Biology Chapter 1: Cell Biology and Transport

Study Notes

Cell Biology

Eukaryotic cells: have genetic material (DNA) in a nucleus, examples include animal and plant cells
Prokaryotic cells: do not have a nucleus, have a single loop of DNA, examples include bacteria
Cell components:
- Cell membrane: controls movement of substances in and out of the cell
- Nucleus: contains DNA
- Mitochondria: where energy is released through respiration
- Cytoplasm: jelly-like substance where chemical reactions happen
- Cell wall (plants): made of cellulose, strengthens the cell
- Chloroplasts (plants): contain chlorophyll, absorb light energy for photosynthesis
- Permanent vacuole (plants): contains cell sap
- Ribosomes: site of protein synthesis

Microscopy

Light microscope: uses light to form images, relatively cheap, low magnification, low resolution
Electron microscope: uses a beam of electrons to form images, expensive, high magnification, high resolution
Magnification calculation: magnification = image size / actual size

Specialised Cells

Differentiation: cells in animals and plants differentiate to form different types of cells
Examples of specialised cells:
- Sperm cell: has lots of mitochondria to release energy, no nucleus, and a tail to swim to the ovum
- Red blood cell: contains haemoglobin that binds to oxygen, flat bi-concave disc shape to increase surface area-to-volume ratio
- Muscle cell: contains protein fibres that can contract, relax, and shorten the cell
- Nerve cell: has branched endings (dendrites), impulses, and a myelin sheath to insulate the axon
- Root hair cell: absorbs mineral ions and water, has a long projection to increase surface area

Transport

Diffusion: the spreading of particles from an area of higher concentration to an area of lower concentration
Osmosis: the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
Active transport: the movement of particles from an area of lower concentration to an area of higher concentration using energy from respiration
Factors affecting diffusion rate: difference in concentration, temperature, and surface area of the membrane
Examples of transport:
- Oxygen diffuses from the air into the blood in the capillaries through the process of diffusion, which occurs due to the concentration gradient between the air and the blood. This process is essential for the body's use of oxygen for cellular respiration.
- Carbon dioxide diffuses from the blood in the capillaries into the air through the process of exhalation. This occurs because the concentration of carbon dioxide in the blood is higher than in the air, causing the molecules to move from an area of higher concentration to an area of lower concentration.
- Nutrients from the small intestine diffuse into the capillaries and are absorbed into the bloodstream. This process is facilitated by the villi and microvilli in the small intestine, which increase the surface area for absorption.
- Urea diffuses from cells into the blood for excretion in the kidney, where it is removed from the body through the process of urination. The kidneys play a crucial role in maintaining proper levels of urea in the bloodstream.
- Active transport is used to absorb mineral ions into the root hair cells of plants. This process is driven by the ATP-dependent pumps that transport ions against their concentration gradient.