgi apparatus chemically modifies, stores and packages the substances in vesicles for secretion out of the cell
How the Golgi apparatus works
- Vesicles containing substances made in the ER pinch off from the ER
- Vesicles then fuse with the Golgi apparatus
- The substances in the vesicles are released into the Golgi apparatus and are chemically modified
- Secretory vesicles containing the modified substances pinch off from the Golgi apparatus and move towards the cell surface membrane
- The secretory vesicles fuse with the cell surface membrane and release contents into exterior of cell
Mitochondria
Site for aerobic respiration where glucose is oxidised to release energy for cellular activities (enzymes are involved)
Glucose+ Oxygen+ Carbon dioxide+ water + large amount of energy
Chloroplasts
Oval structures containing pigment chlorophyll which is required for photosynthesis to occur
Vacuoles
- Store substances within the cell
- Animal cells have many vacuoles containing water and food substances
- Plant cells have a large central vacuole containing cell sap ( The large central vacuole can store a lot of water, so the cell can swell up, maintaining its shape by the cell wall so the cell will not burst. This makes the cell firm, allowing the plant to stay upright)
Differentiation
The process by which a cell becomes specialised for a specific function
Examples of specialised cells are red blood cells and root hair cells
Muscle cells
- Elongated and cylindrical in shape
- has multiple cells fuse together to form a long fibre
- Rich in mitochondria and nuclei to release a lot of energy to compensate for the muscle’s constant contraction and expansion
Red blood cell
Haemoglobin in the cytoplasm of red blood cells transports oxygen from lungs to all parts of the body
A red blood cell has no nucleus, thus enabling it to have more space in the cytoplasm to contain more haemoglobin and hence transports more oxygen when oxygen binds to form oxyhaemoglobin
It has a circular, biconcave shape, increasing the surface area to volume ratio. This increase the rate of diffusion of oxygen molecules into and out of the cell. It has a cave-in structure to have thinner central portion, to have a larger surface area but same volume, this is it to increase rate of absorption of oxygen
