Biology

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  • Created on: 16-10-10 00:44

Cell Activity - Plant Cells vs. Animal Cells

Both types of cell have these:

- Nucleus

- Cytoplasm

- Cell membrane

- Mitochondria (Energy is released here by respiration)

Only plant cells have these:

- Cell wall

- Large vacuole

- Chloroplasts

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Cell Activity - Specialised Cells

Root hair cell in Plants: It is adapted to do its job of taking in water and nutrients by having:

- a large surface area

- a thin cell membrane

The Sperm cell is an example of a specialised animal cell.

Red Blood Cell - Carries oxygen around the body.

Adaptations: No nucleus, large surface area, so maximum area for oxygen carriers: haemoglobin.

White Blood Cell – Fight disease, some make antibodies.

Adaptations - Irregular shape, they can change shape to squeeze out of blood vessels and get to the site of infection. Others have cytoplasm which can flow making it possible for the cell to change shape, surround and engulf bacteria. Can increase in numbers to fight disease.

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Cell Activity - Cells, Tissues, Organs and Systems

All living things are made up of Cells.

A group of Cells e.g. Heart Muscle makes up a Tissue e.g. Heart Muscle Tissue.

A group of Tissues makes up an Organ e.g. Heart.

A group of Organs makes up a System e.g. Circulatory System.

A group of Systems make up an Organism e.g. Humans.

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Cell Activity - Diffusion

Diffusion = movement of molecules, from a region of high concentration to a region of low concentration.

Oxygen diffuses into cells, and the waste carbon dioxide diffuses out.

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Cell Activity - Osmosis

Osmosis = movement of water molecules, across a partially permeable membrane, from a region of high concentration of water to a low concentration of water molecules.

It allows plants to take in water through their roots.

It is used in kidney dialysis machines to filter the blood.

Partially Permeable Membrane

Small molecules, such as water can pass through the small holes in the membrane. But larger molecules like sugar cannot pass through the membrane.

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Cell Division - Introduction

Mitosis and Meiosis are the two types of cell division.

Mitosis enables growth and repair to occur. Meiosis is for the production of sex cells.

Mitosis is used in asexual reproduction. Meiosis is used to produce gametes for sexual reproduction.

Mitosis prodcues cells with identical number of chromosomes and genetic information are produced (46 in humans). Meiosis produces daughter cells with half the number of chromosomes of the parent (23 in humans).

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Cell Division - Meiosis (Sexual)

Meiosis is the type of cell division by which germ cells (eggs and sperm) are produced.

1. Each Chromosome replicates.

2. The pairs move to each end.

3. The cell divides for the first time.

4. And for a second time.

5. 4 Daughter cells, each has 23 (human) chromosomes.

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Cell Division - Mitosis (Asexual)

Mitosis is a process of cell division which results in the production of two daughter cells from a single parent cell.

The daughter cells are identical to one another and to the original parent cell.

1. Each chromosome replicates.

2. The pairs line up and the cell divides.

3. 2 Daughter cells form each genetically identical as the parent cell.

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Summary - Cell Activity and Cell Division

- Specialised cells are adapted for a specific function e.g. root hair cell, red blood cell.

- Cells > tissues > organs > systems > organism.

- Diffusion = movement of particles from a region of high concentration to low concentration e.g. alveoli.

- Mitosis = asexual reproduction. Daughter cells have the same number of chromosomes as parent cells.

- Meiosis = sexual reproduction. Daughter cells (gametes) have ½ the number of chromosomes as parent cells.

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